Monday, May 31, 2010

Splenic Artery Aneurysms

Splenic artery aneurysms are found in up to 10% of autopsy series and are the second most common intraabdominal aneurysm (after aortoiliac aneurysms). They are found four times more often in women than in men, likely due to the hormonal and hemodynamic stresses of pregnancy. The main concern is rupture, half of which occur in pregnant women with a mortality rate of 70%-90%. Splenic artery aneurysms in women of childbearing age or in pregnant women, therefore, are usually treated.

Older patients with incidentally detected aneurysms are a different story. Asymptomatic patients over 60 with aneurysms less than 2 cm in diameter can be managed conservatively with follow-up CT (6-12 months). Those with symptomatic aneurysms or those with aneurysms larger than 3 cm in diameter can be treated with embolization. Aneurysms between 2 cm and 3 cm are in a gray zone.

References

Kenningham R, Hershman MJ, McWilliams RG, Campbell F. Incidental splenic artery aneurysm. J R Soc Med. 2002 Sep;95(9):460-1.

Sunday, May 30, 2010

Phakomatoses: Bullet Points

Phakomatoses, also known as neurocutaneous disorders, are a broad group of diseases that involve the central nervous system, skin, and retina.
  • Neurofibromatosis type 1
    • Also known as peripheral neurofibromatosis or von Recklinghausen syndrome.
    • Most common of the phakomatoses.
    • Plexiform neurofibromas
    • CNS: Optic pathway gliomas (typically juvenile pilocytic astrocytoma) that can involve any part of the optic pathway: optic nerve, optic chiasm, optic tracts, lateral geniculate bodies, and optic radiations. Astrocytomas can also occur elsewhere in brain. Unidentified bright objects on T2-weighted images in dentate nuclei of cerebellum, brainstem, basal ganglia, and thalami, less commonly in cerebrum. These are not visible on T1-weighted images and don't enhance.
    • Chest: Focal thoracic scoliosis, posterior vertebral scalloping, dumbbell-shaped neurofibromas expanding the neural foramina. Weakness of meninges in the spine leads to arachnoid cysts or lateral meningoceles.
    • MSK: Anterolateral bowing of the tibia with or without a hypoplastic fibula, often with focal narrowing and intramedullary sclerosis or cystic change at the apex of the angulation. Characteristic rib abnormalities due to bone dysplasia or erosion from adjacent neurofibroma ("ribbon ribs"). Sphenoid wing dysplasia (can lead to pulsatile exophthalmos and herniation of the temporal lobe). Uncommon: Subperiosteal hemorrhage of the tibia.
    • Vascular: Intracranial aneurysms, stenosis, and moyamoya syndrome
    • 10% risk of development of malignant peripheral nerve sheath tumors
  • Neurofibromatosis type 2
    • Also known as central neurofibromatosis, or MISME (Multiple Inherited Schwannomas, Meningiomas, and Ependymomas) syndrome. Radiologists like this because definitive diagnosis, unlike neurofibromatosis type 1, requires imaging.
    • CNS/PNS: Bilateral vestibular schwannomas, meningiomas, gliomas, ependymomas (intramedullary mass in spine), and congenital cataracts. Schwannomas can involve multiple cranial nerves, spinal nerve roots, peripheral nerve sheaths. Intraspinal schwannomas also dumbbell-shaped and expand neural foramina (most commonly intradural/extramedullary but may be extradural or both).
  • Tuberous sclerosis:
    • Also known as Bourneville syndrome
    • Classic triad of epilepsy, mental retardation, and facial angiofibroma (adenoma sebaceum is misnomer) uncommonly seen
    • CNS: Hamartomas: Retinal hamartomas; Cortical or subependymal tubers (may calcify), subependymal nodules, and subependymal giant cell astrocytomas (SEGA, not generally seen >~20 years). White-matter abnormalities: "migration lines" seen as bands of myelination defect or gliosis.
    • Chest: Pulmonary lymphangioleiomyomatosis, multifocal micronodular pneumocyte hyperplasia, cardiac rhabdomyoma.
    • Abdomen: Multiple renal cysts, renal angiomyolipoma.
    • MSK: Periungal fibroma
  • Sturge-Weber-Dimitri:
    • Also known as encephalo-trigeminal angiomatosis.
    • MSK: Cutaneous capillary angioma (port-wine stain) typically in V1 distribution.
    • CNS: Intracranial leptomeningeal angiomatosis ("tram-track" calcification of cortex), congenital glaucoma and choroidal angioma on same side as port wine stain. Imaging may show an enlarged globe from glaucoma (possibly related to the choroidal angioma).
  • von Hippel-Lindau:
    • Also known as retino-cerebellar hemangioblastoma.
    • CNS: Retinal and central nervous system hemangioblastomas and endolymphatic sac tumors. Retinal hemangioblastomas (also known as retinal angiomas) may lead to retinal detachment.
    • Abdomen: renal cysts and tumors, pancreatic cysts and tumors (neuroendocrine tumors and serous cystadenoma), pheochromocytomas, and epididymal cystadenomas.

Practical points

  • In NF1 all nerve sheath tumors are neurofibromas. In NF2, almost all are schwannomas or mixed tumors.
  • Dumbbell-shaped lesions: If Solitary, think Schwannoma, which occurs more commonly in the Sensory root. If Multiple, think Neurofibroma.

