Balance reactions in healthy elderly persons, persons with Essential Tremor, and persons with the combination of Essential Tremor and early-stage Parkinson's disease

Background and purpose. The relationship between Essential Tremor (ET) and Parkinson's disease (PD) is controversial. Most studies focus on epidemiological and family studies. There are no reports investigating postural responses in these groups that could help to establish if there is a link between the two diseases. The purpose of this study is to investigate the relationship between Essential Tremor (ET) and Essential Tremor with Parkinson's Disease (ETPD) from balance reactions and posture-evoked responses. Subjects. Thirty-three persons with ET, 16 persons with ETPD (diagnosed with PD below H & Y 3), and 33 healthy elderly were tested while off medications. Methods. Balance tests included (1) sensory organization tests (SOT), (2) dynamic limits of stability tests (LOS), (3) posture evoked response tests in the ankle muscles during toes-up perturbations of 4...