What is hydranencephaly
Hydranencephaly is a rare central nervous system disorder in which the brain’s cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid (CSF). Affected infants may appear and act 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 a few months of life, seizures and hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain) may develop. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual disabilities. Hydranencephaly is considered to be an extreme form of porencephaly (a rare disorder characterized by a cyst or cavity in the cerebral hemispheres) and may be caused by vascular infections or traumatic disorders after the 12th week of pregnancy. Diagnosis may be delayed for several months because early behavior appears to be relatively normal. Some infants may have additional abnormalities at birth including seizures, myoclonus (spasm or twitching of a muscle or group of muscles), and respiratory problems.
Hydranencephaly prognosis is typically poor with many affected children dying before one year of age. In rare cases, children may survive for several years or more 1. Hydranencephaly has been suspected to be an inherited condition, although some researchers believe it may be caused by prenatal blockage of the carotid artery where it enters the cranium 2. There is no definitive treatment for hydranencephaly. Hydranencephaly treatment is generally symptomatic and supportive. Hydrocephalus may be treated with a shunt (a surgically implanted tube that diverts fluid from one pathway to another) 1.
Hydranencephaly vs Hydrocephalus
Hydrocephalus is the buildup of too much cerebrospinal fluid (CSF) in the brain. Normally, cerebrospinal fluid (CSF) cushions your brain. When you have too much, though, it puts harmful pressure on your brain.
Hydrocephalus can be congenital or present at birth. Causes include genetic problems and problems with how the fetus develops. An unusually large head is the main sign of congenital hydrocephalus.
Hydrocephalus can also happen after birth. This is called acquired hydrocephalus. It can occur at any age. Causes can include head injuries, strokes, infections, tumors, and bleeding in the brain. Symptoms include
- Headache
- Vomiting and nausea
- Blurry vision
- Balance problems
- Bladder control problems
- Thinking and memory problems
Hydrocephalus can permanently damage the brain, causing problems with physical and mental development. If untreated, it is usually fatal. With treatment, many people lead normal lives with few limitations.
Hydrocephalus is most often treated with the surgical placement of a shunt system. A shunt is a flexible but sturdy plastic tube. The shunt diverts the flow of CSF from a site within the central nervous system to another area of the body where it can be absorbed as part of the circulatory process. A limited number of individuals can be treated with an alternative procedure called third ventriculostomy. In this procedure, a small hole is made in the floor of the third ventricle, allowing the CSF to bypass the obstruction and flow toward the site of resorption around the surface of the brain. Medicine and rehabilitation therapy can also help.
Hydranencephaly causes
Hydranencephaly is suspected to be an inherited disorder although the mode of transmission remains unknown. Some researchers believe that prenatal blockage of the carotid artery where it enters the cranium may be a cause of this disorder. However, the reason for the blockage is not known.
An autosomal recessive inheritance has been described in some cases. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. In recessive disorders, the condition does not occur unless an individual inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
Hydranencephaly symptoms
Hydranencephaly can usually be detected at birth due to an enlarged head. Some infants may appear healthy at birth but may later fail to grow at a normal rate. Irritability, poor feeding, infantile spasms or seizures, and spasticity or rigidity of arms and legs are symptomatic of this disorder. Some affected individuals may experience an exaggeration of muscular reflexes (hyperreflexia) and/or increased muscle tone (hypertonia). Poor body temperature regulation, vision impairment and mental retardation may also occur.
Hydrocephalus
Hydrocephalus is often one of the first difficulties faced by the child. According to some experts 78% of the children have hydrocephalus and 96% of those have needed a shunt. Some children have mild hydrocephalus but live their entire life without a shunt and some never do develop an increase in intracranial pressure from fluid.
Irritability
A child with hydranencephaly is often very irritable in the first year. A build up of fluid in their heads is one of the first things to check if your child is irritable. As 57% of the children have gastro esophageal reflux, which can be very painful this is something that should also be checked. As the children grow older, 90% are said to be happy or quiet. Only 6% were still described as being fussy or irritable past the one year mark.
