Effects of voicing and syntactic complexity on sign expression in adductor spasmodic dysphonia

Clients with adductor spasmodic dysphonia (ADSD) tend to exhibit inter- and intraclient variability of signs and symptoms. This variability may result in inaccurate assessment of severity. Accurate assessment of severity requires knowledge concerning the factors that affect the expression of ADSD signs and symptoms. This study examined ADSD sign expression as a function of voicing and syntactic complexity. Fifteen ADSD participants and 15 control participants completed a task consisting of 30 sentences. ADSD signs were significantly more frequent in predominantly voiced sentences than in predominantly voiceless sentences, regardless of level of syntactic complexity. Center-embedded sentences comprising predominantly voiced consonants were found to evoke the greatest number of ADSD signs. These results have important implications for the assessment of ADSD.