Causes of Cerebral Palsy
Acquired cerebral palsy: Approximately 10-20% of children in the United States with cerebral palsy (CP) acquire the disorder after birth. Brain damage in the first few months or years of life, brain infections, such as bacterial meningitis or viral encephalitis, or head injury account for many of the cases of acquired cerebral palsy. In such cases, the disorder may result from brain infections like bacterial meningitis (inflammation of the lining of the brain caused by a bacteria), viral encephalitis (inflammation of the brain caused by a viral infection), head trauma sustained from an accident, fall, or inflicted injuries (such as shaken baby syndrome).
Congenital cerebral palsy: CP that occurs at birth is often the result of specific events during pregnancy or around the time of birth. These events result in damage to the motor centers in the developing brain. Often times, however, congenital cerebral palsy may not be detected for months. However, birth complications account for only about 3-13% of congenital CP cases.
Infections during pregnancy: Viruses such as rubella (German measles) or herpes group B can infect the developing fetus in a pregnant woman and cause damage to the developing nervous system. Brain injury in the developing fetus may also be caused by other infections such as cytomegalovirus (herpesvirus type 5) and toxoplasmosis (a protozoal infection). Infections of the placental may also be associated with cerebral palsy.
Jaundice: If left untreated, severe jaundice can damage the brain. Jaundice is a condition produced when excess amounts of bilirubin circulating in the blood stream dissolve in the subcutaneous fat (the layer of fat just beneath the skin), causing a yellowish appearance of the skin and the whites of the eyes. With the exception of physiologic jaundice in the newborn (normal newborn jaundice in the first week of life), all other jaundice indicates overload or damage to the liver or inability to move bilirubin from the liver through the biliary tract to the gut. Jaundice in an infant, child, or an adult should always be evaluated by a doctor.
Newborn jaundice is common and, unless it is associated with an abnormal condition, it will clear without treatment. Gilbert's syndrome is another hereditary condition in which mild jaundice develops during times of stress. This condition, once recognized, requires no further treatment or evaluation. There are also other more rare hereditary causes of elevated bilirubin levels. All other jaundice is the result of an underlying disease, condition, or toxicity.
A yellow-to-orange color may be imparted to the skin by excessive intake of beta carotene, the orange pigment seen in carrots. Individuals who consume large quantities of carrots or carrot juice or take beta-carotene supplements may develop a distinctly yellow-orange cast to their skin. This condition is called hypercarotenemia or just carotenemia. Hypercarotenemia is easily distinguished from jaundice in that the sclera, or the white of the eyes, remains white, while people with true jaundice have a yellow sclera.
Rh incompatibility: When the mother's body produces immune cells called antibodies that destroy the fetus's blood cells, this may lead to a form of jaundice in the newborn.
Severe lack of oxygen: Hypoxic-ischemic encephalopathy is the name of a condition that occurs when the brain is deprived of oxygen for a prolonged period of time during labor and child delivery. Brain damage may occur. Birth complications, including asphyxia (lack of oxygen to the brain), account for approximately six percent of congenital cerebral palsy cases. Birth asphyxia is associated with spastic quadriplegia, the most commonly occurring form of CP.
Brain hemorrhage: Brain hemorrhage or bleeding may occur in the fetus during pregnancy or in newborns around the time of birth. Bleeding can damage fetal brain tissue and cause neurological problems, including congenital CP. These hemorrhages are a type of stroke that may be caused by broken, abnormal, or clogged blood vessels in or leading to the brain or by respiratory distress, a common breathing disorder in premature infants.
Diagnosis of Cerebral Palsy
Typically, doctors diagnose cerebral palsy (CP) in infants by testing their motor skills and thoroughly analyzing their medical history. A medical history, diagnostic tests, and regular check-ups may be required to confirm the diagnosis of CP or to eliminate the possibility of other disorders.
Unnaturally soft, relaxed, or floppy muscle tone is called hypotonia. Stiff or rigid muscle tone is called hypertonia. Some infants with CP have hypotonia in the first two or three months of life and then develop hypertonia. They also might develop an unusual posture or favor one side of the body.
A newborn held on its back and tilted so its legs are above its head will automatically respond with the Moro reflex, extending its arms in a gesture that resembles an embrace. This reflex usually disappears after about six months. Infants with cerebral palsy often retain it for an abnormally long period.
Signs of hand preference are also observed. When an object is held in front and to the side, infants usually do not display a tendency to use either the right or left hand. This is normal during the first 12 months of life. Infants with spastic hemiplegia, however, often develop hand preference early, indicating one side of their body is stronger than the other.
