Remote F-wave changes after local botulinum toxin application.
OBJECTIVE
Although the therapeutic effects of botulinum toxin A can be explained by its action at the neuromuscular junction, central or more proximal effects have also been discussed.


METHODS
Eleven patients with torticollis spasmodicus and 3 patients with writer's cramp were studied before and 1 and 5 weeks after the first treatment with botulinum toxin. We measured compound muscle action potentials (CMAPs), motor conduction velocities (MCVs), the shortest (SFL) and the mean F-wave latencies (MFL) and F-wave persistence (30 trials) of untreated muscles for each side (ulnar nerve-abductor digiti minimi muscle, peroneal nerve-tibialis anterior muscle).


RESULTS
CMAPs and MCVs showed no significant changes. For both nerves, however, SFL and MFL were prolonged slightly 1 week after treatment and returned to about baseline after 5 weeks (t test). The F-wave persistence was reduced 1 week after treatment for the right ulnar and both peroneal nerves (t test).


CONCLUSIONS
These results are not likely due to an impairment of neuromuscular transmission. Instead, we propose a decreased excitability of alpha-motoneurons supplying non-treated muscles. A reduction of muscle spindle activity or changes of the recurrent inhibition are discussed as possible causes.
Department of Neurology, Medical University, Hannover, Germany. kwohlf@umich.edu
K
K
Wohlfarth
M
M
Schubert
B
B
Rothe
J
J
Elek
R
R
Dengler
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage / Q000627:therapeutic use*; D020821:Dystonic Disorders / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D010543:Peroneal Nerve / Q000503:physiopathology; D013997:Time Factors; D014103:Torticollis / Q000188:drug therapy* / Q000503:physiopathology; D014459:Ulnar Nerve / Q000503:physiopathology
D019274:Botulinum Toxins, Type A