Increased tone
Children with hydranencephaly may have increased tone in their bodies (spasticity). In our study, 41% of the children were described as having increased tone, and 6% were described as being “floppy”. Another 47% were described as having mixed tone. This means that they are sometimes very floppy and sometimes very tight. Physical and Occupational therapy are very helpful in preventing problems from increased tone. However, children do frequently need various orthopedic surgeries as they get older. The therapists will likely suggest a variety of equipment that will also help in preventing a child from developing problems. The children are sometimes referred to as having cerebral palsy or spastic paralysis.
Seizures
Seizures are fairly common in children with hydranencephaly (82%). The type and severity of the seizures vary from child to child. Most of the seizures are fairly short and mild but some children do have longer more severe seizures. There are many different seizure medications children take. Often a child needs more than one medication at a time and they frequently need to have their medications changed. A problem both in diagnosing a child who has hydranencephaly with seizures and in treating them is that EEGs, and medications are geared towards those who are having cortical seizures. Most children with hydranencephaly have no cortex and have brain stem seizures. So, you and your doctor may agree that your child is having seizures, but nothing shows up on the EEG. And, medications geared at controlling cortical seizures may not work well on a child with hydranencephaly. That is why your child may need a variety of medications.
Feeding
Children with Hydranencephaly may have trouble sucking and swallowing. Many families are told that their child will lose these abilities within a few weeks of birth when the “higher” cortical areas of the brain normally kick in. In a study 33% of the children eat orally, 46% eat only by tube and 19% eat both orally and by tube. As the child gets older he may have more trouble eating and eventually need a feeding tube.
Vision/Hearing
In a study, 91% of the children can hear. Some children may not understand what they hear but do respond to sounds and familiar words. However, parents feel that 30% of the children understand at least some of what is said to them. 63% of the children are thought to see at least some of the time. Most of the children have what is called cortical visual impairment. This means that there is nothing wrong with their eyes, but that their brains aren’t able to tell them what they are seeing. This sort of vision can come and go so that children see some things and not others or will see one day and not the next.
Other conditions children with hydranencephaly may have:
- Asthma/Reactive Airways disease: 34%
- Diabetes Insipidus (a high sodium level and excessive urine output): 13%
- Gastro esophageal reflux (food comes up which causes vomiting or excessive acid production): 57% .
- Constipation: 75%
Hydranencephaly diagnosis
The diagnosis of hydranencephaly may be confirmed based upon a thorough clinical evaluation, the identification of characteristic physical findings, a detailed patient history, and advanced imaging techniques, such as transillumination, an x-ray of the blood vessels using dye (angiogram), or computerized tomography (CT scan). During CT scanning, a computer and x-rays are used to create a file showing cross-sectional images of internal structures such as the brain.
In some cases, the disorder may be diagnosed before birth (prenatally) using fetal ultrasonography to identify characteristic physical abnormalities. In fetal ultrasonography, an image of the developing fetus is created using sound waves.
Hydranencephaly treatment
Unfortunately, there is no definitive treatment for hydranencephaly. Management of the condition typically focuses on the specific signs and symptoms present in the affected individual and is mostly supportive. Hydrocephalus (the buildup of too much cerebral spinal fluid in the brain) may be treated with a shunt (a surgically implanted tube that helps to drain fluid from the brain) 2.
Hydranencephaly prognosis
The prognosis for children with hydranencephaly is generally poor, and many children with this disorder die before age 1. However, in rare cases, children with hydranencephaly may survive for several years or more.
Hydranencephaly life expectancy
The life expectancy of individuals with hydranencephaly is statistically noted as a few months to a year. The reality, however, is that children with hydranencephaly oftentimes live many years with an optimistic care team and strong, educated parent advocates – the oldest recorded via Global Hydranencephaly Foundation was 33 years old.
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