What is cerebral palsy?

Causes and Symptoms

Cerebral palsy is not a single disorder. Rather, it is a group of disorders that affect the brain at some time before a child is one month old, resulting in a lack of normal control of movements. While problems with making normal movements may be apparent at birth, this symptom is often not noticeable until the child is nine or ten months of age; on occasion, it may not be apparent before eighteen or twenty-four months of age because the areas of the brain that control movement are immature and not very effective early in life. Until the child reaches an age at which these areas are functional, a lack of function may go unrecognized. For example, problems using the legs may not be evident until the child is old enough to try to walk. Sometimes, a child is so severely affected that the motor problems—noticeable as either decreased or increased motor tone, or tension on the tendons—may be apparent in the first days or months of life.

Abnormal motor function can have both negative and positive symptoms. Negative symptoms can include the inability to do normal motor activities such as reach for a toy, pick up a raisin with the fingers, or walk. Positive symptoms can consist of abnormal movements such as the involuntary flexion of the foot when trying to walk, resulting in toe walking, or the persistence of primitive reflexes (such as the Moro reflex), which impede voluntary movements. These positive manifestations can result in unusual arm or leg postures that make some of these children easily recognizable. On the other hand, many children with cerebral palsy do not have these symptoms and are normal in appearance. Others have motor problems so mild that they are never diagnosed but are simply considered clumsy or maladroit.

By definition, any brain abnormality that causes cerebral palsy is not progressive, which means that the brain does not deteriorate. Actually, most children with cerebral palsy show improved motor coordination as they become older. A child with mild cerebral palsy at one year of age may be able to move normally by the second grade. Children correctly diagnosed with cerebral palsy early in life may no longer suffer from the disorder later in life. Therefore, the number of children with cerebral palsy decreases with age. The rate in developed countries is approximately two per one thousand school-age children. The vast majority of children with cerebral palsy reach adulthood, with most having a full life span. As a group, those who are never able to walk are more likely to die younger.

There is no single cause of cerebral palsy. Any abnormality of the brain that can develop either in utero or before the infant is one month old can cause cerebral palsy. Cerebral palsy is more common among children born prematurely; they account for approximately one-third of all children with cerebral palsy. One theory holds that these children develop a brain abnormality while in the womb which causes the child both to be born prematurely and to have cerebral palsy. Alternatively, especially among very low birth weight infants, their difficult first weeks of life may cause intraventricular hemorrhage and brain injury, most commonly of the white matter adjacent to the lateral ventricles. The pattern referred to as diplegia, in which the legs are more severely affected than the arms, is characteristic in premature infants with cerebral palsy.

Approximately 78 percent of term infants who develop cerebral palsy are healthy at birth. Only later, when they reach the appropriate developmental stage, does their condition become apparent. It is widely believed that these children have a brain abnormality that occurred while the brain was developing in the womb. The underlying cause of such abnormalities is unclear. About 22 percent of term infants with cerebral palsy are unwell at birth. These children have had various physiological insults—including stroke, infection, or lack of oxygen—either in the womb or at the time of birth. Children who suffer a lack of oxygen or hypotension (low blood pressure) during the birth process account for about 10 percent of infants who develop cerebral palsy. Sometimes, maternal hemorrhage or placental abnormalities deprive the infant of oxygen. Errors committed by the delivering doctor or midwife are an uncommon cause of cerebral palsy. Enhanced fetal monitoring during labor and delivery using electronic devices and delivery by cesarean section have not lowered the rate of cerebral palsy.

Since cerebral palsy is a motor disorder, it is classified by motor patterns. Children with cerebral palsy are generally divided into two major groups: those with increased tone (also called spasticity) and those with decreased tone. This is a somewhat artificial distinction since some children have decreased tone in infancy and increased tone later in life, while others may have decreased tone when lying down but increased tone when sitting or standing. A major advantage of this division is the recognition that persistent and severe decrease in motor tone makes walking more difficult, while increased tone makes the development of contractures (shortened tendons) more likely. In addition, children are classified by pattern of limb involvement. The common pattern in children born prematurely is diplegia, in which the legs are more severely affected than the arms. About 50 percent of children affected with diplegia are able to walk. Another common pattern is
hemiplegia, in which the arm and leg on one side are affected and the other side is normal. The arm is more severely involved than the leg, and the prognosis for walking is good, with
almost all these children able to walk if they do not have any other motor problem. When all four limbs are involved, the condition is called
quadriplegia (or double hemiparesis or tetraplegia). These youngsters have the least likelihood of being able to walk and are most likely to have associated problems such as mental retardation. The pattern wherein the limbs produce markedly abnormal movements whenever the child attempts voluntary movements is uncommon. These abnormal movements can be sharp and sudden in nature (called chorea) or slower and more writhing (called athetosis), although often the movements are a combination of the two patterns and thus not easily classified. In the past, this motor pattern was caused by severe hyperbilirubinemia (a very high accumulation of bilirubin) shortly after birth. Today, modern therapies such as exchange transfusion and light therapy usually prevent the
bilirubin level from rising to dangerous levels.

