title: Group I nonreciprocal inhibition in restless legs syndrome secondary to chronic renal failure.
abstract: BACKGROUND
  Neurophysiological investigations disclosed spinal cord hyperexcitability in primary restless legs syndrome (p-RLS). Uremic RLS (u-RLS) is the most common secondary form, but its pathophysiological mechanisms remain unsettled. Aim of this study was to explore spinal cord excitability by evaluating group I nonreciprocal (Ib) inhibition in u-RLS patients in comparison with p-RLS patients and healthy subjects.
  
  
  METHODS
  Eleven u-RLS patients undergoing long-term hemodialysis treatment, nine p-RLS patients and ten healthy subjects were studied. Soleus H reflex latency (HR-L), H(max)/M(max) ratio, and Ib inhibition were evaluated. Ib inhibition was tested measuring the amplitude changes in soleus H reflex following stimulation of the synergist gastrocnemius medialis (GM) nerve at rest. Nerve conduction studies were performed in the uremic patients.
  
  
  RESULTS
  The H(max)/M(max) ratio did not differ in the three groups. The u-RLS patients showed a normal Ib inhibition comparable with the healthy group, whereas the p-RLS group had evidence of a reduced active inhibition compared with both u-RLS patients (P = 0.04) and controls (P = 0.007), prominently at 5 ms (P = 0.007) and at 6 ms (P = 0.02) of conditioning-test interval. Neurophysiological examination disclosed abnormalities ranging from higher HR-L to clear-cut polyneuropathy in most u-RLS patients.
  
  
  CONCLUSIONS
  Unlike p-RLS patients, u-RLS patients had normal Ib inhibition, suggesting a regular supraspinal control of Ib spinal interneurons. Subclinical peripheral nerve abnormalities were detected in most uremic patients. Peripherally disrupted sensory modulation may represent the major pathophysiological determinant of uremic RLS.
authors.affiliation: Dipartimento di Scienze Neurologiche, Università di Bologna IRCCS, Institute of Neurological Sciences of Bologna, Bologna, Italy. sara-7902@libero.it
authors.forename: Sara
authors.initials: S
authors.lastname: Marconi
authors.forename: Cesa
authors.initials: C
authors.lastname: Scaglione
authors.forename: Fabio
authors.initials: F
authors.lastname: Pizza
authors.forename: Giovanni
authors.initials: G
authors.lastname: Rizzo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Plazzi
authors.forename: Roberto
authors.initials: R
authors.lastname: Vetrugno
authors.forename: Gaetano
authors.initials: G
authors.lastname: La Manna
authors.forename: Claudio
authors.initials: C
authors.lastname: Campieri
authors.forename: Sergio
authors.initials: S
authors.lastname: Stefoni
authors.forename: Pasquale
authors.initials: P
authors.lastname: Montagna
authors.forename: Paolo
authors.initials: P
authors.lastname: Martinelli
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004558:Electric Stimulation; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000150:complications / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology*; D009460:Neurologic Examination; D011115:Polyneuropathies / Q000209:etiology; D011930:Reaction Time; D006435:Renal Dialysis / Q000379:methods; D012148:Restless Legs Syndrome / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013997:Time Factors