The congenital form of myotonic dystrophy type I (CDMI) has ail almost exclusively maternal transmission and is characterized by mental retardation and by moderate/severe ventriculomegaly and white matter hyperintensities on brain magnetic resonance imaging (MRI). We report a 20-year-old case of CDM1 with paternal inheritance showing mental retardation and normal brain MRI, and presenting at birth with hypotonia, facial weakness and feeding difficulties. We reviewed the literature for studies addressing the brain neuroimaging in paternally transmitted CDM1 and found four Studies reporting diffuse cerebral, frontal lobe or mild parietal cortical atrophy, or mild ventricular dilatation, without white matter abnormalities. To our knowledge, this is the first report describing normal brain MRI in a mentally retarded CDM1 patient with paternal transmission. (C) 2008 Elsevier B.V. All rights reserved.