F-Wave Duration as a Specific and Sensitive Tool for the Diagnosis of Restless Legs Syndrome/Willis-Ekbom Disease

Abstract

Study Objectives: Restless legs syndrome, also known as Willis-Ekbom disease (RLS/WED), is a frequent condition, though its pathophysiology is not completely understood. The diagnosis of RLS/WED relies on clinical criteria, and the only instrumental tool, the suggested immobilization test, may lead to equivocal results. Recently, neurophysiological parameters related to F-wave duration have been proposed as a diagnostic aid. The aim of this study is to assess and compare the diagnostic values of these parameters in diagnosis of RLS/WED. Methods: Fifteen women affected by primary RLS/WED and 17 age-and sex-matched healthy subjects. A complete electroneurographic evaluation, including nerve conduction studies (NCS), cutaneous silent period (CSP), and F-wave parameters, namely amplitude, F-wave duration (FWD), and the ratio between FWD and duration of the corresponding compound muscle action potential (FWD/CMAPD). Results:No subject showed alterations of the NCS. However, FWD and FWD/CMAPD of both upper and lower limbs were significantly longer in patients than controls. Tibial FWD/CMAPD best discriminated RLS/WED patients from controls. A cutoff of 2.06 yielded a sensitivity of 69.2%, a specificity of 94.1%, a positive predictive power of 90%, and a negative predictive power of 80% (area under the curve = 0.817; 95% confidence interval = 0.674-0.959). The combination of ulnar or tibial FWD/CMAPD increases the sensitivity (85.7%) while slightly decreasing the specificity (87.5%, positive predictive value: 85.7%, negative predictive value: 87.5%). Conclusions: Lower limb FWD/CMAPD ratio may represent a supportive diagnostic tool, especially in cases of evening lower leg discomfort of unclear interpretation.

Use of cutaneous silent period parameters as a diagnostic indicator in patients with restless legs syndrome-a study in south Indian population

“…Oz O et al, [12] found that while the CSP latency was longer, the CSP duration was shorter in RLS patients compared to controls. While similar findings were reported by Isak B et al, [11] a recent study by Congui P et al, [10] did not find any significant abnormality in CSP in RLS patients probably due to the small sample size or minor differences in the methodology. Han JK et al, [15] investigated the patho-physiological relationship between RLS and small fiber neuropathy using the CSP and found that while the CSP latencies did not differ between RLS patients and healthy controls, the mean CSP duration was significantly longer in RLS patients than in controls.…”

“…It is therefore imperative that RLS which is a common under-diagnosed condition in India be recognized at an early stage of its inception and prompt treatment be started to improve the patient's 'quality of life'. The diagnosis of RLS primarily depends on the clinical criteria and the only instrumental tool, the suggested immobilization test leads to equivocal results [10]. Some authors have suggested the use of F-wave duration and its ratio with the corresponding muscle action potential as a possible supportive diagnostic tool for RLS patients: both of these were significantly longer when compared to controls [10,11].…”

Circadian variation of flexor withdrawal and crossed extensor reflexes in patients with restless legs syndrome

“…(). With central sensitization there would be hyperexcitability (Woolf, ), as seen with alterations in reflex responses shown in previous studies (Bara‐Jimenez et al ., ; Congiu et al ., ; Gunduz et al ., ; Isak et al ., ) as well as in the current study, and hyperalgesia (Woolf, ), which has also been shown in patients with RLS (Bachmann et al ., ; Cho et al ., ; Edwards et al ., ; Stiasny‐Kolster et al ., , ).…”

Peripheral Silent Period In Cervical and Generalized Dystonia

“…CuSPs were studied in various movement disorders. CuSP was abnormal in essential tremor, multiple system atrophy, and Parkinson's disease 10,11 . It was normalized after administration of low-dose propranolol in essential tremor 12 .…”