Cramps and small‐fiber neuropathy

: Muscle cramps are a common complaint and are thought to arise from spontaneous discharges of the motor nerve terminal. Polyneuropathy is often causative, but small‐fiber neuropathy ( SFN ) has not been assessed. Methods : We performed skin biopsies on consecutive patients with cramps but without neuropathic complaints. Twelve patients were biopsied, 8 with normal small‐fiber sensation. Results : Seven patients had decreased intraepidermal nerve fiber density ( IENFD ), 2 with non–length‐dependent loss. A cause for neuropathy was found in 1 patient with cramp–fasciculation syndrome. Creatine kinase was elevated in 8 patients, 4 with decreased IENFD . Muscle biopsy, performed in 8 patients, but was diagnostic in only 1, with McArdle disease. Conclusions : Our data show that 60% of patients with muscle cramps who lack neuropathic complaints have SFN, as documented by decreased IENFD . Cramps may originate as local mediators of inflammation released by damaged small nerve that excite intramuscular nerves. Muscle Nerve , 48: 252–255, 2013