Brain MRI features of merosin-negative congenital muscular dystrophy.

The purpose of this article is to report brain MRI findings of merosin-negative congenital muscular dystrophy (CMD) in two cases and to discuss its differentiation from other CMD subtypes. The cases were investigated by 1.5 Tesla MRI equipment using T1-weighted, T2-weighted, fluid-attenuated inversion recovery (FLAIR), 3D fast spoiled gradient recalled (SPGR) and post-contrast gadolinium enhanced sequences and the diagnosis was confirmed by muscle biopsy with immunohistochemical staining for merosin. Magnetic resonance imaging showed bilateral subcortical U-fibre white matter changes with periventricular sparing in the first case. Though this imaging finding is non-specific and could be seen in other white matter diseases like Canavan disease, the absence of other distinguishing MRI and clinical features of those conditions allowed a proper diagnosis. The second case showed diffuse subcortical and deep white matter involvement and cerebellar cysts. There was no brainstem involvement, polymicrogyria or cobblestone lissencephaly in both of our cases which allowed differentiation of merosin-negative CMD from other CMDs. Muscle biopsy in both these patients showed dystrophic changes with absent staining for merosin confirming the diagnosis. Merosin-negative CMD should be considered in the imaging differential diagnosis of white matter diseases. In a patient presenting with features of CMD, MRI can be of help in further differentiation of the various CMD subtypes.