neurosarcoidosis

Neurosarcoidosis refers to neurological involvement caused by sarcoidosis, a multisystem granulomatous disease of unknown origin characterized by noncaseating granulomas in affected tissues. It occurs in a minority of patients with sarcoidosis and can affect the central nervous system, peripheral nerves, or both.

The disease can involve the brain, spinal cord, meninges, or nerve roots (central nervous system and peripheral nervous system). Parenchymal brain lesions, meningeal disease, hypothalamic or pituitary involvement, and cranial neuropathies are common patterns. Peripheral neuropathy and myopathy may also occur. The clinical presentation is heterogeneous and can include headaches, cognitive or behavioral changes, seizures, focal neurologic deficits, cranial nerve palsies (often the facial nerve), optic neuritis, and signs of myelopathy.

Diagnosis relies on a combination of clinical features, imaging, laboratory tests, and tissue diagnosis. MRI often shows leptomeningeal enhancement, parenchymal lesions, or pituitary involvement. Cerebrospinal fluid typically reveals mild to moderate lymphocytic pleocytosis, elevated protein, and sometimes low glucose. Serum and cerebrospinal fluid angiotensin-converting enzyme (ACE) levels may be elevated but are not specific. A definitive diagnosis frequently requires histologic evidence of noncaseating granulomas, usually from a biopsy of accessible extraneural tissue (lung, lymph node, skin, or conjunctiva) or, less commonly, CNS tissue when safely obtainable. Other conditions that mimic neurosarcoidosis, such as infections or neoplasms, must be excluded.

Treatment is centered on immunosuppression. First-line therapy is corticosteroids, with long-term maintenance in many cases. Additional immunosuppressants (e.g., methotrexate, azathioprine, mycophenolate) or biologics (e.g., TNF inhibitors) are used for refractory disease. Management may include treatment of complications such as hydrocephalus. Prognosis is variable; many patients respond to therapy, but relapse and chronic disability can occur.