This is a condition in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid. Usually the cerebellum and brainstem are formed normally.
An infant with hydranencephaly may appear normal at birth. The infant's head size and spontaneous reflexes; such as, sucking, swallowing, crying, and moving the arms and legs may all seem normal; however, after a few weeks the child usually becomes irritable and has increased muscle tone (hypertonia or increased rigidity, tension, and spasticity of the muscles).
After several months of life, seizures and hydrocephalus may develop. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual deficits.