Heterogeneity in spasmodic dysphonia. Neurologic and voice findings
K. D. Pool, F. J. Freeman, T. Finitzo, M. M. Hayashi, S. B. Chapman, Sr. Devous MD, L. G. Close, G. V. Kondraske, D. Mendelsohn, S. D. Schaefer and al. et
Dallas (Tex) Center for Vocal Motor Control, Neuroscience Research Center.
Spasmodic dysphonia is a disturbance of phonation with laryngeal spasms. We
report voice and neurologic examination findings in 45 subjects. Neurologic
abnormalities were found in 32 subjects (71.1%). Rapid alternating movement
abnormalities, weakness, and tremor were common. Incoordination and
spasticity were rare. Lower extremity findings were frequent. Abnormalities
were bilateral. Spasmodic dysphonia severity was related to age. Type,
severity, and duration of vocal symptoms were not different for subjects
with or without neurologic abnormalities. Vocal tremor was more frequent in
neurologically abnormal subjects. Involvement of a
pallidothalamic-supplementary motor area system could account for
neurologic findings, brain imaging findings, and clinical heterogeneity.
The view emerging is that spasmodic dysphonia is a manifestation of
disordered motor control involving systems of neurons rather than single
anatomical sites.
