Monday, October 31, 2011

Imaging Evaluation of Leukocoria

A recent discussion with an ophthalmologist friend prompted research into the topic of appropriate imaging for the evaluation of leukocoria.

Retinoblastoma accounts for 50%-60% of cases of leukocoria in children, followed by persistent hyperplastic primary vitreous, Coats disease, toxocariasis, retinopathy of prematurity, and retinal astrocytic hamartoma. The diagnosis can be made by the ophthalmologist using ophthalmoscopy and ocular ultrasound. Advanced imaging is used when the diagnosis remains uncertain and for evaluating the extent of disease if a diagnosis of retinoblastoma is made.

The European Retinoblastoma Imaging Collaboration (ERIC) has developed consensus guidelines on imaging children with leukocoria. The most important change to the way leukocoria may be currently imaged in some centers is a move away from CT in favor of ultrasound and MRI. This is not only because of general concern about the use of radiation in children, but also the possibility of an additional risk of radiation-induced cancer in patients with hereditary retinoblastoma, who are already at higher risk for developing second primary cancers.

The only supposed benefit of CT, the detection of calcifications, is now matched by improving technology in ultrasound and MRI. Indeed, a recent study showed that combining data from ophthalmoscopy, ultrasound, and MRI resulted in the detection of all calcifications seen by CT.

Ocular ultrasound is usually performed by ophthalmologists with the child under general anesthesia. Calcifications present as highly reflective foci with characteristic acoustic shadowing. Histologically, 95% of retinoblastomas have calcifications, and ultrasound can detect calcifications in 92%–95% of these cases. These calcifications, however, can obscure visualization of the optic nerve, limiting the use of ultrasound in determining risk factors for metastasis.

Ultarsound can also demonstrate retinal detachment, which is important in defining the pattern of tumor growth.

While diagnosis of retinoblastoma can almost always be made with ophthalmoscopy and ocular ultrasound, MRI is the modality of choice for evaluating an intraocular mass and determining disease extent in retinoblastoma (e.g., optic nerve infiltration past the cribriform lamina, infiltration of choroid and sclera, and determination of extraocular and intracranial extension).

ERIC has put together minimal requirements for MRI evaluation of leukocoria in children, the details of which are outlined in the reference below. In brief, high-resolution images of the orbits, eyes, and optic nerves prior to and following intravenous contrast are advocated. The imaging protocol should also include sequences of the whole brain to exclude trilateral retinoblastoma and leptomeningeal metastases.

References

de Graaf P, Göricke S, Rodjan F, Galluzzi P, Maeder P, Castelijns JA, Brisse HJ; on behalf of the European Retinoblastoma Imaging Collaboration (ERIC). Guidelines for imaging retinoblastoma: imaging principles and MRI standardization. Pediatr Radiol. 2011 Aug 18.

Sunday, October 30, 2011

Adhesive Capsulitis

Adhesive capsulitis is a self-limited clinical syndrome characterized by painful, gradual loss of active and passive glenohumeral motion. Patients are typically women between 40 and 60 years of age who have had symptoms for at least a month, but sometimes for years. Interestingly, the nondominant hand is more frequently involved. While considered a self-limited condition, complete resolution of symptoms can sometimes take years.

The term frozen shoulder is often used interchangeably with adhesive capsulitis; however, many conditions can cause a stiff and painful shoulder. The term adhesive capsulitis should be reserved for the distinct pathological entity of inflammation of the joint capsule and synovium, leading to thickening, contraction, and formation of adhesions.

The process can be primary (idiopathic) or secondary. Causes of secondary adhesive capsulitis include trauma (10% of cases), surgery, degenerative disease, rotator cuff tear, inflammatory disease, metabolic disease (e.g., diabetes, thyroid dysfunction), and autoimmune disease.

Four clinical and arthroscopic stages of adhesive capsulitis have been described.
  • Stage 1: This stage represents acute synovitis without adhesions or capsular contracture. Patients present with less than 3 months of pain (typically at the deltoid insertion) that is achy at rest and sharp with movement. Night pain is a common complaint. Limitation of movement, if present, is reversed by intra-articular injection of anesthetic. The symptoms are nonspecific and can be similar to those of calcific tendinitis, early osteoarthritis, and rotator cuff injury.
  • Stage 2: This stage represents acute synovitis and progressive capsular contracture due to subsynovial scar formation. This stage is also known as the freezing stage. Patients still have pain, which may have increased in severity and is worse at night. Motion is restricted and is partially restored with intra-articular injection of anesthetic.
  • Stage 3: This stage represents "burned out" synovitis and a hypercellular, collagenous capsule. Also referred to as the frozen stage, this stage is characterized clinically by 9 to 15 months of significant stiffness with or without pain at the end range of motion. The restricted motion does not improve with intra-articular injection of anesthetic.
  • Stage 4: This stage is characterized by fully mature adhesions. Also known as the chronic or thawing stage, patients present with minimal pain, sometimes with a gradual improvement in motion. The latter is controversial, as patients tend to under-estimate the range of motion when compared to objective assessments.
Radiographs are performed at the the initial stage to exclude other causes of a stiff shoulder (arthritis, calcific tendinosis). MRI can be performed to exclude rotator cuff tear.

MRI findings cannot reliably differentiate the different stages with two exceptions. In stage 2 disease, there is increased signal intensity of the joint capsule and synovium, reflecting the acute synovitis. The capsular and synovial thickening, as measured in the axillary pouch (pink arrow), is greatest in stage 2 disease (mean thickness of 7.5 mm, compared to ~4 mm for stages 1 and 4 and 5.5 mm in stage 3).

Other MRI findings are not specific to the stage of disease. Soft tissue signal intensity has been described in the rotator interval (white arrows) with or without encasement of the superior glenohumeral and coracohumeral ligaments and extension to the biceps tendon anchor. The soft tissue usually has increased signal intensity on PD-FS images and enhances on post-contrast sequences. This is best seen on sagittal images. Axial images are also useful, but partial volume averaging of the subscapularis muscle may mimic a rotator interval lesion.

Thickening of the coracohumeral ligament can also be seen, although earlier studies have not found a significant difference in thickness between symptomatic patients and control subjects.

On arthrography, the tight joint manifests as decreased capacity to joint injection, although no significant difference has been found in articular fluid volumes between patients with adhesive capsulitis and asymptomatic controls.

Treatment consists of physical therapy, intra-articular corticosteroid injection, closed manipulations, hydrodilatation, and anterior capsulotomy.

References

  • Connell D, Padmanabhan R, Buchbinder R. Adhesive capsulitis: role of MR imaging in differential diagnosis. Eur Radiol. 2002 Aug;12(8):2100-6.
  • Emig EW, Schweitzer ME, Karasick D, Lubowitz J. Adhesive capsulitis of the shoulder: MR diagnosis. AJR Am J Roentgenol. 1995 Jun;164(6):1457-9.
  • Neviaser AS, Hannafin JA. Adhesive capsulitis: a review of current treatment. Am J Sports Med. 2010 Nov;38(11):2346-56. Epub 2010 Jan 28.
  • Sofka CM, Ciavarra GA, Hannafin JA, Cordasco FA, Potter HG. Magnetic resonance imaging of adhesive capsulitis: correlation with clinical staging. HSS J. 2008 Sep;4(2):164-9.

Saturday, October 29, 2011

Vertebrobasilar Dolichoectasia

Vertebrobasilar dolichoectasia (dilatative arteriopathy) refers to the elongation or widening of the intracranial vertebral and/or basilar arteries. The etiology is unclear, but is thought to be related to atherosclerosis and/or hypertension.

Also known as S-shaped aneurysm, megadolichobasilar anomaly, fusiform aneurysm, basilar artery ectasia, tortuous vertebrobasilar system, vertebrobasilar dolichoectasia is usually diagnosed subjectively. Research criteria have also been proposed and can be used to guide diagnosis. These include:
  • Basilar artery diameter > 4.5 mm in any location along its course
  • Basilar artery origin the level of the pontomedullary junction
  • Basilar artery bifurcation above the suprasellar cistern
  • Basilar artery lateral to the margin of the clivus or dorsum sellae
  • Basilar artery with lateral deviation > 10 mm perpendicular to a straight line joining its origin to its bifurcation

  • Vertebral artery diameter > 4.0 mm along its intracranial course
  • Vertebral artery above the level of the pontomedullary junction
  • Vertebral artery > 10 mm perpendicular to a straight line joining its intracranial entry point to the basilar artery origin
Most cases of vertebrobasilar dolichoectasia are asymptomatic, but patients can present with cranial neuropathy (from cranial nerve compression), brainstem compression, hydrocephalus, and infarction.

