Remote Effects of Chronic Botulinum Toxin Treatment: Electrophysiologic Results Do Not Indicate Subclinical Remodelling of Noninjected Muscles

Abstract

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.

Botulinum Toxin for Lower Limb Spasticity in Children with Cerebral Palsy

“…Dutton 29 reported that patients receiving 200 units or more for torticollis have abnormal neuromuscular transmission in muscles as distant as the anterior tibialis muscle. However, Fertl et al 30 investigated the remote effects of botulinum toxin by examining the motor unit architecture of the vastus lateralis muscle. The electrophysiologic results did not indicate subclinical remodeling of noninjected muscles.…”

Botulinum toxin A during pregnancy: a survey of treating physicians

“…15 Another study using single fibre EMG indicated that there was no evidence of remote re-innervation or subclinical remodelling of motor units in the vastus lateralis muscles of patients treated with btxA. 16 The methodological limitations of our study are those that are inherent to questionnaire/survey studies. Firstly, there could be sample selection bias, as the sample of physicians we surveyed was identified by their use of commercially available btxA, and perhaps some end users in a group practice were not identified to participate.…”

Abnormal surface EMG during clinically normal wrist movement in cervical dystonia

“…comm.]. In contrast, other studies demonstrate that there is no (distant) leg muscle atrophy [20] or subclinical muscle weakness [21]. In addition, it has been reported that BTX treatment in CD may even normalize the displaced topography of corticomotor projection of the (clinically non-dystonic) abductor pollicis brevis muscle [12].…”