Hydranencephaly

Overview
Hydranencephaly is a type of cephalic disorder. This is a rare condition in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid.

In "hemihydranencephaly", only half of the brain is filled with fluid.

Presentation
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 infant usually becomes irritable and has increased muscle tone (hypertonia). 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.

Some infants may have additional abnormalities at birth including seizures, myoclonus (involuntary sudden, rapid jerks), and respiratory problems.

Causes
Hydranencephaly is an extreme form of porencephaly, which is characterized by a cyst or cavity in the cerebral hemispheres, and may be caused by vascular insult or injuries, infections, or traumatic disorders after the 12th week of pregnancy.

Diagnosis
Diagnosis may be delayed for several months because the infant's early behavior appears to be relatively normal. Transillumination, an examination in which light is passed through body tissues, usually confirms the diagnosis.

Prognosis
There is no standard treatment for hydranencephaly. Treatment is symptomatic and supportive. Hydrocephalus may be treated with a shunt.

The prognosis for children with Hydranencephaly is generally quite poor. Death usually occurs in the first year of life.

In a survey completed by 88 families of children with Hydranencephaly from 2006-2007, 69% of the children who had died, did so after their first birthday. The oldest of the children who had died was in their 20s. 62% of the children represented in the survey were over the age of 1 at the time it was filled out. The first year is the hardest for children with Hydranencephaly but survival is possible.

In 2003, the oldest known survivor was 20 1/2 years old.

Noncortical responses to auditory stimuli have been observed in some patients.