Muscle channelopathies and metabolic myopathies
Compared to the increasing data regarding the diagnostic value of neuromuscular MRI in patients presenting with dystrophic myopathies or non-dystrophic congenital myopathies, data concerning MRI findings in muscle channelopathies or metabolic myopathies are rather limited. A recently published study focussed on patients with myotonia congenital type Becker, a non-dystrophic generalised myotonia caused by mutations in the muscle chloride gene. Although all patients presented with a severe disabling myotonia, no fatty degeneration or muscle oedema could be detected by using a whole-body high-field MRI protocol [67]. These findings suggest that conventional MRI techniques are less sensitive in the detection of changes in channelopathies. Recent experimental studies using 23Na-MRI instead of or in combination with 1H-MRI have shed some light on the muscle cell function and disease process in Na-channelopathies by demonstrating Na-accumulation during episodes of weakness [33, 68].