Overall, cerebral palsy affects somewhere between 1 in 500 and 1 in 1,000 newborns, though some of these are only mildly affected. The risk is highest in premature and underweight babies. The number of new cases of cerebral palsy has actually risen slightly in recent years, partly because better intensive care is keeping more premature babies alive but also because fertility treatments have led to a rise in twin and multiple births, which are more likely to result in a baby with cerebral palsy.
- Having a mother who has an infection (e.g., rubella [German measles], toxoplasmosis, herpes, cytomegalovirus) while pregnant.
- Having a mother with an incompatible blood type (Rh incompatibility is an immune problem in which the mother generates antibodies that attack and destroy red blood cells in the fetus, interfering with oxygen supply to the child's organs - it rarely happens in first pregnancies).
- Being exposed to toxic substances in the womb.
- Having a mother with intellectual disability, or with a history of thyroid problems or seizure disorders.
- Having a complicated delivery (e.g., breech birth).
- Having a low apgar score (a test carried out several times in the hours after delivery that assigns a score based on heart rate, reflexes, skin colour, and muscle tone).
- Having severe jaundice after birth, especially if left untreated.
- Having seizures as an infant.
Although cerebral palsy is often considered a congenital (present at birth) syndrome, it can also develop after birth. A brain injury resulting from a brain infection (e.g., meningitis, encephalitis) or from a fall or accident such as a near drowning is termed acquired cerebral palsy. On the other hand, congenital cerebral palsy is a result of something going wrong during fetal development or during the birth process itself. It used to be believed that lack of oxygen during delivery was the main cause, but researchers now think this only account for about 10% of cases.
A fetus develops from a single cell, which divides repeatedly to eventually become billions of cells. During the process, groups of cells become specialized to form all the different body tissues. Likewise, various types of nerve cells form and migrate to take up their proper places throughout the brain. This process is highly complex and, not surprisingly, errors sometimes occur that disturb the normal architecture of the brain.
Errors could occur as a result of the following:
- A fetal stroke that cuts off blood supply to the developing brain, causing brain damage. This can be caused by maternal infections or high blood pressure.
- Maternal or fetal infections can damage the white matter in the brain, which causes nerve transmission problems between the brain and the body.
- Mutations can occur in genes that control fetal brain development, caused by maternal infections, fever, trauma, or fetal exposure to toxins.
- Prolonged lack of oxygen to the brain because of a complicated labour and delivery, severely low maternal blood pressure, uterus rupture, or problems with the placenta or umbilical cord.
We are only now beginning to understand some of the issues surrounding the development of the fetal brain. Hopefully, more research in this area will allow us to eventually explain the exact causes of cerebral palsy.
Symptoms and Complications
The signs of cerebral palsy are usually first noticed by the parents after the child is 6 months old. Likely first signs include:
- adopting unusual positions and favouring one side of the body when they move
- excessive rigidity (increased muscle tone) or floppiness (decreased muscle tone)
- crossed eyes
- failure to develop at a normal rate - not reaching milestones like sitting up, smiling, or walking
- muscle wasting, slow or uneven growth
- unresponsiveness or apparent deafness
There is no set pattern of symptoms in cerebral palsy because it's an umbrella term covering many symptoms. However, there are certain broad categories that distinguish the various motor (muscle) symptoms.
- Spastic cerebral palsy is the most common form, affecting about three-quarters of sufferers. Muscles tend to be permanently contracted. This may be severe enough to bend the joint permanently or to cause paralysis. The spasticity may affect both legs, both arms, all four limbs, or one leg and one arm. Affected limbs may grow more slowly than healthy ones, producing unusually small feet, legs, and hands. People with spastic cerebral palsy who are able to walk often have a scissors gait, in which the knees almost touch and the feet cross inwards over an imaginary line drawn down the centre of the body.
- Athetoid cerebral palsy affects 1 in 5 sufferers. It's characterized by slow, writhing movements, usually in the limbs, but it may also affect facial muscles including the tongue. This can lead to drooling, strange facial expressions, and an inability to form some words or sounds. Speech defects due to muscle disorders (dysarthria) should be distinguished from language difficulties due to mental retardation, which is a very different problem.
- Ataxic cerebral palsy affects fewer than 1 in 20 sufferers. Poor coordination and depth perception makes people with ataxic cerebral palsy unsteady walkers, with a wide-based gait. They also have difficulty with quick and precise movements like writing. They may suffer from intention tremor, in which the arm or hand trembles when reaching for an object, and the trembling gets worse the closer the hand gets to the target.
A great many people with cerebral palsy have mixtures of these forms. The most common mixture is spastic-athetoid cerebral palsy. In all types, the symptoms can be very mild or very severe. Some people's only challenge is shaky writing, while others are paralyzed from the neck down.
A wide range of other problems can go along with nerve and muscle symptoms in cerebral palsy. By far the most important is intellectual impairment. One-third of all people with cerebral palsy have severe intellectual impairment, with a mental age that will never advance beyond 3 or 4. Another one-third have mild intellectual impairment, and the remaining one-third are unaffected intellectually. But even with normal intelligence, the vision, hearing, and speech problems; social isolation; resentment; and depression that can accompany cerebral palsy can lead to learning disabilities unless the child is helped and encouraged every step of the way.
