Diffusion-weighted imaging and magnetization transfer imaging of tardive and edentulous orodyskinesia

Oral dyskinesias occur in elderly individuals in relation to drug use (tardive dyskinesia, TD) or edentulousness (edentulous orodyskinesia, EOD) but their characterization remains incomplete. Our aim was to investigate whether magnetic resonance techniques such as diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) of the brain could be used to differentiate dyskinetic patients from control subjects. Eight drug-treated patients with TD, 12 EOD patients, 8 drug-treated patients without TD, and 10 control subjects were recruited and examined by DWI and MTI. Measurements in the caudate nucleus, putamen, and globus pallidus yielded globally different apparent diffusion coefficient (ADC) values between drug treated patients with TD and control subjects but the magnetization transfer ratios showed no significant variations. The discrimination between dyskinetic patients and control subjects offered by ADC values was however slightly poorer than the discrimination offered by the previously published choline/creatine ratios measured by MR spectroscopy in the basal ganglia. The results are consistent with the pathophysiological hypothesis of damage to cholinergic interneurons.