Electrical activity of extrinsic laryngeal muscles in subjects with and without dysphonia

Objective: To compare dysphonic individuals to nondysphonic with regards to electrical activity of extrinsic laryngeal muscles related to perceptual and acoustic vocal parameters.

Hypothesis: Dysphonic individuals have higher electrical activity in the supra and infrahyoid muscles than those nondysphonic.

Study design: Prospective, cross-sectional, case series study.

Methods: Forty-one subjects, divided into two groups according to the presence of dysphonia, underwent evaluation of surface electromyography, auditory-perceptual, and acoustic evaluations of voice during the vocal rest and sustained emissions of the vowel /ε/ and count of 20 to 30 at usual and strong intensities.

Results: The dysphonic group differed significantly from the nondysphonic by (1) lower electrical activity normalized by the maximum sustained voluntary activity evaluated in all tasks of phonation in the suprahyoid group; (2) lower recruitment of electrical activity in emissions of strong intensity compared with those of usual intensity in the suprahyoid muscles to emit the vowel /ε/ (13.66 ± 5.17 in dysphonic group and 35.20 ± 7.60 in the nondysphonic group, P = 0.029) and in the infrahyoid muscles in the count of 20 to 30 (14.90 ± 4.69 vs. 42.01 ± 6.15; P < 0.001) and to emit the vowel /ε/ (11.47 ± 6.52 vs. 22.66 ± 9.05, P < 0.001); (3) lower vocal intensity to produce the vowel /ε/ in usual and strong intensities and count in strong intensity. The electrical activities of the maximum sustained voluntary activity were reduced with increasing degree of dysphonia.

Conclusions: There was lower electrical activity of the extrinsic laryngeal muscles in dysphonic individuals compared with nondysphonic, and related to the degree of dysphonia.