Fetal hydrocephalus

Fetal hydrocephalus is a congenital finding that affects the brain. The contents of the brain consist primarily of the brain tissue, blood and cerebrospinal fluid (CSF). Fetal hydrocphalus is the buildup of CSF in the ventricular system of the brain, which results from a lack of absorption, blockage of flow, or overproduction of CSF. It may potentially cause increased pressure in the head and an expansion of the skull bones. Hydrocephalus occurs in approximately 1 in every 1000 births.

Diagnosis

Hydrocephalus can be detected through ultrasound (sonogram). Evaluation of the brain and cranial structure is part of the routine ultrasound examination done by many obstetricians as part of their prenatal care. However, sometimes hydrocephalus may not develop until the third trimester, and therefore, may not be diagnosed until the end of the pregnancy. If it is detected on ultrasound, the patient may undergo a fetal brain MRI (magnetic resonance imaging) to determine the severity of the finding. More here on fetal MRI.

Treatment

If a baby is diagnosed with fetal hydrocephalus before he is born, the surgeons and nurses at Children's Memorial Hospital spend time counseling parents about what to expect when their baby is born. Patients will receive both pre-natal and post-natal evaluation by neurosurgeons and neurologists. As soon as the baby is born, parents should bring their child in for a detailed examination. A physical examination is performed and measurements of the infant's skull are taken.

Treatment depends on the type of hydrocephalus and can range from medical management to procedures that draw out the extra CSF. One type of surgery involves placing a shunt, or tube, into the child's head to drain the CSF and redirect the additional fluid to another part of the body to be absorbed. The other type of surgery that may be performed is called endoscopic third ventriculostomy (ETV). In this procedure, the neurosurgeon creates a small hole in the bottom of one of the ventricles (or spaces in the brain) causing the CSF to bypass the obstruction and flow into the natural pathways.

Long-term outlook

The long-term outlook for a child born with hydrocephalus depends greatly on the severity of the problem and the presence of other associated abnormalities. Hydrocephalus can affect the brain and a child's development to varying degrees. It is recommended that these children receive follow-up care and evaluations to prevent infection and monitor the ongoing functionality of the shunt.

Content last reviewed: August 2008

Spina bifida

Expert care from a team of specialists has allowed Aaron to lead a happy, active life, despite the challenges of spina bifida. Read more.

Spina bifida is not a new disease but one that was recognized as early as 2000 years BC. Nor is it rare, occurring in two out of every 1,000 children born. Although spina bifida exists in forms that have no effect on function (spina bifida occulta), the term is used here interchangeably with myelomeningocele.

The disease is more than an open spine (bifida = split in two, Latin). It involves the spinal cord (myelo) and its coverings (meninges), and often the spinal cord and nerves are in a sac (cele), protruding from the child's back. The defect originates during the first month of pregnancy. The area involved can be anywhere along the spine but usually occurs at the bottom of the spine.

Why does this happen?

The cause of spina bifida continues to elude scientists. Many theories have been advanced, but no one theory seems to be consistent with all the facts. The best explanation today is that multiple factors are involved, some environmental and some genetic.

Read about a spina bifida patient who takes on her next challenge - medical school.

When the right (or wrong) combination of these factors is present, the normal sequence of events in development of the spinal cord is altered early in pregnancy, and spina bifida occurs. Spina bifida develops during the first month of pregnancy, usually before the woman realizes she is pregnant. Neither parent is to blame; factors beyond their control are the cause.

Occasionally, even today, a child is born with a defect so extensive that his life cannot be saved. However, most children born with spina bifida are vigorous, active newborns, but they possess a defect that, if left untreated, is potentially lethal. Early closure of the back by a neurosurgeon and control of hydrocephalus ensures survival and preserves function.

A superficial look at a child with spina bifida would seem to suggest that the condition involves only paralysis of the legs. Certainly, these children do share some of the same physical challenges as children with less common diseases such as polio, spine injuries, and muscular dystrophy. But the involvement of a brain malformation and hydrocephalus add a complexity not present in these other diseases.

This complexity necessitates a global view of spina bifida and a team approach by the professionals involved. Most children with spina bifida have problems; usually evident at birth are bladder and bowel dysfunction, paralysis of the legs and lack of sensation. The goal for these children and their families is to have as normal a life experience as possible. The task of the parents, with the support and backing of the professional team, is to enhance and encourage this normalization.

What are the nervous system problems?

The major initial crisis of the newborn child with spina bifida involves the nervous system (brain, spinal cord, and peripheral nerves). The primary problem is that a portion of the nervous system is exposed to the outside world and vulnerable to infection. This must be dealt with promptly to prevent infection and loss of function. Functional disturbances of the nervous system are also of concern.

The nervous system operates by small electrical impulses much the same as a telephone system. Continuing with that analogy, the brain acts as the computerized central telephone office. The spinal cord functions as the main cable from the central office, and the peripheral nerves of the arms, legs, bladder and bowel act as individual phone lines. Messages flow to and from the brain as electrical impulses along these lines —t he nerves.

In spina bifida, problems exist at several levels in the system. The individual lines — the peripheral nerves of the legs, bladder and bowel—are part of the deformity on the child's back. Often they are lost during development or destroyed as the sac expands on the child's back. The closer a nerve is to the end of the spinal cord the more likely it is to be involved and lost. Unfortunately, the nerves for bladder and bowel function come from the very tip end of the spinal cord and are almost always lost.

The next nerves upward to leave the spinal cord are those for the feet, ankles, calf, knee, thigh, hip etc., progressing up the child's trunk. Thus, as spina bifida becomes more extensive or higher on the child's back, the more likely is the loss of more and more function. However, only in rare cases is the lesion high enough to involve the arms.

