hydranencephaly

Hydranencephaly is a severe birth defect where the brain lacks cerebral hemispheres. Instead, fluid-filled sacs occupy the space where the brain should be. This condition develops after the 12th week of pregnancy and can be caused by a stroke, injury, or infection. While infants may appear normal at birth, they often develop irritability, excessive muscle tone, seizures, and hydrocephalus (an accumulation of cerebrospinal fluid) within weeks or months. Sadly, death typically occurs within the first year of life, though some individuals have been reported to survive into their late teens or early twenties.1