References

Saturday, May 29, 2010

Metaphyseal Lesions

The differential diagnosis for metaphyseal lesions includes:
  • Metastases:
  • Osteomyelitis: In children. May cross an open physis, but this isn't typical.
  • Enchondroma: Expansile lesion with chondroid matrix. When in the digits, it's a predominantly lucent lesion.
  • Non-ossifying fibroma (shown above): "An eccentric, well-defined, lucent lesion in the metaphysis of a tubular bone a short distance from the physis in a child or adolescent is almost diagnostic of a fibrous cortical defect or non-ossifying fibroma." (Resnick)
  • Aneurysmal bone cyst: Eccentric, multicystic, septated, expansile lesion with sclerotic margins and periosteal reaction. Age: 10-30 years
  • Unicameral bone cyst: Centrally located, expansile lesion with sclerotic margin and no periosteal reaction. Age: 10-20 years
  • Chondromyxoid fibroma: Benign bone tumor most often seen in young patients, and usually found in the long tubular bones, especially the tibia and femur near the knee joint.



  • Giant cell tumor: Originates on the metaphyseal side of growth plate and extends to the epiphysis in adults. Stays in the metaphysis when it occurs in kids.
  • Chondrosarcoma:
  • Cortical/periosteal desmoid:
  • Desmoplastic fibroma:
  • Lipoma:
  • Osteoblastoma: Tends to involve the metaphysis and proximal diaphysis.
  • Osteosarcoma: 90% occur in metaphyses

Friday, May 28, 2010

Adnexal Masses in Children

Differential diagnosis for adnexal masses in children based on ultrasound appearance:
  • Cystic:
    • Simple cyst: Most common adnexal lesion.
    • Teratoma
    • Cystadenoma: Serous: Large anechoic, thin-walled cyst with posterior acoustic enhancement. Mucinous: Multiloculated cyst, each component of which may show low-level echoes and differing echogenicity (echogenic locule may mimic solid component). Papillary projections less common than in serous cystadenoma.
    • Cystadenofibroma: Large cystic lesion that may have septations, solid nodules, and/or papillary projections
    • Hydrosalpinx:
  • Complex:
    • Complex cyst
    • Teratoma
    • Tuboovarian abscess
    • Granulosa cell tumor: Large solid and cystic adnexal mass with a thickened endometrial stripe (hormonally active). Atypical hyperplasia or endometrial carcinoma can be seen in 5% of cases.
    • Dysgerminoma: Germ cell tumor. Ovarian analog of seminoma of the testis. Pure form of dysgerminoma is not associated with endocrine hormone secretion, but 5% of cases contain cells that produce HCG. Ultrasound shows a multilobulated solid ovarian mass with heterogeneous echogenicity. Speckled calcification may be present. Anechoic areas represent necrotic portions. Prominent flow in fibrovascular septae may be seen on color Doppler.
  • Solid:
    • Hemorrhagic cyst
    • Torsion
    • Teratoma
    • Dysgerminoma: See above

References

Wu A, Siegel MJ. Sonography of pelvic masses in children: diagnostic predictability. AJR Am J Roentgenol. 1987 Jun;148(6):1199-202.

Thursday, May 27, 2010

Hook-Like Osteophytes

Hook osteophytes (white arrow) along the radial aspect of the distal metacarpals can be seen in both calcium pyrophosphate dihydrate deposition or hemochromatosis arthropathy, although they are more prevalent in the latter. Chondrocalcinosis (black arrow along the triangular fibrocartilage complex) may also be seen in both calcium pyrophosphate dihydrate deposition or hemochromatosis arthropathy.

Joint space narrowing also follows a similar pattern in the two diseases. Both involve the radiocarpal and midcarpal compartments of the wrist with diffuse joint space narrowing and intra-articular and periarticular calcifications, which are not seen with osteoarthritis

One must, therefore, use other features to help differentiate the two. In hemochromatosis arthropathy, there is uniform loss of joint space at all metacarpophalangeal joints, including those of the ring and small fingers, while in calcium pyrophosphate dihydrate deposition disease, there is narrowing of predominantly the index and middle finger metacarpophalangeal joints.

In more advanced disease, other differences become apparent. Scapholunate dissociation is more common in advanced calcium pyrophosphate dihydrate deposition disease, while advanced hemochromatosis is more likely to have metacarpophalangeal joint narrowing in the absence of radioscaphoid narrowing.

Osteoporosis is usually a feature of hemochromatosis, but is usually not present in calcium pyrophosphate dihydrate deposition disease.

References

Adamson TC 3rd, Resnik CS, Guerra J Jr, Vint VC, Weisman MH, Resnick D. Hand and wrist arthropathies of hemochromatosis and calcium pyrophosphate deposition disease: distinct radiographic features. Radiology. 1983 May;147(2):377-81.

Wednesday, May 26, 2010

Neurogenic Bladder on Cystography

Neurogenic bladder is bladder dysfunction due to lesions of the nervous system and not an appropriate imaging diagnosis. The appearance of the bladder on cystography depends on the level of injury:
  • Detrusor hyperreflexia: Caused by suprapontine lesions. The micturition reflex is intact but the detrusors are spastic. The bladder is persistently smooth and rounded due to uninhibited detrusor contractions. There are prominent interureteric indentations during voiding. Trabeculations may be seen in longstanding disease.
  • Detrusor hyperreflexia with detrusor-sphincter dyssynergia: Caused by spinal cord lesions above T12/conus medullaris. Bladder contracts with an open internal sphincter and closed external sphincter. The bladder neck dilates during contractions (open internal sphincter and closed external sphincter). The bladder itself is elongated and trabeculated ("pine cone," "pine tree," "fir tree," or "Christmas tree" bladder). Detrusor-sphincter dyssynergia is the most common cause of a dilated posterior urethra.
  • Autonomous neurogenic bladder: Lesions of conus medullaris, cauda equina, sacral nerve roots, or peripheral nerves (e.g., diabetes, alcoholism, trauma). The end result is loss of sensation and loss of contraction. Loss of contraction means that the normal urethral resistance cannot be overcome and the bladder expands until the pressure is high enough to push urine through the urethra (overflow incontinence). The bladder contour is typically smooth, but the pine tree bladder can also be seen.

