Whole-body high-field MRI shows no skeletal muscle degeneration in young patients with recessive myotonia congenita.
BACKGROUND
Muscle magnetic resonance imaging (MRI) is the most sensitive method in the detection of dystrophic and non-dystrophic abnormalities within striated muscles. We hypothesized that in severe myotonia congenita type Becker muscle stiffness, prolonged transient weakness and muscle hypertrophy might finally result in morphologic skeletal muscle alterations reflected by MRI signal changes.


OBJECTIVE
To assess dystrophic and/or non-dystrophic alterations such as fatty or connective tissue replacement and muscle edema in patients with severe recessive myotonia congenita.


METHODS
We studied three seriously affected patients with myotonia congenita type Becker using multisequence whole-body high-field MRI. All patients had molecular genetic testing of the muscle chloride channel gene (CLCN1).


RESULTS
Molecular genetic analyses demonstrated recessive CLCN1 mutations in all patients. Two related patients were compound heterozygous for two novel CLCN1 mutations, Q160H and L657P. None of the patients showed skeletal muscle signal changes indicative of fatty muscle degeneration or edema. Two patients showed muscle bulk hypertrophy of thighs and calves in line with the clinical appearance.


CONCLUSIONS
We conclude that (i) chloride channel dysfunction alone does not result in skeletal muscle morphologic changes even in advanced stages of myotonia congenita, and (ii) MRI skeletal muscle alterations in myotonic dystrophy must be clear consequences of the dystrophic disease process.
Kornblum
C
C
Department of Neurology, University of Bonn, Bonn, Germany. cornelia.kornblum@ukb.uni-bonn.de
Lutterbey
G G
GG
Czermin
B
B
Reimann
J
J
von Kleist-Retzow
J-C
JC
Jurkat-Rott
K
K
Wattjes
M P
MP
D000273:Adipose Tissue / Q000473:pathology; D000293:Adolescent; D000328:Adult; D018118:Chloride Channels / Q000235:genetics*; D003238:Connective Tissue / Q000473:pathology; D004487:Edema; D005260:Female; D005808:Genes, Recessive; D006801:Humans; D006984:Hypertrophy / Q000473:pathology; D007866:Leg / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*; D009135:Muscular Diseases / Q000235:genetics / Q000473:pathology; D009154:Mutation; D009224:Myotonia Congenita / Q000235:genetics* / Q000473:pathology*; D010375:Pedigree
C086321:CLC-1 channel; D018118:Chloride Channels