Botulinum toxin type A in cerebellar tremor caused by multiple sclerosis

The intention tremor seen in chronic progressive multiple sclerosis is often disabling and existing treatments are of limited benefit The present pilot study was designed to assess the role of Botulinum toxin type A (BOTOX®) in such cases. Five patients with the condition received 40 mouse units of toxin into the flexor and extensor compartments of the forearm. Two of these went on to receive a further 100 mouse units 2 months after the previous injection. Tremor was assessed at 0, 2 and 8 weeks post-injection using a validated clinical rating scale, spirography and handwriting samples, and a clinician's global rating scale; functional capacity was measured using an activities of daily living (ADL) scale adapted for use in tremor. No statistically significant improvement occurred in intention tremor, although there was a trend toward a mild improvement in the clinician's global rating scale. Patients noted an increase in their pre-existing corticospinal weakness which proved to be dose-limiting. No change occurred in ADL scores. It is concluded that pre-existing weakness limits the use of Botulinum toxin in the intention tremor seen in multiple sclerosis, but further work in disabling primary and secondary cerebellar degenerations without corticospinal weakness may be worthwhile.