Prevalence of essential tremor in an idiopathic Parkinson's disease patient population.

Essential tremor (ET) and Parkinson's disease (PD) tremor differ in type, frequency and distribution. Despite being two separate disorders, there have been cases reported of comorbidity for ET-PD. Studies have reported an increase in the incidence of ET in relatives of patients with PD, yet the risk of developing PD in ET patients has not been thoroughly investigated. Our study set out to determine the incidence of precedent ET in PD patients. We conducted a retrospective chart review analysis of 332 idiopathic PD patients to determine how many of them had ET prior to the diagnosis of PD and the percentage of them who were also diagnosed with ET. Our results indicate that the prevalence of precedent ET among a population of idiopathic PD patients was not any higher than the prevalence of ET in a comparable general population. Our results support the notion that ET and PD are mutually independent disorders. Further studies are needed to understand the exact relationship between these two disorders.