Case series or trialsthat evaluated use of botulinum toxin for voice restoration in patients with documented voice failure following laryngectomy were eligible for inclusion. Studies were excluded if outcome measures were not fully explained.
Most of the included studies were in North America. All of the included studies performed objective and/or instrumental measurement to confirm hypertonicity or spasm of the pharyngoesophageal segment; the most commonly used method was videofluoroscopy, followed by an air insufflation test. (The authors used the terms pharyngoesophageal hypertonicity and spasm as indicators for botulinum toxin use interchangeably in this review.) Almost half of the studies used local anaesthetic infiltration into the constrictor muscles with resultant improvement in tracheoesophageal puncture voice as a confirmatory step before botulinum toxin injection. Correct positioning of the needle was generally confirmed with videofluoroscopy, but also with electromyogram (EMG) testing. Dose of botulinum toxin varied among studies; most used between 15 and 100 units of Botox and the total injection volume ranged from 0.5mL to 6mL.
The included studies measured improved tracheoesophageal puncture voice as the subjective outcome and used different objective methods, which included: different surgical voice restoration scales; patient qualitative rating of their voice improvement; improvement in stomal pressure; acoustic voice analysis; and improvement in mean phonatory time (other details were reported in the review). The other relevant outcomes were complications.
The authors did not report how many reviewers performed study selection.