Objective: To study the therapeutic response of primidone in different age groups of Essential Tremor (ET) patients, based on age at onset.

Background: Essential Tremor has a bimodal distribution of age at onset, with an early peak in the 20’s and another late-onset in the 60’s. A difference in clinical features, mode of progression, pathophysiology, co-morbidities, and mortality have been reported between the early and late-onset ET. Therapeutic effect of medications is also highly variable. Response to tremor medications in different age groups based on age at onset is not clear. This study was designed to examine differences in therapeutic response to primidone in different age groups.

Method:

We examined the medical records of 1074 Essential Tremor patients, seen in the Parkinson’s Disease Research, Education and Clinical Center (PADRECC), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA from September 1, 2001 – March 31, 2018. Age groups were classified based on MDS tremor task group classification of age at onset.¹ Response to primidone was classified as none, mild, moderate, and excellent based on subjective feedback. Mild response was graded as improvement in tremor but no changes in functional abilities, moderate response was improvement in tremor and functional abilities but consistent use of adaptive strategies, whereas excellent response was improvement in tremor with minimal use of adaptive strategies.

Results: 321 ET subjects took primidone with documented therapeutic response. In the adolescent group (age at onset 1-20 years, n=30) 33% reported no, 30% mild, 27% moderate and 10% excellent response. Ten% of the early adulthood group (age 21-45 years, n=72) reported no response, while mild, moderate, and excellent responses were reported in 35%, 47% and 8% of the group. The middle age group (age 46-60 years, n=100) had response rates of none (23%), mild (19%), moderate (49%) and excellent (9%). In the elderly age group (age ≥ 61, n=119) responses were none (20%), mild (23%), moderate (50%) and excellent (7%).

Conclusion: In this chart review study, least favorable response was noted in adolescent age group. Moderate response was the most common therapeutic response in all age groups except the adolescent age group.

References: 1. Bhatia KP, Bain P, Bajaj N, Elble RJ, Hallett M, Louis ED, et al. Consensus Statement on the classification of tremors. from the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord. 2018;33(1):75-87

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MDS Abstracts - https://www.mdsabstracts.org/abstract/age-at-onset-and-therapeutic-efficacy-of-primidone-in-essential-tremor-patients/