Cerebellar Pathology in Early Onset and Late Onset Essential Tremor.

Abstract

Early onset and late onset essential tremor (ET) cases differ in several respects. Whether they differ with respect to cerebellar pathologic changes remains to be determined. We quantified a broad range of postmortem features (Purkinje cell (PC) counts, PC axonal torpedoes and associated axonal changes, heterotopic PCs, and hairy basket ratings) in 30 ET cases with age of tremor onset <50years, 30 ET cases with age of tremor onset ≥50years, and 30 controls (total n=90). We also used two alternative age of onset cut-points (<40 vs. ≥40years, and <60 vs. ≥60years) to define early onset vs. late onset ET. We found that ET cases with tremor onset <50years and tremor onset ≥50years had similar PC counts (8.78±1.70 vs. 8.86±1.24, p=0.839), PC axonal torpedo counts (17.87±18.27 [median =13.00] vs. 12.90±10.60 [median =9.0], p=0.486) and associated axonal pathology (all p values >0.05), heterotopic PC counts (9.90±11.55 [median =6.00] vs. 5.40±5.10 [median =3.50], p=0.092), and hairy basket ratings (1.95±0.62 [median =2.00] vs. 2.05±0.92 [median =2.00], p=0.314). When using the age of onset cut-points of 40 or 60years, results were similar. Early onset and late onset ET cases share similar cerebellar postmortem features. These data do not support the notion that these age-of-onset related forms of ET represent distinct clinical-pathological entities.