April 30, 2011

Anaplastic Astrocytoma

Axial T2W (fig. 1) and T1W post contrast (fig. 2) images of the brain demonstrate a large ill-defined mass (arrows) centered in the right insula with extension to the frontal and temporal lobes. The mass shows a heterogeneous high T2 signal intensity, cystic areas (arrowheads), mass effect and minimal enhancement.

Facts: WHO grading system for primary astrocytic tumor and imaging features
  • Grade I = circumscribed glioma including pilocytic astrocytoma -- no mass effect, no enhancement
  • Grade II = diffuse astrocytoma (cytological atypia alone) -- mass effect, no enhancement
  • Grade III = anaplastic astrocytoma (anaplasia and mitotic activity) -- complex enhancement
  • Grade IV = glioblastoma (also show microvascular proliferation) -- necrosis (ring enhancement)
  • Imaging grading is imprecise but can be used as a preliminary assessment
  • Grading is not applicable to pediatric patients or special astrocytomas
  • Low grade gliomas usually hypodense on CT, hypointense on T1WI and hyperintense on T2WI. High T2 signal intensity commonly extends beyond the tumor volume. Most do not enhance.
  • Anaplastic gliomas may or may not enhance. Calcifications and cysts occur in 10-20%.
  • Glioblastomas usually enhance on the rim, representing cellular tumor but tumor cells often extend beyond 1.5 cm of the enhanced ring. Nonenhancing center may represent necrosis or associated cyst.
  • On imaging, factors affecting prognosis are location (eloquent vs. non-eloquent) and tumor size
Our case: anaplastic astrocytoma.

Greenburg MS. Handbook of neurosurgery, 7th edition, 2010.

April 25, 2011


Bulleted ListFrontal radiograph of the hand demonstrates widening of the terminal tufts (between long arrows), bases of the distal phalanges, thickening of the digit soft tissues (between arrowheads) and widening of the metacarpophalangeal joints (between short arrows).

Facts: Acromegaly
  • Acromegaly = large extremities
  • Syndrome caused by hypersecretion of growth hormone (GH) secondary to pituitary adenoma, or hyperplasia.
  • GH hypersecretion leads to different skeletal manifestations depending on patient's age.
  • In mature skeleton (like in our patient), there is increased bone width and soft tissue enlargement particularly in the acral parts of the skeleton.
  • Complication: secondary osteoarthritis
  • Soft tissues: thickening of the digits, enthesopathy
  • Bones: bone enlargement, squaring of phalanges and metacarpals, spade-like terminal tufts
  • Joints: widening of joint spaces due to thickening of articular cartilage
Guglielmi G, Van Kuijk C, Genant HK. Fundamentals of hand and wrist imaging. Springer-Verlag 2001.

April 20, 2011

Swyer-James Syndrome

A frontal chest radiograph of a 56-year-old man demonstrates a unilateral left hyperlucent lung with a normal lung volume.

An axial inspiratory and expiratory (not shown) chest CT shows evidence of air trapping of the left lung parenchyma, parts of the right lung and cystic bronchiectases. Note small pulmonary arteries in the areas of air trapping.

Facts: Swyer-James Syndrome
  • Original description on x-ray: unilateral small lung with hyperlucency and air trapping
  • Typically a result of viral respiratory infection in infancy or childhood (it is a post-infectious form of bronchiolitis obliterans)
  • Diagnosis based on radiologic and clinical findings rather than pathologic examination. If pathologic examination is performed, there are bronchiolitis obliterans with various degrees of chronic inflammation, fibrosis and dilatation of airways and air spaces distal to the obstructed bronchioles.
  • Clinicians need to exclude other causes of air trapping such as obstructing tumor or foreign body
  • X-ray: unilateral hyperlucent lung, or bilateral asymmetric hyperlucency of the lungs. Lung volumes are usually decreased on the site of lucency, but can be normal or increased
  • CT: air trapping usually more extensive than on x-ray, and usually bilateral. May or may not have bronchiectasis
  • It is important to look for causes of air trapping on CT such as obstructing tumor or foreign body, as it may obviate the need for bronchoscopy
Moore ADA, Godwin JD, Dietrich PA, et al. Swyer-James syndrome: CT findings in eight patients. AJR 1992; 158:1211-1215.