References

  • Gamut H-113. in Gamuts in Radiology - Reeder and Felson - 4th ed (Springer, 2003).
  • Zagoria RJ and Tung GA (1997). Chapter 6. in Genitourinary Radiology: The Requisites.

Tuesday, May 25, 2010

Bladder Rupture

Bladder ruptures may be classified as extraperitoneal, intraperitoneal, or both.

Extraperitoneal rupture usually involves the anterolateral bladder wall. 90% of cases are associated with a fracture of the anterior ring of the pelvis. The classic appearance on cystography has been described as "flame-shaped," referring to the jagged irregular margins of the extraperitoneal contrast. Contrast may spill into the perineum, scrotum, or thigh if there is rupture of the urogenital diaphragm.

Inraperitoneal rupture typically involves a horizontal tear along the dome of the bladder. On cystography, the peritoneal organs are outlined by contrast and there is a homogeneous, cloud-like appearance to the contrast. Pelvic fractures are associated with 75% of inraperitoneal ruptures.

References

Zagoria RJ and Tung GA (1997). Chapter 6. in Genitourinary Radiology: The Requisites.

Monday, May 24, 2010

Classification of Blunt Urethral Trauma

Blunt urethral trauma can be classified into five types:
  • Type I: Intact but stretched posterior urethra (Colapinto and McCallum type I).
  • Type II: Tear of the membranous urethra above the urogenital diaphragm (Colapinto and McCallum type II). On urethrography, contrast material extravasates into the pelvic extraperitoneal space.
  • Type III: Most common type. Combined anterior and posterior urethral injury with disruption of the urogenital diaphragm (Colapinto and McCallum type III). On urethrography, contrast material extravasates into the perineum with or without extension into the pelvic extraperitoneal space..
  • Type IV: Bladder neck injury extending to the urethra. Injury of the base of the bladder with periurethral extravasation may simulate a type IV injury and is classified as type IVA.
  • Type V: Partial or complete pure anterior urethral injury. Associated with perineal crush or straddle injuries.

References

Goldman SM, Sandler CM, Corriere JN Jr, McGuire EJ. Blunt urethral trauma: a unified, anatomical mechanical classification. J Urol. 1997 Jan;157(1):85-9.

Sunday, May 23, 2010

Male Urethra

The male urethra is divided into posterior and anterior parts, separated by the urogenital diaphragm. The posterior urethra is divided into prostatic and membranous portions, while the anterior urethra is divided into bulbous and penile segments.

Posterior Urethra



Prostatic Urethra

The prostatic urethra contains an elevation along its posterior wall called the verumontanum (mountain ridge).

Müllerian duct cysts, cystic lesions that are derived from the caudal ends of fused Müllerian ducts, can originate at the level of the verumontanum and extend posteromedially. Müllerian duct cysts are usually isolated abnormalities (rarely associated with renal agenesis) and usually present in the 3rd and 4th decades of life. They do not communicate with the urethra, but are connected to the verumontanum by a thin stalk. These findings are in contrast to another midline cyst arising from the verumontanum, the prostatic utricle cyst (see below), which is seen in children in association with other abnormalities and communicates with the prostatic urethra. Mnemonic: Müllerian duct cysts in Men.

The prostatic utricle is an indentation at the inferior verumontanum and is a remnant of the Müllerian duct system. On each side of the prostatic utricle are the ejaculatory ducts.

A prostatic utricle cyst, which may mimic a Müllerian duct cyst (see above), presents as a cyst along the midline posterior margin of the prostate. It is seen in children in association with hypospadias or incomplete testicular descent. The prostatic utricle cyst communicates with the prostatic urethra.

On each side of the verumontanum are openings for the ducts of the prostate.

Membranous Urethra

The membranous urethra is the shortest, narrowest, and least distensible part of the male urethra and is surrounded by the external urethral sphincter (EUS in image). The membranous urethra is susceptible to iatrogenic stricture formation. The membranous urethra is the most common site of stricture formation following transurethral resection of the prostate. The Cowper (bulbourethral) glands live posterolateral to the membranous urethra. Cowper glands are developmentally similar to Bartholin glands in women. Like Bartholin glands, the Cowper glands secrete lubricant.

Anterior Urethra

Iatrogenic strictures may be found at the penoscrotal junction of the anterior urethra. Multiple openings for the glands of Littré can be found throughout. In cases of stricture proximally, the ducts for the glands of Littré expand and can fill with contrast on retrograde urethrogram.

Bulbar Urethra

The bulbar urethra is the widest part of the urethra. The ducts of the Cowper glands empty here. Post-gonococcal strictures are typically located in the proximal bulbar urethra. In such cases, there may be backflow of contrast into the ducts of the Cowper glands on retrograde urethrography. Strictures may occur here following TURP due to current leakage from insufficient lubricant isolation.

Penile Urethra

The distal portion of the penile urethra opens up into the fossa navicularis. Strictures can occur at the meatus following TURP due to inappropriate sizing of the instrument in relation to the diameter of the urethral meatus.