The doctor will look for other conditions that can be linked to CP, such as seizures, mental impairment, and vision or hearing problems.
Intelligence tests often are given to a child with CP to evaluate mental impairment, but the results can be misleading and there is a risk of underestimating intelligence. For instance, a child with movement, sensation, or speech problems associated with CP would have difficulty performing well on such tests.
Rule out other conditions: If motor skills decline over time, there may be genetic disease, muscle or metabolic disorder, or tumor in the nervous system, either coexistent or instead of CP. The doctor must rule out other disorders that cause movement problems (such as Huntington's disease), identify any coexisting disorder, and determine if the condition is changing.
Lab tests: A chromosome analysis may be performed to identify a genetic anomaly (such as in Down syndrome or Huntington's disease) when abnormalities in features or organ systems are present. Thyroid function tests may reveal low levels of thyroid hormone, which can produce several congenital defects and severe mental retardation. Hyperammonemia, or a high level of ammonia in the blood, may lead to central nervous system toxicity (including movement disorders). A deficiency in any of the enzymes involved in breaking down amino acids can cause hyperammonemia. This may be due to a liver disorder or a defect in metabolism.
Visual tests: Imaging tests are helpful in diagnosing hydrocephalus (condition in which abnormal accumulation of cerebrospinal fluid causes pressure in the brain), structural abnormalities, and tumors. An electroencephalogram (EEG) traces electrical activity in the brain and can reveal patterns that suggest a seizure disorder. Computed tomography (CT scan) can show congenital (birth) malformations and hemorrhage (excessive bleeding) in infants. Magnetic resonance imaging (MRI) uses a magnetic field and radio waves to create pictures of the internal structures of the brain. This study is performed on older children. It defines abnormalities of white matter and motor cortex more clearly than other methods. Ultrasound uses the echoes of sound waves projected into the body to form a picture called a sonogram. It is often used in infants before the bones of the skull harden and close to detect cysts and abnormal structures in the brain.
Electromyography (EMG) and nerve conduction velocity (NCV) studies may be performed when a nerve or muscle disorder is suspected. These tests, which can be used in combination, are often referred to as EMG/NCV studies. NCV is administered before EMG and measures the speed at which nerves transmit electrical signals which can help diagnose CP. During NCV, electrodes are placed on the skin over a nerve that supplies a specific muscle or muscle group. A mild, brief electrical stimulus is delivered through the electrode and the response of the muscle is detected, amplified, and displayed. The strength of the signal is also measured. Neurological conditions can cause the NCV to slow down or to be slower on one side of the body. EMG measures nerve impulses within the muscles. Tiny electrodes are placed in the muscles in the arms and legs and the electronic responses are observed using an oscilloscope (an instrument that displays movement of an electric current). As muscles contract, they emit a weak electrical signal that can be detected, amplified, and tracked using the oscilloscope, providing information about how well the muscles are working.
Signs And Symptoms of Cerebral Palsy
Spastic cerebral palsy: Spastic cerebral palsy (CP) is the most common form, affecting approximately 70% of CP patients. This form is characterized by stiff and permanently contracted muscles. Spastic CP has a jerky, unpredictable effect on movement, causing difficulty in moving from position to position. Spastic cerebral palsy consists of subcategories, including diplegia (both arms of both legs are affected), hemiplegia (either the right arm and leg or left arm and leg are affected), quadriplegia (all arms and legs are affected), monoplegia (only one arm or leg affected), and triplegia (three arms or legs affected).
Spastic diplegia: Spastic diplegia affects the legs more than the arms. The legs often turn in and cross at the knees. This causes a scissors gait, in which the hips are flexed, the knees nearly touch, the feet are flexed, and the ankles turn out from the leg, causing toe-walking. Learning disabilities and seizures are less common than in spastic hemiplegia.
Spastic hemiplegia: Individuals with spastic hemiplegia (hemiparesis) also may experience hemiparetic tremors or uncontrollable shaking of the limbs on one side of the body. Severe hemiparetic tremors can seriously impair movement. The arm is generally affected more than the leg. Learning disabilities, vision problems, seizures, and dysfunction of the muscles of the mouth and tongue are classic symptoms.
Spastic quadriplegia: Spastic quadriplegia involves all four limbs. There is dysfunction of the muscles of the mouth and tongue, seizures, medical complications, and increased risk for cognitive difficulties.
