Cerebral palsy (CP) is the term used for a group of nonprogressive disorders of movement and posture caused by abnormal development of, or damage to, motor control centers of the brain. CP is caused by events before, during, or after birth. The abnormalities of muscle control that define CP are often accompanied by other neurological and physical abnormalities.
Voluntary movement (for example, walking, grasping, chewing) is primarily accomplished using skeletal muscles (muscles attached to bones). Control of the skeletal muscles originates in the cerebral cortex, the largest portion of the brain. Palsy means paralysis but may also be used to describe uncontrolled muscle movement. Therefore, cerebral palsy encompasses any disorder of abnormal movement and paralysis caused by abnormal function of the cerebral cortex. CP does not include conditions due to progressive disease or degeneration of the brain. For this reason, CP is also referred to as static (nonprogressive) encephalopathy (disease of the brain). Also excluded from CP are any disorders of muscle control that arise in the muscles themselves and/or in the peripheral nervous system (nerves outside the brain and spinal cord). CP is not a specific diagnosis but is more accurately considered a description of a broad but defined group of neurological and physical problems.v
Because CP is not one disorder, it is difficult to classify. It has been divided into four general types: spastic, athetoid, ataxic, and mixed. Another general categorization describes spastic, dyskinetic, and ataxic CP as follows:
- Spastic refers to diplegic impairment of either legs or arms, quadriplegic involving all four extremities, hemiplegic or one-sided involvement of arms and legs, or double hemiplegic impairment of both sides, arms and legs. Spasticity means having an increased stretch reflex.
- Dyskinetic refers to abnormal movements caused by inadequate regulation of muscle tone and coordination. The category includes athetoid or choreoathetoid CP; both are hyperkinetic forms of the disease.
- Ataxic refers to disturbances in coordination of voluntary movements; it includes mixed forms of CP, with mixed characteristics and symptoms.
Muscles that receive defective messages from the brain may be constantly contracted and tight (spastic), exhibit involuntary writhing movements (athetosis), or have difficulty with voluntary movement (dyskinesia). A lack of balance and coordination with unsteady movements (ataxia) may also be present. Spastic CP and mixed CP constitute the majority of cases. Effects on the muscles can range from mild weakness or partial paralysis (paresis) to complete loss of voluntary control of a muscle or group of muscles (plegia). CP is also designated by the number of limbs affected. For instance, affected muscles in one limb is monoplegia, both arms or both legs is diplegia, both limbs on one side of the body is hemiplegia, and in all four limbs is quadriplegia. Muscles of the trunk, neck, and head may be affected.
About 50 percent of all cases of CP diagnosed are in children who are born prematurely. Advances in the medical care of premature infants since the 1980s have dramatically increased the rate of survival of these fragile newborns. However, as gestational age at delivery and birth weight of a baby decrease, the risk for CP dramatically increases. A term pregnancy is delivered at 37–41 weeks gestation. The risk for CP in a preterm infant (32–37 weeks) is increased about five-fold over the risk for an infant born at term. Survivors of extremely preterm births (less than 28 weeks) face as much as a 50-fold increase in risk.
Two factors are involved in the risk for CP associated with prematurity . First, premature babies are at higher risk for various CP-associated medical complications, such as intracerebral hemorrhage, infection, and difficulty in breathing, to name a few. Second, the onset of premature labor may be induced, in part, by complications that have already caused neurologic damage in the fetus. A combination of both factors may play a role in some cases of CP. The tendency toward premature delivery runs in families, but genetic mechanisms are not fully clear.
An increase in multiple births in the early 2000s, especially in the United States, is associated with the increased use of fertility drugs. As the number of fetuses in a pregnancy increases, the risks for abnormal development and premature delivery also increase. Twins , for example, have four times the risk of developing CP as children from singleton pregnancies, owing to the fact that more twin pregnancies are delivered prematurely. The risk for CP in one of triplets is up to 18 times greater. Furthermore, evidence suggests that a baby from a pregnancy in which its twin died before birth is at increased risk for CP.
