Objective: Investigate shared and disorder-specific brain abnormalities in essential and dystonic tremor of voice using functional and structural brain imaging.

Background: Essential tremor of voice (ETv) is a common manifestation of essential tremor (ET) that affects vocal folds during both active and passive laryngeal tasks [1, 2]. The clinical characteristics of ETv differ from those of dystonic tremor of voice (DTv), which co-occurs with spasmodic dysphonia, is task-induced and predominantly affects speech production [3]. Little is known about the neural representations of ETv symptomatology and its differences from DTv, which impacts the development of accurate diagnostic markers of these disorders.

Method: We acquired high-resolution structural T1-weighted and functional images during symptomatic speech production on a 3T scanner in 18 ETv (age 62.5±12.2 years, 15 females/3 males), 25 DTv (age 60.2±10.8 years, 22 females/3 males) and 25 healthy controls (age 54.2±8.5 years, 18 females/7 males). Structural images were analyzed for cortical thickness (CT) and subcortical volume measures; functional images were processed following the standard analytic pipeline. Between-group statistical significance was assessed using two-tailed independent t-tests at FWE-corrected p < 0.05.

Results: Compared to controls, DTv patients showed increased activity and decreased CT bilaterally in primary sensorimotor cortex along with additionally decreased activity in left superior frontal gyrus, inferior parietal cortex and cerebellum. Compared to controls, ETv patients were characterized by more prominent subcortical changes with decreased activity in left putamen and decreased gray matter volume of left nucleus accumbens. Shared abnormalities in ETv and DTv compared to controls were associated with decreased CT in right angular and left lingual gyri and functional changes in the right insula, the activity of which was increased in DTv and decreased in ETv. A direct comparisons showed that ETv had greater activity in right cerebellum and both greater activity and CT in right inferior frontal gyrus, while DTv had greater CT in left primary sensorimotor cortex.

Conclusion: Our findings suggest that ETv and DTv share similar brain alterations but are characterized by distinct neural representations within the circuits responsible for motor planning and preparation in ETv and motor execution in DTv.

References: 1. Blitzer, A., M.F. Brin, and L.O. Ramig, Neurologic Disorders of the Larynx. 2011: Thieme. 256. 2. Sulica, L. and E.D. Louis, Clinical characteristics of essential voice tremor: a study of 34 cases. Laryngoscope, 2010. 120(3): p. 516-528. 3. Mor, N. and A. Blitzer, Diagnosis and Treatment of Laryngeal Dystonia : Past , Present and Future Directions. Tremor and other hyperkinetic movements, 2016. 6: p. 1-12.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-neural-representations-of-the-voice-tremor-spectrum/