Effects of botulinum toxin on motor system excitability in patients with writer's cramp.
OBJECTIVE
To investigate botulinum toxin (BTX) effects on central and peripheral motor excitability in writer's cramp.


METHODS
Using transcranial magnetic stimulation over the motor cortex and brainstem and peripheral electrical stimulation, the authors investigated measures of motor cortical and peripheral motor excitability on the affected and unaffected side before and 2 to 4 weeks after BTX A injection into the affected muscles in six patients with writer's cramp. The following motor excitability measures were studied: resting and active motor threshold, cortical silent period, intracortical inhibition and facilitation using the double-pulse technique, recruitment curves, motor evoked potentials following magnetic brainstem stimulation, and maximum M-response amplitude following supramaximal peripheral nerve stimulation.


RESULTS
BTX injection improved function and reduced the M response. No other measures of motor system excitability showed significant changes following BTX injection, and there was no difference in these measures between sides.


CONCLUSIONS
BTX A effects on motor system excitability seem to be based mainly on its peripheral mechanisms of action. There was no difference in the motor system excitability between the clinically affected and unaffected sides in this group of patients.
Boroojerdi
Babak
B
Neurologische Klinik, Universitätsklinikum, Aachen, Germany. bboroojerdi@ukaachen.de
Cohen
Leonardo G
LG
Hallett
Mark
M
D000328:Adult; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D001933:Brain Stem / Q000187:drug effects / Q000503:physiopathology; D020821:Dystonic Disorders / Q000503:physiopathology*; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000187:drug effects* / Q000503:physiopathology; D009465:Neuromuscular Agents / Q000494:pharmacology*; D017933:Peripheral Nervous System / Q000187:drug effects* / Q000503:physiopathology
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A