Nodular Fasciitis

Nodular fasciitis, formerly known as pseudosarcomatous fasciitis, is a mass-forming, rapidly growing proliferation of fibroblasts and myofibroblasts. It is most commonly found in the subcutaneous tissue, but can also be intramuscular, fascial, or even dermal (rare) locations. In about 50% of cases, it is found in the upper extremity (especially the volar aspect of the forearm). Other locations include the trunk, head and neck, and lower extremities.

Histologically, nodular fasciitis may be mistaken for a sarcoma because of abundant spindle-shaped cells and mitotic activity. Unlike sarcomas, however, atypical mitotic figures should not be seen. Intravascular fasciitis and cranial fasciitis are histologically similar lesions. Intravascular fasciitis extends into the lumens of small to medium-sized vessels, most commonly veins, and is also usually subcutaneous in location. Cranial fasciitis characteristically involves the outer table of the skull and adjacent soft tissues of the scalp. Intracranial extension to the meninges can also occur.

Some have suggested a traumatic etiology, especially in the case of cranial fasciitis (birth trauma). Patients are most commonly between 20 and 40 years of age and usually present with a rapidly growing mass, usually smaller than 5 cm. Tenderness and pain may be present.

The signal characteristics on MRI depend on the histology of the lesion. Hypercellular lesions (case shown above) are nearly isointense to skeletal muscle on T1-weighted images and hyperintense to fat on T2-weighted images. Collagenous lesions are hypointense on T1- and T2-weighted images. Post-contrast images usually reveal diffuse enhancement, but peripheral enhancement can also be seen.

Differential considerations include:

• Extra-abdominal desmoid tumor:
• Neurofibroma:
• Soft-tissue sarcoma:
• Early myositis ossificans: Intramuscular lesions.

References

• Dinauer PA, Brixey CJ, Moncur JT, Fanburg-Smith JC, Murphey MD. Pathologic and MR imaging features of benign fibrous soft-tissue tumors in adults. Radiographics. 2007 Jan-Feb;27(1):173-87.
• Evans HL and Bridge JA. Nodular fasciitis. in Pathology and Genetics of Tumours of Soft Tissue and Bone. Fletcher CDM, Unni KK, Mertens F (eds). IARCPress Lyon, 2002. pp 48-49.

Problems with a Type II Accessory Navicular

The type-II accessory navicular bone is an accessory ossification center that is connected to the navicular proper by a fibrocartilaginous synchondrosis. The posterior tibial tendon attaches to the type-II accessory navicular instead of the navicular tuberosity.

While most people with a type II accessory navicular are asymptomatic, some present with problems related to this bone. These include:

• Flat-foot deformity: Attachment of the posterior tibial tendon to the Type II accessory navicular may lead to straightening of the tendon, causing adduction forces.
• Tendinosis/Tear: Can occur due to increased stress caused by decreased leverage of the medial malleolus on the tendon from a more proximal insertion. Prevalence of type-II accessory navicular bones in patients with posterior tibial tendon dysfunction is higher than in the general population.
• "Symptomatic accessory navicular": Due to repetitive shearing stress forces acting on the type-II accessory navicular synchondrosis. Resultant bone remodeling may result in osteonecrosis surrounding the synchondrosis. MRI will reveal bone marrow signal abnormalities in the accessory navicular and navicular proper adjacent to the synchondrosis.

References

• Bernaerts A, Vanhoenacker FM, Van de Perre S, De Schepper AM, Parizel PM. Accessory navicular bone: not such a normal variant. JBR-BTR. 2004 Sep-Oct;87(5):250-2.
• Mellado JM, Ramos A, Salvadó E, Camins A, Danús M, Saurí A. Accessory ossicles and sesamoid bones of the ankle and foot: imaging findings, clinical significance and differential diagnosis. Eur Radiol. 2003 Dec;13 Suppl 6:L164-77.
• Miller TT, Staron RB, Feldman F, Parisien M, Glucksman WJ, Gandolfo LH. The symptomatic accessory tarsal navicular bone: assessment with MR imaging. Radiology. 1995 Jun;195(3):849-53.

