Treatment of childhood myoclonus with botulinum toxin type A

Because of inadequate response to or intolerable side effects of oral medic ation, nine patients with segmental,generalized, and focal myoclonus were t reated with intramuscular botulinum toxin type A. All patients were evaluat ed with neuroimaging, routine and limb-monitored electroencephalography, el ectromyography, evoked potentials and appropriate biochemical studies. Pati ents were aged 2 to 22 years, with duration of myoclonus from 1 month to 10 years. Multiple medication trials included antiepileptic drugs, benzodiaze pines, tryptophan, L-dopa/carbidopa, baclofen, and dantrolene. Patients wer e injected with botulinum toxin in their affected area with electromyograph ic guidance to affected muscles with different doses (8 to 20 units/kg), ex cept two patients who were injected with 32 and 45 units/kg, respectively, at 4- to 8-month intervals. One patient did not complete botulinum toxin tr eatment because of subjective weakness, although there were virtually no si de effects reported in patients completing therapy. Patients reported a dra matic reduction in painful myoclonus. In addition, patients exhibited impro ved functional skills, as demonstrated by markedly improved use of affected extremities and improvements in ambulation. One patient, who was nonambula tory prior to treatment, was able to walk afterward. Long term benefits cou ld be related to higher dosage used or negative feedback effect.