References

  • Balbay MD, et al. Development of urethral stricture after transurethral prostatectomy: a retrospective study. Int Urol Nephrol. 1992;24(1):49-53.
  • Donkol RH, Monib S, Moghazy K. Müllerian duct cyst as a cause of acute infantile-onset epididymitis. Pediatr Radiol. 2006 Nov;36(11):1197-9.
  • Rassweiler J, Teber D, Kuntz R, Hofmann R. Complications of transurethral resection of the prostate (TURP)--incidence, management, and prevention. Eur Urol. 2006 Nov;50(5):969-79.
  • Thurnher S, Hricak H, Tanagho EA. Müllerian duct cyst: diagnosis with MR imaging. Radiology. 1988 Jul;168(1):25-8.
  • Zagoria RJ and Tung GA (1997). Chapter 6. in Genitourinary Radiology: The Requisites.

Saturday, May 22, 2010

Renal Ultrasound in Transplanted Kidneys

Some points to consider:
  • Corticomedullary differentiation may be exaggerated due to superficial location of transplanted kidney.
  • Pelvicaliectasis: Usually due to overhydration, but reflux and obstruction may be seen as well.
  • Main renal artery velocity: < 200 cm/s.
  • Resistive indices (RI): Normal is less than 0.7. Between 0.7-0.8 is indeterminate. Above 0.8 is considered abnormal, but it has low sensitivity and specificity. Abnormally elevated resistive indices can be seen with any of the following:
    • Rejection
    • Acute tubular necrosis (more below)
    • Pyelonephritis
    • Renal vein thrombosis (more below)
    • Ureteral obstruction
    • Extrinsic compression
    • Drug toxicity
  • Reversal of diastolic flow (seen in the image above) is nonspecific, but is a poor prognostic indicator. It can be seen in:
    • Acute tubular necrosis
    • Acute rejection
    • Renal vein thrombosis
Immediate (first week) complications:
  • Acute tubular necrosis (ATN): Reversible ischemic damage. More likely in cadaveric transplant, with long ischemic times, and patient hypotension. Kidney may look normal or edematous. Elevated resistive indices may be seen in severe acute tubular necrosis, but can be normal.
  • Accelerated acute rejection: Presents within a few days to a few weeks following transplantation. Nonspecific sonographic findings similar to those of acute tubular necrosis.
  • Renal vein thrombosis: Occurs in about 1% of cases. Ultrasound shows an enlarged kidney with absent venous flow. There may be reversal of arterial flow in diastole. Look for correctable causes: Clot in the renal vein or compression of the renal vein by fluid collection.
  • Renal artery thrombosis: No arterial flow on Doppler. Angiography can be used for confirmation
Early (1-4 weeks) complications:
  • Acute rejection: Look for fluid around the kidney. The kidney may be edematous (loss of corticomedullary differentiation, obliteration of renal sinus echo complex). Also look for edema in the walls of the collecting system. There may be parenchymal infarctions. Resistive indices may be elevated, but has low sensitivity and specificity.
  • Urine leak or fistula: Due to ischemia and necrosis of the distal ureter. Look for fluid collections. Lymphoceles (usually late complication) or mature hematomas can look the same. Ultrasound-guided aspiration can be used.
  • Ureteral obstruction: Look for hydronephrosis, but beware that overhydration and reflux can fake you out.
Late (> 4 weeks) complications:
  • Drug toxicity
  • Renal artery stenosis: Up to 10% of cases. Normal peak systolic velocity in renal artery is < 200 cm/s. A ratio of greater than 3-3.5:1 between the iliac artery and the renal artery is also suggestive. RI can be decreased.
  • Recurrence of native renal disease
  • Lymphocele: Occurs in up to 15% of cases. Well-defined and may have fine septations.
Special thanks to Dr. Hansel Otero for the images.

References

  • Friedewald SM, Molmenti EP, Friedewald JJ, Dejong MR, Hamper UM. Vascular and nonvascular complications of renal transplants: sonographic evaluation and correlation with other imaging modalities, surgery, and pathology. J Clin Ultrasound. 2005 Mar-Apr;33(3):127-39.
  • Kaveggia LP, Perrella RR, Grant EG, Tessler FN, Rosenthal JT, Wilkinson A, Danovitch GM. Duplex Doppler sonography in renal allografts: the significance of reversed flow in diastole. AJR Am J Roentgenol. 1990 Aug;155(2):295-8.
  • Zwirewich CV. Renal Transplant Imaging and Intervention: Practical Aspects.

Friday, May 21, 2010

Testicular Epidermoid Cysts

Testicular epidermoid cysts are benign and a cure is possible with complete resection.

On ultrasound, a testicular epidermoid cyst appears as a heterogeneous intratesticular mass without flow on color Doppler. Echogenic foci with posterior sonic shadowing representing calcifications may be present. The lesion may have a hypoechoic or echogenic rim. These findings are nonspecific and usually resection is carried out. The more specific onion skin appearance of alternating hypo- and hyperechoic layers may be present in some cases.

On MRI, T2-weighted images show a hyperintense mass surrounded by hypointense rim. Low-signal-intensity foci representing calcifications may or may not be present. Contrast enhancement is typically not seen. The typical onion skin or target appearance may be present in some cases.

References

Cho JH, Chang JC, Park BH, Lee JG, Son CH. Sonographic and MR imaging findings of testicular epidermoid cysts. AJR Am J Roentgenol. 2002 Mar;178(3):743-8.

