Hemi-Hydranencephaly: Living with Half a Brain

Background: Hemi-hydranencephaly (HHE) is a rare brain anomaly with absent cerebral cortex, which gets replaced by a cerebrospinal fluid (CSF) filled membranous sac. Prenatal vascular disruption leads to unilateral carotid artery disease, resulting in an encephaloclastic process with cerebral resorption. Genetic and acquired causes can be implicated in the pathogenesis. Clinical features encompass a range of manifestations, including motor impairment, reduced mental development, seizures and ocular signs. Treatment targets the underlying deficit encountered by the patient and physical rehabilitation. Case Presentation: We present a case of a 22-year-old female, with atonic seizures and a significant past history of generalized tonic clonic seizures, with development of right hemiparesis and facial asymmetry at 9 months of age. On examination, she had disuse atrophy with contractures of the right upper and lower limbs. Magnetic resonance imaging (MRI) suggested replacement of the left cerebral hemisphere with CSF and the MR angiography showed narrowing of the left internal carotid artery with its branches, confirming the diagnosis of HHE. Anti-epileptic treatment was initiated, and physical rehabilitation was started for the limb contractures. Conclusion: Cognitive development in HHE is a natural experiment with special interest in long term language and neuropsychological development.