April 15, 2011

Gastric Diverticulum

Fig. 1: Axial contrast-enhanced T1W MR image shows a mass (arrows) in the gastrohepatic ligament with internal low signal intensity, incidentally seen on the study performed for other reason in a young male.

Fig. 2: A coronal-reformatted CT image shows that the mass is filled with air and oral contrast material with a narrow communication (arrows) with the gastric lesser curvature.

Facts: Gastric Diverticulum
  • Incidence: 0.02% in autopsy studies, 0.04% on upper GI studies
  • True diverticula have complete wall, believed to be congenital. False diverticula are either traction or pulsion, and associated with inflammation or other diseases
  • True diverticula commonly arises from the posterior wall of the cardia, 2 cm below the EG junction or 3 cm from the lesser curvature.
  • Most are asymptomatic but they may cause epigastric pain, dysphagia, belching, bloating and early satiety.
  • Rare complications: bleeding, diverticulitis, perforation and cancer
  • Thin-walled, air-containing outpouching from the stomach. May contain fluid or gastric content
  • Size 1-5 cm, mostly less than 4 cm
  • If it is filled only with fluid, it can be difficult to differentiate from cystic tumor on cross-sectional imaging.
1. McKay R. Laparoscopic resection of a gastric diverticulum: a case report. JSLS 2005; 9:225-228.
2. Coakley F. Pearls and pitfalls in abdominal imaging: pseudotumors, variants and other difficult diagnoses. Cambridge University Press, 2010.

April 10, 2011

Hangman's Fracture

A lateral cervical spine radiograph shows grade I anterolisthesis of C2 on C3 (arrow) with fractures of the C2 pars interarticulares (arrowheads).

  • Traumatic spondylolisthesis of C2
  • Combination of soft tissue and bony injuries believed to start from anterior longitudinal ligament (ALL) tear, avulsion of C2/3 disc from either inferior or superior endplate - then bony malignment and posterior element fractures.
  • Posterior element fractures are often extra-articular, involving the pars interarticulares (pedicles)
  • Named "hangman" because of mechanism of injuries mimic that of hanging (neck hyperextension with compression of posterior elements)
  • Displaced fractures often are associated with neurologic injuries (apnea, complete paralysis, sensory loss distal to lesion)
Mandavia DP, Newton EJ, Demetriades D. Color Atlas of Emergency Trauma, 2003.

April 5, 2011

The Fat Pad Sign

A lateral radiograph of the elbow shows a posterior fat pad sign (arrows) and elevation of the anterior fat pad (arrowheads) in a patient with a radial neck fracture (seen anteriorly on this image).

  • Normal: elbow fat pads are intracapsular but extrasynovial, they are visible anteriorly to the elbow joint but not posteriorly.
  • Effusion: elevation of both anterior and posterior fat pads are seen on lateral x-ray
  • In an acute injury to the elbow, elevated posterior fat pad suggests the possibility of an intracapsular fracture
  • Most common causes in children are supracondylar fracture, lateral epicondyle and separation of medial epicondylar ossification center
  • Most common causes in adults are radial head or neck fractures, olecranon fractures, dislocations and fracture/dislocations
  • Value of the posterior fat pad sign depends on its ability to predict an occult fracture in the absence of a radiographically visible fracture
  • False-negative fat pad sign may occur if there is poor radiographic positioning, extracapsular abnormality or capsular rupture
  • False-positive fat pad sign can be seen when the elbow is extended
1. Goswami GK. The fat pad sign. Radiology 2002;222:419-420.
2. Skaggs DL, Mirzayan R. The posterior fat pad sign in association with occult fracture of the elbow in children. J Bone J Surg 1999;81:1429-1433.