Essential tremor 10, 20, 30, 40: Clinical snapshots of the disease by decade of duration

Background and purpose: Essential tremor (ET) is a chronic, progressive neurological disorder in which disease burden may slowly accrue. There are few long-term studies, and the clinical and functional status of patients, with each decade of disease duration, has not been documented in detail. We used cross-sectional data on 335 patients with ET (disease duration 1-81years) to produce clinical snapshots of the disease at each 10-year milestone (i.e. <10, 10-19, 20-29, 30-39, ≥40years). We hope these data will be of value in clinical-prognostic settings both to patients and their treating physicians. Methods: In this cross-sectional, clinical-epidemiological study at Columbia-University Medical Center, each patient underwent a single evaluation, including self-reported measures of tremor-related disability, performance-based measures of function, and neurologist-assessments of tremor type, location and severity. Results: A variety of metrics of tremor severity increased across the 10-year time intervals. By ≥40years duration, one-third of patients had tremor in at least two cranial locations (neck, voice, jaw), and the proportion with high-amplitude tremor reached 20.3% (while drawing spirals), 33.8% (spilling while drinking) and 60.8% (spilling while using a spoon). Yet even in the longest tremor duration group, very few (<10%) were incapacitated (i.e. completely unable to perform the above-mentioned tasks), and one-third continued to exhibit no cranial tremor. Conclusions: These data paint a picture of progressive decade-by-decade decline in ET. Yet patients with long disease duration did not relentlessly converge at the same end-stage of severe, functionally incapacitating, diffuse tremor. In this respect, long-duration ET patients presented a heterogeneous picture.