Although vertebrobasilar dolichoectasia can be demonstrated on routine CT (as was the case presented here), MRI using high-resolution sequences (e.g., FIESTA, CISS) is the most sensitive techniques for determining the cause of cranial nerve symptoms.

The images above are from a cervical spine myelogram in an 80-year-old woman. Incidentally seen is ectasia and tortuosity of the vertebral artery with significant compression of the medulla.

References

  • Tay KY, U-King-Im JM, Trivedi RA, Higgins NJ, Cross JJ, Davies JR, Weissberg PL, Antoun NM, Gillard JH. Imaging the vertebral artery. Eur Radiol. 2005 Jul;15(7):1329-43.
  • Ubogu EE, Zaidat OO. Vertebrobasilar dolichoectasia diagnosed by magnetic resonance angiography and risk of stroke and death: a cohort study. J Neurol Neurosurg Psychiatry. 2004 Jan;75(1):22-6.

Friday, October 28, 2011

Extensor Carpi Ulnaris Tendon: Normal Signal Intensity

The normal extensor carpi ulnaris (ECU) tendon can have central increased signal intensity at the level of the distal radioulnar joint (the extensor carpi ulnaris tendon pseudolesion). It has been suggested that the increased signal is due to the tendinous slips from the proximal and distal muscle bellies interdigitating at the level of the wrist with spiraling or decussating fibers that approach the magic angle. This explanation is needed because the main fibers of the tendon are parallel to the forearm and at a 90° angle relative to B0 in the standard wrist position during MR imaging. That is, the main tendon fibers are no where near the magic angle.

Extensor carpi ulnaris tendinosis can be diagnosed when you see diffuse, full-thickness high signal intensity within the tendon or when there is thickening or attenuation of the tendon.

The image above shows a normal extensor carpi ulnaris tendon with central high signal or T1- and T2-weighted images.

References

Timins ME, O'Connell SE, Erickson SJ, Oneson SR. MR imaging of the wrist: normal findings that may simulate disease. Radiographics. 1996 Sep;16(5):987-95.

Thursday, October 27, 2011

Osteopetrosis

Osteopetrosis (Albers-Schonberg disease, marble bone disease) is a bone disease caused by osteoclast failure and impared bone resorption. The primary event can be an osteoclast-autonomous defect or microenvironmental changes that affect ability of osteoclast progenitors to mature, resorb bone, or both. It is a rare condition with autosomal recessive and dominant modes of inheritance.
  • Autosomal dominant form:
    • Type 1: Not currently classified as osteopetrosis, because the defect has been shown to be due to an osteoblast defect that enhances bone formation. There is generalized mild osteosclerosis and normal hematological findings. Fractures are uncommon.
    • Type 2 (ADO): The most common form of osteopetrosis. The course is heterogeneous, ranging from asymptomatic to fatal (rare). Patients present with hematological and neural defects with a range of disease severity. Generally seen in adults, it is characterized by sclerosis of the skull base and pelvis and a typical "bone-within-bone" appearance of the vertebral bodies due to endplate sclerosis ("sandwich" spine").

      A variant, centrifugal osteopetrosis, presents with sclerosis of the distal appendicular skeleton and the skull.
  • Autosomal recessive:
    • Severe form (ARO): Also known as malignant osteopetrosis, this form usually results in stillbirth or early death. Infants who survive present in early childhood with fractures, as well as diffuse marrow space obliteration leading to pancytopaenia. Patients also commonly have neurological complications due to increased intracranial pressure from calvarial expansion, as well as cranial nerve, spinal cord, and vascular compression due to narrowing of cranial and spinal foramina.
    • Intermediate severity form (IRO): Infantile osteopetrosis with distal renal tubular acidosis and cerebral calcifications ("marble brain syndrome"). Patients present with mental retardation, muscle weakness, hypotonia, and fractures.
  • X-linked: Rare. Associated with osteopetrosis, lymphedema, anhidrotic ectodermal dysplasia, and immunodeficiency (OL-EDA-ID syndrome).
The images above are from a young woman with autosomal dominant osteopetrosis. There is sclerosis and widening of the diploic space and a hair-on-end appearance of the skull. The spine images show the classic sandwich vertebrae sign (differentiate by some from the rugger jersey spine). The femur demonstrates increased sclerosis and an Erlenmeyer flask deformity.

References

Wednesday, October 26, 2011

Bing-Neel Syndrome

Bing-Neel syndrome refers to Waldenström macroglobulinemia with central nervous system infiltration. Waldenström macroglobulinemia is defined by the World Health Organization as a "lymphoplasmacytic lymphoma with bone marrow involvement and IgM monoclonal gammopathy of any concentration." Patients with Waldenström macroglobulinemia have anemia and lymphoplasmacytic infiltration of the bone marrow. Lymph nodes and the spleen are often also involved, but involvement of the central nervous system (Bing-Neel syndrome) is rare.

While patients with Waldenström macroglobulinemia can present with stroke and other focal or multifocal brain syndromes, diffuse encephalopathy, and/or subarachnoid hemorrhage due to hyperviscosity of blood or thrombocytopenia, Bing-Neel syndrome refers to perivascular infiltration of small lymphocytes, lymphoplasmacytoid cells, and plasma cells in the brain parenchyma and/or spine. The infiltration can be diffuse or tumoral. In diffuse Bing-Neel syndrome, lymphoid infiltration is seen predominantly in the pons, medulla, periventricular white matter, and leptomeningeal spaces. In the tumoral form, unifocal or multifocal lesions are most commonly located in the deep subcortical white matter.

Patients with Bing-Neel syndrome can present with seizures, confusion, cognitive decline, headache, blurry or cloudy vision, psychiatric symptoms, pain, numbness, paresthesias, hearing loss, and weakness.

On MRI, one may see enhancing lesions and/or thickening or enhancement of meningeal sheaths. Multiple infarctions can also be seen as a result of neoplastic vascular obstruction. The images above reveal pachymeningeal enhancement and FLAIR-hyperintensity.

References

  • Kim HJ, Suh SI, Kim JH, Kim BJ. Brain magnetic resolution imaging to diagnose bing-neel syndrome. J Korean Neurosurg Soc. 2009 Dec;46(6):588-91.
  • Malkani RG, Tallman M, Gottardi-Littell N, Karpus W, Marszalek L, Variakojis D, Kaden B, Walker M, Levy RM, Raizer JJ. Bing-Neel syndrome: an illustrative case and a comprehensive review of the published literature. J Neurooncol. 2010 Feb;96(3):301-12.

Tuesday, October 25, 2011

Tracheal Bronchus

A tracheal bronchus is an aberrant bronchus that arises from the trachea directly. It is seen normally in swine, cattle, sheep, goats, camels, giraffes, and whales. In humans, it is an anatomic variant that can be associated with other bronchopulmonary anomalies, tracheal stenosis, or Down syndrome. While usually asymptomatic, a tracheal bronchus is occasionally the etiology for chronic pulmonary disease such as emphysema, bronchiectasis, atelectasis, and persistent or recurrent pneumonia. A tracheal bronchus should be considered in intubated patients with right upper lobe complications.

A tracheal bronchus usually arises from the right lateral wall of the trachea less than 2 cm above the carina. It can supply only the apical segment or the entire upper lobe. A right tracheal bronchus has a prevalence of 0.1%–2%, while a left tracheal bronchus a prevalence of 0.3%–1%.

Analogous to the replaced/accessory terminology in variant hepatic arterial supply, a tracheal bronchus can be displaced or supernumerary. A displaced (not replaced) right tracheal bronchus is more common and arises from the trachea in the setting of an absent apical branch of the anatomic right upper lobe bronchus. A supernumerary (not accessory) right tracheal bronchus exists in the setting of a normal trifurcation of the right upper lobe bronchus.

Since its original description as a right upper lobe bronchus originating from the trachea, the term tracheal bronchus has been confusingly expanded to include origins from the carina and even mainstem and distal bronchi. These may be properly referred to as ectopic bronchi, reserving the term tracheal bronchi for the subset that arise from the trachea.

