Symptom‐related changes in current perception threshold of restless legs syndrome

Abstract

Few studies have investigated the mechanisms responsible for the symptoms of restless legs syndrome (RLS). However, these studies were mainly performed during the asymptomatic period and therefore their findings might not apply to changes in sensory processing that occur during the symptomatic period. The objective of this study was to investigate the function of sensory nerve fibres in RLS patients using the current perception threshold (CPT) test during the daytime and in the presence of symptoms. Ninety‐three patients with RLS and 34 healthy controls were included in the study. RLS patients were further divided into two subgroups, those who were experiencing RLS symptoms during the CPT test (symptom+) and those without symptoms (symptom−). Demographic data, RLS rating scale score and visual analogue scale were collected. Of the 127 enrolled subjects, CPT values were significantly lower in RLS patients than in controls for all three frequencies. Among the control and RLS subgroups (53 symptom+, 40 symptom−), symptom+ patients showed lower CPT values than controls. This finding indicates a relative hyperaesthetic state in the sensory afferents of peripheral nerves in symptom+ patients. There were no significant differences between the symptom− group and controls. The significantly lower CPT values for all three frequencies in symptom+ patients suggest that central sensory processing disturbance of sensory nerve fibres’ input may be involved in the development of symptoms in RLS patients.

Association between restless legs syndrome and peripheral neuropathy: A systematic review and meta‐analysis

“…These data suggest the presence of small and large fibre dysfunction according to a circadian rhythm in patients with iRLS. showed similar values to controls [86].…”

“…Studies with LEP were consistent both with central and peripheral sensory dysfunction in patients with RLS [84]. Finally, studies with CPT showed data consisting of fluctuating small and large fibre dysfunction [85,86]. Alterations in QST, LEP and CuST do not discriminate between central or peripheral dysfunction along somatosensory pathways.…”

“…These data suggest the presence of small and large fibre dysfunction according to a circadian rhythm in patients with iRLS. The same group reported significantly lower CPT values in 93 RLS patients compared with 34 controls for all three frequencies during daytime; however, when they divided RLS patients into those with and without RLS symptoms during the study (53 and 40 patients, respectively), the lower CPT values were only found in the group with RLS symptoms, whilst the other group showed similar values to controls [86].…”

<p>Increased Gray Matter Density and Functional Connectivity of the Pons in Restless Legs Syndrome</p>

“…Peripheral sensory thresholds of RLS patients have been reported to be normal. 30,31 Thus, altered central processing rather than enhanced peripheral detection may underlie the sensation of limb discomfort in RLS. The increased gray matter density in pons_2 may be associated with sensory sensitivity.…”

Restless Legs Syndrome; Inflammation, Electroneuromyography Findings, and Disease Severity

“…Studies with laser-evoked potentials have shown central and peripheral sensory dysfunction in patients with RLS. Seok et al showed small and large ber dysfunction in their study with the current perception threshold (28,29,30). Therefore, these studies cannot distinguish between central or peripheral nervous system dysfunction in somatosensory pathways.…”