Substantia nigra neuromelanin-MR imaging differentiates essential tremor from Parkinson's disease.

BACKGROUND

Essential tremor (ET) is a very common movement disorder that has no diagnostic markers. Differentiation with Parkinson's disease (PD) can be clinically challenging in some cases, with a high rate of misdiagnosis. Magnetic resonance imaging (MRI) studies have been able to identify neuromelanin changes in the substantia nigra (SN) of PD patients, but they have thus far not been investigated in ET. In this study, we aimed to characterize neuromelanin-MR signal changes in ET and evaluate its diagnostic accuracy in the differential diagnosis with PD.

METHODS

The inclusion criteria were patients with ET and untreated "de novo" PD patients; in addition, age-matched controls were enrolled. These were studied with a high-resolution T1-weighted MRI sequence at 3.0 Tesla to visualize neuromelanin. The primary outcomes were the area and width of the SN region with high signal.

RESULTS

A total of 15 ET patients and 12 "de novo" PD patients were evaluated. The area and width of the T1 high signal in the SN region were markedly decreased in the PD group compared with the ET and age-matched controls, and a greater decrease was seen in the ventrolateral segment. The neuromelanin measures in the ET group, although slightly lower, were not significantly different from the healthy control group. We obtained a sensitivity of 66.7% and a specificity of 93.3% in discriminating ET from early-stage PD.

CONCLUSIONS

Neuromelanin-sensitive MRI techniques can discriminate ET from early-stage tremor-dominant PD and can be a useful clinical tool in the evaluation of tremor disorders. © 2015 International Parkinson and Movement Disorder Society.