Preoperative Brain Atrophy as a Predictor of Motor Outcomes after Subthalamic Nucleus Deep Brain Stimulation in Parkinson’s Disease

INTRODUCTION: Brain atrophy is common in Parkinson's disease (PD) and contributes to motor and cognitive decline. However, the predictive value of neuroimaging-based volumetric measures for motor outcomes following deep brain stimulation (DBS) remains unclear. Notably, subclinical dementia may play a key role in DBS response. This study examines whether preoperative volumetric assessment can predict motor outcomes after subthalamic nucleus (STN) DBS in PD. METHODS: Preoperative T1-weighted 3D MP-RAGE magnetic resonance images scans were analyzed to measure subcortical, ventricular, and cortical volumes using Brainlab software. Motor outcomes were assessed by changes in the Movement Disorder Society - Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS-III) scores pre- and postoperatively in 39 participants. Stepwise logistic regression was performed to determine associations between brain volumes and DBS response. RESULTS: Smaller substantia nigra compacta volume {0.81 (interquartile range [IQR]: 0.74-0.85) vs. 0.72 [IQR: 0.69-0.73]), larger ventricular system (26.1 [IQR: 21.4-30.05] vs. 34.1 [IQR: 28.6-40.87]), and lower atrophy ratio (41.76 [IQR: 37.59-50.71] vs. 29.63 [IQR: 25.9-36.55]) were significantly associated with reduced motor improvement following STN-DBS. The predictive model based on these values demonstrated excellent performance (area under the receiver operating characteristic curve = 0.95, 95% CI: 0.87-1; p < 0.01) in forecasting poorer DBS treatment outcomes as measured by the MDS-UPDRS-III scale. Additionally, lower thalamic volume and poorer executive function (assessed by the Frontal Assessment Battery) correlated positively with a lower atrophy ratio. CONCLUSION: Our findings highlight the impact of enlargement of ventricular system and brain atrophy, particularly of the substantia nigra, on motor outcomes after STN-DBS. The association between atrophy measures and executive dysfunction suggests that subclinical dementia may underlie poor DBS response. Brain atrophy could serve as an early marker of cognitive decline, influencing postoperative disease progression and treatment outcomes. Future studies should further explore the role of neurodegeneration in DBS response to optimize patient selection and electrode targeting.