A nomenclature has been proposed using terms like eparterial, hyparterial, preeparterial, posteparterial, prehyparterial, and posthyparterial that vary depending on which side we're talking about. Those interested in the terminology can refer to the excellent review by Ghaye and colleagues.

References

Monday, October 24, 2011

Riedel's Lobe of the Liver

Riedel's lobe of the liver is an inferior, tonguelike projection of the anterior border of the right lobe of the liver to the right of the gallbladder inferior to the costal margin. Clinically, this may be confused for a mass, prompting imaging referral. Recognition of this normal variant, can therefore be reassuring to the referring clinician. Riedel's lobe can also pose a challenge during right-sided laparoscopic procedures, and a case of gastric outlet obstruction due to a Riedel's lobe has been reported.

The etiology of Riedel's lobe has been debated. It has been attributed to edema from cholecystitis and appendicitis, hepatic tumors, and constriction from tight corsets (it is more common in women). More recent work has shown that its prevalence increases with age, being seen on imaging in about 60% of people between 45 and 65 years of age, and 25% of people between 20 and 45 years of age. The observation that the craniocaudal extent of the liver actually diminishes with age, while the prevalence of Riedel's lobe increases with age has led some to suggest that Reidel's lobe is the result of skeletal degenerative changes.

References

  • Akbulut S, Cakabay B, Sevinc MM, Basak F. Gastric outlet obstruction caused by Riedel's lobe of the liver: a diagnostic and therapeutic challenge for surgeons. Hepatogastroenterology. 2011 Mar-Apr;58(106):589-92.
  • Chien GW, Orvieto MA, Galocy RM, Sokoloff MH, Shahav AL. Technical considerations for laparoscopic right renal surgery in presence of Riedel's lobe of the liver. J Endourol. 2005 Apr;19(3):300-2.
  • Gillard JH, Patel MC, Abrahams PH, Dixon AK. Riedel's lobe of the liver: fact or fiction? Clin Anat. 1998;11(1):47-9.

Sunday, October 23, 2011

Osseous Manifestations of Tuberous Sclerosis Complex

Bony manifestations of tuberous sclerosis complex include both sclerotic and lucent lesions. The sclerotic lesions are most commonly found in the axial skeleton, while the lucent lesions are found most commonly in the hands and feet.

Other skeletal manifestations include hyperostosis of the inner table of the calvaria, scoliosis, and macrodactyly.

Sclerotic Bone Lesions

Sclerotic bone lesions are the third most common imaging finding in patients with tuberous sclerosis (after brain tubers and renal angiomyolipomas). Histologically, they represent areas of concentric osteosclerosis in the medullary cavity.

Sclerotic bone lesions are almost always located in the spine and commonly in the pelvis, but can also be seen in the ribs (as in the left posterior 5th rib in the case above), sternum and the axial skeleton. Involvement of the skeleton is usually extensive. The lesions are usually round or oval, but can also be flame-shaped.

Lucent Lesions

Lucent lesions are thought to represent hamartomas and are found in the phalanges of the hands and feet in 2/3 of patients. Because they are asymptomatic, they are seen incidentally on radiographs of the hands and feet obtained for other reasons.

On radiographs, they are irregularly circumscribed lucent lesions with a sclerotic appearance peripherally. A distinct wavy periosteal reaction has been described along the shafts of the metacarpals and metatarsals. While the lucent lesions are more common in the hands, the periosteal reaction tends to be more common in the feet.

References

  • Avila NA, Dwyer AJ, Rabel A, Darling T, Hong CH, Moss J. CT of sclerotic bone lesions: imaging features differentiating tuberous sclerosis complex with lymphangioleiomyomatosis from sporadic lymphangioleiomymatosis. Radiology. 2010 Mar;254(3):851-7.
  • Bernauer TA, Mirowski GW, Caldemeyer KS. Tuberous sclerosis. Part II. Musculoskeletal and visceral findings. J Am Acad Dermatol. 2001 Sep;45(3):450-2.
  • Holt JF, Dickerson WW. The osseous lesions of tuberous sclerosis. Radiology. 1952 Jan;58(1):1-8.
  • Lustberg H, Gagliardi J, Lawson J. Digital enlargement in tuberous sclerosis. Skeletal Radiol. 1999 Feb;28(2):116-8.
  • Tung HE, Shih SL. Tuberous sclerosis with rare presentation of macrodactyly. Pediatr Radiol. 2009 Aug;39(8):878.
  • Umeoka S, Koyama T, Miki Y, Akai M, Tsutsui K, Togashi K. Pictorial review of tuberous sclerosis in various organs. Radiographics. 2008 Nov-Dec;28(7):e32.

Saturday, October 22, 2011

Episternal Ossicles

Episternal ossicles are accessory bones that are located posterior or cephalad to the manubrium. They result from supernumerary ossification centers and are seen in less than ~2% of the population.

They range in diameter from 2 mm – 15 mm and are hard to see on radiographs. Cross sectional imaging reveals unilateral or bilateral triangular ossicles in a retro- or supra-manubrial location. In three dimensions, they are quadrilateral pyramids whose bases articulate with the manubrium. The apices point medially, but rounding of the corners may mask this appearance.
Recognition is important to differentiate them from calcified lymph nodes, fracture fragments, vascular calcifications, and foreign bodies.

References

Friday, October 21, 2011

Intraarticular Methylmethacrylate Cement

Intraarticular leakage/displacement of methylmethacrylate cement is an uncommon complication of percutaneous injection of bone lesions (usually acetabular). It can also be seen, as in this case, by displacement of intramedullary cement during revision surgery.

In cases reported in the literature, the intraarticular leakage of liquid cement has been associated with transitory aggravation of pain (due to the intraarticular location of the cement) and one case of rapid (2 months) chondrolysis. Intraarticular displacement of solid cement can also cause pain from the mechanical effect of the foreign body.

Surgical extraction of the cement fragment can be performed when this complication is observed.

References

Leclair A, Gangi A, Lacaze F, Javier RM, Bonidan O, Kempf JF, Bonnomet F, Limbach FX, Kuntz JL, Dietmann JL, Sibilia J. Rapid chondrolysis after an intra-articular leak of bone cement in treatment of a benign acetabular subchondral cyst: an unusual complication of percutaneous injection of acrylic cement. Skeletal Radiol. 2000 May;29(5):275-8.

Thursday, October 20, 2011

Sutural Hyperostosis

Sutural hyperostosis, also known as sutural sclerosis, is a normal variant in adults. It most commonly affects the coronal and lambdoid sutures as seen here.

In children, the most common cause of increased sclerosis of the sutures is craniosynostosis. Sutural sclerosis has also been reported in Torg-Winchester syndrome and NAO (nodules, arthropathy and osteolysis) syndrome.

References

  • Freyschmidt J, Brossmann J, Wiens J, Sternberg A. Cranial Vault. In Freyschmidt's Köhler and Zimmer: Borderlands of normal and early pathologic findings in skeletal radiography. Fifth revised edition. Thieme (2003). P 369.

Wednesday, October 19, 2011

Bridged Sella

The paired anterior and posterior clinoid processes are connected by interclinoid ligaments. Calcification of the ligaments can be seen radiographically, an appearance that has been called the "bridged sella." This calcification can be complete or partial and is seen in ~5% - ~15% of the population.

A bridged sella is usually an incidental finding. Calcifications of the interclinoid ligaments can, however, be seen along with calcifications of the falx in patients with basal cell nevus syndrome.

References

Cederberg RA, Benson BW, Nunn M, English JD. Calcification of the interclinoid and petroclinoid ligaments of sella turcica: a radiographic study of the prevalence. Orthod Craniofac Res. 2003 Nov;6(4):227-32.

