Benign Fasciculation Syndrome as a Manifestation of Small Fiber Neuropathy (P01.139)

Abstract

OBJECTIVE: To determine whether patients with Benign Fasciculation Syndrome (BFS) have a small fiber neuropathy.

BACKGROUND: BFS is characterized by widespread involuntary muscle activity consisting of muscle twitching or fasciculations. The cause is unknown and no anatomical or physiologic lesions have been identified to date.

DESIGN/METHODS: We searched the computerized medical records registry at the Weill Cornell Peripheral Neuropathy Center for patients presenting with fasciculations who underwent skin biopsies for small fiber neuropathy and who, on further evaluation, had no weakness or pathological reflexes, normal EMG and nerve conduction studies without evidence for denervation, and normal blood tests for known causes of neuropathy.

RESULTS: Fourteen patients (10 men, 4 women) were identified with an average age=40.7 (range: 29-60) and average symptom duration=2.2 years (range: 1 month-6 years). Thirteen had skin biopsies at the calf and thigh, and one at the foot and thigh. Epidermal nerve fiber density (ENFD) was determined in all 14 patients, and sweat gland nerve fiber density (SGNFD) in 11. In 4 of the 14 patients (36%), the ENFD was significantly decreased in the calf, with a mean value of 4.8 fibers/mm (nl > 5.4), and normal at the thigh, and in 10 the ENFD was normal at both biopsy sites. Six of 11 patients tested (54%), had significantly decreased SGNFD; 2 at both the calf and thigh, 2 at the calf only, 1 at the thigh only, and 1 at the foot. The mean values of the abnormal SGNFD were 25.4 (nl > 37.8) at the thigh, 25.9 (nl >36.5) at the calf, and 26.9 (nl > 34.8) at the foot.

CONCLUSIONS: Many patients with BFS exhibit a significant decrease in SGNFD or ENFD, with the SGNFD preferentially affected. Small fiber neuropathy should be investigated as a potential cause or contributing factor to BFS.

Disclosure: Dr. Tzatha has nothing to disclose. Dr. Langsdorf has nothing to disclose. Dr. Carey has nothing to disclose. Dr. Chin has received personal compensation for activities with Grifols Bioscience.