Breathing but Not Living: The Deceptive Stability of Hydranencephaly

Hydranencephaly is a rare, fatal congenital brain malformation characterized by near-complete absence of cerebral hemispheres with preservation of posterior fossa structures. We report a male neonate born at 35 weeks with severe respiratory distress, profound hypotonia, and bulging anterior fontanelle. Transfontanellar ultrasound identified the pathognomonic "falx sign." Cranial computed tomography confirmed Type II hydranencephaly with complete bilateral hemispheric absence, preserved thalami and brainstem, and intact cerebellum. The infant required mechanical ventilation but was successfully extubated on day 5, demonstrating preserved brainstem function. However, this early stability does not alter the universal grave prognosis (median survival 5-6 months). This case emphasizes the importance of rapid neuroimaging in neonates presenting with hypotonia and respiratory distress, and the critical need for honest prognostic counseling and early palliative care involvement.