Abstract
Electromyographic (EMG) assessment of involuntary spasm activity in the cricothyroid (CT) and vocalis (V) muscles was correlated to clinical voice measures in 32 patients with clinically diagnosed spastic dysphonia (SD). Sub jec tive voice rating, and quantified fluency and laryngeal diodochokinesis measure were obtained pre botulinum toxin injection (Botox). Pre Botox EMG was performed using a monopolar needle electrode. Each muscle was se quen tial ly examined at rest, during vocal click, scale, sustained "E" at different pitches, and repeated "E" voicings. A three point EMG severity scale was used to grade each muscle. There were no significant cor re la tions between the summed EMG severity scales for all 4 muscles, the combined EMG se ver i ty for the V of CT muscles, or the combined EMG severity for the right or left CT and V muscles and pre-Botox subjective rating, fluency, repeated sound production or post-botox change in subjective rating. EMG did discriminate between adductor and ab duc tor patterns, but could not correctly classify mixed SD. Those with adductor SD displayed in vol un tary "spasm" activity in the V and CT mus cles, while those with abductor SD displayed more "spasm" activity in the cT than the V mus cles. Sequential EMG assessment of CT and involuntary activity in SD does not predict clin i cal severity of out come following Botox injection of the V muscle.

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