Convulsions during superior laryngeal nerve block--a case report.

Complications following local anesthesia for fiberoscope-assisted intubation are rare. We report a case with surgical condition indicating awake endotracheal intubation for general anesthesia, suffering from convulsions after receiving left superior laryngeal nerve block to facilitate the procedure. The possible cause may be accidental injection of the local anesthetic into the vertebral artery. Although the amount of local anesthetic injected was small, its concentration in the brain might be high enough to cause convulsion. The central nervous system toxicity of local anesthetic depends not only on the dosage used, but also on the rate of injection, as well as the site at which it is injected. Starting from a small dose together with careful monitoring of patient's response is advised when nerve block in the neck is performed. Here, we also emphasize the importance of availability of resuscitation equipment for maintaining adequate ventilation and circulation in case of emergency.