Discrepancies between the MRI- and the electrophysiologically defined subthalamic nucleus

Area of Science:

• Neurosurgery
• Neurology
• Medical Imaging

Background:

• Deep brain stimulation (DBS) for Parkinson's disease relies on accurate targeting of the subthalamic nucleus (STN).
• Image-guided targeting using Magnetic Resonance Imaging (MRI) is standard, but its precision relative to electrophysiological data is debated.
• Microelectrode recording (MER) is an intraoperative technique used to refine target localization.

Purpose of the Study:

• To evaluate discrepancies between MRI-defined and electrophysiologically-defined STN.
• To determine if MER offers additional information to MRI-guided STN targeting in DBS.
• To contribute to the understanding of MER's role in improving DBS surgical accuracy.

Main Methods:

• Investigated 44 STNs in 22 Parkinson's disease patients.
• Generated 3D MRI-defined STN from T2-weighted images.
• Performed intraoperative MER at 1,487 locations to define electrophysiological STN (MER-STN).
• Reconstructed and fused 3D MER-STN with MRI data.
• Compared estimated borders of MRI-STN and MER-STN.
• Utilized Student's t-test, Mann-Whitney rank sum, and Fisher's exact tests for statistical analysis.

Main Results:

• MER-STN volumes outside the MRI-STN ranged from 0 to 87 mm³, with a mean of 45 mm³.
• A mean of 44% of MER-STN volumes exceeded the MRI-STN.
• 53.4% of MERs were concordant, while 46.6% were discordant with the MRI-defined STN.
• Discrepancies in dorsal border localization were observed, particularly on the second operated side (mean 1.51 mm).

Conclusions:

• Microelectrode recording (MER) provides supplementary information beyond high-resolution MRI.
• MER can aid in detecting the extent and direction of brain shift during DBS surgery.
• Electrophysiological data refines anatomical targeting, potentially enhancing DBS efficacy and safety.