Diffusion Imaging in Tremor

Diffusion-weighted magnetic resonance imaging (DWI) of the brain is a magnetic resonance technique that probes the motion of free water undergoing spontaneous diffusion in living tissue. Unlike conventional, structural MRI, DWI provides insights into the microscopic composition, integrity and orientation of structures in the human brain. DWI and its derivative measures enable the study of the microstructure of the brain and its white-matter connectivity. These non-invasive measures offer a window into the neuropathology of tremor, and the underlying tremor disorders. In Parkinson’s disease (PD), changes in diffusion-derived parameters such as mean diffusivity (MD) and fractional anisotropy (FA) have been reported in the substantia nigra and its connections to the striatum when compared to control subjects, suggesting that these imaging measures are sensitive to the degeneration of the nigral dopaminergic neurons and their striatal projections. In essential tremor (ET), a link between diffusion-derived measures and the severity of tremor has been shown. DWI-derived diffusion tractography (DT) enables the study of connectional targets that mediate the effects of deep brain stimulation (DBS) for tremor, and carries the promise to help guide stereotaxic surgical targeting in the future. DT has also provided insight into the motor circuits putatively affected by accidental, tremor-causing brain lesions. In conclusion, DWI is a promising tool in the study of tremor disorders. Further research is needed to determine if DWI may be useful to plan stereotaxic surgery for tremor.