What is cerebral palsy?
Cerebral palsy is an umbrella term for describing a group of chronic disorders that impair a person's ability to control body movement and posture. These disorders result from injury to the motor areas of the brain. Cerebral palsy affects two to six infants out of every 1,000 births, and is the most common disability among children in the U.S. The problem causing cerebral palsy may occur while the infant is still in the womb or after birth, and the problem is not always detectable during a child's first year of life. Children with mild cerebral palsy may only have a minor limp or an uncoordinated walk, while patients with severe cases will require care and supervision throughout their lives. Many of the infants born with cerebral palsy also experience some degree of mental retardation and/or have seizures.
Spastic cerebral palsy
Spastic cerebral palsy is the most common form and is the type seen in 75 to 80 percent of cases. Patients with this form are unable to relax their muscles, which respond by tightening further if the patient or someone else tries to stretch them. This spasticity affects the function of individual muscles, especially flexor muscles.
When spasticity occurs in the arms, the flexors tighten, pulling the elbows toward the body, and hands and wrists toward the chin. The hands themselves form tight fists. This constant tightened state may in turn weaken the extensor muscles, stretching them to the point where some of their functionality is lost. When spasticity occurs in the legs, the flexor muscles in the calves are affected. When this happens, the heels become raised, pushing the toes downward and often causing a child to walk on their toes.
Spasticity in the legs also affects the adductor muscles (the inner thigh muscles). Adductor muscles pull a body part toward its midline, such as those that pull the arms to a person's side or close a person's legs. In patients with cerebral palsy, the inward pull of the adductor muscles is so strong that the legs cross over each other or scissor. This motion also rotates the legs inward at the hips, pulling them away from the hip sockets, which can lead to abnormal socket development and hip dislocation.
Other conditions associated with spastic cerebral palsy may include an exaggerated response to startle stimulation, a degree of mental impairment, and weak respiration. Some children with spastic cerebral palsy develop a curvature of the spine. This results from remaining in a constant upright position, which prevents the trunk muscles needed for supporting the spine from developing properly.
Whereas spastic cerebral palsy doesn't permit the muscles to relax, with athetosis, the muscles are subjected to excessive and uncontrollable movement. These movements also increase with a child's excitement and in response to surrounding environmental stimulation. Likewise, the more relaxed a child is, the less often these abnormal movements occur. When a child is sleeping, the movements stop altogether.
The movements of a stimulated child form what is called an extensor thrust. When this happens, the arms rapidly extend outward and back, the palms turn toward the floor, the fingers spread and overextend, the knees come together, and the feet turn inward with the toes up. The child's neck flexes, pulling the head back and to the side, and the mouth opens with the tongue sticking out. These movements can present extreme difficulty for a child when eating and drinking. The child may also have shallow and irregular respiration, which affects oxygen flow to the brain and increases the chance for respiratory infections. Patients with athetotic cerebral palsy also have difficulty with balance and walking.
The characteristics of each of these syndromes are not mutually exclusive, and a child may have spastic cerebral palsy in his or her legs as well as a degree of athetosis elsewhere.
What are causes cerebral palsy?
While some of the causes of cerebral palsy are still unknown, there are many known factors that can cause or contribute to brain damage before or after birth. Preventive methods, such as proper prenatal care, can eliminate some causes, while others are as yet unpreventable.
Some of the known causes or contributors to cerebral palsy include:
- An infection, such as rubella (German measles) or toxoplasmosis (a tissue infection), during pregnancy
- Drugs and/or alcohol abuse during pregnancy
- Blood type differences between mother and fetus
- Anemia (has too few red blood cells) during pregnancy
- Premature birth with internal bleeding in the baby's head
- Lack of oxygen to the baby during development or delivery
- Early separation of the placenta or damage to the umbilical cord
- Excessive bile pigment (jaundice) in the baby's brain after birth
- A viral infection that affects the brain (encephalitis)
- An infection of the membranes surrounding the brain and spinal cord (meningitis)
- A severe head injury in the baby
- Severe convulsions in the baby
What are the symptoms of cerebral palsy?
Patients with cerebral palsy can have a variety of symptoms. These symptoms usually do not worsen over time and include:
- Difficulty with fine motor skills, such as writing and using scissors
- Involuntary muscle movements
- Difficulty maintaining balance and walking
- Learning problems
- Vision defects, such as crossed eyes
- Speech difficulty
- Sucking and swallowing problems
Cerebral palsy may affect one arm or leg, an arm and leg on the same side, only the legs, all four limbs, or any combination of arms and legs. Whatever the affected areas may be, the muscle types involved are often the same. Muscles that enable people to bend their arms and legs are called flexor muscles. Extensor muscles are the opposite of flexors and enable a person to straighten these limbs back out. It is the inability to control these and other muscles that defines the most common cerebral palsy syndromes.