title: Further studies using higher doses of botulinum toxin type F for torticollis resistant to botulinum toxin type A.
abstract: OBJECTIVE
  A previous study of botulinum toxin type F (BTX-F) treatment for torticollis had shown a dose of 520 MU to be effective, but for a much shorter duration than is usual with botulinum toxin type A (BTX-A). The objective was to assess the effect of a higher dose of BTX-F.
  
  
  METHODS
  Four of the previously treated patients, plus an additional patient, were treated with a higher dose of 780 MU BTX-F. All were secondary nonresponders to BTX-A due to neutralising antibodies. A test injection of 40 MU BTX-F was also given into the extensor digitorum brevis muscle (EDB), to examine the time course of the biological effect of the toxin electrophysiologically. Patients were followed up at two, four, eight, and 12 weeks.
  
  
  RESULTS
  All patients reported subjective improvement lasting from seven to 11 (mean 8.6) weeks accompanied by a significant reduction in mean clinical severity scores at two weeks. Four patients had pain which was substantially reduced. The electrophysiological studies confirmed biological sensitivity to the toxin in all patients, showing a significant change beginning at two weeks and returning to baseline at 12 weeks. The time course of this effect paralleled roughly that of the clinical response. The four patients who had previously received 520 MU BTX-F reported that the response was better and longer in duration with 780 MU. Dysphagia was more common than reported with the lower dose.
  
  
  CONCLUSIONS
  Better results are possible with higher doses of BTX-F but the duration of benefit is still shorter than with BTX-A, seemingly due to a shorter duration of neuromuscular junction blockade.
authors.affiliation: The National Hospital for Neurology and Neurosurgery, London, UK.
authors.forename: M K
authors.initials: MK
authors.lastname: Houser
authors.forename: G L
authors.initials: GL
authors.lastname: Sheean
authors.forename: A J
authors.initials: AJ
authors.lastname: Lees
mesh_terms: D000328:Adult; D001905:Botulinum Toxins / Q000008:administration & dosage*; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004576:Electromyography / Q000187:drug effects; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000187:drug effects; D009460:Neurologic Examination / Q000187:drug effects; D014103:Torticollis / Q000188:drug therapy*; D016896:Treatment Outcome
chemical_list: D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A; C096321:botulinum toxin type F