Doctors classify cerebral palsy into three principal categories-spastic, athetoid, and ataxic-according to the type of movement disturbance. A fourth category can be a mixture of these types for any individual.
- Spastic cerebral palsy – In this form of cerebral palsy, which affects 70 to 80 percent of patients, the muscles are stiffly and permanently contracted. Doctors will often describe which type of spastic cerebral palsy a patient has based on which limbs are affected, i.e spastic diplegia (both legs) or left hemi-paresis (the left side of the body). The names given to these types combine a Latin description of affected limbs with the term plegia or paresis, meaning paralyzed or weak. In some cases, spastic cerebral palsy follows a period of poor muscle tone (hypotonia) in the young infant.
- Athetoid, or dyskinetic cerebral palsy – This form of cerebral palsy is characterized by uncontrolled, slow, writhing movements. These abnormal movements usually affect the hands, feet, arms, or legs and, in some cases, the muscles of the face and tongue, causing grimacing or drooling. The movements often increase during periods of emotional stress and disappear during sleep. Patients may also have problems coordinating the muscle movements needed for speech, a condition known as dysarthria. Athetoid cerebral palsy affects about 10 to 20 percent of patients.
- Ataxic cerebral palsy – This rare form affects the sense of balance and depth perception. Affected persons often have poor coordination; walk unsteadily with a wide-based gait, placing their feet unusually far apart; and experience difficulty when attempting quick or precise movements, such as writing or buttoning a shirt. They may also have intention tremor. In this form of tremor, beginning a voluntary movement, such as reaching for a book, causes a trembling that affects the body part being used and that worsens as the individual gets nearer to the desired object. The ataxic form affects an estimated 5 to 10 percent of cerebral palsy patients.
- Mixed forms – It is not unusual for patients to have symptoms of more than one of the previous three forms. The most common mixed form includes spasticity and athetoid movements but other combinations are also possible.