Neurosarcoidosis: a review of its intracranial manifestation

Sarcoidosis is a multisystem disease of unknown cause and with a worldwide distribution. Involvement of the central nervous system occurs in a relatively small number of patients with sarcoidosis. Isolated neurosarcoidosis without signs of systemic disease is a rarity. Because of its non-specific clinical presentation and neuroradiological imaging characteristics, intracranial neurosarcoidosis remains a very difficult diagnosis, particularly in the absence of systemic signs of the disease. Intracranial neurosarcoidosis has a predilection for the basal leptomeninges commonly affecting the cranial nerves, but any part of the brain may be involved, resulting in a wide spectrum of clinical syndromes. Cranial nerve involvement is the most common single symptom. Intracranial sarcoid manifests as nodular or diffuse leptomeningeal thickening and extraor intra-axial parenchymatous lesions. Intracranial sarcoid may mimic various forms of meningitis, including carcinomatous and intracranial mass lesions such as meningioma, lymphoma and glioma, based on neuroradiological imaging. Magnetic resonance imaging is a very sensitive diagnostic tool for detecting intracranial abnormalities due to neurosarcoidosis. Lumbar puncture is useful in ruling out other neurological disorders, in particular infectious, but cerebrospinal fluid findings are not specific. Angiotensin-converting enzyme in serum and cerebrospinal fluid may be increased, decreased or normal. Therapy consists of immunosuppressive agents and should be initiated with corticosteroids. Other immunosuppressive drugs should be added in severe cases or after frequent recurrences. We review here all aspects of intracranial neurosarcoidosis from the clinical point of view, with special emphasis on presentation, diagnostic procedures, differential diagnostic considerations and treatment.