Although CP is the leading cause of disability in children, its incidence in the United States did not changed much between the 1980s and the early 2000s. Advances in medicine have decreased the incidence from some causes. Rh disease, for example, has been controlled by the advent of anti-Rh globulin; its administration to Rh-negative mothers has reduced one risk factor for CP. The risk has still increased from other causes, however, notably prematurity and multiple-birth pregnancies. The cause of most cases of CP remains unknown, but it has become clear in the early 2000s that birth difficulties are not to blame in most cases. Rather, developmental problems before birth, usually unknown and generally undiagnosable, are largely responsible. The rate of survival for preterm infants has leveled off in the early 2000s, and methods to improve the long-term health of these at-risk babies are being sought.
Approximately 500,000 children and adults in the United States have CP, and it is newly diagnosed in about 6,000 infants and young children each year, representing about two to three children in 1,000 live births. No particular ethnic group seems to be at higher risk for CP. However, some low income families may be at higher risk due to poorer access to proper prenatal care and advanced medical services.
Causes and symptoms
CP can be caused by a number of different mechanisms at various times of life, ranging from several weeks after conception, through birth, to early childhood. In the twentieth century, it was accepted that most cases of CP were due to brain injuries received during a traumatic birth, a condition known as birth asphyxia. However, extensive research in the 1980s showed that only 5 to 10 percent of CP can be attributed to birth trauma. Other possible causes include abnormal development of the brain, prenatal factors that directly or indirectly damage neurons in the developing brain, premature birth, and brain injuries that occur in the first few years of life.
The causes of CP could be grouped into those that are genetic and those that are non-genetic, although most would fall somewhere in between. Grouping causes into those that occur during pregnancy (prenatal), those that happen around the time of birth (perinatal), and those that occur after birth (postnatal), is preferable. CP related to premature birth and multiple births is somewhat different and considered separately.
Although much was learned about human embryology in the last couple of decades of the twentieth century, a great deal remains unknown in the early 2000s. Studying prenatal human development is difficult because the embryo and fetus develop in a closed environment—the mother's womb. However, the development of a number of prenatal tests has opened a window on the process. Add to that more accurate and complete evaluations of newborns, especially those with problems, and a clearer picture of what can go wrong before birth is possible.
The complicated process of brain development before birth is susceptible to many chance errors that can result in abnormalities of varying degrees. Some of these errors will result in structural anomalies of the brain, while others may cause undetectable, but significant, abnormalities in how the cerebral cortex is wired. An abnormality in structure or wiring is sometimes hereditary but is most often due to chance or some unknown cause. The possible role genetics plays in a particular brain abnormality depends to some degree on the type of anomaly and the form of CP it causes.
Several maternal-fetal infections are known to increase the risk for CP, including rubella (German measles , now rare in the United States), cytomegalovirus (CMV), and toxoplasmosis . Each of these infections is considered a risk to the fetus only if the mother contracts it for the first time during that pregnancy. Even in those cases, most babies are born normal. Most women are immune to all three infections by the time they reach childbearing age, but a woman's immune status can be determined using the so-called TORCH (for toxoplasmosis, rubella, cytomegalovirus, and herpes) test before or during pregnancy.
Just as a stroke can occur in an adult and cause neurologic damage in an adult, so too can this type of event occur in the fetus. A burst blood vessel in the brain followed by uncontrolled bleeding (intracerebral hemorrhage) can cause a fetal stroke, or a clot (embolism) can obstruct a cerebral blood vessel. Infants who later develop CP, along with their mothers, are more likely than other mother-infant pairs to have coagulation disorders (coagulopathies) that put them at increased risk for bleeding episodes or blood clots. Certain coagulation disorders are inherited while others may be deficiencies in essential clotting factors or defects in the coagulation process.
Any substance that might affect fetal brain development, directly or indirectly, can increase the risk for CP. Likewise, any substance that increases the risk for premature delivery and low birth weight, such as alcohol, tobacco, or cocaine, among others, might indirectly increase the risk for CP. Links between a drug or other chemical exposure during pregnancy and a risk for CP are difficult to prove.
Because the fetus receives all nutrients and oxygen from blood that circulates through the placenta, anything that interferes with normal placental function might adversely affect development of the fetus, including the brain, or might increase the risk for premature delivery. Structural abnormalities of the placenta, premature detachment of the placenta from the uterine wall (abruption), and placental infections (chorioamnionitis) are thought to pose some risk for CP.
