The role of brain shift, patient age, and Parkinson's disease duration in the difference between anatomical and electrophysiological targets for subthalamic stimulation.

INTRODUCTION

Although microrecording is common in subthalamic stimulation, microelectrode monitoring prolongs surgical time and may increase the risk of haemorrhagic complications. The main reason for electrophysiological mapping is the discrepancy between the calculated anatomical and final electrophysiological targets. The aim of this paper is to describe the relationship between anatomical and electrophysiological targets defined as the best electrophysiological recordings from multiple parallel electrode tracts, explaining the target discrepancy with attention paid to the role of brain shift and patient- and disease-related factors.

MATERIALS AND METHODS

Subthalamic electrodes were stereotactically implanted in 58 patients using microrecording by means of parallel electrodes at defined distances. The relationship between the final electrode placement to its anatomical trajectory and the relationship between the definitive electrodes implanted on the right and left sides were analysed, as was the influence of patient age, Parkinson's disease duration, and late motor complications duration.

RESULTS

Final electrode placement matched the anatomical trajectory in 53.4% of patients on the right side and 43.1% of patients on the left side. Electrode positions were symmetrical in 38.3% of patients. The analysis of left and right electrode positions does not prove a statistically significant prevalence of lateral and posterior final electrode trajectories as could be expected from lateral and posterior movements of the brain caused by brain shift, although there was some tendency for a larger percentage of lateral electrodes on the left side. Age, Parkinson's disease duration, and L-DOPA effect duration were not confirmed as responsible factors.

CONCLUSIONS

The difference between anatomical trajectory and final electrode placement supports the use of functional microelectrode monitoring in subthalamic deep brain stimulation. Brain shift is not the only causative factor of the difference. The possible roles of age, Parkinson's disease duration, and late motor complications duration were also not confirmed by study results.