Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology · 2014
Abnormal gating of axonal slow potassium current in cramp-fasciculation syndrome.
СтатьяПоддержка исследования: вне правительства СШАНазвание и аннотация: Перевод в очереди
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Shimatani Yoshimitsu, Nodera Hiroyuki, Shibuta Yoshiko, Miyazaki Yoshimichi, Misawa Sonoko, Kuwabara Satoshi, Kaji Ryuji
Аннотация
OBJECTIVE: Cramp-fasciculation syndrome (CFS) is a heterogeneous condition with multiple underlying causes. Although dysfunction of slow K(+) channels has been reported in patients with CFS, testing all potential candidates for this problem using conventional in vitro functional analysis would be prohibitively cost- and labor-intensive. However, relatively economical and non-invasive nerve-excitability testing can identify ion channel dysfunction in vivo when combined with numerical modeling.
METHODS: Patients with CFS underwent nerve conduction study, needle electromyography, and nerve excitability testing. Mathematical modeling of axonal properties was applied to identify the pathophysiology.
RESULTS: Four patients had distinct electrophysiological findings (i.e., fasciculation potentials, doublet/multiplet motor unit potentials, and sustained F responses); excitability testing showed the following abnormalities: reduction of accommodation during prolonged depolarization, lack of late sub excitability after a supramaximal stimulation, and reduction of the strength-duration time constant. Mathematical modeling showed a loss of voltage-dependence of a slow K(+) current. None of these patients had a mutation in the KCNQ2, 3, or 5 genes.
CONCLUSIONS: This study showed that patients with CFS might have abnormal kinetics in a slow K(+) current.
SIGNIFICANCE: Nerve-excitability testing may aid the decision to start therapeutic intervention such as administration of slow K(+) channel openers.
METHODS: Patients with CFS underwent nerve conduction study, needle electromyography, and nerve excitability testing. Mathematical modeling of axonal properties was applied to identify the pathophysiology.
RESULTS: Four patients had distinct electrophysiological findings (i.e., fasciculation potentials, doublet/multiplet motor unit potentials, and sustained F responses); excitability testing showed the following abnormalities: reduction of accommodation during prolonged depolarization, lack of late sub excitability after a supramaximal stimulation, and reduction of the strength-duration time constant. Mathematical modeling showed a loss of voltage-dependence of a slow K(+) current. None of these patients had a mutation in the KCNQ2, 3, or 5 genes.
CONCLUSIONS: This study showed that patients with CFS might have abnormal kinetics in a slow K(+) current.
SIGNIFICANCE: Nerve-excitability testing may aid the decision to start therapeutic intervention such as administration of slow K(+) channel openers.