How is peripheral neuropathy in neurosarcoidosis diagnosed?

Updated: Nov 13, 2018
  • Author: Gabriel Bucurescu, MD, MS; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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The diagnosis of peripheral neuropathy as a result of sarcoidosis is determined by establishing, in the first instance, the presence of a peripheral neuropathy; excluding the common causes of peripheral neuropathy, such as hyperglycemic states, deficiencies of vitamins, and presence of toxins such as heavy metals; and establishing a pathologic diagnosis of noncaseating granulomas in neural or extraneural sites.

Findings of cerebrospinal fluid analysis are normal in 30% of cases, specifically in patients with cranial nerve and peripheral nerve involvement. When CSF analysis findings are abnormal, they reflect a nonspecific pattern. Serial CSF analyses may be necessary in some cases.

On skin testing, cutaneous anergy can be seen in systemic or active pulmonary sarcoidosis. However, it almost never occurs in pure neurosarcoidosis.

Small-fiber neuropathy may be evaluated by thermal threshold testing (TTT). On the other hand, sympathetic skin responses and cardiac autonomic testing (by Ewing test and iodine-123 meta-iodobenzylguanidine [123 I-MIBG] myocardial scanning) have been reported to have limited diagnostic value for evaluation of small- fiber neuropathy.

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