Serum Neurofilament Light-Chain Levels in Essential Tremor: A Replication Study.

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Essential tremor (ET) is a highly-prevalent neurological disease. At present, there are no clinical biomarkers. Neurofilament light (NfL) has been studied as a measure of neuronal damage in a considerable number of neurological disorders. There have been three studies of ET, and results are inconsistent. 40 ET cases were enrolled in a research study between February and November 2023 and compared to two control groups from Study 1 (n = 41) and Study 2 (n = 185). Total tremor score was a measure of the severity of action tremor. Blood samples were analyzed for serum NfL level on the Simoa® platform using an NF-Light™ kit as a marker of axonal injury. Serum log NfL levels were higher in ET cases than controls in Study 1 (p<0.001) and Study 2 (p<0.001). In a multivariate linear regression model, ET cases (p = 0.03) and individuals of older age (p<0.001) had higher serum log NfL levels than controls (combined in Studies 1 and 2). There was no association in ET cases between serum log NfL level and total tremor score (Pearson's r = 0.08, p = 0.63). This new study further validates the elevation in serum NfL levels in ET, now representing the third study to do so. In combination, the converging data suggest that there is an overall increase in serum NfL levels in ET. The demonstration of elevated serum levels of NfL in ET adds an additional piece of evidence that there is neuronal damage in ET.