Remote effects of chronic botulinum toxin treatment: electrophysiologic results Do not indicate subclinical remodelling of noninjected muscles.

This study investigates the remote effects of botulinum toxin injections by examining the motor unit architecture of noninjected distant muscles. In 21 dystonia patients treated with botulinum toxin (n = 11, mean cumulative dose = 815 mU; n = 10, mean cumulative dose = 7,207 mU) and 10 control individuals, a blinded single-fiber electromyography of the vastus lateralis muscle was performed. The main outcome measure was fiber density (FD), thus measuring the effect of different cumulative doses on remote reinnervation. FD was normal in all patients treated with botulinum toxin. FD did not differ between the three groups studied. No relationship was found between FD and cumulative dose. Therefore, in this specific patient population, muscles remote to the site of injection showed no FD change months after the injection. We conclude that there was no evidence of remote reinnervation and remodelling of motor units with cumulative chemodenervation. Copyright 2000 S. Karger AG, Basel.