Static mechanical hyperalgesia without dynamic tactile allodynia in patients with restless legs syndrome.
Pain sensitivity was assessed in 11 patients (age 60 +/- 10 years) with 'primary' restless leg syndrome (RLS) (disease duration 18 +/- 15 years) and 11 age- and gender-matched healthy control subjects. Stimulus-response functions for pricking pain were obtained with seven calibrated punctate mechanical stimulators activating Adelta-high threshold mechano-nociceptors. Stimuli at the foot were significantly more painful than at the hand in both patients and healthy control subjects both in the morning and evening. Generally, pin-prick pain ratings in RLS patients were significantly elevated, by a factor of 5.3 in the upper limb and by a factor of 6.4 in the lower limb indicating a significant generalized static hyperalgesia more pronounced in the lower limb. In contrast, pain to light touch (allodynia = dynamic mechanical hyperalgesia) as tested by a battery of three gentle tactile stimuli was never reported. Acute single-dose dopaminergic treatment with 100 mg levodopa + 25 mg benserazide, 90 min prior to the evening measurements, largely resolved patients' RLS symptoms, but had no effect on pin-prick pain. Static hyperalgesia to pin-prick, however, was significantly reversed (median reduction -74%) by long-term individually tailored dopaminergic treatment. Our study shows that patients with RLS exhibit a profound static mechanical hyperalgesia to pin-prick stimuli, but no dynamic mechanical hyperalgesia (allodynia). This type of hyperalgesia is probably mediated by central sensitization to Adelta-fibre high-threshold mechanoreceptor input, a hallmark sign of the hyperalgesia type of neuropathic pain. The reduction of hyperalgesia in RLS patients by long-term dopaminergic treatment suggests that the pathophysiology of RLS includes disturbed supraspinal pain modulation involving the basal ganglia and/or descending dopaminergic pathways.
Stiasny-Kolster
K
K
Department of Neurology, Center of Nervous Diseases, Philipps-University, Marburg, Germany. stiasny@staff.uni-marburg.de
Magerl
W
W
Oertel
W H
WH
Möller
J C
JC
Treede
R-D
RD
D000328:Adult; D000368:Aged; D015259:Dopamine Agents / Q000627:therapeutic use; D004334:Drug Administration Schedule; D005260:Female; D005528:Foot / Q000294:innervation; D006225:Hand / Q000294:innervation; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D008875:Middle Aged; D010147:Pain Measurement; D010812:Physical Stimulation / Q000379:methods; D012148:Restless Legs Syndrome / Q000188:drug therapy / Q000503:physiopathology*
D015259:Dopamine Agents