Tremor in neurodegenerative ataxias, Huntington disease and tic disorder

Introduction: Tremor is the most prevalent movement disorder, defined as rhythmic oscillations of a body part, caused by alternating or synchronic contractions of agonistic or antagonistic muscles. The aim of the study was to assess prevalence and to characterize parameters of tremor accompanying degenerative ataxias, Huntington disease (HD) and tic disorders in comparison with a control group. Material and methods: Forty-three patients with degenerative ataxias, 28 with HD and 26 with tic disorders together with 51 healthy controls were included in the study. For each participant, clinical and instrumental assessment (accelerometer, electromyography [EMG], graphic tablet) of hand tremor was performed. Frequency and severity of tremor were assessed in three positions: at rest (rest tremor), with hands extended (postural tremor), during the 'finger-to-nose' test and during Archimedes spiral drawing (kinetic tremor). Based on the mass load test, the type of tremor was determined as essential tremor type or enhanced physiological tremor type. Results: The incidence of tremor in the accelerometry in patients with degenerative ataxia (50%) significantly differs from controls (10%) (p = 0.001). The dominant tremor was postural, low-intense, with 7-Hz frequency, essential tremor (23%) or other tremor type (23%), while enhanced physiological tremor was the least frequent (2%). Tremor in patients with HD and tic disorders was found in 10% and 20% of patients, respectively, similarly to the control group. Tremor was mild, postural and of essential tremor type, less frequently of enhanced physiological tremor type. No correlation between severity of tremor and severity of disease was found. Conclusions: The prevalence of tremor is considerably higher among patients with degenerative ataxias compared with HD, tic disorder and the control group. The most common type of tremor accompanying ataxias, HD and tic disorders is essential tremor type.