Thursday, May 20, 2010

Atlantoaxial Rotatory Subluxation

Atlantoaxial rotatory subluxation can be idiopathic or be due to infection (pharyngitis or otitis media), recent head or neck surgery, or trauma. When an infectious etiology is present, the condition is referred to as Grisel syndrome.

Fielding and Hawkins classified atlantoaxial rotatory subluxation into 4 types:
  • Type I: Simple rotatory displacement without anterior shift. The transverse ligament is intact and the dens acts as a pivot point.
  • Type II: Rotatory and anterior displacement between 3-5 mm. The transverse ligament is injured and the opposite facet acts as the pivot point.
  • Type III: Rotatory and anterior displacement greater than 5 mm with both lateral atlantoaxial joints anteriorly subluxed. The transverse ligament and facet capsules are injured.
  • Type IV: Posterior subluxation of both lateral atlantoaxial joints. Rare and described in adult patients with rheumatoid arthritis and destruction of the dens.
Diagnosis of rotatory subluxation is made with dynamic CT of the upper cervical spine in neutral, head to the left, and head to the right positions. Fixed rotatory subluxation is diagnosed if the distance from the dens to a C1 anterolateral arch on one side is persistently widened on all images compared to the other side.

Management ranges from conservative to surgical, depending on patient age and the duration of symptoms. Children with acute symptoms can be treated with manual reduction followed by mechanical traction (with a hard cervical collar or with weighted traction). Children with a subacute presentation or recurrence are treated with open fixation. Adults are generally treated surgically.

References

Wednesday, May 19, 2010

Grisel Syndrome

Grisel syndrome is rotary atlantoaxial subluxation associated with pharyngeal infection or surgical trauma that occurs predominantly in children. Pharyngeal infection or surgery results is hyperemia that causes decalcification of the anterior arch of C1 and laxity of the transverse ligament.

References

Harth M, Mayer M, Marzi I, Vogl TJ. Lateral torticollis on plain radiographs and MRI: Grisel syndrome. Eur Radiol. 2004 Sep;14(9):1713-5.

Tuesday, May 18, 2010

Caffey Disease

Caffey disease, also known as infantile cortical hyperostosis, is a benign proliferating bone disease. The typical radiographic picture is cortical hyperostosis and involvement of the adjacent fascia, muscles, and connective tissues.

Caffey disease has prenatal and infantile forms. The prenatal form of Caffey disease is congenital and more severe. There is major angulation of the long bones, generalized symmetrical involvement of the skeleton, and polyhydramnios.

The more common infantile form has different radiographic appearances depending on the phase of the disease. The early phase is characterized by thickening of the periosteum that can extend into adjacent soft tissues. Cortical resorption may be present during this phase. In the subacute phase, there is an ossifying periostitis with production of layers of immature subperiosteal lamellar bone. There may also be deposition of bone in adjacent soft tissues. The late phase is characterized by removal of peripheral bone, beginning along the inner surface and extending outward.

Differential diagnosis:
  • Hypervitaminosis A: There is periosteal new bone formation that may be simliar to Caffey disease.
  • Healing scurvy: Subperiosteal new bone formation during healing phase Uncommon before age 4 months, irregularity of the metaphysis, presence of subperiosteal hemorrhage, decreased alkaline phosphatase levels; marked osteopenia
  • Healing rickets: Stripelike density that parallels the outer cortical margin of long bones, resembling a periosteal reaction Splaying and irregularity of the metaphysis, slower resolution of clinical and radiographic findings
  • Trauma: Especially child abuse.
  • Osteomyelitis: Not usually polyostotic.

Monday, May 17, 2010

Distal Clavicular Resorption

Differential diagnosis of distal clavicular resorption:
  • Chronic rotator cuff tear: Decreased acromiohumeral distance.
  • Iatrogenic: Sharp, flared margin without periosteal reaction.
  • Rheumatoid arthritis: Characteristically, the undersurface is resorbed
  • Distal clavicylar osteolysis/post-traumatic osteolysis:
  • Hyperparathyroidism (shown above): Bilateral and symmetric. Soft tissue calcifications.
  • Progressive systemic sclerosis: Scleroderma. Bilateral and symmetric and may involve acromion. Soft tissue calcification may be seen.
  • Septic joint:

Sunday, May 16, 2010

Abernethy Malformation

Abernethy malformation is a congenital portosystemic shunt that results from persistence of embryonic vessels.

Three types of Abernethy malformation have been described.
  • Type I: There is a congenital absence of the portal vein with complete diversion of portal blood into systemic veins (the inferior vena cava, or renal or iliac veins).
    • Type Ia: There is separate drainage of the superior mesenteric and splenic veins into systemic veins.
    • Type Ib: The superior mesenteric and splenic veins join to form a short extrahepatic portal vein which drains into a systemic vein.
  • Type II: There is a hypoplastic portal vein and portal blood is diverted into the vena cava through a side-to-side, extrahepatic communication.


Abernethy malformation has been associated with:
  • Hepatic encephalopathy: Due to portosystemic shunting. Look for T1 hyperintensity in the lentiform nuclei.
  • Hepatic masses: Focal nodular hyperplasia (thought to be due to the absence of the portal vein), hepatocellular carcinoma, hepatoblastoma
  • Hepatopulmonary syndrome:
  • Pulmonary arteriovenous fistulas: Thought to be due to hyperammonemia. May lead to systemic emboli.
  • Congenital abnormalities: Cardiac defects, biliary atresia, and polysplenia.

References

Howard ER, Davenport M. Congenital extrahepatic portocaval shunts--the Abernethy malformation. J Pediatr Surg. 1997 Mar;32(3):494-7.

