TREATMENT OF OCCUPATIONAL CRAMP WITH BOTULINUM TOXIN - DIFFUSION OF TOXIN TO ADJACENT NONINJECTED MUSCLES

Over a 5-year period, 40 patients, 11 with musician's and 29 with writ er's cramp, were treated with botulinum toxin A using a precise inject ion technique in which the hollow-bore electromyography (EMG) needle w as positioned by both standard EMG and by muscle twitch evoked by stim ulating current passed through it. Moderate to complete improvement in dystonia occurred in 28 patients (70%) after the first injection and in 34 patients (85%) after the second injection with better outcome in nonmusicians than in musicians. Of note, weakness of uninjected muscl es, immediately adjacent to those injected, was found in 25/40 patient s (63%). The most common patterns of toxin spread were from flexor dig itorum sublimis to profundus, extensor carpi radialis to extensor digi torum communis, and extensor indicis proprius to extensor pollicis bre vis. Spread to, and weakness of, adjacent uninjected muscles was a maj or factor contributing to suboptimal outcome in 6/39 (15%) such patien ts. (C) 1997 John Wiley & Sons, Inc.