title: Resistance to botulinum toxin injections for spasmodic dysphonia.
abstract: A known complication of botulinum toxin injections in the treatment of dystonia has been the occasional development of resistance. This has been seen primarily with patients who receive injections for torticollis. We report on 2 patients who, after several years of receiving injections for spasmodic dysphonia, developed clinical resistance by failing to have expected voice improvement after receiving laryngeal reinjection. One of the 2 patients demonstrated antibodies to botulinum toxin by mouse neutralization bioassay. The second patient had negative bioassay results but had no clinical response to the test toxin injection of facial muscles. These cases demonstrate that, although uncommon, resistance to botulinum toxin injections can occur in the treatment of spasmodic dysphonia. We offer suggestions to limit this complication.
authors.affiliation: Division of Otolaryngology-Head and Neck Surgery, University of Utah School of Medicine, Salt Lake City 84132, USA. marshall.smith@hsc.utah.edu
authors.forename: M E
authors.initials: ME
authors.lastname: Smith
authors.forename: C N
authors.initials: CN
authors.lastname: Ford
mesh_terms: D000818:Animals; D018726:Anti-Dyskinesia Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001905:Botulinum Toxins / Q000008:administration & dosage / Q000627:therapeutic use*; D004351:Drug Resistance; D005260:Female; D006801:Humans; D007267:Injections; D007830:Larynx; D051379:Mice; D008875:Middle Aged; D014832:Voice Disorders / Q000188:drug therapy*
chemical_list: D018726:Anti-Dyskinesia Agents; D001905:Botulinum Toxins