Saturday, May 15, 2010

Hangman Fracture Types

Traumatic spondylolisthesis of C2 (hangman fracture) involve bilateral pedicle fractures and can be classified based on the degree of displacement of C2 and C3 on lateral cervical spine radiographs.
  • Type I (hyperextension with axial loading): < 3 mm of anterior C2 displacement and minimal angulation (< 3 degrees). Anterior and posterior longitudinal ligaments and C2-C3 disk are intact; therefore, considered stable.
  • Type II (hyperextension with axial loading followed by flexion and axial compression): > 3mm displacement and > 3 degrees of angulation. Mild disruption of the anterior longitudinal ligament and significant disruption of the posterior longitudinal ligament and C2-C3 disk; therefore, considered unstable.
  • Type IIA (flexion with concomitant distraction): No anterior displacement, but severe angulation. C2-C3 disk disruption and some injury to posterior longitudinal ligament; therefore, considered unstable.
  • Type III (flexion with concomitant axial compression): Severe displacement and severe angulation. C2-C3 disk disruption, unilateral or bilateral C2-C3 facet dislocations and varying degrees of injury to the anterior and posterior longitudinal ligaments. Considered unstable.

Friday, May 14, 2010

Types of Occipital Condyle Fractures

Occipital condyle fractures can be classified based on of the form of applied strain developed by Anderson and Montesano:
  • Type I: Comminuted impaction fracture due to axial loading
  • Type II: Skull base fracture that extends through the occipital condyle
  • Type III: Avulsion fracture mediated through tension in the alar ligament. May be associated with disruption of the alar ligaments and tectorial membrane and result in craniocervical dissociation.
Tuli et al. have also developed a system to guide neurosurgical management:
  • Type 1: Nondisplaced occipital condyle fracture (stable). Require no specific treatment.
  • Type 2A: Displaced occipital condyle fracture with intact ligaments. May be treated with a rigid collar.
  • Type 2B: Displaced occipital condyle fracture with radiographic evidence of craniocervical junction instability. Require surgical instrumentation or halo traction

References

Hanson JA, Deliganis AV, Baxter AB, Cohen WA, Linnau KF, Wilson AJ, Mann FA. Radiologic and clinical spectrum of occipital condyle fractures: retrospective review of 107 consecutive fractures in 95 patients. AJR Am J Roentgenol. 2002 May;178(5):1261-8.

Thursday, May 13, 2010

Noncompaction Cardiomyopathy

Noncompaction cardiomyopathy is thought to be caused by arrest of normal embryogenesis of the endocardium and myocardium. The myocardium starts out as a loose network of interwoven fibers separated by deep recesses. These recesses communicate with the ventricular cavity. They eventually compact down, proceeding from the epicardium to endocardium and from the base of the heart to the apex. This happens around the same time as the coronary circulation develops, and these recesses turn into capillaries.

Arrest of compaction can lead to either:
  • Noncompaction of the ventricular myocardium: Persistence of recesses, which stay in communication with both the ventricular cavity and the coronary circulation, or
  • Isolated noncompaction of the ventricular myocardium (also known as left ventricular hypertrabeculation): Persistence of recesses, which communicate only with the ventricular cavity, not the coronary circulation.
The left ventricle is always affected, but because the right ventricle normally has a trabeculated appearance, differentiating a normal but highly trabeculated right ventricle from a pathological noncompacted ventricle may be difficult. This has led some to dispute the existence of right ventricular noncompaction.

Non-compaction can be found in normal subjects, where it is more commonly found in the apical segments (91% of subjects) compared to mid-cavity levels (78% of subjects) and basal segments (21% of normal subjects). For this reason, a ratio of >2.0 between the thickness of the non-compacted and compacted myocardial layers in systole is considered diagnostic on echocardiography. A ratio of >2.3 between the thickness of the non-compacted and compacted myocardial layers in diastole is considered diagnostic on cardiac MRI, with, with sensitivity, specificity and positive and negative predictive values of 86%, 99%, 75%, and 99%, respectively.

The ratio is calculated using long-axis (horizontal and vertical long-axis and left ventricular outflow tract) views during diastole. In each view, the segment with the most pronounced trabeculation (excluding the apex) is chosen to calculate the ratio. The highest ratio wins. A segment is considered non-compacted if the visual appearance clearly suggests the presence of two myocardial layers with different degrees of tissue compaction.

Complications include systemic embolization and regional wall motion abnormalities.

References

Wednesday, May 12, 2010

Haglund Syndrome

Haglund syndrome is characterized radiographically on the lateral view by the following:
  • Prominent calcaneal bursal projection: See below
  • Retrocalcaneal bursitis: On the lateral radiograph of the heel, the normal retrocalcaneal recess (rr) extends at least 2 mm below the bursal projection and has a sharp interface along the anterior edge of the Achilles tendon. When this interface is not seen, retrocalcaneal bursitis is suggested.
  • Thickening of the Achilles tendon: Anteroposterior diameter larger than 9 mm, 2 cm above the bursal projection and loss of the sharp tendinous interface.
  • Convexity of the superficial soft tissues at the level of the Achilles insertion ("pump-bump").
Different methods have been proposed for the detection of the prominent bursal projection. The posterior calcaneal angle of Fowler is formed by the intersection of a line tangent to the anterior tubercle (a) and the medial tuberosity (m) of the calcaneus with the line tangent to the posterior surface of the bursal projection (bp) and the posterior tuberosity (p). An angle larger than 75 degrees is considered positive.