Nasal Septal Perforation

Nasal septal perforation can be seen with the following conditions:

• Cocaine use: Most common cause of nasal septal perforation.
• Trauma: Ischemic necrosis due to compression from hematoma, iatrogenic.
• Wegener granulomatosis: Associated with soft tissue.
• Sarcoidosis: Associated with soft tissue.
• Non-Hodgkin Lymphoma: Associated with soft tissue.
• Infection: Invasive fungal sinusitis, Nasal septal abscess, Klebseilla (rhinoscleroma), syphilis (look for saddle nose deformity), tuberculosis, leprosy.
• Squamous cell carcinoma:
• Melanoma:

References

• STATdx.
• Case review series: Head and Neck (2nd ed.).

Peroneus Quartus Muscle

The peroneus quartus is an accessory peroneus muscle that is seen in about 15%-20% of the population. The muscle is name the fourth peroneal because the name peroneus (fibularis) tertius was already been assigned to the muscle that runs with the extensor digitorum longus to insert on the dorsal surface of the base of the fifth metatarsal.

The peroneus quartus muscle commonly originates from the peroneal muscles in the distal leg and attaches to either the retrotrochlear eminence of the calcaneus, the cuboid, or the peroneus longus tendon. The muscle can be further classified based on these insertions as peroneocalcaneus externum (calcaneus), peroneocuboideus (cuboid), or peroneoperoneolongus (peroneus longus tendon).

While peroneus quartus muscles are usually asymptomatic, they may cause crowding in the retromalleolar groove and predispose people with this normal variant to peroneus brevis tendon dislocation and tear.

Axial images are usually best for defining the muscle (white arrow). It is found posteromedial to the peroneus brevis muscle (pink arrow) and is usually separated from the peroneus brevis muscle by a fat plane. The peroneus longus muscle is indicated by the blue arrow.

Interestingly, it has been suggested that the peroneus quartus muscle represents an intermediate evolutionary stage in the development of bipedal posture, with the muscle allowing our ancestors to lift the lateral edge of their feet and stabilizing hind-foot pronation.

References

• Cheung YY, Rosenberg ZS, Ramsinghani R, Beltran J, Jahss MH. Peroneus quartus muscle: MR imaging features. Radiology. 1997 Mar;202(3):745-50.
• Saupe N, Mengiardi B, Pfirrmann CW, Vienne P, Seifert B, Zanetti M. Anatomic variants associated with peroneal tendon disorders: MR imaging findings in volunteers with asymptomatic ankles. Radiology. 2007 Feb;242(2):509-17.
• Wang XT, Rosenberg ZS, Mechlin MB, Schweitzer ME. Normal variants and diseases of the peroneal tendons and superior peroneal retinaculum: MR imaging features. Radiographics. 2005 May-Jun;25(3):587-602.

Tracheal Stenosis

Short Segment:

• Iatrogenic: Endotracheal intubation, tracheostomy.
• Wegener granulomatosis: Irregularity and thickening. Subglottic involvement common. Circumferential involvement.
• Sarcoid: Irregularity and thickening.
• Amyloidosis: Localized tumor-like nodules, causing irregular narrowing and stenosis of the lumen. May have calcifications.
• Infection: Tuberculosis or histoplasmosis. Irregularity and thickening.
• Extrinsic compression: Tumor, lymph node.

Long Segment:

• Relapsing polychondritis: Thickening of the cartilaginous part of the wall (posterior wall spared). Collapse on expiratory images.
• Amyloidosis: Diffuse or multifocal submucosal infiltration, causing irregular narrowing and stenosis of the lumen. May have calcifications. May be circumferential.
• Tracheobronchopathia osteochondroplastica (TPO): Very rare. Multiple submucosal nodules of bone and cartilage protrude into the lumen of the distal trachea and central bronchi. Posterior wall spared. Presence of calcification/ossification may give an appearance similar to amyloidosis and relapsing polychondritis.

Tracheal neoplasms:

• Primary Tumor: Squamous cell carcinoma (most common primary tracheobronchial malignancy), adenoid cystic carcinoma, mucoepidermoid carcinoma, and carcinoid.
• Metastases: Renal cell carcinoma, breast cancer, colon cancer, hepatocellular carcinoma, and melanoma.
• Papillomatosis: Associated with HPV and increased risk of squamous cell carcinoma. Multiple irregular filling defects. Usually seen in young people, particularly children. Larynx most commonly affected with occasional extension into the trachea and proximal bronchi.

