Types of Cerebral Palsy

In order to understand what distinguishes one type of cerebral palsy from another, one must understand the term muscle tone.

Muscle tone describes the degree of resistance to movement there is in a muscle. It is what enables us to maintain a certain position and to move. For example, if you bend your arm you are engaging in two opposing muscle tone actions: you are shortening (increasing the tone of) the biceps muscles in your arm and you are lengthening (reducing the tone of) the triceps muscles of your arm. The brain sends messages to each muscle group to change its resistance as determined by the desired movement.

Cerebral palsy damages the area of the brain which controls muscle tone resulting in either increased muscle tone, reduced muscle tone, or a combination of the two (fluctuating tone). The parts of a person’s body affected by the abnormal muscle tone is a function of where the brain damage occurs.

Cerebral palsy is divided into 4 main categories:

Spastic Cerebral Palsy
Accounting for nearly 80 percent of all cases, this is the most common type of cerebral palsy. People with this type of C.P. have at least one tight muscle groups which restrict movement and they have stiff and jerky movements often having a hard time changing from one position to another. It is hard for them to hold and let go of objects.

Athetoid Cerebral Palsy
Accounting for about 10 percent of C.P. cases, Athetoid cerebral palsy is caused by damage to the cerebellum or basal ganglia, areas of the brain that facilitate coordinated movements and maintaining body posture. Damage to these areas may cause a person to develop involuntary movements in the face, arms, and trunk. These involuntary movements interfere with skills requiring coordinated movements like grasping, reaching, feeding and speaking. Uncontrolled grimacing and tongue thrusting can result in slurred speech, swallowing problems and drooling which will increase during periods of emotional stress. People with Athetoid cerebral palsy have low muscle tone and have difficulty sitting and walking.

Ataxic Cerebral Palsy
A rare form of C.P., which affects 5-10% of C.P. victims, it is characterized by low muscle tone and poor coordination of movements. People with this type of C.P. appear unsteady and shaky and their sense of balance and depth perception is affected. They often have poor coordination and walk unsteadily placing their feet unusually far apart. They suffer from shakiness, like a tremor in a very old person, particularly when they are handling or holding a small object like a pen.

Mixed Cerebral Palsy
When the cerebral palsy affects both the pyramidal and extrapyramidal areas of the brain which occurs in approximately 10 percent of C.P. cases) this results in mixed-type cerebral palsy. This is characterized by both the tight muscle tone of spastic cerebral palsy and the involuntary movements of athetoid cerebral palsy. Usually the spasticity is initially more obvious, with involuntary movements increasing after the child reaches nine months of age.

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