Tuesday, October 18, 2011

Soft Tissue Mass with Calcification

Differential considerations for a soft tissue mass with calcifications includes:
  • Vascular tumors: Phleboliths can be seen in hemangioma, angioleiomyoma, arterovenous malformation, aneurysm, lymphangioma.
  • Myositis ossificans: Peripheral calcifications typical.
  • Soft tissue chondroma: Punctuate or ring and arc calcification.
  • Schwannoma: Cystic areas with hemorrhage and calcification.
  • Synovial chondromatosis: Juxtaarticular osteocartilaginous mass
  • Lipoma:
  • Hamartoma:
  • Fibromatosis:
  • Fat necrosis:
  • Abscess:
  • Synovial cell sarcoma: Nonspecific dystrophic calcifications in a slowly growing lower extremity mass in a young adult is the classic presentation. Calcification in ~30% of cases with a central distribution.
  • Infantile myofibromatosis:
  • Metastatic or extraskeletal osteosarcoma:
  • Mesenchymal chondrosarcoma:
  • Pilomatricoma:

References

Gartner L, Pearce CJ, Saifuddin A. The role of the plain radiograph in the characterisation of soft tissue tumours. Skeletal Radiol. 2009 Jun;38(6):549-58.

Monday, October 17, 2011

Peroneal Intraneural Ganglion Cyst

Intraneural ganglia are mucinous cysts that are thought to arise when joint fluid dissects into an articular branch of a nerve through a capsular tear. As a result, intraneural ganglia are typically tubular in shape. This is in contrast to the more common extraneural ganglion cysts, which tend to be globular. Both intra- and extra-neural ganglion cysts can be present in the same patient.

Peroneal intraneural ganglion cysts are almost always symptomatic, with patients presenting with pain and neuropathy. The much more common extraneural ganglion cysts are usually asymptomatic, but when symptomatic, patients usually present with pain rather than neuropathy

The most common location for intraneural ganglia is the peroneal nerve near the fibular neck.

The MRI findings of a peroneal intraneural ganglion are characteristic. But to appreciate the findings, an understanding of the course of the common peroneal nerve and its articular branch is necessary.

The sciatic nerve (pink, SN) descends along the posterolateral knee and terminates above the knee into the larger tibial nerve (yellow, TN) and the common peroneal nerve (green with dots, PN). The tibial nerves descends centrally along the popliteal fossa. The common peroneal nerve curves anterolaterally along the fibular head. An articular branch (green) crosses transversely ("transverse limb") across the anterior aspect of the fibular neck and then ascends ("tail") to supply the proximal tibiotalar joint. The other branches of the common peroneal nerve are not shown.

In the case of a peroneal intraneural ganglion, fluid is thought to dissect from the proximal tibiofibular joint (pink oval) via the articular branch into the common peroneal nerve. Occasionally, enough pressure exists for the fluid to dissect further into the sciatic nerve.

Three MRI signs have been described:
  • The transverse limb sign: This refers to the appearance of the articular nerve branch as it transversely crosses over the anterior surface of the fibular neck. This is said to be pathognomonic.
  • The signet ring sign: This refers to the eccentric displacement of fascicles by the cyst within the outer epineurium of the common peroneal nerve. Commonly seen, this sign may be absent when there is limited proximal extension of the cyst.
  • The tail sign: This refers to a cystic connection between the articular branch of the common peroneal nerve and the joint. Due to low spatial resolution, differentiation of a neural from a non-neural connection to the joint is often not possible.
The diagram on the top right is an oblique view of the proximal calf, showing the nerves of interest. The T1-weighted images in the left column trace the sciatic nerve (SN) from the top down, as it divides into the tibial nerve (TN, yellow arrow) and common peroneal nerve (PN, green arrow). The bottom images show the transverse limb of the articular branch on T1- and T2-weighted sequences. An extraneural cyst can also be seen posterior to the tibia (red X).

The two T2-weighted images also show evidence of denervation (orange) in the muscles of the anterior compartment. The more cephalad T2-weighted image also shows the tail of the articular branch (green arrow), as well as nerve fascicles arranged eccentrically within the epineurium (signet ring, white arrow). The sagittal T2-weighted image shows both the transverse limb and the tail (green arrows).

Intra- and extra-neural ganglion cysts are treated differently, underscoring the need for accurate diagnosis. Intraneural ganglion cysts are usually treated by decompression (not resection) of the cyst followed by disconnection of the articular branch (to reduce the chance of recurrence). Extraneural ganglion cysts are treated by resection. Treatment for both types of cysts also involves resection of the proximal tibiofibular joint.

References

Spinner RJ, Luthra G, Desy NM, Anderson ML, Amrami KK. The clock face guide to peroneal intraneural ganglia: critical "times" and sites for accurate diagnosis. Skeletal Radiol. 2008 Dec;37(12):1091-9.

Sunday, October 16, 2011

Canal for the Intermediate Branch of the Supraclavicular Nerve

A transclavicular course for branches of the supraclavicular nerve can be seen in about 5% of the population. These canals are slightly more common on the left side and are thought to be formed by enclosure of the nerve within the clavicle during development.

One canal that is sometimes seen through the superior border of clavicle along its middle third transmits the intermediate (middle) branch of the supraclavicular nerve (this is incorrectly referred to as the medial fascicle in Borderlands). The canal can be duplicated in some people, in which case two lucencies are seen on radiographs.

While usually asymptomatic, patients can present with compression of the intermediate (middle) branch of the supraclavicular nerve within the canal. In addition, a stretch injury to the neck can result in trauma to the nerve as it traverses through the clavicle. In these cases, bony decompression of the nerve can alleviate symptoms.

References

  • Freyschmidt J, Brossmann J, Wiens J, Sternberg A. Clavicle and Sternoclavicular Joint. In Freyschmidt's Köhler and Zimmer: Borderlands of normal and early pathologic findings in skeletal radiography. Fifth revised edition. Thieme (2003). P 307.
  • Jelev L, Surchev L. Study of variant anatomical structures (bony canals, fibrous bands, and muscles) in relation to potential supraclavicular nerve entrapment. Clin Anat. 2007 Apr;20(3):278-85.
  • Keats TE and Anderson MW. Atlas of Normal Roentgen Variants That May Simulate Disease. 8th edition, page 453. Mosby (2004).
  • Tubbs RS, Salter EG, Oakes WJ. Anomaly of the supraclavicular nerve: case report and review of the literature. Clin Anat. 2006 Oct;19(7):599-601.

Saturday, October 15, 2011

Suprarenal Inferior Vena Cava Filter Placement

A suprarenal position for an inferior vena cava filter may not always represent a complication. In fact, suprarenal filter placement may be indicated when the traditional infrarenal position may be dangerous or impossible. A suprarenal inferior vena cava filter may be indicated in the following settings:
  • Narrowed infrarenal vena cava: Can be due to intrinsic (e.g., thrombosis, congenital) or extrinsic (e.g., compression) factors.
  • Thrombosis above the level of the renal veins: These thrombi render an infrarenal filter useless in preventing pulmonary emboli.
  • Renal or gonadal vein thrombosis: These thrombi can bypass an infrarenal filter to embolize to the lungs.
  • Pregnancy: The theory is that the gravid uterus can compress the infrarenal inferior vena cava and filter, leading to complications such as injury to the uterus, inferior vena cava, or the filter itself.
The risk of filter migration may be higher due to the the larger diameter of the suprarenal inferior vena cava and its variability due to venous return, blood volume, and the respiratory cycle. Renal failure has also been reported with suprarenal filter placement. Long-term follow-up of patients with suprarenal filters, however, has found that their efficacy and safety are comparable to those of infrarenal filters.

References

  • Ganguli S, Tham JC, Komlos F, Rabkin DJ. Fracture and migration of a suprarenal inferior vena cava filter in a pregnant patient. J Vasc Interv Radiol. 2006 Oct;17(10):1707-11.
  • Greenfield LJ, Proctor MC. Suprarenal filter placement. J Vasc Surg. 1998 Sep;28(3):432-8.
  • Kalva SP, Chlapoutaki C, Wicky S, Greenfield AJ, Waltman AC, Athanasoulis CA. Suprarenal inferior vena cava filters: a 20-year single-center experience. J Vasc Interv Radiol. 2008 Jul;19(7):1041-7.

Friday, October 14, 2011

New Proposed Criteria for Diagnosis of Nephrogenic Systemic Fibrosis

Cowper and colleagues have proposed a new system "to guide and standardize the evaluation and diagnosis of nephrogenic systemic fibrosis." In contrast to the old Cowper criteria, this is a scoring system that uses clinical and histopathological features to yield two scores: a clinical score and a histologic score. The combination is used to give the clinician an idea of how strongly nephrogenic systemic fibrosis should be suspected. Like the old system, there is no role for radiology in the diagnosis, but it's good to know how our colleagues in dermatology and pathology will be diagnosing one of the complications associated with our practice.

