Athetoid cerebral palsy is the second most common type of cerebral palsy, caused by damage to structures deep in the brain that coordinate movement. It accounts for roughly 15% to 20% of all cerebral palsy cases, compared to about 80% for the spastic type. The hallmark is involuntary, uncontrollable movements that make everyday tasks like reaching for a glass, speaking clearly, or sitting still significantly harder.
What Happens in the Brain
The basal ganglia and thalamus sit deep in the center of the brain. They act as a relay station, filtering and refining movement signals before those signals reach the muscles. When these structures are damaged, the brain loses its ability to fine-tune movement. The result is a kind of “volume knob” problem: instead of smooth, controlled motion, the body produces extra, unwanted movement it can’t shut off.
About 70% of people with this condition have visible lesions in the basal ganglia or thalamus on brain MRI. One leading theory is that damage to a specific area called the globus pallidus reduces its normal braking function on the thalamus. With less inhibition, the thalamus becomes overactive and sends excessive movement signals, producing the writhing, twisting motions characteristic of the condition. However, roughly half of people with dyskinetic cerebral palsy have MRIs that appear normal on standard imaging, which means the damage can be present at a cellular level that conventional scans don’t pick up.
Three Patterns of Involuntary Movement
The involuntary movements in athetoid cerebral palsy fall into three overlapping patterns, and many people experience more than one:
- Athetosis: Slow, continuous writhing movements, especially in the hands, fingers, feet, and toes. These can look like the fingers are constantly searching for something.
- Chorea: Quick, irregular, dance-like jerks that jump unpredictably from one body part to another, including the face.
- Dystonia: Sustained muscle contractions that twist the limbs or trunk into abnormal postures. These can be slow or fast and tend to worsen with effort or stress.
Children with primarily choreic and athetoid movements generally retain more functional ability than those with dominant dystonia. Research comparing these subgroups found that children with dystonia-predominant cerebral palsy scored significantly worse on standardized measures of gross motor function, hand use, and communication.
What Causes the Brain Damage
Unlike spastic cerebral palsy, which is often linked to premature birth and damage to the brain’s white matter, athetoid cerebral palsy typically results from injury to the deep gray matter structures during or shortly after birth.
One of the most well-understood causes is severe newborn jaundice, or kernicterus. When bilirubin (the yellow pigment that causes jaundice) rises too high, it crosses into the brain and is directly toxic to the globus pallidus and surrounding structures. Normally, a protein called albumin binds bilirubin in the blood and keeps it from reaching the brain. But in sick or premature newborns, several factors can overwhelm this protective system: infection, low oxygen levels, acidosis, low albumin levels, and certain medications that compete for albumin binding. Any of these can lower the threshold at which bilirubin becomes dangerous. Autopsy studies from early research on kernicterus found yellow staining and cell death concentrated in the globus pallidus, with additional damage in areas involved in eye movement, balance, and hearing.
Other causes include oxygen deprivation during birth (acute hypoxic events that specifically injure the deep brain structures), stroke in the newborn period, bleeding inside the brain, and brain infections such as meningitis or encephalitis. In each case, the common thread is damage centered on the basal ganglia and thalamus rather than the white matter tracts affected in spastic cerebral palsy.
Speech and Swallowing Challenges
The same involuntary movements that affect the arms and legs also affect the muscles of the mouth, tongue, throat, and face. This creates two related but distinct problems: difficulty speaking clearly (dysarthria) and difficulty swallowing safely (dysphagia).
Swallowing difficulties affect up to 85% of children with cerebral palsy overall. The core issues are insufficient chewing, limited tongue mobility, and poor coordination between breathing and swallowing. These problems disrupt every phase of the swallowing process, from forming a ball of food in the mouth to moving it safely past the airway. When swallowing goes wrong, food or liquid can enter the lungs, leading to aspiration pneumonia. Chronic swallowing problems also contribute to poor nutrition, weight loss, and reduced quality of life. Studies of adults with cerebral palsy found that choking on food and difficulty chewing were among the most commonly reported symptoms affecting daily life.
Speech is affected because producing clear sounds requires precise, rapid coordination of the lips, tongue, jaw, and vocal cords. When those muscles are subject to involuntary movements, speech can sound slurred, overly slow, or difficult to understand. Research has found that dysarthria was present in every child who had oral-phase swallowing difficulties, highlighting how closely linked these two challenges are.
How It’s Diagnosed
Diagnosis is primarily clinical, meaning doctors identify the condition by observing the child’s movement patterns over time. Involuntary movements may not be obvious in the first few months of life and often become more apparent as the child grows and attempts more complex motor tasks. A brain MRI helps confirm the diagnosis and identify the location of damage. When lesions are present, they typically appear in the putamen, thalamus, or both. Some children also show damage extending into the surrounding white matter, which generally correlates with more severe functional limitations.
Functional ability is graded using standardized scales that range from Level I (walking independently with minor limitations) to Level V (transported in a wheelchair with limited ability to control head and trunk position). Separate scales assess hand function and communication ability using the same five-level structure.
Managing Movement and Daily Life
There is no cure for athetoid cerebral palsy, but a combination of therapies can improve function and comfort. Physical therapy focuses on building core strength and stability, since the trunk muscles are often affected by involuntary movements that make sitting and standing difficult. Occupational therapy helps with fine motor tasks like eating, dressing, and writing, often using adapted tools with weighted or ergonomic grips that are easier to control during involuntary movements.
Speech therapy addresses both communication and swallowing. Therapists work on strengthening oral muscles, improving coordination of breathing and swallowing, and finding food textures that are safer and easier to manage. For children and adults whose speech is very difficult to understand, communication technology can be transformative.
Communication Technology for Involuntary Movements
Standard keyboards, touchscreens, and switches pose an obvious challenge when your body makes movements you didn’t intend. The field of augmentative and alternative communication has developed several workarounds. Eye-tracking systems allow users to select letters, words, or phrases on a screen simply by looking at them. One university student with athetoid cerebral palsy uses eye-gaze technology to write papers, send emails and text messages, and hold face-to-face conversations.
For people who have some reliable voluntary movement but struggle with precision, wearable sensors incorporating accelerometers and gyroscopes can learn to distinguish between intentional and unintentional movements. This eliminates the need for precise positioning, which is a major practical barrier. Traditional switches require exact placement, and if the person shifts even slightly, a caregiver must reposition the device. Wearable sensors work regardless of the user’s position, increasing independence. Hybrid systems that combine eye tracking with switch scanning offer another option: the user’s eyes narrow down the target area on screen, and a single switch press makes the final selection, reducing the precision demanded of either system alone.
Deep Brain Stimulation
Deep brain stimulation, a surgical procedure that delivers electrical pulses to targeted brain areas through implanted electrodes, has shown benefit for some movement disorders but remains unproven for athetoid cerebral palsy. A prospective multicenter study of 16 pediatric patients found modest improvements in self-identified functional goals and physical health scores at 12 months, but the primary quality-of-life measure did not reach statistical significance. The researchers concluded that evidence is not yet sufficient to recommend deep brain stimulation as a routine treatment for this population.