Use of botulinum toxin in chronic whiplash-associated disorder.

Whiplash-associated disorders (WADs) occur as a result of trauma and are often due to motor vehicle accidents and sports injuries. Cervical injury is attributed to rapid extension followed by neck flexion. The exact pathophysiology of WAD is uncertain but probably involves some degree of aberrant muscle spasms and may produce a wide range of symptoms. Initial treatment of pain associated with whiplash usually includes oral medications, such as muscle relaxants and nonsteroidal anti-inflammatory drugs. However, these agents are limited by potential systemic adverse effects. Some patients with chronic WAD may benefit from radiofrequency neurotomy. A new approach to treatment is the use of botulinum toxin, which acts to reduce muscle spasms. Type A toxin (Botox) has been studied in small trials of patients with WAD and has generally been found to relieve pain and improve range of motion. In addition, recent preliminary data from a small trial showed that type B toxin (Myobloc) produced almost immediate pain relief for most patients with post-whiplash headache. Although botulinum toxin has not been evaluated in large long-term trials, these initial data are promising and suggest a role for this agent in the treatment of WAD. Additional study is needed to identify the subset of patients with WAD who are most likely to respond to treatment with botulinum toxin.