Major clinical criteria:
  • Patterned plaques: Red to violaceous thin, fixed skin plaques showing polygonal, reticular, or "amoeboid" morphologies.
  • Joint contractures:
  • Cobblestoning:
  • Marked induration/Peau d'orange: Unpinchable, firm, bound-down skin over the extremities. Peau d'orange refers to follicular dimpling. Must be present in the upper extremity or in the lower extremity above the knee.
Minor clinical criteria:
  • Puckering/linear banding:
  • Superficial plaque/patch: Thin, irregularly bordered hypopigmented, pink, or flesh-colored macules coalescing into patches or thin plaques. Common on the upper extremities and unusual on the trunk.
  • Dermal papules: Slightly brawny papules without epidermal changes.
  • Scleral plaques: There are new-onset white/yellow scleral plaques with dilated capillary loops in a patient younger than 45 years.
Clinical scenario
Clinical score
> 1 major criteria
4
1 major criterion
3
≥ 1 minor criteria
2
1 or no minor criteria
1
Diagnostic of another entity
0


Histologic findings:
  • Increased dermal cellularity: Increased numbers of spindled and/or epithelioid cells with few other inflammatory cells in the dermis. (Histologic score +1).
  • CD34+ cells with tram-tracking: CD34+ spindle or epithelioid cells in a reticular or parallel arrangement forming a complex network. (Histologic score +1).
  • Thick and thin collagen bundles: Both fine and ropey collagen surrounded by clefts. (Histologic score +1).
  • Preserved elastic fibers : Use elastic stain to assess elastic content. (Histologic score –1 if absent, otherwise unchanged).
  • Septal involvement : Expansion of interlobular septa by collagen, cells, and other matrix elements. Spindle cells encroach on fat lobules. (Histologic score +1).
  • Osseous metaplasia: A highly specific feature. Nonmineralized osseous tissue around elastic fibers, some of which protrude beyond the zone of ossification. (Histologic score +3).
Histologic
Clinical score
score
0
1
2
3
4
0
 
Consider alternative diagnosis
1
    Not NSF
Inconsistent
2
   
Suggestive
Consistent
3
   
Consistent
NSF
4
 
Inconsistent
   

References

Girardi M, Kay J, Elston DM, Leboit PE, Abu-Alfa A, Cowper SE. Nephrogenic systemic fibrosis: Clinicopathological definition and workup recommendations. J Am Acad Dermatol. 2011 Jul 1. [Epub ahead of print]

Thursday, October 13, 2011

Spiculated Periosteal Reaction: Pathophysiology

The spiculated pattern of periosteal reaction is an aggressive form of periosteal in which spicules of bone extend perpendicularly (hair-on-end) or radially (sunburst) away from the cortex. The hair-on-end type is suggestive of Ewing sarcoma, but can be seen in osteosarcoma, osteomyelitis, leukemia, lymphoma. The sunburst type is characteristically seen in osteogeosarcoma, but can also be seen with Ewing sarcoma, and hemangioma. Bone metastases, most commonly from prostate carcinoma, can also produce a spiculated pattern of periosteal reaction.

The appearance has to do with the way the periosteum is attached to the cortex. Millions of fibrous bands, called Sharpey's fibers, connect the periosteum to the cortex. New bone forms along these fibers after the periosteum is elevated. The spaces between these bony pillars can be invaded by blood vessels, and more bone can grow along these vessels.

The mechanism of this bone formation is not intuitive. It was thought that osteoblasts in the tumor are responsible for the bone formation. However, the reaction occurs in the soft tissue mass of osteosarcoma, a place where differentiated osteoblasts are not seen. In addition, spiculated periosteal reaction can also be seen in tumors that don't have osteoblasts.

An animal model of sunburst periosteal reaction has suggested a mechanism. Hamster ovary cells were transfected with bone morphogenic protein-4 and injected into the bone of nude mice. The resulting tumors were then found to have a periosteal reaction with a sunburst appearance. This has led to the suggestion that the bone inducing factors secreted by tumors lead to induction of osteoblastic activity and subsequent periosteal bone formation.

The images above are from a young man with osteosarcoma.

References

  • Bloom RA, Libson E, Husband JE, Stoker DJ. The periosteal sunburst reaction to bone metastases. A literature review and report of 20 additional cases. Skeletal Radiol. 1987;16(8):629-34. Review.
  • Rana RS, Wu JS, Eisenberg RL. Periosteal reaction. AJR Am J Roentgenol. 2009 Oct;193(4):W259-72.
  • Wyche LD, de Santos LA. Spiculated periosteal reaction in metastatic disease resembling osteosarcoma. Orthopedics. 1978 May-Jun;1(3):215-21.
  • Yoshikawa H, Shimizu K, Nakase T, Takaoka K. Periosteal sunburst spiculation in osteosarcoma. A possible role for bone morphogenetic protein. Clin Orthop Relat Res. 1994 Nov;(308):213-9.

Wednesday, October 12, 2011

Synovial Hemangioma

Synovial hemangiomas (intrasynovial hemangiomas) are rare masses that arise within the subsynovial connective tissue. They can be localized or diffuse and are most commonly seen in the knee. Less common sites include elbow, ankle, wrist, temporomandibular joint, and tendon sheaths.

Patients are usually children and adolescents who present with pain, limited range of motion, or a mass that shrinks when the affected limb is elevated. Adjacent cutaneous or soft tissue hemangiomas are occasionally seen.

Synovial hemangiomas can intermittently bleed, causing a hemosiderotic synovitis with pain and joint swelling. The bleeding is rarely as severe as that seen with the bleeding diatheses (e.g., hemophilia) and early osteoarthritis is usually not seen.

Radiographic findings can mimic a soft tissue mass or a joint effusion. When seen, phleboliths and bone erosions can suggest the diagnosis. Angiography can reveal contrast pooling in dilated vascular spaces with early venous drainage. CT may reveal a lobulated mass with heterogeneous attenuation and areas of fat. MRI reveals an intra-articular or juxta-articular mass with intermediate signal intensity on Tl-weighted images and high signal intensity on T2-weighted images. Hypointense channels or septa can be seen on T2-weighted images. And fluid-fluid levels can occasionally be seen.

References

  • Cotten A, Flipo RM, Herbaux B, Gougeon F, Lecomte-Houcke M, Chastanet P. Synovial haemangioma of the knee: a frequently misdiagnosed lesion. Skeletal Radiol. 1995 May;24(4):257-61.
  • Greenspan A, Azouz EM, Matthews J 2nd, Décarie JC. Synovial hemangioma: imaging features in eight histologically proven cases, review of the literature, and differential diagnosis. Skeletal Radiol. 1995 Nov;24(8):583-90.
  • Nielsen GP, Rosenberg AE, O'Connell JX, Kattapuram SV, Schiller AL. Tumors and diseases of the joint. Semin Diagn Pathol. 2011 Feb;28(1):37-52.

Tuesday, October 11, 2011

Gadolinium Contrast Agents

Because of the toxicity of free gadolinium (Gd3+), MRI contrast agents contain gadolinium bound to chelates. The stability of the gadolinium ion in the agent is, therefore, an important factor in its safety profile. Factors that can affect stability are the shape (linear vs. cyclic) and ionicity (ionic vs. non-ionic) of the chelate.

The nine gadolinium contrast agents currently available for clinical use can be classified as ionic or non-ionic and linear or cyclic. Ionic agents have negatively charged groups that tend to offer better binding of the positively charged gadolinium ion compared to the non-ionic agents.

Cyclic agents are constructed so as to encircle the gadolinium ion in a cage, which is thought to prevent its dissociation. Linear agents, on the other hand, have a flexible open chain that has a lower tendency to hang on to the the gadolinium ion.

Theoretically, of the four combinations possible (see table), the ionic cyclic agents should provide the best protection for the gadolinium ion, and the non-ionic linear agents would provide the least protection. In vivo studies, while confirming the low stability of the non-ionic linear agents, have not found a significant difference in stability between ionic and non-ionic cyclic agents.

With the revised FDA labeling, the use of Magnevist, Omniscan, and Optimark is contraindicated in patients with acute kidney injury or chronic, severe kidney disease (GFR < 30 mL/min/1.73m2).

