Severe Nervous System Complications After Botulinum Type A Therapy: Three Case Reports With Reviews of FDA-Reported Nervous System Adverse Effects

The short-term safety of botulinum toxin type A (BoNT/A) has been established in numerous double-blind trials, but as many authors have pointed out, long-term drug safety is an unresolved issue [1-3]. We report 3 cases of central nervous system complications with encephalitic clinical features that occurred shortly after treatment of focal dystonia with BoNT/A. The goal of this study is to raise awareness and increase the vigilance of health care providers regarding the possible occurrence of adverse events that may be related not directly to the toxin but to other mechanisms that have not yet been well studied. We suggest an algorithm for safer toxin use until further research is conducted. We also offer a summary of toxin-related nervous system adverse events reported to the U.S. Food and Drug Administration (FDA) between September 1992 and May 2009.