Another method involve construction of parallel pitch lines. As described above, a line is drawn tangent to the anterior tubercle (a) and the medial tuberosity (m) of the calcaneus. A line parallel to this one is drawn from the posterior articular facet of the talus (t). A bursal projection above this line is considered abnormal.

More recent work, however, has found no statistically significant difference in these measures between patients with symptomatic Haglund syndrome and normal controls. The presence of retrocalcaneal exostoses and Achilles tendon calcifications, on the other hand, were statistically significantly different between these two groups.

References

  • Lu CC, Cheng YM, Fu YC, Tien YC, Chen SK, Huang PJ. Angle analysis of Haglund syndrome and its relationship with osseous variations and Achilles tendon calcification. Foot Ankle Int. 2007 Feb;28(2):181-5.
  • Pavlov H, Heneghan MA, Hersh A, Goldman AB, Vigorita V. The Haglund syndrome: initial and differential diagnosis. Radiology. 1982 Jul;144(1):83-8.

Tuesday, May 11, 2010

Fenestral Otosclerosis

Fenestral otosclerosis/otospongiosis is abnormal lucency at the fissula ante fenestram (a cleft of fibrocartilaginous tissue between inner & middle ears just anterior to oval window).

Bone algorithm CT will show relatively lucent foci at anterior margin of the oval window (black arrow). Late findings during the healing phase include new bone along oval and round window margins. The anterior (blue) and posterior (red) crura of the stapes are indicated in the oval window. The bottom image is from a normal subject.

Monday, May 10, 2010

Distal Clavicular Osteolysis

Distal clavicular osteolysis is characterized by shoulder pain following relatively minor trauma or following chronic repetitive stress (most common in young weight lifters).

Radiographic findings include subarticular erosions, tapering, and widening of the acromioclavicular joint, and are seen weeks to months after the initial insult. Late findings may also be seen at the acromion, and include erosion and dystrophic calcification.

MRI shows bone marrow edema, abnormalities of the acromioclavicular joint, and subchondral cysts in the distal clavicle. Recently, subchondral fractures have been seen in a number of cases of Distal clavicular osteolysis.

The images above show bone marrow edema, a joint effusion, and a subchondral fracture. Radiographs obtained around the same time show lucencies in the distal clavivle with areas of sclerosis.

More broadly speaking, post-traumatic osteolysis occurs most frequently at the distal calvicle, followed by the pubuc and ischial rami, distal ulna, distal radius, the carpal bones, and the femoral neck.

References

  • Kaplan PA, Resnick D. Stress-induced osteolysis of the clavicle. Radiology. 1986 Jan;158(1):139-40.
  • Kassarjian A, Llopis E, Palmer WE. Distal clavicular osteolysis: MR evidence for subchondral fracture. Skeletal Radiol. 2007 Jan;36(1):17-22.
  • Levine AH, Pais MJ, Schwartz EE. Posttraumatic osteolysis of the distal clavicle with emphasis on early radiologic changes. AJR Am J Roentgenol. 1976 Nov;127(5):781-4.

Sunday, May 9, 2010

Kienböck Disease

Kienböck disease, also known as lunatomalacia, is an idiopathic necrosis of the lunate. It has been suggested that chronic microfractures lead to vascular compromise and subsequent osteonecrosis. Chronic microfractures may occur due to external factors (e.g., work-related), or anatomic variations (see below).

The variable blood supply has been also suggested as a predisposing factor. The blood supply of the lunate is through proximal carpal arcades, usually along its palmar and dorsal surfaces, but up to 1/4 of lunates may have a single supply (either dorsal or palmar).

Mechanical anatomic factors that have been suggested to predispose patients include:
  • Smaller lunate
  • Flatter radial inclination : Angle between a line from the ulnar side of the carpal surface of the radius to the tip of the radial styloid and a line perpendicular to the axis of the ulna.
  • More radial tilt of the lunate.
  • Negative ulnar variance: Disputed by more recent work.
  • High uncovering index of the lunate: Length of the proximal surface of the lunate that does not articulate with the radius divided by the total proximal surface of the lunate. Disputed by more recent work.
  • A trapezoidal shape of the lunate
  • The presence of a medial lunate facet articulating with the hamate
The patient here had was on chronic steroid therapy and started having wrist pain after an episode of wrist trauma a while back.

References

  • Ledoux P, Lamblin D, Wuilbaut A, Schuind F. A finite-element analysis of Kienbock's disease. J Hand Surg Eur Vol. 2008 Jun;33(3):286-91.
  • Schuind F, Eslami S, Ledoux P. Kienbock's disease. J Bone Joint Surg Br. 2008 Feb;90(2):133-9.
  • Thienpont E, Mulier T, Rega F, De Smet L. Radiographic analysis of anatomical risk factors for Kienböck's disease. Acta Orthop Belg. 2004 Oct;70(5):406-9.

Saturday, May 8, 2010

Lunate Fractures

The blood supply of the lunate is through proximal carpal arcades usually along its palmar and dorsal surfaces, but up to 1/4 of lunates may have a single supply (either dorsal or palmar). Lunate fractures make up less than 1% of all carpal fractures. Acute fractures are classified into five groups:
  • Frontal fractures of the palmar pole: The palmar nutrient arteries are involved
  • Osteochondral fractures of the proximal articular surface: No substantial damage to nutrient vessels
  • Frontal fractures of the dorsal pole
  • Transverse fractures of the body
  • Transarticular frontal fractures of the body

References

Rockwood and Green's Fractures in Adults. 7th ed. p 804.

