title: Thermal hypoaesthesia differentiates secondary restless legs syndrome associated with small fibre neuropathy from primary restless legs syndrome.
abstract: This study aimed to assess thermal and mechanical perception and pain thresholds in primary idiopathic restless legs syndrome and secondary restless legs syndrome associated with small fibre neuropathy. Twenty-one patients (age: 53.4 + or - 8.4, n = 3, male) with primary restless legs syndrome and 13 patients (age: 63.0 + or - 8.2, n = 1, male) with secondary restless legs syndrome associated with small fibre neuropathy were compared with 20 healthy subjects (age: 58.0 + or - 7.0; n = 2, male). Differential diagnosis of secondary restless legs syndrome associated with small fibre neuropathy was based on clinical symptoms and confirmed with skin biopsies in all patients. A comprehensive quantitative sensory testing protocol encompassing thermal and mechanical detection and pain thresholds, as devised by the German Research Network on Neuropathic Pain, was performed on the clinically more affected foot between 2 pm and 1 am when restless legs syndrome symptoms were present in all patients. Patients with primary restless legs syndrome showed hyperalgesia to blunt pressure (P < 0.001), pinprick (P < 0.001) and vibratory hyperaesthesia (P < 0.001). Patients with secondary restless legs syndrome associated with small fibre neuropathy showed thermal hypoaesthesia to cold (Adelta-fibre mediated) and warm (C-fibre mediated) (all P < 0.001) and hyperalgesia to pinprick (P < 0.001). Static mechanical hyperalgesia in primary and secondary restless legs syndrome is consistent with the concept of central disinhibition of nociceptive pathways, which might be induced by conditioning afferent input from damaged small fibre neurons in secondary restless legs syndrome.
authors.affiliation: Department of Clinical Neurophysiology, Georg August University, Robert Koch Strasse 40, D-37075 Goettingen, Germany. cbachma@gwdg.de
authors.forename: Cornelius G
authors.initials: CG
authors.lastname: Bachmann
authors.forename: Roman
authors.initials: R
authors.lastname: Rolke
authors.forename: Uta
authors.initials: U
authors.lastname: Scheidt
authors.forename: Christine
authors.initials: C
authors.lastname: Stadelmann
authors.forename: Martin
authors.initials: M
authors.lastname: Sommer
authors.forename: Goran
authors.initials: G
authors.lastname: Pavlakovic
authors.forename: Svenja
authors.initials: S
authors.lastname: Happe
authors.forename: Rolf-Detlef
authors.initials: RD
authors.lastname: Treede
authors.forename: Walter
authors.initials: W
authors.lastname: Paulus
mesh_terms: D000368:Aged; D003080:Cold Temperature; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D017288:Pain Threshold; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D017440:Photoperiod; D010812:Physical Stimulation; D011312:Pressure; D012148:Restless Legs Syndrome / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D012684:Sensory Thresholds; D012867:Skin / Q000473:pathology; D055698:Touch Perception / Q000502:physiology*; D014732:Vibration