The neurobiological basis of tremor in patients with Essential tremor (ET) may localize in part to the cerebellum. Previous studies have described reductions in cerebellar volume in the dentate nucleus and pathways through the red nucleus and inferior olive, as they may underlie the tremor etiology. In contrast, Parkinson’s disease (PD) related tremor may have a distinct or overlapping localization, involving the cerebellothalamocortical circuit. One potential limitation of cerebellar volume investigations is the meticulous manual labor to segment the cerebellar lobules properly. Here, we apply a high throughput, automatic cerebellar segmentation to assess differences in cerebellar lobar volumes.

To assess differences in cerebellar lobar volumes in Essential tremor and Parkinson’s disease patients.

Cerebellar segmentation of 28 lobules was performed using an automated multi-atlas lobar segmentation and individually reviewed for accuracy.  A general linear regression model was used to assess differences in lobule volume between ET and PT patients while correcting for age and total intra-cranial volume. False discovery rate was controlled at 0.1 to correct for multiple comparisons. 

A cohort of 348 patients diagnosed with ET (n=103, males=41, disease duration=22 years) or PD (n=245, males=149, disease duration=9 years) underwent T1-weighted Magnetic Resonance Imaging (MRI) under general anesthesia for Deep Brain Stimulation surgical planning. ET patients showed significant lower volumes in the deep cerebellar nuclei, caudal lobules (VIIIa and VIIIb), lower anterior lobules (III, IV, V), and vermis VIIIa (p<0.05). 

ET patients appear to have greater levels of atrophy in cerebellar lobules than in PD individuals, proposing that ET may be affecting the cerebellum differently than PD. Our findings relate with degeneration of the dentate nucleus as this is contained within the deep cerebellar nuclei. In addition, reduction of the anterior and posterior lobule volume are consistent with areas that influence ET clinical symptoms of motor and cognitive deficits respectively.