title: Clinical, electrophysiologic, and genetic study of non-dystrophic myotonia in French-Canadians.
abstract: Thirty-three French-Canadian families with non-dystrophic myotonia were identified. Fifty subjects were recruited and submitted to a complete clinical, electrophysiologic and genetic evaluation. Thirteen mutations were identified in CLCN1 and five mutations were identified in SCN4A. Onset in the lower extremities, presence of tongue myotonia and transient weakness suggested recessive CLCN1 mutations. Lid myotonia, absence of hypertrophy and exacerbation with cold temperature suggested SCN4A mutations. Pain was not a feature of dominant CLCN1 mutations while it could be seen in the others, more frequently in SCN4A mutations. Warm up phenomenon, hand grip myotonia, percussion myotonia, lid lag and hormonal effects were not distinguishing features. Repetitive nerve stimulation and short exercise test showed either a large (>50%) or mild-moderate (10-50%) decrement with recessive CLCN1 mutations while they showed only mild or no decrement with dominant CLCN1 and SCN4A mutations. The French-Canadian population shows wide phenotypic and genotypic heterogeneity in non-dystrophic myotonias.
authors.affiliation: Department of Neurological Sciences, CHAUQ (Enfant-Jésus), Faculty of Medicine, Laval University, Quebec City, QC, Canada. nicdupre@aol.com
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dupré
authors.forename: Nicolas
authors.initials: N
authors.lastname: Chrestian
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bouchard
authors.forename: Elsa
authors.initials: E
authors.lastname: Rossignol
authors.forename: Denis
authors.initials: D
authors.lastname: Brunet
authors.forename: Damien
authors.initials: D
authors.lastname: Sternberg
authors.forename: Bernard
authors.initials: B
authors.lastname: Brais
authors.forename: Jean
authors.initials: J
authors.lastname: Mathieu
authors.forename: Jack
authors.initials: J
authors.lastname: Puymirat
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018118:Chloride Channels / Q000235:genetics*; D003080:Cold Temperature / Q000009:adverse effects; D004252:DNA Mutational Analysis; D017079:Exercise Tolerance / Q000235:genetics; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005820:Genetic Testing; D005838:Genotype; D006801:Humans; D007866:Leg / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000235:genetics / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009154:Mutation / Q000235:genetics*; D009222:Myotonia / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology*; D062553:NAV1.4 Voltage-Gated Sodium Channel; D011792:Quebec / Q000208:ethnology; D015222:Sodium Channels / Q000235:genetics*; D014059:Tongue / Q000503:physiopathology; D055815:Young Adult
chemical_list: C086321:CLC-1 channel; D018118:Chloride Channels; D005819:Genetic Markers; D062553:NAV1.4 Voltage-Gated Sodium Channel; C106251:SCN4A protein, human; D015222:Sodium Channels