What It Is

Hydranencephaly (or hydroanencephaly) is a congenital condition in which the brain's cerebral hemispheres are absent to varying degrees and the resulting empty cranial cavity is filled with cerebrospinal fluid. Hydranencephaly is one of several types of cephalic disorders. These disorders derive from either damage to, or abnormal development of, the fetal nervous system in the earliest stages of development in utero. Cephalic is the medical term for “head” or “head end of body.” This particular rare neurological condition, an extreme form of porencephaly, occurs after the 12th week of pregnancy, after the brain has begun developing. 

Hydranencephaly does not have any definitive identifiable cause factor. As with all cephalic conditions, there is an obvious interruption in normal development of the nervous system. A traumatic occurrence of sorts, resulting in prenatal stroke, is believed to be the primary cause of hydranencephaly. Some possibilities include: intrauterine infection, environmental exposure to toxins, vascular insult of another nature, and twin-to-twin transfusion.  Some researchers have also suggested the possibility of a genetic component, though only one case has been documented in which a family has been presented this diagnosis for more than one child.

What This Means

The prognosis for a child born with hydranencephaly is presented as very poor: death in utero, within weeks, or no longer than a year. While some children given this diagnosis may not survive past their first birthday, each case is unique and there are a growing number of cases where children can defy this prognosis and live several years. The oldest individual with a confirmed case of hydranencephaly celebrated his 33rd birthday before his passing.

A diagnosis can be made in utero, though often inaccurate or unconfirmed until birth. In other cases, diagnosis is delayed for several weeks or even months since the infant appears developmentally normal at birth. As the child matures, delays become much more apparent. In extremely rare cases, damage causing hydranencephaly can occur in infancy following infections such as meningitis, stroke, intracerebral hemorrhage, and traumatic brain injury.


Not all apparent signs are identifiable at birth. Despite the generalized prediction of complications at birth, or even before birth resulting in death, many children display none initially.

Symptoms such as increased irritability, increased muscle tone, and the lack of purposeful movement generally initiate suspicion of an underlying cause. In several cases, the infant’s head circumference may increase dramatically while other signs become more obvious as well. Seizures, reduced ability to such effectively, inability to maintain body temperature, the suspicion of visual impairment, failure to thrive or lack of growth, involuntary movements, chronic respiratory and gastrointestinal complications, obvious cerebral palsy, and global delays may present themselves as the child ages. 

Still other infants display no obvious symptoms at birth, going many months without a confirmed diagnosis of hydranencephaly. In some cases a severe hydrocephalus, or other cephalic conditions, diagnosis is misdiagnosed.

Treatments & Therapies

There is no cure for hydranencephaly. Treatment is symptomatic; meaning associated conditions are treated to ensure the best quality of life possible. While the inevitable cannot be avoided entirely; with proper management of these associated symptoms and a proactive care team, the ability for the child to thrive is far greater.

Surgery for placement of a shunt, in cases where hydrocephalus (accumulation of excess cerebrospinal fluid) is apparent, is advised. Not only has this proven to reveal a less than terminal alternate diagnosis in rare cases, with the presentation of “simply” hydrocephalus without the lack of cerebral cortex, but also ensures the child is not living in unnecessary discomfort. While hydrocephalus is common amongst children given this diagnosis, several children display as microcephalic (smaller than average cranial circumference) or present as typical in appearance as well. 

The description of this disease is provided courtesy the Global Hydranencephaly Foundation, the NIH, and other sources.

The information provided on this web site should NOT be used as a substitute for seeking professional medical diagnosis, treatment or care. You should not rely on any information in these pages to replace consultations with qualified health professionals.