Botulinum toxin for treating spasmodic dysphonia (laryngeal dystonia): a systematic Cochrane review.
BACKGROUND
Spasmodic dysphonia is a neurological voice disorder characterized by involuntary adductor (towards midline) or abductor (away from midline) vocal fold spasms during phonation which result in phonatory breaks. Botulinum toxin is currently the gold standard of treatment.


OBJECTIVE
To determine the efficacy of botulinum toxin therapy for the treatment of spasmodic dysphonia.


METHODS
Systematic Cochrane review.


METHODS
The search strategy for this review complied with Cochrane standards. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to February 2005), EMBASE (1974 to February 2005), CINAHL (through February 2005), Dissertation Abstracts International (1975 to February 2005) and PsycINFO (1975 to February 2005). The search engine FirstSearch was also used (February 2005). Reference lists for all the obtained studies and other review articles were examined for additional studies.


METHODS
All randomized control trials where the participants were randomly allocated prior to intervention and in which botulinum toxin was compared to an alternative treatment, placebo or non-treated control group were included.


METHODS
Two reviewers independently evaluated all potential studies meeting the selection criteria noted above for inclusion.


RESULTS
Only one study in the literature met the inclusion criteria. This was the only study identified which reported a treatment/no treatment comparison. It reported significant beneficial effects for fundamental frequency (Fo), Fo range, spectrographic analysis, independent ratings of voice severity and patient ratings of voice improvement.


CONCLUSIONS
The evidence from randomized controlled trials supporting the effectiveness of botulinum toxin for management of spasmodic dysphonia is deficient. The lack of supporting evidence from randomized controlled trials results in an inability to draw unbiased generalized conclusions regarding the effectiveness of botulinum toxin for all types of spasmodic dysphonia.
Department of Communication Sciences and Disorders, James Madison University, Harrisonburg, VA 22840, USA. wattscr@jmu.edu
Christopher
C
Watts
Chad
C
Nye
Renata
R
Whurr
D000328:Adult; D018726:Anti-Dyskinesia Agents / Q000627:therapeutic use*; D001905:Botulinum Toxins / Q000627:therapeutic use*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D013035:Spasm / Q000188:drug therapy*; D014832:Voice Disorders / Q000188:drug therapy*
D018726:Anti-Dyskinesia Agents; D001905:Botulinum Toxins