Neurosarcoidosis

Presentation may be with cranial nerve deficits from a basal meningitis, the most common being neuropathies that affect cranial nerves (CNs) VII, V, VIII, and II. Facial nerve (CN VII) involvement may be unilateral or bilateral; when bilateral, it may occur simultaneously or sequentially on the two sides. Endocrine disturbances from hypothalamic-pituitary involvement may manifest as hypothyroidism, hypogonadism, hypoadrenalism, or hypopituitarism; diabetes insipidus sometimes occurs. An intraparenchymal lesion may lead to seizures; masquerade as a cerebral tumor, producing focal deficits and increased intracranial pressure; lead to a nonspecific encephalopathy; cause obstructive hydrocephalus; or result in a myelopathy or myeloradiculopathy if the spinal cord is affected. Neurosarcoid may affect the peripheral nervous system, causing a simple or multiple mononeuropathy or a polyneuropathy. A myopathy has also been described.

The diagnosis is established with certainty only by histopathologic examination of a biopsy specimen. All patients with suspected neurosarcoidosis require evaluation for extraneural involvement that may serve as a site for biopsy. An elevated serum angiotensin-converting enzyme (ACE) may be helpful for diagnosis but is not specific, and normal findings do not exclude the diagnosis. Cerebrospinal fluid is often abnormal and may simulate an infective process, with an increased cell count (usually a mononuclear pleocytosis) and elevated protein concentration; glucose level is normal or reduced. The immunoglobulin G (IgG) index may be increased, and oligoclonal bands may be present. The cerebrospinal fluid (CSF) ACE level is sometimes elevated, a suggestive but nonspecific finding. Chest radiographs or computed tomography (CT) scans often reveal hilar adenopathy and allow for mediastinal lymph node biopsy. Cranial CT or magnetic resonance imaging (MRI) may document the site and extent of neurologic involvement and also identify a site for biopsy, if diagnostic uncertainty persists or the response to therapy is poor.

Controlled treatment trials are not available to guide therapy, but treatment with corticosteroids is the generally accepted approach. The duration of treatment is determined individually depending on disease location, severity, and response to therapy. Other immunomodulatory approaches have also been used in patients who fail or are unable to tolerate corticosteroids. In only rare instances is resection of a mass lesion necessary, although placement of a ventricular drain may be important in patients with hydrocephalus. Endocrinologic abnormalities require correction.

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