See the related post on Mounier-Kuhn Syndrome for a discussion of causes of tracheal widening.

References

Park CM, Goo JM, Lee HJ, Kim MA, Lee CH, Kang MJ. Tumors in the tracheobronchial tree: CT and FDG PET features. Radiographics. 2009 Jan-Feb;29(1):55-71.

Köhler Osteochondrosis

Osteochondrosis of the tarsal navicular (Köhler disease) is characterized by sclerosis and diminished size of the tarsal navicular, sometimes called the "Alka-Seltzer-on-end appearance." There is usually loss of the normal trabecular pattern of the navicular.

Because abnormalities in the size and shape of the normal navicular ossification center may lead to an identical radiographic appearance, the diagnosis requires the presence of pain and tenderness in the area of the tarsal navicular associated with the radiographic features described above.

There is a male-to-female ratio of 5:1. Patients are usually between 4 and 6 years of age and most commonly present with pain and a limp. Physical examination most commonly reveals tenderness over the tarsal navicular. 20% of cases are bilateral.

While Köhler disease is self-limited, cast immobilization may result in faster resolution of symptoms.

References

Canale ST. Osteochondroses and Related Problems of the Foot and Ankle In: DeLee JC, Drez D, eds. DeLee and Drez's Orthopaedic Sports Medicine. 2nd ed. Philadelphia , Pa. : Saunders; 2003: pp. 2587-2623.

Olecranon Bursitis

Differential considerations for olecranon bursitis include:

• Trauma:
• Infection:
• Gout:
• Rheumatoid arthritis:
• Amyloidosis:

Longitudinal Tear of the Peroneus Brevis Tendon

Longitudinal tears of the peroneus brevis are common injuries that may be found in symptomatic young adults and asymptomatic older patients. The injury is thought to be due to dynamic compression of the tendon against the retromalleolar groove by the overlying peroneus longus tendon during ankle dorsiflexion. Healing is prevented by continuing insinuation of the peroneus longus tendon into the longitudinal tear.

MRI reveals a C-shaped appearance of the tendon in the retromalleolar groove, as opposed to its normally flat shape in this region. The tendon partially encircles the peroneus longus tendon and the split fragments may be found medial, lateral, or posterior to the peroneus longus tendon.

References

Rosenberg ZS, Beltran J, Cheung YY, Colon E, Herraiz F. MR features of longitudinal tears of the peroneus brevis tendon. AJR Am J Roentgenol. 1997 Jan;168(1):141-7.

Soft Tissue Uptake on Bone Scan

Tc-99m MDP can be taken up by soft tissues, usually due to ossification and calcification. The most common causes for each organ are listed.

• Brain: Infarction.
• Heart: Infarction, among other possibilities.
• Kidneys: Renal cortical uptake greater than spine uptake is abnormal. Can be seen with metastatic calcification from hypercalcemia (e.g., in hyperparathyroidism), renal cortical necrosis (radiation, drugs), hemoglobinopathies (e.g., sickle cell disease).
• Liver: Usually metastases if focal. Diffuse uptake may indicate excess aluminium.
• Lungs: Metastatic calcification from hypercalcemia (e.g., in hyperparathyroidism), pleural effusion, fibrothorax, neoplasm (primary or metastatic), alveolar microlithiasis, radiation.
• Muscle: Rhyabdomyolysis or polymyositis if diffuse. Myositis ossificans or tumor if focal.
• Spleen: Infarction (e.g., in sickle cell disease).
• Stomach: Metastatic calcification from hypercalcemia (e.g., in hyperparathyroidism).

Plantar Fasciitis: MRI Findings

Plantar fasciitis is the most common cause of heel pain in the athlete and represents a low-grade inflammation involving the plantar aponeurosis and surrounding structures.

MRI findings of acute plantar fasciitis include increased intrasubstance signal intensity on T2-weighted and STIR images, with or without associated fascial thickening. The normal plantar fascial thickness is less than about 4 mm. The average thickness of the plantar fascia in patients with plantar fasciitis is about 7.5 mm.

