RETURN TO ABSTRACT LISTING


Background
Sarcoidosis is an idiopathic, systemic granulomatous disease of unknown origin, characterized by the presence of noncaseating granulomas in affected organs. It can affect all organ systems of the body. Pulmonary and lymph node involvement is most common. Extra-pulmonary sarcoidosis has been found in 30% of patients with the disease. Central nervous system (CNS) involvement is reported in 25% of cases at autopsy in patients with systemic sarcoidosis. Only 3 - 5% patients have symptomatic CNS disease. Facial nerve palsy is the most common presentation. Other symptoms include headache, seizure, and signs of meningeal irritation. Diagnosis of neurosarcoidosis is evaluated as definite, probable, and possible. The disease is graded as ‘definite’ when detected on histological specimens. It is labelled as probable when laboratory tests are positive for CNS inflammation (elevated levels of cerebrospinal fluid protein or MRI features compatible with neurosarcoidosis; detection of systemic sarcoidosis (positive histology and/or least two indirect indicators from gallium scan, chest imaging and serum angiotensin-converting enzyme); the disease is considered possible when previous criteria are not satisfied.

Educational Goals / Teaching Points
This educational exhibit reviews the epidemiology, clinical features and imaging spectrum of neurosarcoidosis on MRI and the differential diagnosis that should be considered. It is important to recognize and be familiar with imaging manifestations of neurosarcoidosis as accurate imaging diagnosis minimizes additional invasive testing.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The disease shows a special predilection for the basal cisterns of the brain; cranial nerve involvement is frequent, influencing the clinical manifestation of disease. Spectrum of findings in Neurosarcoidosis include leptomeningeal involvement, perivascular involvement, cavernous sinus involvement, cranial nerve involvement, sellar/suprasellar involvement, periventricular involvement, hydrocephalus, dural involvement, vascular involvement with ischemic lesions, lacrimal and parotid gland enlargement, osseous involvement, intraspinal medullary and nerve root involvement. Leptomeningeal involvement is the most common imaging presentation seen in about 40% patients. Spinal sarcoidosis is reported in about 4 – 28 % of cases; and has a poor prognosis and occurs predominantly in old patients.

Conclusion
The imaging features of neurosarcoidosis mimics various benign and malignant entities. MRI is highly sensitive for diagnosis of neurosarcoidosis, but not specific. Hence, neurosarcoidosis is a diagnosis of exclusion using combination of clinical features, imaging findings, diagnostic testing and tissue sampling. Imaging plays a key role in assessing treatment response and surveillance of new lesions.