Background/purpose: To investigate nerve excitability changes in patients with fibromyalgia and the correlation with clinical severity. Methods: We enrolled 20 subjects with fibromyalgia and 22 sex and age-matched healthy subjects to receive nerve excitability test and nerve conduction study to evaluate the peripheral axonal function. Results: In the fibromyalgia cohort, the sensory axonal excitability test revealed increased superexcitability (%) (P = 0.029) compared to healthy control. Correlational study showed a negative correlation between increased subexcitability (%) (r = −0.534, P = 0.022) with fibromyalgia impact questionnaire (FIQ) score. Computer modeling confirmed that the sensory axon excitability pattern we observed in fibromyalgia cohort was best explained by increased Barrett–Barrett conductance, which was thought to be attributed to paranodal fast K+ channel dysfunction. Conclusion: The present study revealed that paranodal sensory K+ conductance was altered in patients with fibromyalgia. The altered conductance indicated dysfunction of paranodal fast K+ channels, which is known to be associated with the generation of pain.
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