Locus Coeruleus Degeneration in Essential Tremor With Mild Cognitive Impairment: A Neuromelanin MRI Study.

Objective: Our aim was to research the neuromelanin-sensitive magnetic resonance imaging (NM-MRI) features of the locus coeruleus (LC) in essential tremor (ET) patients of various cognitive states and to explore the relationships between these features and cognition.

Methods: We recruited three groups of participants, including 30 ET patients with mild cognitive impairment (ET-MCI), 57 ET patients with normal cognition (ET-NC), and 105 healthy controls (HCs). All participants underwent MRI scanning and clinical evaluation. Through NM-MRI images, we compared the contrast-to-noise ratio of LC (CNR) between groups and evaluated the relationships between CNR and cognitive scales.

Results: Compared to HCs, ET-MCI patients had a substantially lower CNR value (p = 0.017). The CNR of ET-NC patients was intermediate between that of ET-MCI patients and HCs. Furthermore, a partial correlation analysis in ET-MCI patients, controlling for age, gender, and education level, showed that higher CNR values correlate with better performance on the Montreal cognitive assessment test and the trail making test A.

Conclusion: LC degeneration in ET patients may partially contribute to cognitive decline, suggesting that the LC norepinephrine system deserves further research on the mechanism of cognitive decline of ET patients as well as the development of targeted drugs.