Identifying the white matter fiber pathways responsible for tremor in Multiple Sclerosis (MS).
MS-related tremor is characteristically resistant to treatment, affecting 25% and 58% of the patients with MS.
Patients with MS-related tremor (n=36) had 3.0 T MRI scans with T1-weighted, FLAIR, and diffusion-weighted (DWI) sequences. Subjects were gender and age-matched with a control MS group (n = 36) without tremor.
Using regional brain diffusivity measures obtained from MRICloud and diffusion connectometry findings from DSI Studio, we identified 53 tracts-of-interest associated with MS-related tremor.
Tractography of the identified tracts was performed in DSI Studio. The diffusion data were reconstructed using generalized q-sampling. A supervised atlas-based tractography method was used to segment the pathways using tract-specific parameters set based on neuroanatomical topology and standardized across subjects.
We obtained the partial spearman correlation coefficients (rs) for tremor severity with mean tract diffusivity measures adjusting for possible confounders.
Of the 53 tracts, 5 showed negative correlation between mean tract fractional anisotropy (FA) and tremor severity: the left medial lemniscus (rs = -0.55, p = < .001), the forceps minor of the corpus callusom (rs = -0.45, p = 0.009), the right anterior corticostriatal tract (rs = -0.413, p = 0.017), the forceps major of the corpus callusom (rs = -0.376, p = 0.031), and the fornix (rs = -0.367, p = 0.035). Of these tracts 3 had radial diffusivity (RD) values significantly correlating with tremor severity, namely the left medial lemniscus (rs = 0.429, p = 0.013), the right anterior corticostriatal tract (rs = 0.379, p = 0.029), and the forceps minor of corpus callosum (rs = 0.369, p = 0.034).
Using two independent techniques, we identified pathways associated with MS-related tremor. For the first time, we show that commissural, medial lemniscus, and striatal tracts correlate with tremor severity.