LARYNGEAL MUSCLE-ACTIVITY DURING SPEECH BREAKS IN ADDUCTOR SPASMODIC DYSPHONIA

To determine the laryngeal muscle activation abnormalities that are as sociated with speech symptoms in adductor spasmodic dysphonia (ADSD), electromyographic measures of extrinsic and intrinsic laryngeal muscle s during speech compared 1) muscle activity when ADSD patients had bre aks in words with when they produced the same words without breaks; an d 2) muscle activity in ADSD patients during speech without voice brea ks with normal controls producing phonetically similar words. Simultan eous electromyographic recordings were made from the thyroarytenoid (T A), cricothyroid (CT), sternothyroid (ST), thyrohyoid (TH) and the pos terior cricoarytenoid (PCA) muscles during speech testing in 11 ADSD p atients and 10 control subjects. Speech breaks were identified and mea n muscle activity measured starting 100 ms preceding a voice break and for the remainder of the word. Mean muscle activity level was signifi cantly greater on break than non break words in ADSD patients only for the thyroarytenoid muscle (p<.001). No significant differences were f ound between the ADSD and control subjects during non break words for any of the laryngeal muscles studied. The results demonstrated that 1) only the thyroarytenoid, of the muscles tested, was affected in ADSD, 2) that muscle activation abnormalities were spasmodic, only appearin g when symptoms occurred and 3) no imbalances of muscle tone were evid ent when speech disruptions did not appear.