White matter differences between essential tremor and Parkinson disease

Abstract

ObjectiveTo assess white matter integrity in patients with essential tremor (ET) and Parkinson disease (PD) with moderate to severe motor impairment.MethodsSedated participants with ET (n = 57) or PD (n = 99) underwent diffusion tensor imaging (DTI) and fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity values were computed. White matter tracts were defined using 3 well-described atlases. To determine candidate white matter regions that differ between ET and PD groups, a bootstrapping analysis was applied using the least absolute shrinkage and selection operator. Linear regression was applied to assess magnitude and direction of differences in DTI metrics between ET and PD populations in the candidate regions.ResultsFractional anisotropy values that differentiate ET from PD localize primarily to thalamic and visual-related pathways, while diffusivity differences localized to the cerebellar peduncles. Patients with ET exhibited lower fractional anisotropy values than patients with PD in the lateral geniculate body (p < 0.01), sagittal stratum (p = 0.01), forceps major (p = 0.02), pontine crossing tract (p = 0.03), and retrolenticular internal capsule (p = 0.04). Patients with ET exhibited greater radial diffusivity values than patients with PD in the superior cerebellar peduncle (p < 0.01), middle cerebellar peduncle (p = 0.05), and inferior cerebellar peduncle (p = 0.05).ConclusionsRegionally, distinctive white matter microstructural values in patients with ET localize to the cerebellar peduncles and thalamo-cortical visual pathways. These findings complement recent functional imaging studies in ET but also extend our understanding of putative physiologic features that account for distinctions between ET and PD.

Neural Representations of the Voice Tremor Spectrum

“…A somewhat unexpected finding of this study was the absence of significant white matter alterations in patients with ETv and DTv. This is a discrepancy from previous studies that reported white matter changes in the cerebellum, corpus callosum, thalamocortical visual pathways in ET, [48][49][50] as well as the posterior limb of the internal capsule in DTv. 12 Possible explanations may include the stringent criteria for selection of homogeneous patient populations and the methodological constraints, such as differences in diffusion-weighted imaging sequence acquisition and a stringent statistical thresholding employed in this study that might have excluded smaller clusters of between-group differences reported in the previous literature.…”

Modern Brainstem MRI Techniques for the Diagnosis of Parkinson's Disease and Parkinsonisms

“…Using diffusion kurtosis imaging, Ito et al (90,91) described a ratio of midbrain tegmentum diffusion to pontine crossing tract diffusion to distinguish between patients with PSP, MSA or PD and controls (90,91). Interestingly, Juttukonda et al (92) also found an FA decrease in the pontine crossing tract in patients with essential tremor vs. PD (92).…”

Mechanisms and Pharmacotherapy for Ethanol-Responsive Movement Disorders

“…Electrophysiology, structural magnetic resonance imaging (MRI), diffusion MRI, and positron emission tomography (PET) studies have revealed various abnormalities in cerebello-thalamo-cortico-cerebellar circuits in ET ( 45 , 46 ). Based on that, a recent study revealed the distinctive white matter microstructural values localize to the cerebellar peduncles and thalamo-cortical visual pathways via diffusion tensor imaging (DTI) and fractional anisotropy, suggesting that a cerebello-thalamo (posterior) cortical network rather than a cerebello-thalamo-motor cortical network takes part in ET ( 47 ).…”