Group I nonreciprocal inhibition in restless legs syndrome secondary to chronic renal failure

Sara Marconi, Cesa Scaglione, Fabio Pizza, Giovanni Rizzo, Giuseppe Plazzi, Roberto Vetrugno, Gaetano La Manna, Claudio Campieri, Sergio Stefoni, Pasquale Montagna, Paolo Martinelli

Research output: Contribution to journalArticle

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.

Original languageEnglish
Pages (from-to)362-366
Number of pages5
JournalParkinsonism and Related Disorders
Volume18
Issue number4
DOIs
Publication statusPublished - May 2012

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Keywords

  • Group I nonreciprocal (Ib) inhibition
  • Restless legs syndrome
  • Spinal reflexes
  • Uremia

ASJC Scopus subject areas

  • Geriatrics and Gerontology
  • Clinical Neurology
  • Neurology

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