Essential head tremor is associated with cerebellar vermis atrophy: a volumetric and voxel-based morphometry MR imaging study

Abstract

Background and purpose: Our aim was to investigate the presence of brain gray matter (GM) abnormalities in patients with different forms of essential tremor (ET).

Materials and methods: We used optimized voxel-based morphometry (VBM) and manually traced single region-of-interest analysis in 50 patients with familial ET and in 32 healthy subjects. Thirty patients with ET had tremor of the arms (a-ET), whereas the remaining 20 patients had both arm and head tremor (h-ET).

Results: VBM showed marked atrophy of the cerebellar vermis in the patients with h-ET with respect to healthy subjects (P(corrected) < .001). Patients with a-ET showed a trend toward a vermal GM volume loss that did not reach a significant difference with respect to healthy controls (P(uncorrected) < .01). The region-of-interest analysis showed a reduction of the cerebellar volume (CV) in the h-ET group (98.2 +/- 13.6 mm(3)) compared with healthy controls (110.5 +/- 15.5 mm(3), P < .012) as well as in the entire vermal area (790.3 +/- 94.5 mm(2), 898.6 +/- 170.6 mm(2), P < .04 in h-ET and control groups, respectively).

Conclusions: Atrophy of the cerebellar vermis detected in patients with h-ET strongly supports the evidence for the involvement of the cerebellum in the pathophysiology of ET. The lack of a significant CV loss observed in patients with a-ET suggests that a-ET and h-ET might represent distinct subtypes of the same disease.

Fig 1.

Sample manual region-of-interest tracings assessing planimetric measurements of the vermal-functional areas by using the MRreg software. Data are shown for a control subject with no atrophy. A, The anterior lobule. B, The posterior superior lobule. C, The posterior inferior lobule. A + B + C = midsagittal vermal area.

Fig 2.

Results from an optimized VBM analysis showing significant cerebellar atrophy at the level of the anterior lobe, above that occurring globally, selectively in patients with both a-ET and h-ET (P_corrected < .001). Data analyses have been further corrected for age and sex. The maps are superimposed on the T1-weighted image averaged across all participants. The bar graphs give the mean and SD GM volume of voxels showing peak differences in the vermis. Patients with only a-ET display a tendency toward a CV loss.