Description, Causes and Risk Factors:
A granulomatous disease of unknown etiology involving the central nervous system [CNS], usually with concomitant systemic involvement.
Neurosarcoidosis generally occurs only in cases of sarcoidosis with substantial systemic involvement, and signs of neurologic involvement usually are seen in patients known to have active disease. Strictly neurologic forms are seen in fewer than 10% of patients; a subset has predominantly neuromuscular involvement.
Neurosarcoidosis occurs in approximately 5% of patients with sarcoidosis, and approximately half the patients with neurosarcoidosis present with neurologic difficulties when sarcoidosis is first diagnosed. Peripheral neuropathy is seen in 5-15% of those with neurosarcoidosis. In a series from Johns Hopkins University, 2 of 33 patients with neurosarcoidosis had peripheral neuropathy; of this population, 85% was African American and 15% was white. Pediatric neurosarcoidosis is rarely reported.
Definitive diagnosis of neurosarcoidosis requires the exclusion of other causes of neuropathy and the identification of noncaseating sarcoid granulomas by histologic analysis of nerve and muscle biopsy specimens. Neurosarcoidosis is also seen in the Puerto Rican population, reaching prevalence as high as 175 cases per 10000 population in one retrospective study.
Neurosarcoidosis has no known cure. Spontaneous remission has been observed, but long-term therapy often is required. Immunosuppression is the principal method of controlling the disease, and corticosteroids are the cornerstone of therapy.
The prognosis for patients with neurosarcoidosis varies. Approximately two-thirds of those with the condition will recover completely; the remainder will have a chronically progressing or on-and-off course of illness. Complications resulting from immunosuppressive treatments, such as cryptococcal and tuberculous meningitis, progressive multifocal leukoencephalopathy, and inclusion body myositis, may be fatal for a small percentage of individuals.
Symptoms of cranial neurosarcoidosis are varied and commonly include headache, ataxia, visual disturbances, fatigue, nausea and vomiting. Others include weakness, sensory disturbances, seizures, cognitive dysfunction, eye pain, depression, aphasia, and tremor. The combination of symptoms present in an individual depends on the localization of the inflammatory process.
The diagnosis of neurosarcoidosis often is difficult. Definitive diagnosis can only be made by biopsy (surgically removing a tissue sample). Because of the risks associated with brain biopsies, they are avoided as much as possible. Other investigations that may be performed in any of the symptoms mentioned above are computed tomography (CT) or magnetic resonance imaging (MRI) of the brain, lumbar puncture, electroencephalography (EEG) and evoked potential (EP) studies. If the diagnosis of sarcoidosis is suspected, typical X-ray or CT appearances of the chest may make the diagnosis more likely; elevations in angiotensin-converting enzyme and calcium in the blood, too, make sarcoidosis more likely. In the past, the Kveim test was used to diagnose sarcoidosis. This now obsolete test had a high (85%) sensitivity, but required spleen tissue of a known sarcoidosis patient, an extract of which was injected into the skin of a suspected case.
Only biopsy of suspicious lesions in the brain or elsewhere is considered useful for a definitive diagnosis of neurosarcoid. This would demonstrate granulomas (collections of inflammatory cells) rich in epithelioid cells and surrounded by other immune system cells (e.g. plasma cells, mast cells). Biopsy may be performed to distinguish mass lesions from tumors (e.g. gliomas).
MRI with gadolinium enhancement is the most useful neuroimaging test. This may show enhancement of the pia mater or white matter lesions that may resemble the lesions seen in multiple sclerosis.
Lumbar puncture may demonstrate raised protein level, pleocytosis (i.e. increased presence of both lymphocytes and neutrophil granulocytes) and oligoclonal bands. Various other tests (e.g. ACE level in CSF) have little added value.
A lumbar puncture may show signs of inflammation. Increased levels of angiotensin-converting enzyme may be found in the blood or cerebrospinal fluid (CSF). However, this is not a reliable diagnostic test.MRI of the brain may be helpful. A chest x-ray often reveals signs of the sarcoidosis of the lungs. Nerve biopsy of affected nerve tissue confirms the disorder.
There is no agreed upon standard of treatment for neurosarcoidosis. Doctors generally recommend corticosteroid therapy as first-line therapy for individuals with the condition. Additional treatment with immunomodulatory drugs such as hydroxychloroquine, pentoxifylline, thalidomide, and infliximab, and immunosuppressive drugs such as methotrexate, azathioprine, cyclosporin, and cyclophosphamide, have benefited some individuals. While the use of corticosteroids and other immunosuppressive drugs is effective, these medications also have undesirable side effects. Side effects and experience with certain drugs may play a role in medication choices.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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