Signal abnormality may predominantly involve the perifascial soft-tissues (deep and/or superficial) and adjacent calcaneus. Enhancement of the inflamed perifascial soft tissues may be also seen.

Calcaneal enthesophytes rarely cause plantar fasciitis and can be seen in patients with plantar fasciitis and asymptomatic controls.

The image above reveals a normal-thickness plantar fascia associated with abnormal peri fascial and calcaneal signal intensity.

References

• Berkowitz JF, Kier R, Rudicel S. Plantar fasciitis: MR imaging. Radiology. 1991 Jun;179(3):665-7.
• Theodorou DJ, Theodorou SJ, Farooki S, Kakitsubata Y, Resnick D. Disorders of the plantar aponeurosis: a spectrum of MR imaging findings. AJR Am J Roentgenol. 2001 Jan;176(1):97-104.

Cystic Changes at Supraspinatus and Infraspinatus Tendon Insertion Sites

An association between rotator cuff tears and bony abnormalities of the greater tuberosity has been suggested based on radiographs. More recent work with MRI, however, has shown that not all greater tuberosity cysts are created equal. Cysts at the infraspinatus insertion (posterior cysts) are more common than those associated with the supraspinatus and are not associated with rotator cuff pathology. On the other hand, cysts at the suraspinatus insertion (anterior cysts) are closely associated with cuff disorders.

References

Fritz LB, Ouellette HA, O'Hanley TA, Kassarjian A, Palmer WE. Cystic changes at supraspinatus and infraspinatus tendon insertion sites: association with age and rotator cuff disorders in 238 patients. Radiology. 2007 Jul;244(1):239-48.

Central Acetabular Osteophytes

Central acetabular osteophytosis has been shown to represent an early radiological manifestation of hip osteoarthritis and has recently been been likened to a saber tooth. These osteophytes arise from the acetabular notch above the transverse ligament and progress to involve the acetabular notch circumferentially or even to occlude the acetabular notch completely, resulting in lateralization of the femoral head.

The above image reveals advanced osteoarthritis of the left hip joint with a large central osteophyte that almost completely bridges the acetabular notch and results in mild lateralization of the femoral head.

References

• Varich L, Pathria M, Resnick D, Hodler J, Bruser D, Bosch E, Trudell D, Tyson R. Patterns of central acetabular osteophytosis in osteoarthritis of the hip. Invest Radiol. 1993 Dec;28(12):1120-7.
• Mofidi A, Shields JS, and Stubbs AJ. Central acetabular osteophyte (saber tooth sign), one of the earliest signs of osteoarthritis of the hip joint. Eur J Orthop Surg & Traumatology. Published online, July 24, 2010.

Hyperattenuating Renal Cyst

A hyperattenuating (hyperdense, in radiology slang) renal mass that does not contain fat can be considered a hemorrhagic or proteinaceous cyst (Bosniak II) if the following CT criteria are met:

• Shape: Round
• Margin: Smooth and sharply marginated
• Size: Diameter ≤ 3 cm
• Attenuation: 40–90 HU and homogeneous in attenuation, when examined using narrow window settings.
• Enhancement: None, when examined using narrow window settings. Masses that increase in attenuation by 10 HU or less are considered non-enhancing.
• Extent: Must extend outside of the kidney at least approximately one-fourth of its circumference so that the smoothness of some of the wall can be evaluated.

Note: There is at least one case of a cystic renal cell carcinoma that fulfilled all of the above CT criteria for a benign hyperattenuating cyst, so we can't rule out renal cell carcinoma completely.

References

• Bosniak MA. The small (less than or equal to 3.0 cm) renal parenchymal tumor: detection, diagnosis, and controversies. Radiology. 1991 May;179(2):307-17.
• Hartman DS, Weatherby E 3rd, Laskin WB, Brody JM, Corse W, Baluch JD. Cystic renal cell carcinoma: CT findings simulating a benign hyperdense cyst. AJR Am J Roentgenol. 1992 Dec;159(6):1235-7.

Geyser Sign

Passage of fluid from the glenohumeral joint into the acromioclavicular joint on arthrography is referred to as the geyser sign. It can be seen with chronic rotator cuff tendon tear or after injury of the acromial undersurface during surgery.

