Neurobiochemical alterations in patients with idiopathic Parkinson's disease in sensorimotor cortex using ¹H-MRS

The sensory motor cortex (SMC) plays a crucial role in motor function and is implicated in the pathophysiology of idiopathic Parkinson's disease (iPD). Asymmetric motor symptomatology in iPD suggests lateralized neurochemical alterations that may underlie disease progression and severity. Single-voxel in vivo proton magnetic resonance spectroscopy using PRESS (20 × 20 × 20 mm³) and MEGA-PRESS (30 × 30 × 30 mm3) sequences were performed on bilateral SMC in 25 iPD patients and 23 healthy controls (HC) at 3 T. Spectra were analyzed using LCModel and Gannet software. In iPD, reductions in total N-acetylaspartate (tNAA; N-acetylaspartate + N-acetylaspartylglutamate) and Glx (glutamine + glutamate) were observed in the hemisphere contralateral to the most affected side. Patients with right most affected hemisphere exhibited a decreased Glx and increased total choline to total creatine ratio (tCho/tCr), while left most affected hemisphere revealed reduced tNAA in the contralateral hemisphere. Compared to healthy controls (HC), right most affected hemisphere had elevated tCho/tCr. Correlation analysis revealed a positive correlation of tCho with Unified Parkinson's Disease Rating Scale (UPDRS) part III and total UPDRS scores, while tNAA negatively correlated with UPDRS part I scores and disease duration in the contralateral hemisphere. Late-onset PD (LOPD) patients had lower glutamine to total creatine ratio (Gln/tCr) levels compared to early-onset PD (EOPD). No significant group differences were observed in GABA + concentrations. These findings suggest that neuronal loss (tNAA), neurotransmitter imbalance (Glx) and gliosis (tCho) may serve as potential in vivo biomarkers to assess asymmetry, progression, and clinical severity in iPD.