Sarcoidosis
Findings:
Coronal and axial postcontrast T1WI show thickened irregular enhancing meninges over the cerebral convexities with some extent into the interhemispheric region.

Differential Diagnosis:
This pattern has a wide differential diagnosis, including infection, mets/carcinomatosis, intracranial hypotension, idiopathic, and sarcoidosis among others. TB would be unlikely since the basilar meninges are spared.

Discussion:
The CNS is affected in a minority of sarcoidosis, with up to 15% noted at autopsy. Less than 3% of neurosarcoidosis occurs without systemic manifestations, and up to 50% may be subclinical. Symptoms depend on location of involvement, but seizures are rare and should suggest an alternate diagnosis. Sarcoidosis has numerous CNS manifestations, including leptomeningeal disease, WM disease that simulates MS, hypophysitis, hydrocephalus, cranial nerve enhancement, vasculitis, and even enhancing parenchymal masses. The most common manifestation is hydrocephalus due to arachnoiditis. Leptomeninges are commonly involved, with dura involved less frequently.

reference: Osborn, A; Tong, K. Handbook of Neuroradiology: Brain and Skull 2nd edition.1996: Mosby-Year Book Inc. pp.476-477, 590.

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