References

• Craig EV. The geyser sign and torn rotator cuff: clinical significance and pathomechanics. Clin Orthop Relat Res. 1984 Dec;(191):213-5.
• Mohana-Borges AV, Chung CB, Resnick D. MR imaging and MR arthrography of the postoperative shoulder: spectrum of normal and abnormal findings. Radiographics. 2004 Jan-Feb;24(1):69-85.

Ureteral Strictures

Differential considerations for ureteric strictures include:

• Tuberculosis: May have distal distal ureteral calcifications. Starts proximally and extends distally.
• Schistosomiasis: Starts at bladder and extends proximally. Look for bladder calcifications. Increased risk of squamous cell carcinoma.
• Trauma: Iatrogenic
• Endometriosis: Smooth, extrinsic lesions.
• Transitional cell carcinoma:
• Calculus:
• Radiation therapy:
• Metastases:

Intrauterine Filling Defect

Filling defects on hysterosalpingography may be due to:

• Air bubbles:
• Mucus:
• Blood clot:
• Retained products of conception:
• Foreign body:
  
• Asherman syndrome:
• Leiomyomas:
• Polyps: Case shown above. Two polyps are seen at the uterine fundus on hysterosalpingography and sonohysterogram.
• Endometrial carcinoma:

Unilateral Enlarged Kidney

Differential considerations include:

• Obstruction: Most common cause.
• Pyelonephritis:
• Renal vein thrombosis:
• Duplex kidney:
• Compensatory hypertrophy:
• Crossed fused ectopia: One kidney crosses the midline and fuses with the other kidney. The fused kidneys lie to one side of the spine, with the ureter for the crossed kidney crossing the midline to insert into the bladder. More common in males. Left kidney more commonly crosses.
• Tumor:
• Multicystic dysplastic kidney:
• Trauma:
• Acute arterial infarction:

See related post on bilateral enlarged kidneys.

Salpingitis Isthmica Nodosa

Salpingitis isthmica nodosa is an inflammatory process of the fallopian tubes of unknown etiology. Associations with pelvic inflammatory disease, infertility, and ectopic pregnancy have been reported. Hysterosalpingography reveals tubal irregularity and subcentimeter protrusions from the isthmic portion of the fallopian tube. The above image is a case of bilateral salpingitis isthmica nodosa.

References

Steinkeler JA, Woodfield CA, Lazarus E, Hillstrom MM. Female infertility: a systematic approach to radiologic imaging and diagnosis. Radiographics. 2009 Sep-Oct;29(5):1353-70.

Unopacified Kidney on Intravenous Urography

Differential Diagnosis:

• Obstruction:
• Renal artery embolism: Look for cortical rim of contrast from capsular arteries
• Renal vein thrombosis:
• Absent or ectopic kidney:
• Infection: Xanthogranulomatous pyelonephritis.
• Tumor:
• Multicystic dysplastic kidney:

Anconeus Epitrochlearis Muscle

The anconeus epitrochlearis (or accessory anconeus) muscle is thought to represent an atavistic muscle that is usually found as a remnant (epitrochleoanconeus ligament). It can be found intact in ~5% to ~35% of cadavers. A recent MRI study found this muscle in about 25% of patients.

The image above shows anconeus epitrochlearis muscles in 4 different patients. While the anconeus epitrochlearis muscle (white arrows) can cause cubital tunnel syndrome by compression of the ulnar nerve (pink arrows), it is commonly found in asymptomatic elbows.

References

• Husarik DB, Saupe N, Pfirrmann CW, Jost B, Hodler J, Zanetti M. Elbow nerves: MR findings in 60 asymptomatic subjects--normal anatomy, variants, and pitfalls. Radiology. 2009 Jul;252(1):148-56.
• Jeon IH, Fairbairn KJ, Neumann L, Wallace WA. MR imaging of edematous anconeus epitrochlearis: another cause of medial elbow pain? Skeletal Radiol. 2005 Feb;34(2):103-7.

Alkaline-Encrusted Cystitis and Pyelitis

Alkaline-encrusted cystitis and pyelitis refer to stone encrustation in the wall of the urinary tract caused by urea-splitting microorganisms. This is a nosocomial infection that typically occurs in immunocompromised or debilitated patients after urologic procedures.

