title: [The electrophysiologic diagnosis for muscle ion channelopathies].
abstract: The periodic paralysis (PP) and myotonic syndromes have been recognized as muscle ion channelopathies (MIC) consequent to the discovery of genetic abnormalities of muscle ion channels. Genetic studies are therefore indispensable in the diagnosis of MIC. However, it is not practical to examine all muscle ion channels immediately upon identification of clinical symptoms. Clinical symptoms of MIC occur due to the abnormal excitability of the muscle membrane which is in turn related to abnormal ion channel genes. Therefore, a series of electrophysiologic tests is useful in examining the characteristics of abnormal excitability and predicting the abnormal ion channel Needle EMG studies can detect myotonic discharges while the prolonged exercise test can distinguish between primary and secondary PP. For myotonia, pattern I which includes the repeated short exercise test at room temperature or at cold skin temperature is specific for paramyotonia congenita, pattern II is characteristic for myotonia congenita, and pattern III is useful for Na channel myotonia. The decrement of CMAP with 10 Hz repetitive stimulation is related to mutation type in myotonia congenita. Thus, these electrophysiological tests may be of use in screening for MIC to narrow down the diagnosis and the selection of candidates for gene analysis.
authors.affiliation: Department of Neurology and Geriatrics, Kagoshima University Graduate School of Medical and Dental Sciences.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Arimura
authors.forename: Tomonori
authors.initials: T
authors.lastname: Nakamura
authors.forename: Michiyoshi
authors.initials: M
authors.lastname: Yoshimura
authors.forename: Akiko
authors.initials: A
authors.lastname: Uehara
authors.forename: Kimiyoshi
authors.initials: K
authors.lastname: Arimura
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Sakoda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takashima
mesh_terms: D000368:Aged; D053447:Channelopathies / Q000175:diagnosis*; D004576:Electromyography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D020967:Myotonic Disorders / Q000175:diagnosis; D010245:Paralyses, Familial Periodic / Q000175:diagnosis; D055815:Young Adult