Essential tremor is one of the most common movement disorders in the world affecting approximately 4.6% of those 65 years of age or older and approximately 2.2% of the US population, or 7 million people. Approximately 30% of these individuals exhibit a vocal tremor due to essential tremor (ET), or Essential Vocal Tremor (EVT), with the majority being female. EVT significantly impacts quality of life and does not consistently or significantly benefit from medications or medical management approaches that are currently used to treat limb tremor. The differing response to current medical treatments between those with EVT and those with ET without vocal tremor (EVT0) highlights the need for determining differing characteristics between those with EVT compared to EVT0. Individuals with EVT report increased effort during speaking and worsening of their vocal tremor during stressful activities that promote anxiety or require more concentration and effort. To date, EVT has been characterized primarily by acoustic measures of voice modulation resulting in limited understanding regarding speech structure contributions to the onset and progression of this disorder. This is in contrast to longstanding diagnostic characteristics of tremor rate and extent described in the literature for tremor affecting the arms, hands, head, or legs that can be used to distinguish between neurologic etiologies. Insight into the physiologic underpinnings of speech structures affected by tremor and their links to impaired speech production would enable insights regarding optimal clinical approaches for evaluating and managing vocal tremor. Further, determining salient physiologic characteristics associated with vocal tremor could potentially lead to clinical evaluation approaches that enable identification of the different neurogenic causes of vocal tremor (e.g. basal ganglia, cerebellar, extrapyramidal pathways). The goal of this project is to systematically evaluate and model the contribution of tremor affecting the respiratory, laryngeal, and articulatory structures to vocal tremor acoustic patterns. Outcomes of this research will significantly advance our scientific knowledge regarding the physiologic underpinnings of EVT and its correspondence to impaired communication function. Further, outcomes will advance current clinical evaluation and treatment methods and enable future investigation of unique physiologic characteristics across other etiologies of vocal tremor (e.g. Parkinson Disease, Dystonia) that will advance current and future treatment approaches.
/ RELEVANCE TO PUBLIC HEALTH The outcomes of this work will advance our scientific knowledge about the underpinnings of vocal tremor caused by essential tremor and its impact on speech communication and quality of life. Findings from this research will provide insights about differences in tremor patterns in people diagnosed with essential tremor with and without vocal tremor. Consequently, better methods for evaluating and treating individuals with essential tremor and vocal tremor will result.
