Adductor muscle activity abnormalities in abductor spasmodic dysphonia.

OBJECTIVE

To determine laryngeal muscle activation abnormalities associated with speech symptoms in abductor spasmodic dysphonia (ABSD).

STUDY DESIGN

Bilateral laryngeal muscle recordings from the posterior cricoarytenoid, thyroarytenoid, and cricothyroid muscles were conducted in 12 ABSD patients. Patients' measures were compared during speech breaks and during speech without breaks and with 10 normal controls.

RESULTS

Significant group differences were found in the thyroarytenoid muscle; the patients had significantly greater activity on the right side both during speech breaks and nonbreaks in comparison with the controls. Cricothyroid muscle levels were also increased on the right in the patients.

CONCLUSION

An asymmetry in adductor muscle tone between the 2 sides in ABSD may account for difficulties with maintaining phonation and voice onset after voiceless consonants.

SIGNIFICANCE

These abnormalities may indicate why PCA BOTOX injections have not been as effective in ABSD as thyroarytenoid injections have been in adductor spasmodic dysphonia.