Brain MRI studies of patients with XLCD. 1 a-c (male proband of a family with X-linked congenital ataxia) Midsagittal T1-weighted image showing an overall size reduction of the cerebellum predominant in the vermis with widened interfolia sulci. Brainstem is normal (a). Axial T2-weighted image showing global cerebellar hypoplasia without dysplasia (b). Axial T2-weighted image showing normal cortex and ventricles (c). d-f (male patient carrying a OPHN1 mutation): midsagittal T1-weighted image showing hypoplastic cerebellar vermis and enlarged cisterna magna (d) axial T2-weighted image showing cerebellar hypoplasia and vermis dysplasia (e) axial T2-weighted image showing lateral ventricle dilatation and mild cortical atrophy (f). g-i (female patient carrying a CASK mutation): Midsagittal T1-weighted image showing moderate vermis hypoplasia and flat pons (g). Axial T2-weighted image showing simplified gyral pattern and ventricular dilatation (h). Coronal T2-weighted image showing global cerebellar hypoplasia and simplified cortical gyri (i).