Evaluation of Nociceptive Flexor Reflex Response in Patients with Painful Idiopathic Parkinson's Disease

Aim: We aimed to investigate the utility of trigeminocervical reflex (TCR) and nociceptive flexion reflex (NFR) as objective measures for assessing pain—a common NMS—in patients with PD, targeting both the upper and lower body regions. Methods: All subjects were further classified into four groups: Group-I: Healthy individuals without PD or pain, Group-II: Individuals without PD but reporting non-specific musculoskeletal pain, Group-III: PD patients without pain, Group-IV: PD patients with pain as a NMS. The clinical assessment of PD was conducted using the Hoehn and Yahr Staging Scale (HYS) and the Unified Parkinson's Disease Rating Scale (UPDR). We divided the human body into upper and lower regions—utilizing the TCR for upper body pain and the NFR for pain around the lumbar and pelvic areas. Results: The Group-IV had a longer mean disease duration than those in Group-III (8.0±6.6 vs 3.0±3.5 and p=0.121). The mean UPDRS score significantly higher in Group-IV compared to Group-III (42.5±13 vs 27.4±15.3 and p=0.022). The mean VAS score was 7.0±0.7 in Group-II and 6.3±1.3 in Group-IV, with no significant differences in pain localization or VAS scores between the two-groups. Conclusion: Electrophysiological reflex assessments do not appear to be sufficiently reliable in evaluating pain perception in these patients.