CT is the imaging modality of choice for demonstrating encrustation, particularly in the upper urinary tract. CT shows calcifications superficially covering a thickened urothelium. The calcifications can be thin and regular or thick and irregular. Perinephric and periureteral stranding may be seen with severe infection.

Ultrasound may show urothelial calcifications in a dilated renal pelvis or a full bladder. Calyceal calcifications, on the other hand, cannot be reliably differentiated from stag-horn calculi by ultrasound.

Planar radiography may show the calcifications, but is obviously not very sensitive.

Differential considerations include other causes of urothelial wall encrustation:

• Schistosomiasis
• Tuberculosis
• Necrotic urothelial carcinoma
• Leucoplakia
• Intravesical instillation of cyclophosphamide or mitomycin.

References

Thoumas D, Darmallaicq C, Pfister C, Savoye-Collet C, Sibert L, Grise P, Lemaitre L, Benozio M. Imaging characteristics of alkaline-encrusted cystitis and pyelitis. AJR Am J Roentgenol. 2002 Feb;178(2):389-92.

Cystic Suprasellar Lesions

Differential considerations for cystic suprasellar lesions:

• Arachnoid cyst: Follows cerebrospinal fluid signal. No restricted diffusion (as opposed to epidermoids, which are rare in the suprasellar cistern).
• Rathke cleft cyst: Usually hyperintense to cerebrospinal fluid. May have calcifications and about 50% will have an intracystic nodule. A claw of compressed, enhancing pituitary can be seen displaced around the cyst.
• Craniopharyngioma: 90% of childhood craniopharyngiomas are cystic (adamantinomatous type), as opposed to craniopharyngiomas in adults (papillary type), but the majority have some calcifications and nodular or rim enhancement.
• Neurocysticercosis : Cyst fluid doesn't completely suppress on FLAIR.
• Pituitary macroadenoma: May have intra- or extratumoral cystic components.
• Enlarged third ventricle: Not really a lesion and not really a diagnostic dilemma. Look for aqueductal stenosis, hydrocephalus.
• Dermoid cyst: Fat signal with or without calcifications.
• Epidermoid Cyst: Rarely found in suprasellar cistern. Don't suppress completely on FLAIR and show restricted diffusion (as opposed to arachnoid cysts).

Large Eye: Differential Diagnosis

With intraocular mass

• Retinoblastoma: With calcifications
• Melanoma: Without calcifications

Without intraocular mass

• Axial myopia: Most common cause of macrophthalmia. Idiopathic enlargement of the eyeball in the anteroposterior dimension with or without scleral thickening. May be unilateral or bilateral. May also be seen with orbital infections, Grave disease, and staphyloma.
• Buphthalmos: Greek for eye of the ox. Diffuse enlargement of the eye in children due to increased intraocular pressure. Seen in neurofibromatosis type 1, Sturge-Weber syndrome, Lowe syndrome, ocular mesodermal dysplasias (Axenfeld or Rieger anomalies), homocystinuria, aniridia, or acquired glaucoma (rare).
• Glaucoma: Increased intraocular pressure.
• Proteus syndrome: Hamartomas involving mesodermal and ectodermal tissues throughout the body. Macrocrania with multiple skull protuberances, asymmetric limbs, large eye, strabismus, myopia, anisocoria, microphthalmos, cataracts, retinal detachment, chorioretinitis, nystagmus, and heterochromia of the irises.
• Collagen vascular disease: Marfan syndrome (superolateral dislocation of the lenses), homocystinuria (inferomedial dislocation of the lenses), Ehler-Danlos syndrome, and Weill-Marchesani syndrome.
• Staphyloma: Focal thinning of the sclera from infection or inflammation leads to focal enlargement. May be isolated or related to axial myopia. Patients have a high risk for advanced chorioretinal degeneration. Can also be seen with glaucoma, trauma, scleritis, and necrotizing infections.

References

Smith M, Castillo M. Imaging and differential diagnosis of the large eye. Radiographics. 1994 Jul;14(4):721-8.