Certain conditions in the mother during pregnancy might pose a risk to fetal development leading to CP. Women with autoimmune anti-thyroid or anti-phospholipid (APA) antibodies are at slightly increased risk for CP in their children. A potentially important clue points toward high levels of cytokines in the maternal and fetal circulation as a possible risk for CP. Cytokines are proteins associated with inflammation, such as from infection or autoimmune disorders, and they may be toxic to neurons in the fetal brain.
Serious physical trauma to the mother during pregnancy could result in direct trauma to the fetus as well, or injuries to the mother could compromise the availability of nutrients and oxygen to the developing fetal brain.
Birth asphyxia that is significant enough to result in CP is uncommon in developed countries. An umbilical cord around the baby's neck (tight nuchal cord) and the cord delivered before the baby (prolapsed cord) are possible causes of birth asphyxia, as are bleeding and other complications associated with placental abruption and placenta previa (placenta lying over the cervix).
Infection in the mother is sometimes not passed to the fetus through the placenta but is transmitted to the baby during delivery. Any such infection, such as herpes, that results in serious illness in the newborn has the potential to produce some neurological damage.
The remaining 15 percent of CP cases are due to neurologic injury sustained after birth. CP that has a postnatal cause is sometimes referred to as acquired CP, but this is only accurate for those cases caused by infection or trauma.
Incompatibility between the Rh blood types of mother and child (mother Rh negative, baby Rh positive) can result in severe anemia in the baby ( erythroblastosis fetalis ). This may lead to other complications, including severe jaundice , which can cause CP. Rh disease in the newborn is rare in developed countries due to routine screening of maternal blood type and routine prevention of anti-Rh antibodies in Rh negative women after each birth of an Rh positive infant. The routine, effective treatment of jaundice due to other causes has also made it an infrequent cause of CP in developed countries.
Serious infections that affect the brain directly, such as meningitis and encephalitis , may cause irreversible damage to the brain, leading to CP. A seizure disorder early in life may cause CP or may be the product of a hidden problem that causes CP in addition to seizures. Unexplained (idiopathic) seizures are hereditary in only a small percentage of cases. Although rare in healthy infants born at or near term, intracerebral hemorrhage and brain embolism, like fetal stroke, are sometimes genetic.
Physical trauma to an infant or child resulting in brain injury, such as from abuse, accidents, or near drowning/suffocation, might cause CP. Likewise, ingestion of a toxic substance such as lead, mercury, other poisons, or certain chemicals could cause neurological damage. Accidental overdose of certain medications might also cause similar damage to the central nervous system.
The symptoms of CP and their severity are variable. Those who have CP may have only minor difficulty with fine motor skills , such as grasping and manipulating items with their hands. A severe form of CP could involve significant muscle problems in all four limbs, mental retardation , seizures, and difficulties with vision, speech, and hearing.
Although the defect in cerebral function that causes CP is not progressive, the symptoms of CP often change over time. Most of the symptoms relate in some way to the aberrant control of muscles. CP is categorized first by the type of movement/postural disturbance(s) present, rather than by a description of which limbs are affected. The severity of motor impairment is also a factor. Spastic diplegia, for example, refers to continuously tight muscles that have no voluntary control in both legs, while athetoid quadraparesis describes uncontrolled writhing movements and muscle weakness in all four limbs. These may describe CP symptoms generally but do not describe all people with CP. Spastic diplegia is seen in more individuals than is athetoid quadraparesis. CP can also be loosely categorized as mild, moderate, or severe, but these are subjective terms.
A muscle that is tensed and contracted is hypertonic, while excessively loose muscles are hypotonic. Spastic, hypertonic muscles can cause serious orthopedic problems, including curvature of the spine ( scoliosis ), hip dislocation, or contractures. A contracture is shortening of a muscle, aided sometimes by a weak-opposing force from a neighboring muscle. Contractures may become permanent, i.e., fixed, without some sort of intervention. Fixed contractures may cause postural abnormalities in the affected limbs. Clenched fists and contracted feet (equinus or equinovarus) are common in people with CP. Spasticity in the thighs causes them to turn in and cross at the knees, resulting in an unusual method of walking known as scissors gait. Any of the joints in the limbs may be stiff (immobilized) due to spasticity of the attached muscles.
