Tufts OpenCourseware
Authors: John Morgan, Bonnie F. Zimble

Cerebral Palsy:

Definitions, Incidence, Causes and Types

Special Care in Dentistry
John Morgan, DDS
Tufts University School of Dental Medicine, 2008

Study Questions

  1. Define cerebral palsy and describe its most common symptoms.

  2. Comment on the incidence of cerebral palsy.

  3. What are the known and possible causes of cerebral palsy?

  4. Finally, name and describe the three types of cerebral palsy.

What is cerebral palsy?

Cerebral palsy is a general term referring to a group of chronic disorders characterized by abnormalities of motor control.  According to the National Institute of Neurological Disorders and Stroke (NINDS), “the disorders are caused by faulty development of or damage to motor areas in the brain that disrupts the brain's ability to control movement and posture.” Damage can occur before or during birth, or during the first few months after birth.   

Symptoms of cerebral palsy as reported by NINDS include:  

  • Difficulty with fine motor tasks, such as writing or using scissors

  • Difficulty maintaining balance or walking

  • Involuntary movements

“The symptoms differ from person to person and may change over time. Some people with cerebral palsy are also affected by other medical disorders, including seizures or mental impairment, but cerebral palsy does not always cause profound handicap.” 

Click here to visit the NINDS site for cerebral palsy:  

In fact, if you would like to take an interactive tutorial on cerebral palsy, posted on the U.S. National Library of Medicine web site, click here.

How common is cerebral palsy?

Cerebral palsy usually is not diagnosed until a child is about 2 to 3 years of age. About 2 to 3 children in 1,000 persons over the age of three have cerebral palsy. That means that about 500,000 children and adults of all ages in this country have cerebral palsy. 

What are the causes of cerebral palsy? 

Some of the known causes of cerebral palsy include:

  • Infections during pregnancy, such as rubella (German measles)

  • Insufficient oxygen reaching the fetus

  • Jaundice due to high levels of bilirubin

  • Prematurity

  • Complications of labor and delivery

  •  Rh factor incompatibility

  • Head injury 

  • Other birth defects 

 The many possible causes of cerebral palsy include: 

  • Abnormal brain development

  • Insufficient circulation to areas of the brain either before or following birth

  • Infection in or beside the brain

  • Bleeding in the brain

  • Biochemical or genetic factors

  • Other unknown causes

What are the different types of cerebral palsy? 

There are three major types of cerebral palsy, although some individuals may have symptoms of more than one type. The text below (but not the photo) appears on the March of Dimes web site. Click here to visit their site to learn more about cerebral palsy:  

Spastic cerebral palsy.  About 70% to 80% of affected individuals have spastic cerebral palsy, in which muscles are stiff, making movement difficult.  When both legs are affected (spastic diplegia), a child may have difficulty walking because tight muscles in the hips and legs cause the legs to turn inward and cross at the knees (called scissoring).  In other cases, only one side of the body is affected (spastic hemiplegia), often with the arm more severely affected than the leg.  Most severe is spastic quadriplegia, in which all four limbs and the trunk are affected, often along with the muscles controlling the mouth and tongue.  Children with spastic quadriplegia have mental retardation and other problems. 

Dyskinetic or athetoid cerebral palsy.  About 10% to 20% of persons with cerebral palsy have the dyskinetic or athetoid form, which affects the entire body.  This form is characterized by fluctuations in muscle tone (varying from too tight to too loose), and sometimes is associated with uncontrolled movements, which can be slow and writhing or rapid and jerky.  Children often have trouble learning to control their bodies well enough to sit and walk.  Because muscles of the face and tongue can be affected, there also can be difficulties with sucking, swallowing and speech. 

Ataxic cerebral palsy.  About 5% to 10% of persons with cerebral palsy have the ataxic form, which affects balance and coordination.  They may walk with an unsteady gait and have difficulty with motions that require precise coordination, such as writing.”