Friday, May 7, 2010

Femoral Trochlear Dysplasia

Femoral trochlear dysplasia can be picked up on lateral knee radiographs and sagittal knee MRs. A too-shallow trochlear groove is suspected of causing patellar instability.

The floor of the trochlear groove forms a dense line that should be posterior to the trochleae along its entire course and is in continuity superiorly with the anterior cortex of the distal femur. This line should also be parallel to the lateral trochlea (Grelsamer and Tedder, 1992).

A positive lateral trochlear sign is seen when the floor of the trochlear groove intersects the anterior femoral condyle (arrow). This is seen in cases of severe femoral trochlear dysplasia (Grelsamer and Tedder, 1992).

Another way for assessing the depth of the trochlear groove is by drawing a line along the anterior cortex of the distal femoral shaft. If the anteriormost point of the floor of the trochlear groove falls more than 3 mm anterior to this line, the trochlear floor is said to be ventrally prominent (Dejour et al, 1994). The midsagittal MRI can also be used for this purpose.

The lateral radiograph shown here is a bit obliqued, but we can see the crossing sign (arrow). We can also see that the anteriormost point of the floor of the trochlear groove falls more than 3 mm anterior to a line drawn along the anterior cortex of the distal femoral shaft (dashed line). The midsagittal MRI also shows this finding as a step-like transition zone from the anterior femoral cortical bone to the trochlea. A small nipple may also be seen at the superior border of the trochlea.

References

  • Dejour H, Walch G, Nove-Josserand L, Guier C. Factors of patellar instability: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc 1994; 2:19-26.
  • Grelsamer RP, Tedder JL. The lateral trochlear sign. Femoral trochlear dysplasia as seen on a lateral view roentgenograph. Clin Orthop Relat Res 1992:159-162.
  • Pfirrmann CW, Zanetti M, Romero J, Hodler J. Femoral trochlear dysplasia: MR findings. Radiology. 2000 Sep;216(3):858-64.

Thursday, May 6, 2010

Ficat Classification of Avascular Necrosis (AVN) of the Femoral Head

Stage Name Clinical features Radiography
Early
  0 Preclinical    
  I Preradiographic +  
  II   + Osteoporosis, sclerosis, cysts
Transition     Flattening and crescent sign
Late
  III Collapse ++ Irregular contour of head, sequestrum, normal joint space
  IV Osteoarthritis +++ Flattened femoral head, narrowed joint space; collapse of head (see image)

Stage II


Note lucency with well-defined peripheral sclerosis. The frog-leg view is used for assessment of sphericity of the femoral heads. Drawing a circle around the femoral heads on this view will allow for detection of subtle cortical step-offs and early subchondral collapse.

 

Stage IV

References

Ficat RP. Idiopathic bone necrosis of the femoral head. Early diagnosis and treatment. J Bone Joint Surg Br. 1985 Jan;67(1):3-9.

Wednesday, May 5, 2010

Olecranon Sled

An olecranon sled is hardware for fixation of fractures of the olecranon that consists of an outer wire loop (fixed to the ulna with a washer and two cortical screws) connected to two legs that are inserted into the fracture fragment and ulna.

References

Dieterich J, Kummer FJ, Ceder L. The olecranon sled--a new device for fixation of fractures of the olecranon: a mechanical comparison of two fixation methods in cadaver elbows. Acta Orthop. 2006 Jun;77(3):440-4.

Tuesday, May 4, 2010

Supinator Syndrome

The supinator syndrome, also known as deep radial nerve syndrome, is a compression palsy of the posterior interosseous nerve of the elbow (continuation of the deep branch of the radial nerve). MRI findings are related to as atrophy of the muscles supplied by the posterior interosseous nerve, namely the supinator muscle (white arrow) and multiple muscles in the hand. A swollen posterior interosseous nerve can apparently also be detected.

The arcade of Frohse, or the supinator arch, is a fibrous arch at the superior end of the superficial layer of the supinator muscle, and covers the posterior interosseous nerve. It is the most frequent site of posterior interosseous nerve entrapment. Entrapment may also occur in humeral fractures and subsequent callus formation (Holstein-Lewis fracture) and a high radial lesion (before origin of the posterior interosseous nerve). Our case had a ganglion (pink arrow) at the distal radial nerve (blue arrow).

References

  • Furuta T, Okamoto Y, Tohno E, Minami M, Nishiura Y, Ohtomo K. Magnetic resonance microscopy imaging of posterior interosseous nerve palsy. Jpn J Radiol. 2009 Jan;27(1):41-4.
  • Stadnick ME. Posterior Interosseous Nerve Syndrome. MRI Web Clinic - August 2005

Monday, May 3, 2010

Patellar Height

There seem to be a million ways of assessing patellar height, which is usually an indication that none of them are perfect. Here's a short summary of all the different methods.

Sunday, May 2, 2010

Ludloff Spot

An area of lucency in the distal femur between the medial and lateral femoral condyles is usually obscured by the patella on frontal views of the knee. On lateral views, a triangular triangular lucency, called the Ludloff spot, can be appreciated. CT images will show an area of lucency that can be mistaken for a lytic process.

References

De Wilde V, De Maeseneer M, Lenchik L, Van Roy P, Beeckman P, Osteaux M. Normal osseous variants presenting as cystic or lucent areas on radiography and CT imaging: a pictorial overview. Eur J Radiol. 2004 Jul;51(1):77-84.

Saturday, May 1, 2010

Riders' Bursa

The riders' bursa is an adventitious bursa along the medial aspect of the knee, superficial to the medial collateral ligament that comes about from repetitive friction, such as horseback riding.