Athetosis and dyskinesia often occur with spasticity but do not often occur alone. The same is true of ataxia. It is important to remember that mild CP or severe CP refers not only to the number of symptoms present but also to the level of involvement of any particular class of symptoms.
Other neurologically based symptoms may include the following:
- mental retardation/learning disabilities
- behavioral disorders
- seizure disorders
- visual impairment
- hearing loss
- speech impairment (dysarthria)
- abnormal sensation and perception
These problems may have a greater impact on a child's life than the physical impairments of CP, although not all children with CP are affected by other problems. Many infants and children with CP have growth impairment. About one third of individuals with CP have moderate-to-severe mental retardation, one third have mild mental retardation, and one third have normal intelligence .
When to call the doctor
Parents should seek medical advice when they notice what seems to be slow development in movement, speech, or cognitive ability in their young child. If a child does not acquire certain skills within a normal time frame, there may be some cause for concern. However, it is known that children progress at somewhat different rates, and a slow beginning is often followed by normal development.
Normal developmental milestones with typical ages for acquiring them, include the following:
- sits well unsupported at about six months (eight to ten months)
- babbles at about six months (up to eight months)
- crawls at about nine months (up to 12 months)
- finger feeds, holds bottle at about nine months (up to 12 months)
- walks alone at about 12 months (up to 15–18 months)
- uses one or two words other than dada/mama at about 12 months (up to 15 months)
- walks up and down steps at about 24 months (24 to 36 months)
- turns pages in books and removes shoes and socks at about 24 months (to 30 months)
Children do not consistently favor one hand over the other before 12 to 18 months of age, and doing so may be a sign that the child has difficulty using the other hand. This same preference for one side of the body may show up as asymmetric crawling or, later on, favoring one leg while climbing stairs. Because CP is nonprogressive, continued loss of previously acquired milestones may indicate that CP is not the cause of the problem; medical evaluation is needed to determine the cause.
The signs of CP are not usually noticeable at birth. Children normally progress through a predictable set of developmental milestones through the first 18 months of life. Children with CP, however, tend to develop these skills more slowly because of their motor impairments,
No one test is diagnostic for CP, but certain factors increase suspicion. The Apgar score measures a baby's condition immediately after birth. Babies who have low Apgar scores are at increased risk for CP. Presence of abnormal muscle tone or movements may indicate CP, as may the persistence of infantile reflexes. Imaging of the brain using ultrasound, x rays , MRI, and/or CT scans may reveal a structural anomaly. Some brain lesions associated with CP include scarring, cysts, expansion of the cerebral ventricles ( hydrocephalus ), abnormality of the area surrounding the ventricles (periventricular leukomalacia), areas of dead tissue (necrosis), and evidence of an intracerebral hemorrhage or blood clot. Blood and urine biochemical tests, as well as genetic tests, may be used to rule out other possible causes, including muscle and peripheral nerve diseases, mitochondrial and metabolic diseases, and other inherited disorders. Evaluations by a pediatric developmental specialist and a geneticist may be of benefit.
Cerebral palsy cannot be cured, but many of the disabilities it causes can be managed through planning and timely care. Treatment for a child with CP depends on the severity, nature, and location of the primary muscular symptoms, as well as any associated problems that might be present. Optimal care of a child with mild CP may involve regular interaction with only a physical therapist and occupational therapist, whereas care for a more severely affected child may include visits to multiple medical specialists throughout life. With proper treatment and an effective plan, most people with CP can lead productive, happy lives.
Physical, occupational, and speech therapy
Spasticity, muscle weakness, coordination, ataxia, and scoliosis are all significant impairments that affect the posture and mobility of children and adults with CP. Physical and occupational therapists work with the patient and the family to maximize the patient's ability to move affected limbs, develop normal motor patterns, and maintain posture. Assistive technology, including wheelchairs, walkers, shoe inserts, crutches, and braces, are often required. A speech therapist and high-tech aids such as computer-controlled communication devices can make a tremendous difference in the life of those who have speech impairments.
