Is increased spinal nociception another hallmark for Parkinson's disease?

Augmented spinal nociception during the "off" phase has been observed early in Parkinson's disease further increasing with disease duration. To find out whether increased spinal nociception represents a premotor feature, experimental pain sensitivity was assessed in idiopathic REM-sleep behavior disorder (IRBD) patients with or without signs of a neurodegenerative disorder compared to early Parkinson's disease (ePD) patients and healthy controls (HC). Spinal nociception as measured by the nociceptive flexion reflex (NFR) and experimental pain sensitivity as measured by heat and electrical pain thresholds were determined in 14 IRBD, 15 ePD patients in the medication-defined "off" state and 27 HC in an explorative cohort study. No significant differences between IRBD and HC were found with regard to spinal nociception (NFR) and experimental pain sensitivity. However, IRBD patient with anosmia and/or abnormal DaTSCAN tended to increased experimental pain sensitivity. In contrast, early PD patients exhibited increased NFR responses compared to HC, and a tendency for increased spinal nociception compared to IRBD patients. Increased spinal nociception may represent an early but not a premotor, non-motor feature of PD. Whether increased pain sensitivity already presents a premotor feature should be assessed in further studies.