 
Ionic
Non-ionic
Linear Ablavar (gadofosveset trisodium)
Eovist (gadoxetate disodium)
Magnevist (Gadopentetate, Gd-DTPA)
Multihance (Gadobenate, Gd-BOPTA)
Omniscan (Gadodiamide, Gd-DTPA-BMA)
OptiMark (Gadoversetamide, Gd-DTPA-BMEA)
Cyclic Dotarem (Gadoterate, Gd-DOTA) Gadavist (USA)/Gadovist (Europe, Canada) (Gadobutrol, Gd-BT-DO3A)
ProHance (Gadoteridol, Gd-HP-DO3A)


Gadolinium Release and Nephrogenic Systemic Fibrosis

A concept that is important in stability of gadolinium chelates in vivo is transmetalation. This is the process of gadolinium release through replacement by other serum cations (e.g., zinc, iron, copper, and calcium). Zinc's relatively high serum concentration (55–125 μmol/L) makes it the major player in transmetalation. The zinc replaces the gadolinium ion and is excreted in urine as zinc chelate. Measurement of zinc chelate can be used as an indicator of the amount of free gadolinium.

Copper's low serum concentration, calcium's low affinity to organic ligands, and iron's strong bond to ferritin and hemosiderin limits their availability for transmetalation with gadolinium ions.

The released gadolinium ions, in turn, bind to endogenous anions such as phosphate, citrate, hydroxide, and carbonate and deposit in tissues as insoluble compounds. It is thought that the release of cytokines in response to phagocytosis of these insoluble compounds by macrophages is responsible for the development of nephrogenic systemic fibrosis (NSF).

One such cytokine, transforming growth factor beta, is a potent fibrogenic agent that attracts circulating fibrocytes. These deposit in the dermis and other organs that contain the insoluble gadolinium deposits and mature into fibroblasts. The fibroblasts then deposit collagen in the affected organs, leading to fibrosis.

References

Morcos SK. Extracellular gadolinium contrast agents: differences in stability. Eur J Radiol. 2008 May;66(2):175-9.

Monday, October 10, 2011

Phosphaturic Mesenchymal Tumor

Phosphaturic mesenchymal tumors are rare mesenchymal tumors that have a tendency to cause osteomalacia or rickets. The mechanism is thought to be related to secretion of fibroblast growth factor 23 (FGF-23), which inhibits renal phosphate reabsorption (causing phosphaturia) and renal production of 1,25-dihydroxyvitamin-D3. Serum concentrations of 1,25-dihydroxyvitamin-D3 are low in almost all cases.

These tumors have a variable histomorphological appearance and can be classified as:
  • Mixed connective tissue variants: Small spindled cells with and admixture of osteoclast-like giant cells, microcystic areas, prominent blood vessels, cartilage-like matrix, and osseous metaplasia.
  • Osteoblastoma-like tumors: Vascular, osteoblastic fibrous tissue with osteoclast-like giant cells and irregularly deposited osteoid.
  • Non-ossifying fibroma-like tumors: Moderately vascular tumor with swirling bundles of spindle cells and scattered osteoclast-like giant cells with areas of osteoid deposition.
  • Chondromyxoid fibroma-like:
Many oncogenic osteomalacia-associated tumors previously reported in the literature as hemangiopericytoma, osteosarcoma, giant cell tumor, and non-ossifying fibroma may have actually represented one of these variants of phosphaturic mesenchymal tumor.

Most cases of mesenchymal tumor-associated osteomalacia are due to the mixed connective tissue variant. The tumors occur in bone or soft tissue with an equal frequency. Of the bone lesions, involvement of the appendicular skeleton is more common. Patients tend to be middle-aged adults (range 3-73) with a long history of osteomalacia.

Mixed connective tissue variant tumors are usually small, inapparent lesions. The tumors may express somatostatin receptors, making octreotide scanning a helpful imaging technique for localizing these small tumors.

The images above are from a 60-year-old man with a 2-year history of progressive osteomalacia, fractures, and a left supraacetabular lesion. The patient was diagnosed at an outside facility with hemangiopericytoma and oncogenic osteomalacia. More careful evaluation of the slides revealed a diagnosis of phosphaturic mesenchymal tumor, mixed connective tissue variant.

Some tumors may express somatostatin receptors and be positive on octreotide scans.

References

  • Folpe AL, Fanburg-Smith JC, Billings SD, Bisceglia M, Bertoni F, Cho JY, Econs MJ, Inwards CY, Jan de Beur SM, Mentzel T, Montgomery E, Michal M, Miettinen M, Mills SE, Reith JD, O'Connell JX, Rosenberg AE, Rubin BP, Sweet DE, Vinh TN, Wold LE, Wehrli BM, White KE, Zaino RJ, Weiss SW. Most osteomalacia-associated mesenchymal tumors are a single histopathologic entity: an analysis of 32 cases and a comprehensive review of the literature. Am J Surg Pathol. 2004 Jan;28(1):1-30.
  • Rhee Y, Lee JD, Shin KH, Lee HC, Huh KB, Lim SK. Oncogenic osteomalacia associated with mesenchymal tumour detected by indium-111 octreotide scintigraphy. Clin Endocrinol (Oxf). 2001 Apr;54(4):551-4.
  • Roarke MC, Nguyen BD. PET/CT localization of phosphaturic mesenchymal neoplasm causing tumor-induced osteomalacia. Clin Nucl Med. 2007 Apr;32(4):300-1.
  • Suryawanshi P, Agarwal M, Dhake R, Desai S, Rekhi B, Reddy KB, Jambhekar NA. Phosphaturic mesenchymal tumor with chondromyxoid fibroma-like feature: an unusual morphological appearance. Skeletal Radiol. 2011 Nov;40(11):1481-5.
  • Weidner N, Santa Cruz D. Phosphaturic mesenchymal tumors. A polymorphous group causing osteomalacia or rickets. Cancer. 1987 Apr 15;59(8):1442-54.

Sunday, October 9, 2011

Epithelioid Hemangioendothelioma

Epithelioid hemangioendothelioma is a rare, well-differentiated vascular tumor characterized by endothelial cells having an epithelioid appearance (abundant eosinophilic cytoplasm and a rounded or slightly fusiform shape). Epithelioid hemangioendothelioma can occur in bone, lung, and liver.

Epithelioid hemangioendotheliomas belong to the group of vascular tumors that includes benign epithelioid hemangioma on one end of the spectrum and its malignant counterpart, epithelioid angiosarcoma, on the other, all of which have a tendency to develop multifocal disease.

Epithelioid hemangioendothelioma has been called low-grade anaplastic angiosarcoma, cellular hemangioma, histiocytoid hemangioma, and angioendothelioma. It has a peak incidence during the second and third decades of life and tends to affect males more often than females.

The clinical presentation is nonspecific and consists of pain and occasional swelling. Pathologic fractures are uncommon. Multicentric disease is seen in about half of cases. When multiple, they have a tendency to involve a single anatomic region or extremity.

Epithelioid hemangioendotheliomas most commonly affect the long tubular bones of the lower limb, followed by the pelvis, vertebral bodies, ribs, small bones of the feet, and long tubular bones of the upper extremity.

Classically, they appear as poorly marginated lytic lesions commonly with areas of cortical destruction and expansion. Occasionally the lesions may have a coarse trabeculated or honeycomb pattern that suggests a vascular nature. Matrix mineralization can be seen in some cases. Well-defined lesions with or without surrounding sclerosis may be seen, but aren't common. A soft tissue mass is seen in less than 50% of cases.

Differential considerations for multiple lytic lesions in a young patient include Langerhanscell histiocytosis, giant cell tumors, fibrous dysplasia, lymphoma, and metastatic disease. In older patients, metastases and myeloma would be more common. The finding of multiple lytic lesions in a regional distribution, should suggest the diagnosis.

The images above are from an elderly patient with multiple lytic lesions in the right lower extremity.

References

  • Adler B, Naheedy J, Yeager N, Nicol K, Klamar J. Multifocal epithelioid hemangioendothelioma in a 16-year-old boy. Pediatr Radiol. 2005 Oct;35(10):1014-8.
  • Bruegel M, Waldt S, Weirich G, Woertler K, Rummeny EJ. Multifocal epithelioid hemangioendothelioma of the phalanges of the hand. Skeletal Radiol. 2006 Oct;35(10):787-92.

