Elevated cerebral oxygen extraction fraction in Parkinson's disease correlates with motor impairment severity

Parkinson's disease (PD) is the second most common neurological disorder, but its diagnosis remains challenging. Cerebral glucose metabolism has emerged as a promising biomarker for PD based on previous studies. While these studies have established a PD-related pattern of metabolic activity of glucose in the brain, cerebral oxygen metabolism is less explored, and there is no well-established PD-related pattern of cerebral oxygen metabolism. This study investigates cerebral oxygen extraction fraction (OEF) as a measure of cerebral oxygen metabolism to monitor disease progression in early-stage PD. OEF was measured noninvasively using magnetic resonance imaging with the QSM + qBOLD technique in 50 PD patients and 30 healthy controls. Whole-brain and region-of-interest analyses were conducted, focusing on key regions within the basal ganglia. Results revealed significantly elevated OEF in the basal ganglia of PD patients compared to controls. Moreover, OEF showed a positive correlation with Unified Parkinson's Disease Rating Scale Part III scores, indicating an association between increased oxygen extraction and motor impairment severity in early PD. These findings support the potential of cerebral OEF as an early biomarker of motor symptom severity. Therefore, it can enhance our understanding of metabolic dysfunction in the basal ganglia during the early stages of PD.