Torpedoes in the Cerebellar Vermis in Essential Tremor Cases vs. Controls

The study of the postmortem changes in essential tremor (ET) is in its infancy, although recent evidence points to a central role of the cerebellum, where Purkinje cell axonal swellings (torpedoes) are significantly more common in ET than control brains. Yet, all existing studies have been confined to the cerebellar hemispheres, and whether there is a more widely distributed cerebellar problem is presently unknown. Our aims were to address whether: (1) ET cases have greater numbers of torpedoes in the vermis than controls, (2) there a correlation between the extent of vermal torpedo pathology and hemispheric torpedo pathology, and (3) vermal torpedo pathology is correlated with clinical features of the disease. A parasagittal neocerebellar block and a vermal block were harvested from 24 ET and 10 control brains. Paraffin sections (7 mu m) were stained with Luxol fast blue/hematoxylin and eosin, and torpedoes were quantified. All torpedo counts were corrected for Purkinje cell layer length. Vermal corrected torpedo count (VermTc) was higher in ET cases than controls (7.1 +/- 6.8 [median, 4.3] vs. 2.6 +/- 2.5 [median, 2]), p = 0.002). The VermTc and the hemispheric corrected torpedo count (HemTc) were correlated with one another (Spearman's r = 0.54, p = 0.002). ET cases with neck, voice, and jaw tremors had the highest VermTc (p = 0.046). The abundance of torpedoes in the ET brain is not confined to the ponto- or neocerebellum but is more broadly distributed, also involving the spino- or paleocerebellum. These data further confirm the central role of the cerebellum in the underlying pathophysiology of this common neurological disorder.