Types of Cerebral Palsy
Types of Cerebral Palsy
The four major classifications are based upon a description of the different movement impairments that reflect the areas of the brain that are damaged:
Type 1. Spastic Cerebral Palsy
Spastic cerebral palsy results from damage to the cortiospinal tracts or the motor cortex. (See cerebral anatomy for a description of these areas). This condition results in excessive muscle tone or rigidity (called hypertonicity), and is the most common form of cerebral palsy, affecting about 70% of patients. There are three subcategories of spastic cerebral palsy:
- Spastic quadriplegia means that both arms and both legs have some degree of impairment in movement and increased tone. The condition is most often associated with tremors or jerking of the arms and/or legs, and most people with spastic quadriplegia will not walk.
- Spastic diplegia means impairment in the legs but minimal or no impairment of the arms. Most people with diplegia will walk but with an abnormal gait, and hip problems are common because of the tightness of muscles in the legs. Most people with diplegia have normal intelligence and communication skills.
- Spastic hemiplegia means one side of the body is affected—the side of the body opposite from the injured side (called “contralateral” injury). Thus, if the right side of the brain is injured, the left arm and leg will have abnormal movement and tone.
Type 2. Ataxic Cerebral Palsy
Ataxic cerebral palsy is caused by damage to the cerebellum, the part of the brain that controls coordination and how “smooth” motor movement is. It is much less common than the spastic type, affecting about 10% of patients. It causes low tone (called hypotonia) and tremors. Fine motor skills like writing or typing are severely impaired. Loss of balance, especially when walking, can be severe. It is unfortunately common for people with ataxic cerebral palsy to also have visual and hearing impairments.
Type 3-4. Athetoid/Dyskinetic Cerebral Palsy
This type of cerebral palsy has mixed muscle tone, ranging from low (hypotonic) to high or rigid (hypertonic), with the pattern of tone changing in the patient’s early years. Athetoid cerebral palsy is often associated with damage to the basal ganglia in the brain stem. About 30% of cerebral palsy patients display athetoid or dyskinetic features. Athetoid/dyskinetic cerebral palsy is characterized by writhing movements of the hands and sometimes the trunk as well. These involuntary movements make it very difficult to walk and significantly impair any task requiring fine motor skills.
More than 100%
Yes, the percentage of the types total more than 100%. That’s not bad math. First, there’s just no absolutely certain way to quantify the number of patients with each type of cerebral palsy. Second, the damages may overlap, so that a patient whose primary diagnosis is spastic palsy, may also have some injuries associated with another type, thus literally falling within both categories. Thus the percentages are just to give you an idea of how widespread the particular types may be.