The motor impairment can affect more than the child’s limbs. Speech, chewing, drinking, and swallowing can be abnormal when the motor disability affects the face, tongue, and lips. This is most commonly seen in children with quadriplegia. It is widely noted that many of these children have weak face muscles and tend to keep their mouths open and to drool. When speech is affected, the patient often speaks slowly, has a nasal quality to the voice, and has poor enunciation. When this disability is severe, patients may find it impossible to speak any intelligible words even when their understanding of speech is not affected. Children with this type of motor problem may have difficulty with the fine lip and tongue movements necessary for chewing and may be able to eat only soft foods. Some of these children also have difficulty handling liquids such as water and may choke on clear liquids; they may prefer thickened soft foods. The motor disability can be severe enough that the swallowing movements of the esophagus and stomach are disturbed. Normally, there is a well-organized progression of such movements that propel food down the esophagus and through the stomach into the
intestines. When this normal motor progression does not occur, children may regurgitate their food, since the food is inadvertently propelled up and out instead of down and into the intestines. This is referred to as

reflux. When present to a minor degree, reflux can be merely a cosmetic problem, and the child may need to wear a bib much of the day. When present to a more severe degree, reflux can interfere with normal nutrition. Having food returning into the mouth in a child who has difficulty coordinating swallowing can lead to aspiration, the inadvertent passage of food down the windpipe and into the lungs, which can cause frequent bouts of pneumonia.

The brain abnormalities that cause cerebral palsy can produce other brain-related disabilities. In a survey of children with cerebral palsy in Atlanta, 75 percent had another disability, 65 percent had mental retardation, 46 percent had epilepsy, and 15 percent had sensory loss. Many of the children had more than one additional disability. Children with quadriplegia are the most likely to have other disabilities.

Treatment and Therapy

Only in unusual circumstances is there any direct treatment available for the brain abnormality that causes the motor disability of cerebral palsy. On the other hand, a variety of resources are available for helping the child cope with motor problems. Physical aids such as wheelchairs, walkers, and crutches have long been available. Modern ones are extremely adjustable and made of lightweight and durable materials. Lightweight plastic can be custom molded and fitted to supplement or replace the more traditional leg braces. Physical therapy
helps interfere with involuntary and primitive reflex patterns that hinder voluntary movements. Therapy can also facilitate normal patterns of arm and leg use. Occupational therapy
focuses on developing fine motor skills and improving the ability to dress, eat, write, and perform other daily activities. To be successful, all these therapies must be done every day. As a practical matter, this means performing the activities at home with parental assistance under the periodic supervision of a therapist. Orthopedic surgery
, when used judiciously, can improve muscle
balance, release contractures, and correct scoliosis. The surgeon must consider carefully how the child’s growth in height and weight in the years following the surgery might affect the outcome either favorably or adversely.

Abnormal tone is difficult to alter. No medicines exist that can increase tone, while several medications such as diazepam, dantrolene, and baclofen can sometimes decrease tone for children who have spasticity. Side effects such as sleepiness greatly limit the use of such medications. In addition, many children have both weakness and increased tone. The tone often helps them do activities such as standing, since the tone stiffens their legs. The loss of tone can actually make the child less able to stand. A surgical procedure called posterior rhizotomy can decrease the tone for children with diplegia who have mild gait abnormalities. These youngsters can walk with minimal assistance, usually walking up on their toes, and they have no problem with truncal balance. In this surgical procedure performed on the lower back, some of the sensory (posterior) innervating nerves to the leg muscles are severed. The procedure can produce some postoperative sensory loss, which usually disappears. Long-term adverse effects include weakness and scoliosis. It is generally believed that to be effective, the procedure should be accompanied by an aggressive program of physical therapy.

School programs have become increasingly sophisticated in assisting pupils with motor disabilities. Techniques include the use of computers for written work as well as computers with voice simulators for youngsters who cannot speak adequately to participate in the classroom. All schools in the United States are required to be physically accessible to motor-disabled students and to structure gym and recess programs so that all students can participate.

Medications are available that can help control muscle spasms and seizures. Spasticity may be treated with botulinum toxin, baclofen, diazepam, or tizanidine. Glycopyrrolate can be prescribed to help ease drooling. Pamidronate can be given to help treat related osteoporosis.

Perspective and Prospects

The Centers for Disease Control and Prevention reported in September 2012 that cerebral palsy is the most common motor disability to occur during childhood, with an estimated global incident rate of 1.5 to more than four cases per thousand live births or children in a defined age group. The brightest hope lies in research to understand better the abnormalities of fetal development that lead to cerebral palsy, in the expectation of finding preventive measures. In addition, since premature infants are disproportionately represented among those with cerebral palsy, the prevention of prematurity and improvements in the management of children born prematurely also provide hope for decreasing the occurrence of the disorder. Newer medicines such as gabapentin that hold the potential for decreasing the adverse effects of increased tone with fewer side effects are also appearing. Finally, the potential of computers and computer-assisted physical devices to help motor-impaired persons is being actively explored.

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