RESUMEN
Hemihydranencephaly is a rare disorder of the brain characterized by complete or almost complete unilateral absence of cerebral cortex with preservation of meninges, basal ganglia, pons, medulla, cerebellum, and falx. Thirteen year-old male child presented with left sided upper and lower limb weakness with facial asymmetry since the age of six months. His magnetic resonance imaging [MRI] scans demonstrated a nearly complete absence of the right cerebral hemisphere including basal ganglion, which was replaced by cerebrospinal fluid with a small residual rim of the occipital cortex. The imaging features were suggestive of right-sided hemihydranencephaly. Patients with hemihydranencephaly provide an experiment of nature with potential implications for normal cognitive development and illustrate how much there is still to be learned about human development