Paranasal Sinus Calcification

• Fungal sinusitis: Usually Aspergillus. Central in the vast majority of patients with fungal sinusitis (compared to peripheral the vast majority of those with nonfungal sinusitis). Fine punctate calcifications (compared to round or eggshell calcifications in those with nonfungal sinusitis.
• Fungus ball:
• Osteoma:
• Fibrous dysplasia:
• Fracture:
• Inverted papilloma: Actually represent residual bone, not calcification.
• Olfactory neuroblastoma: Also known as esthesioneuroblastoma. Densities represent true calcifications.
• Osteosarcoma:
• Sinolith: Much less common than rinoliths and antroliths. Antroliths originate in the maxillary sinus, whereas sinoliths are found in the frontal and ethmoid sinuses. They are thought to be dystrophic calcification or ossification caused by chronic inflammation of the paranasal sinuses.

References

• Almasi M, Andrasovská M, Koval J. Sinolith in the ethmoid sinus: report of two cases and review of the literature. Eur Arch Otorhinolaryngol. 2010 Oct;267(10):1649-52.
• Som PM, Lidov M. The significance of sinonasal radiodensities: ossification, calcification, or residual bone? AJNR Am J Neuroradiol. 1994 May;15(5):917-22.
• Yoon JH, Na DG, Byun HS, Koh YH, Chung SK, Dong HJ. Calcification in chronic maxillary sinusitis: comparison of CT findings with histopathologic results. AJNR Am J Neuroradiol. 1999 Apr;20(4):571-4.

Glaucoma Drainage Implants on CT

Drainage implants are used for treatment of glaucoma refractory to medical and standard surgical therapy. The Baerveldt glaucoma drainage implant uses a barium-impregnated silicone plate (blue arrow) to increase echographic resolution and allow radiographic identification. The plate is curvilinear and conforms to the curvature of the globe. Aqueous humor is drained into a reservoir (pink arrow) and then absorbed by the adjacent periocular tissues. Radiographs (see reference for image and MRI compatibility) reveal a convex density along the superolateral aspect of the orbit.

References

Ceballos EM, Parrish RK 2nd. Plain film imaging of Baerveldt glaucoma drainage implants. AJNR Am J Neuroradiol. 2002 Jun-Jul;23(6):935-7.

Glomus Jugulare

Glomus jugulare are benign, slow-growing paragangliomas that can arise from 3 bodies around the jugular foramen: The jugular bulb, the tympanic branch of cranial nerve IX (Jacobsen nerve) and the auricular branch of cranial nerve X (Arnold nerve).

CT may reveal a "permeative-destructive" change of adjacent bone (green arrow). Contrast-enhanced CT images will reveal homogeneous intense enhancement (pink arrow). on MRI, the "salt and pepper" appearance on T1-weighted images is typical with the white dots of salt representing hemorrhage or slow flow in vessels and black dots of pepper representing high velocity flow voids from feeding arterial branches. T2-weighted images reveal a heterogeneously hyperintense mass with hypointense foci.

Important considerations include extension to adjacent spaces, most commonly the middle ear, which was clear in this case (yellow arrow). Signs of compression of the neural contents of the jugular foramen (cranial nerves IX, X, and XI) should also be sought. In this case, medial deviation of the left vocal fold (blue arrow) is due to mass effect on the vagus nerve. The left sternocleidomastoid muscle is a bit smaller than the right, possibly reflecting injury to the spinal accessory nerve.

Differential considerations for a jugular foramen mass include:

• Meningioma: Permeative-sclerotic pattern of the adjacent bone with an enhancing dural tail.
• Schwannoma: Relatively uncommon. Usually arise from cranial nerve 9. May cause smooth remodeling and enlargement of the jugular foramen.
• Metastases:

Arachnoid Web

Idiopathic syringomyelia is syringomyelia in the absence of abnormality detectable using standard diagnostic methods. Identifiable causes of syringomyelia include abnormalities at the level of the foramen magnum (e.g., Chiari malformation), spinal injury, previous spinal surgery, infection (e.g., discitis or meningitis), mass (extradural or intradural), disc herniation, or spinal deformity (e.g., tethered cord or myelomeningocele).

