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 .