Before fixed contractures develop, muscle-relaxant drugs such as diazepam (Valium), dantrolene (Dantrium), and baclofen (Lioresal) may be prescribed. Botulinum toxin (Botox), a highly effective treatment, is injected directly into the affected muscles. Alcohol or phenol injections into the nerve controlling the muscle are another option. Multiple medications are available to control seizures, and athetosis can be treated using medications such as trihexyphenidyl HCl (Artane) and benztropine (Cogentin).
Fixed contractures are usually treated with either serial casting or surgery. The most commonly used surgical procedures are tenotomy, tendon transfer, and dorsal rhizotomy. In tenotomy, tendons of the affected muscle are cut, and the limb is cast in a more normal position while the tendon regrows. Alternatively, tendon transfer involves cutting and reattaching a tendon at a different point on the bone to enhance the length and function of the muscle. A neurosurgeon performing dorsal rhizotomy carefully cuts selected nerve roots in the spinal cord to prevent them from stimulating the spastic muscles. Neurosurgical techniques in the brain such as implanting tiny electrodes directly into the cerebellum or cutting a portion of the hypothalamus have very specific uses and have had mixed results.
Asphyxia —Lack of oxygen.
Ataxia —A condition marked by impaired muscular coordination, most frequently resulting from disorders in the brain or spinal cord.
Athetosis —A condition marked by slow, writhing, involuntary muscle movements.
Cerebral palsy —A nonprogressive movement disability caused by abnormal development of or damage to motor control centers of the brain.
Coagulopathy —A disorder in which blood is either too slow or too quick to coagulate (clot).
Contracture —A tightening or shortening of muscles that prevents normal movement of the associated limb or other body part.
Cytokines —Chemicals made by the cells that act on other cells to stimulate or inhibit their function. They are important controllers of immune functions.
Diplegia —Paralysis affecting like parts on both sides the body, such as both arms or both legs.
Dorsal rhizotomy —A surgical procedure that cuts nerve roots to reduce spasticity in affected muscles.
Dyskinesia —Impaired ability to make voluntary movements.
Hemiplegia —Paralysis of one side of the body.
Hypotonia —Having reduced or diminished muscle tone or strength.
Quadriplegia —Paralysis of all four limbs and the trunk below the level of an associated injury to the spinal cord. Also called tetraplegia.
Serial casting —A series of casts designed to gradually move a limb into a more functional position.
Spastic —Refers to a condition in which the muscles are rigid, posture may be abnormal, and fine motor control is impaired.
Spasticity —Increased mucle tone, or stiffness, which leads to uncontrolled, awkward movements.
Static encephalopathy —A disease or disorder of the brain that does not get better or worse.
Tenotomy —A surgical procedure that cuts the tendon of a contracted muscle to allow lengthening.
Cerebral palsy can affect every stage of maturation, from childhood through adolescence to adulthood. At each stage, those with CP, along with their caregivers, must strive to achieve and maintain the fullest range of experience and education consistent with their abilities. The advice and intervention of various professionals are crucial for many people with CP. Although CP itself is not considered a terminal disorder, it can affect a person's lifespan by increasing the risk for certain medical problems. People with mild cerebral palsy may have near-normal lifespan, but the lifespan of those with more severe forms may be shortened. However, over 90 percent of infants with CP survive into adulthood.
Research in the early 2000s is focused on the possible benefits of recognizing and treating coagulopathies and inflammatory disorders in the prenatal and perinatal periods in order to reduce the incidence of CP and other congenital diseases. The use of magnesium sulfate in pregnant women with preeclampsia or threatened preterm delivery may reduce the risk of CP in very preterm infants. Finally, the risk of CP can be decreased through good maternal nutrition , avoidance of drugs and alcohol during pregnancy, and prevention or prompt treatment of infections.
Parents of a child diagnosed with CP may not feel that they have the necessary expertise to coordinate the full range of care their child needs. Although knowledgeable and caring medical professionals are indispensable for developing a care plan, a potentially more important source of information and advice can be gained from other parents who have dealt with the same set of difficulties. Support groups for parents of children with CP can be significant sources of both practical advice and emotional support. Many cities have support groups that can be located through the United Cerebral Palsy Association, and most large medical centers have special multidisciplinary clinics for children with developmental disorders.
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L. Lee Culvert Scott J. Polzin, MS