Article

Botulinum toxin injections ameliorate dystonic symptoms by blocking the
neuromuscular junction and weakening dystonic contractions. We asked if botulinum
toxin injections in dystonia patients might also affect the integrity of
sensorimotor cortical plasticity, one of the key pathophysiological features of
dystonia. We applied a paired associative stimulation protocol, known to induce
long-term potentiation-like changes in the primary motor cortex hand area to 12
patients with cervical dystonia before and 1 and 3 months after botulinum toxin
injections to the neck muscles. Primary motor cortex excitability was probed by
measuring transcranial magnetic stimulation-evoked motor evoked potentials before
and after paired associative stimulation. We also measured the input-output
curve, short-interval intracortical inhibition, intracortical facilitation, short
afferent inhibition, and long afferent inhibition in hand muscles and the
clinical severity of dystonia. Before botulinum toxin injections, paired
associative stimulation significantly facilitated motor evoked potentials in hand
muscles. One month after injections, this effect was abolished, with partial
recovery after 3 months. There were significant positive correlations between the
facilitation produced by paired associative stimulation and (1) the time elapsed
since botulinum toxin injections and (2) the clinical dystonia score. One effect
of botulinum toxin injection treatment is to modulate afferent input from the
neck. We propose that subsequent reorganization of the motor cortex
representation of hand muscles may explain the effect of botulinum toxin on motor
cortical plasticity. (c) 2011 Movement Disorder Society.
CI - Copyright (c) 2011 Movement Disorder Society.

Langue : ANGLAIS

Tiré à part : OUI