Sensory profile in primary restless legs syndrome and restless legs syndrome associated with small fibre neuropathy

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ARTICLE Sir, The association of restless legs syndrome with polyneuropathy, especially with involvement of small sensory fibres, is suggested by several observations (Iannaccone et al. , 1995; Polydefkis et al. , 2000; Gemignani et al. , 2006); however, it is still controversial (Hattan et al. , 2009). Bachmann et al. (2010) investigated 34 consecutive outpatients with restless legs syndrome from their Movement Disorders Clinic and identified 13 patients (38%) with small fibre neuropathy. The main scope of the study was to compare the sensory profile—according to a validated, comprehensive quantitative sensory test protocol—in primary restless legs syndrome versus secondary restless legs syndrome associated with small fibre neuropathy, and the conclusion was that thermal hypoaesthesia characterizes the latter. We have several concerns regarding the methodology of this study. Differential diagnosis of secondary restless legs syndrome associated with small fibre neuropathy was based on clinical symptoms, i.e. patients with small fibre neuropathy were identified as having persistent plus symptoms, mainly painful, whereas patients with primary restless legs syndrome had tingling and dragging paraesthesias; however, even these latter symptoms may be features of small fibre neuropathy (Lacomis, 2002; Hoitsma et al. , 2004). The diagnosis of small fibre neuropathy was confirmed by skin biopsy, which was, however, not performed in any of the patients with putative primary restless legs syndrome. In addition, not all patients with small fibre neuropathy had …