OBJECTIVETo investigate the patterns of spasmodic dysphonia and the outcome treated with botulinum toxin A injections.

METHODSAll subjects were studied with acoustic analysis, laryngostroboscopy and laryngeal electromyography (EMG) including motor unit potential measure (MUP), recruitment pattern analysis and evoked electromyography. All the patients with spasmodic dysphonia were received botulinum toxin A (BOTOX) injections in each affected muscles and mostly under electromyographic guidance.

RESULTSAmong 22 cases of spasmodic dysphonia, 18 cases of adductor dysphonic patients have strained, strangled voice with intermittent breaks in speech as a consequence of hyperadduction and spasm of the vocal folds during phonation. Two patients had synchronous pharyngeal, lingual and velar tremor. Amplitudes of MUP of thyroarytenoid muscle (TA) were greater in patients group than in normal group (P < 0.01); The recruitment activity was increased and the amplitudes were greater than normal group (700-2500 microV) and the duration of activity of the TA during phonation was also notably greater in patients group than in normal group. Four cases of abductor dysphonic patients have a breathy, effortful hypophonic voice with abrupt termination of voicing. Amplitudes of MUP of posterior cricoarytenoid muscle (PCA) in patients group were increased up to 374 to 538 microV. The recruitment activity was increased and the amplitude was greater than normal(3000-5000 microV). In the adductor dysphonic group, patients who were treated with unilateral toxin injection had good results with 2.5 U or more. The average onset of toxin effect in all adductor dysphonic patients was at 6 hours to 2 days (1.4+/-0. 8) days (x +/- s), with a peak effect at 2 weeks and the follow-up EMG showed fibrillation potentials or electric silence in injected muscle. Duration of benefit was 8 to 24 weeks (15.2 +/- 4.9) weeks. The side-effect of toxin injection were including breathy voice or occasional dysphagia and aspiration. The patients with abductor spasms were less well controlled after PCA injections.

CONCLUSIONSSpasmodic dysphonia was regarded as a neuromuscular diseases, so its diagnosis, classification, treatment and follow-up should depend on not only clinical manifestation but also EMG. Presently, for controlling the dystonic symptoms, the most effective therapy for most of those patients is local BOTOX injections. Repeated injections are required to have a stable results.