Document Detail

Exercise test on the patients with normokalaemic periodic paralysis from a Chinese family with a mutation in the SCN4A gene.
MedLine Citation:
PMID:  19080124     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Normokalaemic periodic paralysis (normoKPP) is characterized by transient and recurrent myoasthenia, and some patients also show muscle stiffness induced by cold exposure (paramyotonia congenita, PMC). It is caused by a mutation in the muscle voltage gated sodium channel alpha subunit (SCN4A) gene. Due to the diversity of the clinical manifestations of patients, it is difficult for clinicians to differentiate some of patients with atypical normoKPP from those who suffer from other periodic paralysis and nondystrophic myotonia. So far, for normoKPP there are almost no ways to assist definite diagnosis besides genetic screening. This research was designed to evaluate an exercise test (ET) in confirming the diagnosis of normoKPP and in assessing the therapeutic effectiveness of some drugs on this disease. METHODS: ET, described by McMains, was performed on six subjects from a Chinese family, including four patients with overlapping disease of normoKPP and PMC caused by a mutation of SCN4A Met1592Val that is identified by genetic analysis and two normal control members. The change of compound muscle action potential (CMAP) was recorded. Besides the family, two patients were also tested during treatments with acetazolamide. RESULTS: All patients showed a slight increase in CMAP immediately after exercise, followed by an abnormal gradual decline, which reached its nadir 25-30 minutes after exercise. CMAP amplitude dropped by more than 40% in patients but less than 23% in controls. In the patients who received treatment with acetazolamide, the change of CMAP amplitude was less than 28% and, at any fixed times, less than pretreatment values. CONCLUSIONS: The ET may be used as a predictive, easy and reliable method of diagnosing normoKPP under conditions without genetic screening help, and is an objective way to evaluate the therapeutic effectiveness. According to different response patterns, the ET may also be helpful in reducing the scope of genetic screening.
Yu Feng; Ying Zhang; Zhong-lan Liu; Chao-dong Zhang
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chinese medical journal     Volume:  121     ISSN:  0366-6999     ISO Abbreviation:  Chin. Med. J.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-12-16     Completed Date:  2009-01-06     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7513795     Medline TA:  Chin Med J (Engl)     Country:  China    
Other Details:
Languages:  eng     Pagination:  1915-9     Citation Subset:  IM    
Department of Neurology, First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China.
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MeSH Terms
Action Potentials
Exercise Test*
Middle Aged
Paralyses, Familial Periodic / genetics*,  physiopathology
Sodium Channels / genetics*
Reg. No./Substance:
0/SCN4A protein, human; 0/Sodium Channels

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