IntroductionRestless legs syndrome (RLS) is a sleep disorder characterized by an urge to move the legs associated with uncomfortable paresthesias. Usually, the symptoms manifest in the evening or at night, when the patients take rest, and are relieved by walking or moving the legs (1). Diagnosis of RLS needs to involve the following clinical features: (a) uncomfortable and unpleasant sensations in the legs, (b) worsening of the symptoms during rest, (c) relief of the symptoms by movement, (d) exacerbation of the sensitive disturbance in the evening or at night (1). The majority of RLS cases are commonly classified as idiopathic and include sporadic and inherited forms. Secondary form of RLS has been associated with iron deficiency, renal failure, pregnancy, antidopaminergic therapy, rheumatoid arthritis, or several neurological disorders, including peripheral neuropathy, spinocerebellar ataxia, essential tremor, Parkinson disease, and myelopathies (2-4). The etiopathogenesis of RLS is unknown, yet there is increasing evidence of dopaminergic neurotransmission dysfunction (5-9).RLS prevalence has been reported to be 1.2%-15% and 12.12%-65.1% in the general population and in MS patients, respectively (10-30). RLS symptoms appear usually after the onset of 23,26,27). There is no relationship between MS subtypes and the presence of RLS (18,20,[22][23][24][25]31). There are only three studies that investigated the relationship between functional system involvement and the presence of RLS in MS patients (19,23,25). Two of them showed that there was a significant relationship between some functional system involvement and RLS (19,25). In contrast, Deriu et al. did not find any relationship between the presence of RLS and functional system involvement (23). Some studies suggested that the expanded disability status scale (EDSS) was not related to RLS in MS patients (22,23). However, other studies showed that EDSS score was higher in MS patients with RLS than in those without RLS (18)(19)(20)30).Lesion localization in brain MRI did not show any relationship with the presence of RLS in MS patients in most studies (18)(19)(20)22,23). There is only one study showing that MS patients with RLS (MS/RLS+) and patients without RLS (MS/RLS-) had similar cervical cord lesion load, but with less fractional anisotropy in cervical and brain MRI in the latter.Background/aim: There have been conflicting results in the literature regarding the relationship between functional system involvement, the expanded disability status scale (EDSS), and the presence of restless legs syndrome (RLS) in patients with multiple sclerosis (MS).Materials and methods: Ninety-one patients with MS and 40 patients in a control group (headache, essential tremor, and benign positional paroxysmal vertigo) were studied. The patients underwent a complete neurological examination and Kurtzke functional system scores were calculated. In order to assess the temporal relation between the onset of RLS and MS, a semistructured interview guided by a questionnaire about R...