Arachnoid webs are now being recognized as a cause of "idiopathic" syringomyelia. Arachnoid webs are thought to be rare variants of arachnoid cysts and represent a focal web of arachnoid tissue obstructing the subarachnoid space. Various theories have been proposed for the mechanism of syrinx formation due to arachnoid webs and other obstructions, but none are really good enough to warrant committing to long-term memory.

Because arachnoid webs are usually not completely obstructive, they may be missed on CT myelography. Indirect CT myelographic and standard MRI findings include a relatively abrupt termination of a syrinx cavity and slight ventral displacement and slight change in caliber of the cord at the level of the termination of the syrinx. Heavily T2-weighted volumetric images in the sagittal plane, however, can show the actual web. CSF flow studies can also show the level of obstruction.

References

• Mauer UM, Freude G, Danz B, Kunz U. Cardiac-gated phase-contrast magnetic resonance imaging of cerebrospinal fluid flow in the diagnosis of idiopathic syringomyelia. Neurosurgery. 2008 Dec;63(6):1139-44.
• Sridharan A, Heilman CB. Transverse dorsal arachnoid web and syringomyelia: case report. Neurosurgery. 2009 Jul;65(1):E216-7.

Ureteral Fibroepithelial Polyp

Benign lesions of the ureter are rare, and ureteral fibroepithelial polyps comprise the most common of these benign tumors. They represent hyperplastic fibroconnective tissue with a vascular stroma and a urothelial lining.

Excretory urogram will usually reveal a a smooth, elongated, and cylindric filling defect surrounded by contrast that extends from 1 cm to 5 cm. A corkscrew appearance has also been described. The polyp may be mobile, except for its attachment site.

Differential considerations include radiolucent calculi, blood clots, sloughed papillae, fungus balls, malignant neoplasms, other benign lesions, parasitic infections (e.g., ascariasis), and foreign bodies.

Patients most commonly present with hematuria, but intermittent or recurrent pain may also be seen and are thought to be due to torsion or intussusception of the polyp or to intermittent obstruction.

References

Harvin HJ. Ureteral fibroepithelial polyp on MDCT urography. AJR Am J Roentgenol. 2006 Oct;187(4):W434-5.

Hippocampal Sulcus Remnant

Hippocampal sulcus remnants are cystic structures medial to the temporal horns of lateral ventricles between the cornu ammonis and the dentate gyrus. These are incidental findings that represent remnants of the vestigial primary embryonic hippocampal sulcus. They are found in about 40% of the population and have a higher incidence in older patients.

References

Sasaki M, Sone M, Ehara S, Tamakawa Y. Hippocampal sulcus remnant: potential cause of change in signal intensity in the hippocampus. Radiology. 1993 Sep;188(3):743-6.

Draped Aorta Sign

The draped aorta sign refers to the CT finding of the posterior margin of the aorta abutting and following the contour of the vertebral body. This is associated with a deficient posterior aortic wall and a contained leak. The draped aorta sign on CT scans represents an early stage in contained leaks when hemorrhage is contained anteriorly by the anterior renal fascia and the root of the dorsal mesenteny, but has started to pass posteriorly toward the psoas muscle.

References

Halliday KE, al-Kutoubi A. Draped aorta: CT sign of contained leak of aortic aneurysms. Radiology. 1996 Apr;199(1):41-3.

PHACE(S) Syndrome

PHACE(S) syndrome is an acronym for

• Posterior fossa malformations: Dandy-Walker malformation, ipsilateral cerebellar hypoplasia, and cerebellar vermian hypoplasia and cortical dysgenesis
• Hemangiomas: Large segmental or plaquelike hemangiomas of the scalp and face, most commonly along the trigeminal dermatome.
• Arterial anomalies: Persistent primitive fetal arteries (e.g., persistent trigeminal artery), agenesis of the internal carotid or vertebral arteries (more commonly ipsilateral to hemangiomas), anomalous branches of the internal carotid artery, cerebral aneurysms, and intracranial internal carotid artery and central branch stenoses.
• Cardiac defects: Coarctation of the aorta, ventricular septal defects, and patent ductus arteriosus.
• Eye abnormalities:
• Sternal clefting: Less common feature.

References

Church DG, Lowe LH. Case 103: PHACE syndrome. Radiology. 2006 Dec;241(3):939-42.