Diagnosis

Neurosarcoid

Findings

T2 as well as post contrast T1 weighted images are provided for review. Images reveal an enhancing mass that is centered along the floor of the left middle cranial fossa. There is extension into the pterygopalatine fissure, orbital apex, as well as the infratemporal and anterior cranial fossae. The mass is of low signal intensity on T2 weighted images and there is surrounding mass effect.

Discussion

CNS sarcoid occurs in approximately 1-8% of people with known sarcoidosis, although the number has been shown to be as high as 15% at autopsy. Primary CNS involvement is rare. As in other areas, this is an inflammatory disorder characterized by non caseating granulomas. Most often, the appearance is that of diffuse meningeal enhancement, but can also cause meningeal nodules or as a single intracerebral mass. (as in this case) The meninges and cranial nerves are affected much more commonly than the brain. Classic MRI findings include isointensity to gray matter on T1, hypointensity on T2 (the result of hypercellularity) and homogenous enhancement pattern.. Differential diagnosis in this case may include: metastases, lymphoma, meningioma and sarcoid. The most common clinical findings in patients with neurosarcoid include: 1. Cranial neuropathy secondary to granulomatous infiltration & leptomeningeal fibrosis (50-75%) 2. Aseptic meningitis (20%) 3. Pituitary and hypothalamic dysfunction (5-10%)

1) Osborn. Diagnostic Neuroradiology. Mosby, Baltimore, 1994. p 377. 2) Dahnert. Radiology Review Manual, 3rd ed. Williams & Wilkins, Baltimore, 1996. p 239.