Timber rattlesnake venom-induced myokymia: evidence for peripheral nerve origin.

Facial and limb myokymia occurred in four consecutive cases of timber rattlesnake envenomation and represents the "fasciculations" frequently reported in this entity. The facial myokymia disappears within hours of antivenin therapy and the limb myokymia by increasing serum ionized calcium. These observations suggest that the action of the venom is a biochemical one, increasing peripheral nerve excitability.