Contralateral weakness following botulinum toxin for poststroke spasticity.
BACKGROUND
We describe 2 patients who received botulinum toxin A (BoNT) for poststroke spasticity and developed contralateral limb weakness.


METHODS
Both patients received high doses of BoNT with large dilution volumes and injection in the proximal upper extremity muscles, and developed weakness of the contralateral upper limb. These patients then underwent electrodiagnostic testing of the affected limb.


RESULTS
Repetitive nerve stimulation of the axillary and spinal accessory nerves revealed decrements of 23% and 16%, respectively. EMG revealed abnormal spontaneous activity and small polyphasic motor unit potentials with reduced recruitment. These findings indicated blockade of the neuromuscular junction. Both patients improved.


CONCLUSIONS
Isolated weakness of the contralateral limb after BoNT injection for poststroke spasticity suggests diffusion of toxin through tissue planes from proximal upper extremity muscles, across the midline, to contralateral muscles. High doses of botulinum toxin, high dilution volumes, and injection of proximal upper extremity muscles appear to be risk factors for this adverse effect.
Clinical Neurophysiology Laboratory, Department of Neurology, Mount Sinai Medical Center, One Gustave Levy Place, Box 1052, New York, New York 10029, USA.
Anila M
AM
Thomas
David M
DM
Simpson
D000328:Adult; D019274:Botulinum Toxins, Type A / Q000009:adverse effects* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D009128:Muscle Spasticity / Q000188:drug therapy* / Q000209:etiology; D018908:Muscle Weakness / Q000139:chemically induced*; D018482:Muscle, Skeletal / Q000187:drug effects; D009460:Neurologic Examination; D009465:Neuromuscular Agents / Q000009:adverse effects* / Q000627:therapeutic use; D020521:Stroke / Q000150:complications* / Q000188:drug therapy; D016896:Treatment Outcome
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A