Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 15, 2016

Porencephaly is a very rare disorder of the central nervous system in which a cyst or cavity develops within the brain. The level of disability that this causes patients ranges from mild to severe. Porencephaly can occur before or shortly after birth. Synonyms for the condition include porencephalic cyst, cystic brain degeneration, and congenital brain clefts.


Definition & Facts

Porencephaly describes a fluid-filled cyst or cavity within the brain. The term, porencephaly was first used by Austrian doctor, Richard Heschl in 1859. Porencephaly is associated with congenital vascular hemiparesis, epilepsy, and cerebral palsy. Porencephaly is more likely to affect boys than girls. 

Symptoms & Complaints

The symptoms of porencephaly vary, and they depend on the size, number and location of the cyst(s). The most severe form of porencephaly is called hydranencephaly. In this condition, fluid has replaced virtually the whole cerebrum. An infant with hydrancephaly may appear normal at birth, or they may have hydrocephalus that makes their skull appear abnormally large.

Symptoms of hydrancephaly can include seizures, paralysis, deafness, vision problems including blindness, stunted growth, and intellectual disability. Most children die within the first year, but some survive a few years. 

A related condition is called schizencephaly, in which the patient has slits or clefts in their brain. If the slits occur on both sides of the brain, the patient will have multiple neurological problems including delayed and speech impairment. If the slits occur on only one side, the patient’s symptoms will be less severe: they may have normal intelligence and they may have weakness or paralysis on only one side of the body (hemiparesis).

Common symptoms of both porencephaly and schizencephaly include intellectual disability, hydrocephalus, seizures, paralysis, and low muscle tone. The prognosis for most patients is poor; they usually die before reaching adulthood.

In severe cases like hydrancephaly, the baby shows symptoms shortly after birth. Most cases of porencephaly are diagnosed before the infant is a year old. In the very mildest cases, the patient may show no symptoms at all.


Porencephaly has multiple causes, and there are different types. Familial porencephaly is a birth defect that runs in families and is linked to genetic mutations of the COL4A1 gene.

In non-familial porencephaly, which is sometimes called sporadic porencephaly, the cavities are usually caused by injuries to the brain that take place before the gyri or folds on the cerebrum’s surface have fully developed. They therefore usually develop either before or shortly after birth. The injuries can be caused by infection or a problem with blood flow to the brain. Sporadic porencephaly can also be caused by serious injury or illness in the mother, like trauma to her abdomen or diabetes mellitus. Smoking and drug use during pregnancy can cause porencephaly, as can complications during childbirth.

Regardless of the cause, large cavities, clefts or cysts develop on the surface of the brain. They are lined with smooth tissue and filled with fluid. The cerebral folds around the cavity or cyst develop abnormally and can radiate from the cyst. In some cases, some of the folds that aren’t associated with the cavity will be abnormally small. 

In some cases of porencephaly, the cavities will symmetrically affect both sides of the brain, resulting in a condition called “basket brain.”

Diagnosis & Tests

Porencephaly can often be diagnosed by transillumination of the skull. In this test, the doctor will place a light near the baby’s skull and turn it on. Under normal conditions, the baby’s head should not a let even a strong beam of light pass through it. If the baby has porencephaly, the light will shine through the cavities. 

Other tests used to diagnose porencephaly include magnetic resonance imaging (MRI)s, ultrasounds, and computed tomography (CT) scans. These tests may be administered before or after birth, with ultrasound being the preferred test for fetal imaging.

Porencephaly can be diagnosed as early as 20 weeks after gestation. The various diagnostic tests can be used to determine the number, size and location of the cysts. They can also be used to determine if the patient has any other neurological disorders, like hydrocephalus. 

As the patient gets older, the doctor can administer speech, memory tests, and cognitive tests to help evaluate the severity of their disabilities. 

Treatment & Therapy

The treatment for porencephaly is aimed at easing the symptoms; there is so far no way to replace the missing parts of the brain. Such treatments can include anticonvulsants and a cerebral shunt or drain to remove excess fluid. Seizure medications for porencephaly patients can include valproate, clobozam, and carbamazepine. Some patients may also need physical therapy to treat any mobility problems. In some cases, the cysts can be removed through neurosurgery.

Patients with mild cases of porencephaly can live independent and healthy lives. Those with more severe cases will need lifelong monitoring and treatment. Such patients should be diagnosed as soon as possible and given the necessary medications. Speech therapy can help patients develop the appropriate motor and communications skills for their age. Support groups can assist patients and their families.

Prevention & Prophylaxis

People whose families have a history of porencephaly may wish to have genetic counseling if they plan to have children. The geneticist can advise them of the likely risks and any methods of prevention. 

During pregnancy, a woman’s health should be closely monitored to ensure she does not develop any of the infections that can increase the chance of a child developing porencephaly. She should, for instance, be tested for cytomegalovirus.

Since complications during childbirth can result in porencephaly, the medical team should closely watch the mother during delivery. After childbirth, they should keep a close watch on both mother and child. The best way to prevent porencephaly is to reduce the mother and child’s exposure to the known risk factors.