Spasmodic dysphonia: clinical features and effects of botulinum toxin therapy in 169 patients-an Australian experience.

Adductor spasmodic dysphonia (SD) is a focal laryngeal dystonia, characterised by strangled, effortful speech with breaks in pitch and phonation. Injection of laryngeal muscles with BTX is widely used in the treatment of SD. A consecutive series of 169 patients with SD, of whom 144 were treated with BTX injections, seen at St. Vincent's Hospital between 1983 and 1999 were studied prospectively. Patients underwent neurological, quantitative voice and otolaryngological assessment. Females (62.1%) outnumbered males (37.9%) and the mean age at diagnosis was 56 years (range 19-88). Adductor SD (89.4%) was more frequent than abductor SD (1.8%) or mixed SD (4.7%). Stridor was present in 14 patients (8.3%) and in 7 was the sole manifestation of the laryngeal dystonia. The median treatment outcome score was excellent in 63.2%, very good in 18.5%, satisfactory in 14.7% and unsatisfactory in 3.5%. Poorer treatment outcome was associated with abductor SD (OR = 4.69, CI [1.23, 17.92] p=0.024] and age >65 (OR = 2.83, CI [0.95, 8.42] p=0.049). Mild post-injection paralytic dysphonia was associated with longer lasting treatment (4.42 vs. 3.62 months p<0.001) and superior treatment outcome rating (1.37 vs. 1.81 p<0.001). We conclude that BTX injections are highly effective and severe adverse events are rare. Older age and abductor SD may confer a relatively poorer treatment outcome. Mild post-injection paralytic dysphonia may be a marker for more effective and lasting treatment in adductor SD.