Subthalamic Nuclear Tissue Contrast in Inversion Recovery MRI Decreases with Age in Medically Refractory Parkinson's Disease

Abstract

MRI appearance of subthalamic nucleus (STN) boundaries in Parkinson's patients is often unreliable and not well understood. An objective comparison between FSE T2 and inversion recovery (FSTIR) sequences for stereotactic placement of deep brain stimulators is presented to advance current understanding of STN tissue contrast for refractory Parkinson's disease (PD). We imaged 12 PD (age 53-82) and 12 control patients (age 48-77) using T2 and FSTIR sequences at 1.5 T. To avoid MR contrast variation from hardware and patient dependent sources we used an internal thalamic tissue standard to normalize STN signal intensity and correlated it with patient age for these two groups. Normalized FSTIR-weighted STN contrast decreased with increasing age for PD patients (Spearman Rank correlation = -.5) while remained virtually unchanged for controls with age (Spearman Rank coefficient ≈ 0). T2-weighted STN contrast did not show appreciable changes with age for both the groups (Spearman correlation ≈ -.1). STN, a common stimulation target, shows an age dependent trend for normalized FSTIR MRI contrast. Although larger patient pools are needed, our work points to tissue relaxation-based changes in STN that may provide insight in early stages of brain pathology involving DBS targets in medically refractory Parkinson's disease.