Syntelencephaly, also referred to as the middle interhemispheric variant of holoprosencephaly, is a rare anomaly characterized by a fusion of the hemispheres in the posterior frontal and parietal regions. We report the case of a 9 year-old boy in whom the MRI showed syntelencephaly together with polymicrogyric cortex in the parieto-occipital region, bilaterally. Furthermore, schizencephaly was detected in the parietal region, with the polymicrogyric cortex overlying the cortical mantle of the fissures. It is supposed that the two malformations are the result of the same pathogenetic mechanism.