Disconnect between sensory and motor features of restless legs syndrome during the suggested immobilization test

Abstract

The Suggested Immobilization Test (SIT) was developed as an objective diagnostic tool to quantify motor restlessness periodic limb movements during wakefulness (PLMW) associated with Restless Legs Syndrome (RLS). Limited research has explored the relationship between discomfort and pain associated with motor activity in RLS during the SIT. Twenty-five RLS patients and ten control participants completed the International Restless Legs Syndrome Study Group Severity Scale and the SIT with bilateral recordings of tibialis anterior EMG (PLMW index), as well as pain and discomfort visual analogue scales every 5 min for the 60-min SIT. The discomfort score had the ability to discriminate between RLS and control participants (P = 0.0001); however, the PLMW index did not (P = 0.67). The RLS patients also exhibited greater discomfort and pain in the latter half of the SIT (P < 0.05) compared to the initial phase of the SIT and compared to controls. Despite rating significant levels of discomfort, the majority of the RLS patients did not exhibit PLMW possibly suggesting a disconnect between the sensory and motor components of RLS. These sensory and motor features may be independent and as such presentation of PLMW during the SIT may not be a reliable objective measure of RLS.