Motor and sensory losses

The lines — the peripheral nerves — are of two types: outgoing and ingoing. The outgoing system is the motor nerve system and ends in the muscles of the legs, bladder and bowel. Loss of these nerves breaks the contact with the brain, and the child loses voluntary movement of the muscles involved. In fact, if these nerves are lost early in development prior to birth, the involved limb is not stimulated to develop and remains smaller than normal.

The loss of motor function is not evenly distributed over the limbs and spine. The opposing muscle groups — those on the front of the leg that oppose those on the back — can be partially paralyzed and out of balance. The resulting muscle imbalance tugs and pulls the bone and limbs into various deformities. This compounds the problem of paralysis, making walking much more difficult. Orthopaedic surgeons (bone doctors) can now correct these deformities, allowing children to stand and most to walk with assistance, although sometimes individuals with a significant amount of motor loss might find a wheelchair a better mode of transportation in adult life.

The ingoing system is the sensory system. The sensory loss is usually in same area as the motor loss and means that the sensation of pain, temperature and touch are lost. Without pain, which acts as the body's essential alarm system, the child has a much greater exposure to injury. One of the first ways in which parents need to be on guard against possibly injury is by carefully testing the temperature of the child's bath water. Vigilance to the areas of lost sensation is key to avoiding cuts, bruises, irritation, and pressure sores.

The next level involves the covering of the main cable — the bone, muscle, and skin — which during development does not close properly but remains open like an "open book," leaving the central nervous system exposed. Parts of the cord may actually be destroyed during development or the organization of this portion of nervous tissue may be abnormal; nerves end blindly or make wrong connections and short circuits interfere with the cord's function. Both sensory and motor pathways are involved but usually the sensory system suffers more.

Because of both motor and sensory loss to the urinary system, a variety of abnormal patterns of function are seen. Some children retain large volumes of urine, while others can only hold a small volume of urine and dribble continuously. The valves or sphincters that open and close to control the flow of urine and feces are deprived of voluntary control, and so require artificial aid.

Spina bifida is a condition that requires good communication between physicians and extreme vigilance on the part of families. A slight decline on a muscle test or change in bladder or bowel function may indicate a serious underlying complication such as a shunt malfunction. (Shunts are tubes and valves that carry the fluid to another body cavity where it can be returned to the blood either directly or by absorption through the lining of the body cavity. More on shunts here.)

Muscle changes or changes in bladder or bowel function may also indicate a tethered cord, in which the spinal cord attaches to surrounding tissue and is prohibited from moving freely. Both shunt malfunctions and bladder and bowel changes need immediate intervention to prevent permanent and irreversible damage.

Spina bifida

Expert care from a team of specialists has allowed Aaron to lead a happy, active life, despite the challenges of spina bifida. Read more.

Chiari II malformation

At the level of the brain, the involvement is much more complex. Children born with spina bifida have a deformity of the brain known as the Chiari II malformation. Generally speaking, all children born with spina bifida have this malformation of the brain, regardless of the presence of hydrocephalus.

There are different types of Chiari II malformations, but the kind associated with spina bifida usually is one type: the brain is compressed into the foramen magnum, the bony opening at the base of the skull through which the spinal cord exists. It is not known why this malformation is associated with spina bifida. Fortunately, the internal connections of the brain are correct, and therefore the child can still be expected to have a normal intellect.

However, in many children subtle abnormalities of brain function are recognizable with more sophisticated forms of neuropsychological testing. The most common problem with children with spina bifida is the coordination of hand movements with what they see (hand-eye coordination). With sophisticated testing, a child's particular problem (if any) can be identified, and with proper therapy, the dysfunction can often be corrected or minimized.

Some children may develop more severe manifestations of the Chiari II malformation. These symptoms can include temporary stridor (noisy breathing), and/or apnea (interruption of breathing). Fortunately these problems are rare. Different therapies are used for children exhibiting signs of the Chiari II malformation, ranging from letting the child "grow out" of the problems to performing surgery.

About hydrocephalus

Another major difficulty that may be present at birth or shortly afterward is hydrocephalus (hydro = water, cephalus = head).

The brain and spinal cord share a circulation of a salt water-like liquid called cerebrospinal fluid (CSF). The fluid is continuously made deep within the brain and flows through the brain by passing through some large compartments (ventricles) and narrower passages interconnecting the ventricles. CSF finally passes out of the brain at the back of the head and then over the surface of the brain and spinal cord to ultimately return to the blood system at the top of the brain. Any obstruction to this circulation acts much like a dam in a river.

The river below the dam decreases in size and the river above the dam expands into a lake. This extending lake of fluid fills up the ventricles within the child's brain. The increased pressure causes the child's brain and skull to expand to accommodate this enlarging system of lakes at the center of the brain.

Fortunately, today we can control hydrocephalus. This reflects the improved diagnostic equipment available to pediatric neurosurgeons who can now differentiate between progressive hydrocephalus and an enlarging head that will eventually stabilize.

Because of the Chiari II deformity in children with myelomeningocele, dams or obstructions are formed along the river. In 30% of the cases, the obstructions are low ones, partially obstructing the fluid but CSF eventually spills over and the progression becomes relentlessly progressive. With early treatment, the brain impairment is reversible, but left untreated the brain can be permanently damaged. Today, this is a treatable condition, and the hydrocephalus can be controlled.

Breathing difficulties

Paralysis of the vocal cords occurs in a small percentage (2 to 3%) of children with spina bifida. It usually occurs in those children who have hydrocephalus. It is characterized by noisy breathing (stridor). Stridor is usually present at first only when the child is upset.

It may progress from airway obstruction to difficult breathing requiring an opening (tracheostomy) be made at the wind pipe (trachea) below the vocal cords, thus bypassing the obstruction. Complications of hydrocephalus to this degree are rare.

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