Hemimegalencephaly on magnetic resonance imaging scan (MRI) consists of cortical gray matter almost uniformly abnormal, areas of increased thickness of the cortical gray matter (GM), abnormal gyral patterns, blurring of the grey-white matter transition, atrophy or hemispheric hypertrophy, demyelination, gliosis. We present a case of ten-year-old boy with a history of infantile spasms and developmental delay who presented to the pediatric neurology room with an episode of disinhibited behavior in family environment. An MRI was performed and isolated hemimegalencephaly with polymicrogyria of the right occipital lobe was diagnosed.