Objective: To investigate neurofilament light chain protein (sNfL) concentrations in serum in Essential Tremor (ET) compared to healthy controls and to assess whether sNfL is associated with disease severity and other markers of disease progression in ET.

Background: Neuronal and axonal destruction are hallmarks of neurodegenerative diseases. Quantitation of sNfL using a single molecule array (Simoa) enables to reliably assess and monitor neuro-axonal damage in the peripheral blood. There is a long going debate if ET represents a “benign” tremor syndrome or if it is linked to neurodegeneration especially in the cerebellum.

Method: We included 37 patients with ET from our PROMOVE cohort (mean age 65.3±6.55 years, 20 male, 17 female, 20 had a follow-up-visit after a mean period of 4.89±0.99 years) and 37 age and gender matched healthy controls (HC). sNfL levels were measured by Simoa at baseline and follow up and all participants underwent 3T brain MRI and a detailed clinical examination at both time points.

Results: ET showed significant higher sNfL levels compared to healthy controls at baseline (ET: 13.78±6.52 pg/ml, HC: 10.38±3.81 pg/ml; p=0.022) and follow-up (ET: 15.32±4.53 pg/ml, HC: 11.93 ±4.08 pg/ml; p=0.017).
There was a significant increase in sNfL over time (repeated-measure anova p-value for time 0.004), but no significant group-difference (p-value for time*group 0.981).
There was no significant correlation between sNfL and MRI-volumetry and R2* in cerebellar, thalamic-, basal ganglia- and cortical-regions and no correlation to disease duration and the Fahn-Tolosa-Marin tremor rating scale.
We found a significant negative correlation between sNfL at baseline and CERAD total scores corrected for age as well as CERAD z-score: CERAD total score 1 (beta -0.489, p=0.009), CERAD total score 2 (beta -0.486, p=0,008), CERAD memory-score (beta -0.483, p=0.007) and CERAD z-score (beta -0.390; p=0.021).

Conclusion: The significantly increased concentrations of sNfL in ET may indicate an underlying degenerative process in a subgroup of patients with ET, clinically associated with subtle cognitive abnormalities and MRI changes. Our findings support the new tremor classification that regards ET as a heterogeneous syndrome rather than one disease entity. sNfL may be useful in subclassifying patients with ET, which is mandatory in order to uncover the so far unknown various aetiologies of this common tremor syndrome.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neurofilament-light-chain-protein-nfl-is-elevated-in-essential-tremor/