Strabismus is a common problem for people with cerebral palsy. This symptom is often described as crossed eyes. But in young children whose eyes aren't aligned, there's a tendency for the brain to completely ignore signals from one eye, leading to major deterioration of eyesight in that eye. Deafness, while not common, is more common in children with cerebral palsy than in the general population. Sometimes, the sense of touch is also deficient.
Bladder and bowel function are often impaired by the lack of proper nervous signals coming from the brain. This can lead to constipation or, most likely, urinary incontinence, which can take several forms. Bedwetting, a sudden release upon exercise or coughing, or a constant dribble are all possible. The same lack of nervous signals can make chewing and swallowing difficult.
Epilepsy is common in people with cerebral palsy. Seizures may be mild or severe.
The most common complication of cerebral palsy is muscle contracture, which generally occurs in children. As the bones grow, the muscles normally keep pace. In cerebral palsy, there's a tendency for sufferers not to use their weaker or less coordinated limbs, leading to muscle atrophy. This can prevent the muscle from growing with the bone, which can cause the joint to become permanently flexed and paralyzed. Once this happens, surgery is usually required to fix it.
Symptoms don't generally get worse over time, as the underlying disease isn't progressive. Atrophy, however, can worsen muscular symptoms and, in children, prevent proper growth. Weaker, less coordinated limbs often end up withered or undersized.
There's a lack of research on the effects of cerebral palsy in older adults. Some doctors believe that people with cerebral palsy may age faster after middle age, but for the moment there's no evidence one way or the other. Statistics on life expectancy for people with this disease are also lacking.
Despite these unknowns, cerebral palsy is certainly not considered a fatal condition.
Making the Diagnosis
Although all newborn babies with cerebral palsy have impairments caused by the disease, it's usually impossible to diagnose the condition until the child starts missing developmental milestones, like crawling or grasping objects.
However, by observing a newborn infant, it's sometimes possible to predict which babies are at higher risk of having cerebral palsy.
Signs of increased risk include:
- abnormally small head or lower jaw
- hernia in the groin
- low apgar score
- low levels of the thyroid hormone thyroxine
- malformations of the spine
- severe jaundice at birth or shortly after birth
A few babies are obviously disabled at birth, but most are brought in to the doctor by worried parents after 3 to 18 months. While there's no chemical or blood test for cerebral palsy, there are several clinical tests that help with diagnosis. Because so many children with cerebral palsy have some limbs that are far more affected than others, they are likely to develop a preference (left- or right-handedness) far earlier than healthy babies, who have no preference in their first year. If a baby always grabs an object with the right hand even when it's far closer to the left, this is a possible sign of cerebral palsy.
Newborns have certain baby reflexes that they lose after a few months, but children with cerebral palsy hold onto these reflexes far longer. There are several tests for this. In the Moro reflex, for example, a baby will extend both arms if laid on their back with the feet elevated above the head. If a baby still does this long after 6 months, it's a sign of developmental delay that may signify cerebral palsy.Sometimes, scans such as magnetic resonance imaging (MRI) and computed tomography (CT) can reveal abscesses or other physical damage in the brain. It's important to eliminate the possibility of progressive neurological disease.
There are also intelligence, sight, and hearing tests to establish if other problems accompany cerebral palsy.
Treatment and Prevention
There's no cure for cerebral palsy, as the brain doesn't get a second chance to grow. The aim of treatment is to provide as normal a life as possible and to maximize independence in people whose mental capacities allow it.
The first goal is to minimize disability. Above all, this means preventing or repairing muscle contractures. These are less likely if you exercise the affected limb as much as possible. Physical therapy aims to prevent contractures and poor growth caused by atrophy. Most doctors agree that exercising impaired limbs is the best way to keep them healthy and get the most out of them. Once contractures occur, surgery is often necessary. The muscle can take months to heal properly from such an operation, so prevention is usually better than cure. Botulinum toxin* injections are sometimes given for severe contractures. The toxin paralyzes the muscle, allowing it to relax.
As a child approaches school age, therapy tends to concentrate more on improving communication and minimizing socially problematic symptoms like drooling. Every effort is made to place children of normal intelligence in regular schools. Much of the work of therapy is actually performed by the parents, once they've learned the techniques.
Seizures and spasticity can often be controlled with antiseizure and muscle relaxant medications (e.g., baclofen, diazepam), and most children with cerebral palsy will be on some form of medication. When symptoms can't be eliminated, their effects can be minimized with modern devices like computerized speaking aids and electric wheelchairs.
While it's unlikely that cerebral palsy can be eliminated completely, there are some risk factors that can be managed. Anything that increases risk of premature birth, such as tobacco, alcohol, and illegal drugs, will also increase the risk of cerebral palsy. Birth defects are more likely when the mother smokes and drinks during pregnancy.
Getting vaccinated against German measles (rubella) is one of the easiest steps a woman can take. She should get the immunization shot before she becomes pregnant, because this preventative measure is too late once a woman is pregnant.
Any steps that reduce the risk of head injury in a baby or infant will also reduce the risk of cerebral palsy. A properly fitted child car seat is probably the most important measure parents can take in this regard. Meningitis can't always be prevented, but the risk can be reduced by having your child receive recommended vaccinations, and taking your child to the doctor for any ear infections or severe headache with fever. A doctor should examine any infant below the age of 4 to 6 months that has a fever.