Saturday, October 8, 2011

Osteitis Condensans Ilii

Osteitis condensans ilii is a benign sclerosis of the ilium that is commonly seen in young women and has an estimated prevalence of between 1.0% to 3%. The condition is thought to be related to pregnancy, althout it can be seen in men and nulliparous women. When related to pregnancy, it is hypothesized that ligamentous laxity at the sacroiliac joints leads to instability and subsequent sclerosis.

While usually an incidental finding, patients with osteitis condensans ilii are more likely to have sacroiliac joint tenderness compared to controls. A high prevalence of back pain has been reported in patients with osteitis condensans ilii, but controlled studies have not been performed, and the association may be coincidental. In other words, a finding of osteitis condensans ilii should not be taken as an explanation of back pain witout excluding other etiologies.

On imaging, osteitis condensans ilii is characterized by sclerosis, predominantly involving the iliac bone, although the sacrum may also be involved. The sclerosis is usually bilateral (but can be unilateral) and triangular in shape and abuts an otherwise normal sacroiliac joint. Irregularity or narrowing at the sacroiliac joint should raise concern for an inflammtory or infectious cause for sacroiliitis. Bone scintigraphy may or may not show focal uptake at the site of sclerosis.

If patients are followed long enough, the majority show improvement or resolution of radiographic findings, which may explain the rarity of this condition in older patients.

References

  • Anonymous. Osteitis condensans ilii. Radiology. 1953 Jun;60(6):895-6.
  • Cidem M, Capkin E, Karkucak M, Karaca A. Osteitis condensans ilii in differential diagnosis of patients with chronic low back pain: a review of the literature. Mod Rheumatol. 2011 Sep 23.
  • Isley JK Jr, Baylin GJ. Prognosis in osteitis condensans ilii. Radiology. 1959 Feb;72(2):234-7.
  • Jenks K, Meikle G, Gray A, Stebbings S. Osteitis condensans ilii: a significant association with sacroiliac joint tenderness in women. Int J Rheum Dis. 2009 Apr;12(1):39-43.
  • Gemmel F, de Coningh AV, Collins J, Rijk P. SPECT/CT of osteitis condensans ilii: one-stop shop imaging. Clin Nucl Med. 2011 Jan;36(1):59-61.
  • Numaguchi Y. Osteitis condensans ilii, including its resolution. Radiology. 1971 Jan;98(1):1-8.

Friday, October 7, 2011

Multifocal Osteosarcoma

Multifocal osteosarcoma (multicentric osteosarcoma, osteosarcomatosis, multiple sclerotic osteosarcoma), is the occurrence of primary osteosarcoma at two or more sites. Multifocal osteosarcoma can be further classified as synchronous (more than one lesion is seen at presentation) or metachronous (new lesions develop after the initial treatment of primary osteosarcoma).

Multifocal osteosarcoma accounts for less than 5% of cases of osteosarcoma and is thought to be more common in children, who tend to have many symmetric lesions. Older patients tend to have fewer lesions, which are asymmetrically distributed.

There is debate whether multifocal osteosarcoma actually represents multiple primary osteosarcomas or presentation with metastatic disease. In a majority of cases, a large dominant lesion is seen, which may represent the primary lesion.

Some definitions of multifocal osteosarcoma require an absence of pulmonary metastases, which does not appear to be supported by the available evidence. Firstly, no significant difference has been found in clinical and pathologic features of patients with multifocal osteosarcoma with or without pulmonary metastases. Secondly, the absence of pulmonary metastases was initially defined by chest radiography, which is not as sensitive as CT for detection of these metastases.

In children, differential considerations include chronic recurrent multifocal osteomyelitis, hyperparathyroidism with multiple brown tumors, osteopetrosis and osteopoikilosis.

The case above shows a dominant lesion in the left distal femur with a skip metastasis, as well as another lesion at the right greater trochanter.

References

  • Daffner RH, Kennedy SL, Fox KR, Crowley JJ, Sauser DD, Cooperstein LA. Synchronous multicentric osteosarcoma: the case for metastases. Skeletal Radiol. 1997 Oct;26(10):569-78.
  • Lerner C, Gaca A. Osteosarcomatosis. Pediatr Radiol. 2007 Jul;37(7):724.
  • Murphey MD, Robbin MR, McRae GA, Flemming DJ, Temple HT, Kransdorf MJ. The many faces of osteosarcoma. Radiographics. 1997 Sep-Oct;17(5):1205-31.

Thursday, October 6, 2011

Intramuscular Cysts of the Rotator Cuff

An intramuscular cyst of the rotator cuff is a secondary sign of rotator cuff injury that should prompt a careful search for a tendon tear. Interestingly, the torn tendon is not necessarily that of the muscle with the cyst. About 50% of rotator cuff tears associated with these cysts are partial-thickness.

Intramuscular cysts are most commonly found in infraspinatus and supraspinatus muscles, followed by the subscapularis and teres minor muscles. Cysts can also be seen in two different muscles.

It is thought that tendon defects from a tear allow joint or bursal fluid to track along the tendon fibers and intramuscular planes to form the intramuscular cyst. The problem with this theory is that the cysts are not always associated with tendon tears. Indeed, Manvar and colleagues found that ~25% of these cysts were not associated with rotator cuff tears on conventional MRI.

The images above reveal a cyst (white arrow) within the supraspinatus muscle associated with a tear (pink arrow) of the supraspinatus tendon.

References

Wednesday, October 5, 2011

Askin Tumor

Askin tumors are primitive neuroectodermal tumors of the Ewing sarcoma family of tumors (ESFT) that arise in the soft tissues of the chest wall, but can also arise in bone, and (rarely) in the periphery of the lung. Patients are usually young and female. There is evidence of metastatic disease at presentation in 10%-40% of cases.

On imaging, the tumors can be large and have both intrathoracic and extrathoracic components, with tumor extension to the pleura with associated effusion being a frequent occurrence. Destruction of adjacent anatomic structures can also be seen.

CT reveals a heterogeneous lesion with evidence of rapid growth (large size, destruction of adjacent structures, etc). T2-weighted images reveal heterogeneously increased signal intensity representing focal areas of hemorrhage or necrosis. Small tumors can be more homogeneous.

References

Winer-Muram HT, Kauffman WM, Gronemeyer SA, Jennings SG. Primitive neuroectodermal tumors of the chest wall (Askin tumors): CT and MR findings. AJR Am J Roentgenol. 1993 Aug;161(2):265-8.

Tuesday, October 4, 2011

Post-Thyroidectomy Ultrasound in Patients with Differentiated Thyroid Cancer

The European Thyroid Association, the National Comprehensive Cancer Network, and the American Thyroid Association have similar recommendations for management of patients with differentiated thyroid cancer after thyroidectomy.

The guidelines recommend serial serum thyroglobulin levels and neck ultrasound as primary tests to diagnose recurrences, with diagnostic whole body radioiodine scans reserved for follow-up of patients with intermediate or high risk of persistent disease. Low-risk patients following radioiodine ablation don't seem to benefit from diagnostic whole body radioiodine scans due to the low sensitivity of these scans.

Neck ultrasound, on the other hand, is highly sensitive in the detection of cervical metastases in patients with differentiated thyroid cancer. The American Thyroid Association (2010) recommends neck ultrasound to evaluate the thyroid bed and cervical nodal compartments (see below) initially at 6 and 12 months and then annually for at least 3–5 years, depending on the patient's thyroglobulin status and risk for recurrent disease.

Stratification of patients is done after initial surgery and remnant ablationas.
  • Low-risk: There are no local or distant metastases, all macroscopic tumor has been resected, there is no tumor invasion of locoregional tissues or structures, the tumor does not have aggressive histology or vascular invasion, and no 131I uptake is seen outside the thyroid bed on the first posttreatment wholebody radioiodine scan (if 131I was given).
  • Intermediate-risk: There was microscopic invasion of tumor into the perithyroidal soft tissues at initial surgery or the tumor had aggressive histology or vascular invasion.
  • High-risk patients: There was macroscopic tumor invasion, incomplete tumor resection, distant metastases, or 131I uptake outside the thyroid bed on the post-treatment scan.

Technique

The entire neck is imaged using a high-frequency (8 MHz to 12 MHz) linear transducer. Larger patients may benefit from additional scans using a 6-MHz linear transducer. A curved or sector array transducer is then used to image the supraclavicular area. Color Doppler can be used to differentiate small lymph nodes from vessels and to help identify the vascular hilum of lymph nodes.

