Hydranencephaly is a rare and extreme form of porencephaly. The hemispheres of the cerebrum are absent and replaced by sacs filled with cerebrospinal fluid (CSF). In most cases, the cerebellum and brainstem are formed normally.

Causes of Hydranencephaly

Vascular injuries, infections, or trauma after the 12th week of pregnancy result in malformations of the brain.

Signs and Symptoms of Hydranencephaly

Some infants with hydranencephaly may have seizures; sudden, rapid, involuntary twitches or jerks (myoclonus), and respiratory problems at birth. Most appear normal and have normal spontaneous reflexes (e.g., sucking, swallowing, crying, moving the arms and legs). Within a few weeks these infants become irritable and develop an abnormal increase in muscle tone (hypertonia). Seizures and hydrocephalus usually follow within a few months, and there may be symptoms of visual impairment, lack of growth, deafness, blindness, paralysis, and intellectual deficits.

Diagnosis of Hydranencephaly

Because of the infant's relatively normal initial appearance and early behavior, diagnosis of hydranencephaly may take several months. Diagnosis is confirmed by means of a procedure in which light is passed through body tissues (transillumination), CT scan, and MRI scan.

Treatment for Hydranencephaly

Treatment is symptomatic and supportive. A shunt may be installed to control hydrocephalus.

Prognosis for Infants with Hydranencephaly

Prognosis is poor. Most infants die within their first year.


Schizencephaly is a form of porencephaly in which the brain's hemispheres are marked by abnormal slits or clefts. The clefts may occur in one hemisphere (unilateral) or occur in both hemispheres (bilateral).

Causes of Schizencephaly

Research strongly suggests schizencephaly occurs early in fetal development. The cause may be genetic or may stem from vascular injury or the mother's exposure to certain medications or toxins during pregnancy.

Signs and Symptoms of Schizencephaly

Individuals born with small, unilateral clefts have weakness on one side of the body and may have average or nearly average intelligence. Persons with bilateral clefts usually have serious developmental disabilities, delayed speech and language skills, and brain cortex/spinal cord problems.

Associated conditions include varying degrees of microcephaly, mental retardation, reduced muscle tone (hypotonia), seizures, and weakness or paralysis on one side of the body (hemiparesis) or in all four limbs (quadriparesis). Hydrocephalus also may occur.

Treatment for Schizencephaly

Individuals with schizencephaly may benefit from physical therapy and treatment to control seizures. Cases involving hydrocephalus may call for implantation of a shunt.

Prognosis for Infants with Schizencephaly

Prognosis depends on the size of the clefts and the extent of the neurological deficits.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Jan 2000

Last Modified: 03 Sep 2015