TY - JOUR
T1 - Group I nonreciprocal inhibition in restless legs syndrome secondary to chronic renal failure
AU - Marconi, Sara
AU - Scaglione, Cesa
AU - Pizza, Fabio
AU - Rizzo, Giovanni
AU - Plazzi, Giuseppe
AU - Vetrugno, Roberto
AU - La Manna, Gaetano
AU - Campieri, Claudio
AU - Stefoni, Sergio
AU - Montagna, Pasquale
AU - Martinelli, Paolo
PY - 2012/5
Y1 - 2012/5
N2 - 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.
AB - 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.
KW - Group I nonreciprocal (Ib) inhibition
KW - Restless legs syndrome
KW - Spinal reflexes
KW - Uremia
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U2 - 10.1016/j.parkreldis.2011.12.002
DO - 10.1016/j.parkreldis.2011.12.002
M3 - Article
C2 - 22197122
AN - SCOPUS:84860381780
VL - 18
SP - 362
EP - 366
JO - Parkinsonism and Related Disorders
JF - Parkinsonism and Related Disorders
SN - 1353-8020
IS - 4
ER -