gms | German Medical Science

Objective: The aim of our study was to investigate which subcorticalfiber tracts and cortical areas are involved in the occurrence of side-effects in deep brain stimulation for Parkinson’s disease.

Methods: 21 patients with Parkinson’s disease and bilaterally implanted electrodes in the subthalamic nucleus were investigated. Diffusion weighted images (DWI) with 64 gradient directions were included in the routine preoperative imaging procedure for deep brain stimulation. Post-operative CT scans were fused to the DWI data set and the position of the individual contacts of the electrodes were determined. Probabilistic fiber-tracking was performed with seed regions based on each individual contact of the electrodes and the resulting anatomical fiber tracts and cortical areas were determined. We compared the connectivity pattern of contacts, which induced side effects with the connectivity pattern of contacts that did not.

Results: Electrode-contacts that provoked motoric side-effects were significantly more often connected with the primary motor cortex than contacts without this effect. However, theywere not connected more frequently with fibers of the pyramidal tract than contacts without motoric side effects. Although paresthesia provoking contacts had a positive contingency with the superior parietal lobe, they were not significantly more often connected to the medial lemniscus than non-provoking contacts (82.4% of provoking and 77.8% of non-provoking contacts; p= 0.502). Oculomotor side effects were positively associated with connections to the inferior frontal gyrus and the lateral part of the anterior limb of the capsula interna. A positive contingency for hyperkinesia existed with the supplementary motor area.

Conclusion: Contacts that evoked side effects were connected to the expected cortical areas but less so to their adjacent subcortical fiber tracts. Categorization of subcortical fiber tracts seems to be error-prone.