Restless Legs Syndrome (RLS) is a neurological disorder whose sufferers demonstrate profound sleep disruption and reduced quality of life.
While substantial comorbidities have been noted between RLS and pain conditions such as fibromyalgia, few studies have evaluated potential abnormalities in pain perception in RLS.
We evaluated psychophysical responses to noxious thermal and pressure stimuli in both treated and untreated RLS patients, compared to matched controls.
Thirty-five RLS patients (20 treated, 15 untreated; 54% female, mean age=61) were compared to 22 controls with no sleep disorders.
RLS patients demonstrated somewhat reduced heat pain thresholds (assessed on the forearm) relative to controls (p< .07).
Pressure pain thresholds assessed on the trapezius, quadriceps, and thumb were also lower among RLS patients (p’s< .05). Moreover, significant group differences emerged on measures of temporal summation of heat pain (p’s< .05), an index of spinal sensitizability, with RLS patients demonstrating enhanced temporal summation of pain relative to controls.
• The groups of treated and untreated RLS patients were virtually identical in their pain responses, suggesting that pharmacologically ameliorating RLS symptoms may not result in normalization of nociceptive processing.
• Collectively, none of the differences between RLS patients and controls were attributable to pain-related psychosocial processes.
• However, both treated and untreated RLS patients reported disrupted sleep relative to controls, and indices of poor sleep were related to enhanced pain sensitivity.
• Globally, these findings suggest that central nervous system pain processing may be dysregulated in RLS, perhaps as a consequence of disrupted and shortened sleep periods, which may have lifelong implications for pain-related quality of life in these patients.
• RLS patients, even those whose symptoms are effectively managed, may be at elevated long-term risk for the development or maintenance of persistent pain conditions.
Further studies in this area could help to improve the prospects for pain management in RLS patients.
Source: American Pain Society Annual Scientific Meeting May 7-9, 2009, poster #171, May 2009. Edwards R. Johns Hopkins, Baltimore, Maryland, USA.