The thyroid bed and the nodal compartments of the neck must be meticulously scanned. The neck is divided into central and lateral compartments. The central compartment contains the resection bed, as well as the paratracheal and paraesophageal nodal chain and level I (submental and submandibular) lymph nodes. The lateral margins of the central compartment are defined by the carotid sheath.

The lateral compartments contains levels II, III, IV, and V (superior, middle, and inferior jugular, cervical and supraclavicular lymph nodes. The trapezoid muscles determine the lateral margins of the lateral compartments, and the subclavian veins determine their inferior margin.

What to Expect

Scanning can be tedious. The postoperative thyroid bed should appear as a narrow area of increased echogenicity between the common carotid artery laterally and the trachea medially.

Cervical lymph nodes are commonly seen in the lateral compartments and can present a diagnostic challenge (see below).

Local Recurrence

Any focal mass should raise concern for recurrence in the thyroid bed. Shin and colleagues compared the ultrasound appearance of recurrent and non-recurrent lesions in the resection bed and found that "the distinction between recurrent thyroid cancer and nonrecurrent benign lesions cannot be made on the basis of the sonographic features."

Benign lesions such as nodular thyroid remnants, postoperative scar, suture granuloma, muscle tissue, and fat necrosis can mimic malignancy. However, anechoic lesions seem to correspond to benignity and microcalcifications and cystic areas within a mass should raise concern for malignancy.

The images above are from four patients with differentiated papillary thyroid cancer. The top row shows the appearance of a normal resection bed, with the trachea (Tr), common carotid artery (C), the internal jugular vein (IJ), and the normal echogenic resection bed (pink arrow). The bottom row shows lesions in the resection bed (green arrows). The lesion in the left panel (L) was recurrent disease, while a similar lesion in the right panel was benign, underscoring the difficulty in differentiating benign from malignant lesions in the resection bed.

Lymph Nodes

Lymph nodes with cystic areas or punctate calcifications are highly (100% in one study) specific for metastatic thyroid cancer. Unfortunately, these findings are not very common and not very sensitive (between 10% and 50%).

The other usual techniques for differentiating benign from malignant lymph nodes are not reliable. Size does not seem to be helpful in differentiating benign from malignant lymph nodes. Round shape and loss of the echogenic hilum and hypoechoic cortex by themselves are also not specific for malignancy, especially since the echogenic hilum can be difficult to see in smaller lymph nodes.

When in doubt, fine needle aspiration is the most conservative approach.

References

  • Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F, Schlumberger M, Sherman SI, Steward DL, Tuttle RM. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, Thyroid. 2009 Nov;19(11):1167-214.
  • Sheth S, Hamper UM. Role of sonography after total thyroidectomy for thyroid cancer. Ultrasound Q. 2008 Sep;24(3):147-54.
  • Shin JH, Han BK, Ko EY, Kang SS. Sonographic findings in the surgical bed after thyroidectomy: comparison of recurrent tumors and nonrecurrent lesions. J Ultrasound Med. 2007 Oct;26(10):1359-66.

Monday, October 3, 2011

Spindle Cell Lipoma

Spindle cell lipomas are benign tumors in which mature fat is replaced by collagen-forming spindle cells. Pleomorphic lipoma is a variant of spindle cell lipoma that contains a marked cellular pleomorphism and scattered bizarre giant cells. Histologically, these lesions may be difficult to differentiate from liposarcoma.

Patients present with a solitary, well-circumscribed nodule that is slow-growing and painless. Patients are most often men between 45 and 65 years of age. Multiplicity of lesions is uncommon, with several cases of familial and nonfamilial multiple spindle cell lipomas in the literature (incidentally, all of these occurred in male patients).

The lesions are most commonly located in subcutaneous fat of the posterior neck and shoulder area. An intramuscular location is uncommon. Occurrence in the lower extremity should suggest a different diagnosis, as it is an extremely rare presentation.

Imaging findings are nonspecific and can mimic those of liposarcoma. Spindle cell lipomas are complex fatty mass masses with variable lipomatous and nonlipomatous components. The finding of a well-defined complex fatty mass located in the subcutis (especially in the posterior neck or shoulder) of a middle-aged man should suggest the diagnosis.

The images above are from a 55-year-old man who presented with a 3-year history of a slowly growing left shoulder mass. The lesion is heterogeneously hypoechoic on ultrasound and contains foci of fat attenuation on CT. The foci of fat are better seen on the T1-weighted images as hyperintense spots that lose signal with fat saturation (PD and T1 post-contrast). The bulk of the lesion, however, is T1-hypointense, T2-hyperintense, and avidly enhancing.

References

Sunday, October 2, 2011

Isolated Reticular Infiltrations of the Mesentery and Omentum

Isolated reticular infiltrations of the mesentery and omentum (i.e., those without irregular and nodular thickening) can be challenging on imaging, as it may be impossible to differentiate among the possibilities:
  • Inflammation:
  • Infection: For example, tuberculosis
  • Maliganncy: Lymphoma, mesothelioma, metastases.
Percutaneous biopsy is often requested to guide treatment decisions. However, these types of lesions also present a challenge at biopsy, because they tend to be softer and even more mobile than nodular mesenteric or omental lesions.

Lee and colleagues recently looked at the performance of ultrasound-guided percutaneous biopsy in 45 patients with isolated reticular infiltrations of the mesentery and omentum.

Almost all biopsies were technically successful, with adequate specimens obtained from all but one of their patients. Two patients who were diagnosed with nonspecific inflammation at biopsy went on to be diagnosed with malignancies at surgery (colon and pancreatic carcinoma).

Overall, the diagnostic accuracy of imaging-guided percutaneous biopsy is in the range of 84%-92% (including data from an earlier study by Pombo and colleagues). The sensitivity and specificity for detecting malignancy are 89% and 100%, respectively. The sensitivity and specificity for detecting tuberculosis were 75% and 100%, respectively (the study was performed in Korea). The sensitivity and specificity for detecting nonspecific inflammation were 90% and 83%, respectively.

The image above is from a patient with cirrhosis and ascites who was found to have reticular areas of increased attenuation in the omental fat. Concern for omental caking and mesothelioma was raised at an outside facility. Percutaneous biopsy of the omentum showed chronic inflammation and focal mesothelial hyperplasia without evidence of malignancy.

References

  • Lee JK, Baek SY, Lim SM, Lee KH. Reticular Infiltrations Alone without Mass in the Mesentery and Omentum Identified at Contrast-enhanced CT: Efficacy of US-guided Percutaneous Core Biopsy. Radiology. 2011 Oct;261(1):311-7. Epub 2011 Aug 24.
  • Pombo F, Rodriguez E, Martin R, Lago M. CT-guided core-needle biopsy in omental pathology. Acta Radiol. 1997 Nov;38(6):978-81.

Saturday, October 1, 2011

Plantar Aponeurosis: Anatomy

The plantar aponeurosis (plantar fascia) is composed of central, medial, and lateral segments. The base is attached to the calcaneus and has fibers continuous with those of the Achilles tendon.
  • Medial segment (purple): Arises from the central segment and attaches to the inferior portion of the abductor hallucis muscle.
  • Central segment (tan): The thickest component. Its proximal attachment is to the posterior aspect of the medial calcaneal tuberosity (posterior to the origin of the flexor digitorum brevis tendon). Its distal attachments are at the level of the metatarsophalangeal joints, dividing into five pairs of superficial and deep fasicles. The deep branches (blue) insert onto the metatarsophalangeal joints. The superficial branches bifurcate into sagittal septa, which attach onto the plantar plates (red), interosseous ligament, and deep transverse metatarsal ligaments of the 2nd through 5th digits and the plantar plate and sesamoid bones (white) of the great toe.
  • Lateral segment (green): Attaches proximally to the lateral aspect of the medial process of the calcaneal tuberosity and is continuous medially with the central segment. Distally, it has a medial band inserts onto the plantar plate of the fourth and sometimes third metatarsophalangeal joints, and a lateral band that attaches to the base of the fifth metatarsal.

References

Moraes do Carmo CC, Fonseca de Almeida Melão LI, Valle de Lemos Weber MF, Trudell D, Resnick D. Anatomical features of plantar aponeurosis: cadaveric study using ultrasonography and magnetic resonance imaging. Skeletal Radiol. 2008 Oct;37(10):929-35.