Ataxic cerebral palsy: Ataxic cerebral palsy is much less common that spastic, affecting approximately 5- 10% of CP patients. The main effect of this type is on the child's sense of depth perception and balance. This is often accompanied by poor coordination and children affected by ataxic cerebral palsy can display an abnormal gait when walking, as well as difficulty with precise movement. Another characteristic of ataxic cerebral palsy is the intention tremor. These tremors are initiated by a voluntary movement, such as reaching for a light switch, and become more severe as the individual gets closer to the objective.
Athetoid cerebral palsy: Athetoid or dyskinetic cerebral palsy affects about 10-20% of patients. Athetoid CP is characterized by athetosis (slow, uncontrolled, writhing movements of the hands, feet, arms, or legs). Patients also may have chorea (abrupt, irregular, jerky movements), choreoathetosis (a combination of athetosis and chorea), or dystonia (slow rhythmic movements with muscle tone abnormalities and abnormal postures).
Mixed cerebral palsy: Mixed cerebral palsy is a condition where two or more types of CP exist. This occurs in 10% of CP cases.
Speech: Just as patients have problems with muscle control in their arms and legs, they also have difficulties controlling their tongue, mouth, lips, jaw, and breath flow. As a result, they might have problems with speech. The most common speech problem is called dysarthria. This condition causes speech to be slow and slurred and, in some cases, hypernasal (too much air flow through the nose) or hyponasal (not enough air flow through the nose).
Drooling: There are a number of treatments available to combat the problem of drooling, including surgery, anticholinergics (drugs that reduce saliva flow), and biofeedback (helps allow patients to know when they are drooling).
Eating: Cerebral palsy can affect the muscle groups involved in the face and jaw, which can lead to difficulty eating. In severe cases, this can result in malnutrition and poor growth and development.
Incontinence: Incontinence is more commonly known as poor bladder control. This can take a number of forms, including enuresis or bed wetting, urination during physical activity, or a slow leak from the bladder.
Complications of Cerebral Palsy
Some individuals with cerebral palsy (CP) have other conditions, such as impaired intellectual development, seizures, failure to grow and thrive, and vision and sense of touch problems.
Roughly one-third of patients with CP also have mild intellectual impairment or a decrease in intelligence. Another one-third are moderately or severely impaired and the remainder are intellectually normal. Mental impairment is most common in children with spastic quadriplegia.
As many as one-half of all patients with cerebral palsy have seizures in which uncontrolled bursts of electricity disrupt the brain's normal pattern of electrical activity. Seizures that recur without a direct trigger, such as a fever, are classified as epilepsy. Seizures generally are tonic-clonic or partial. Tonic-clonic seizures spread throughout the brain, typically causing the patient to cry out, followed by unconsciousness, twitching legs and arms, convulsive body movements, and loss of bladder control. Partial seizures are confined to one part of the brain and may be simple or complex. Simple partial seizures cause muscle twitching, chewing movement, and numbness or tingling. Complex partial seizures can produce hallucinations, staggering, random movement, and impaired consciousness or confusion.
Children with moderate-to-severe cerebral palsy, especially those with spastic quadriplegia, often experience failure to grow or thrive. Infants fail to gain weight normally, young children may be abnormally short, and teenagers may be short for their age and may have slow sexual development. These phenomena may be caused by a combination of poor nutrition and damage to the brain centers that control growth.
Some individuals, particularly those with spastic hemiplegia, have muscles and limbs that are smaller than normal. Limbs on the side of the body affected by CP may grow slower than those on the other side. Hands and feet are most severely affected. The affected foot in cases of hemiplegia usually is the smaller of the two, even in patients who walk, suggesting the size difference is due not to disuse but to a disrupted growth process. Limbs affected by CP in most instances do not reach normal physical size.
Vision and hearing problems are more common in people with cerebral palsy than in the general population. Differences in the left and right eye muscles often cause the eyes to be misaligned. This condition, called strabismus, causes double vision. In children, however, the brain often adapts by ignoring signals from one eye. Because strabismus can lead to poor vision and impaired depth perception, some physicians recommend corrective surgery.
Patients with hemiparesis may have hemianopia, a condition marked by impaired vision or blindness in half of the visual field in one or both eyes. A related condition, called homonymous hemianopia, causes impairment in the right or left half of the visual fields in both eyes.
Sensations of touch or pain may be impaired. An individual with stereognosis, for example, has difficulty perceiving or identifying the form and nature of an object placed in their hand using the sense of touch alone. A decrease in feeling may contribute to the difficulty in perception.
Hip dislocation, scoliosis (curvature of the spine), incontinence (inability to control the urine flow), constipation, dental caries (tooth decay), bronchitis (inflammation of the bronchial tubes), skin sores, and asthma are other complications commonly experienced by people with CP .
