How does BTA work?
(The following section presents a brief overview of the technical and biological aspects of BTA. Some readers may wish to skip this section.) Botulinum neurotoxins are produced by certain strains of Clostridium bacteria and are classified into 7 serotypes, A through G (Shantz & Johnson, 1992). Most clinical work has been done with serotype A. The biological effects of BTA are well understood. An injection of BTA into the muscle creates a localized muscle paralysis by causing a highly specific binding to presynaptic cholinergic peripheral nerve terminals. The toxin is then internalized into the nerve terminal and inhibits the release of acetylcholine at the neuromuscular junction. Neurotransmission recovers when the axon terminal sprouts new nerve endings and forms new synaptic contacts on adjacent muscle fibers (Jankovic & Brin, 1991). Over time the original neuromuscular junction starts to work again highlighting the reversible nature of the treatment (De Paiva et al., 1999). In human
