Cerebral palsy (CP) is a general term used to describe a group of disorders that permanently affect a person’s ability to move and maintain posture. These conditions arise from damage to the developing brain, typically occurring before or shortly after birth. Athetoid cerebral palsy represents a specific type within this group, distinguished by its unique pattern of involuntary, uncontrolled movements. While it is less common than the most prevalent type, spastic CP, understanding the specific characteristics of the athetoid form is important for accurate diagnosis and effective care.
Defining Athetoid Cerebral Palsy
Athetoid cerebral palsy is formally recognized as Dyskinetic Cerebral Palsy (ICD-10 code G80.3). This form accounts for approximately 10 to 20 percent of all cerebral palsy cases, making it the second most frequent type after the spastic classification. The defining feature is a noticeable fluctuation in muscle tone, constantly shifting between being too tight (hypertonia) and too loose (hypotonia). This inability to regulate muscle tone results in involuntary, unpredictable movements.
The term “dyskinetic” refers to the issue with voluntary movement control. Unlike spasticity, where muscles are persistently stiff, the dyskinetic type involves a constant, dynamic change in the muscles’ state. This instability prevents the individual from sustaining a stable posture or executing smooth, purposeful actions. Uncontrolled movements often become more pronounced when the person attempts a voluntary action or experiences heightened emotions.
Identifying the Underlying Causes
The neurological origin of Athetoid Cerebral Palsy lies in damage to the basal ganglia, deep brain structures responsible for initiating and controlling movement. The basal ganglia help refine the motor programs needed for smooth, coordinated action. Damage to this area disrupts the brain’s ability to regulate muscle tone and movement, resulting in the characteristic involuntary motions.
The injury typically occurs in the perinatal period (shortly before, during, or soon after birth). One historically recognized cause is severe, untreated neonatal jaundice, known as kernicterus. Kernicterus involves high levels of bilirubin in the blood, which damages the basal ganglia tissue. While preventative strategies have reduced its incidence, it remains a significant cause of this specific form of CP.
Another common cause is a brief lack of oxygen or blood flow to the brain, termed hypoxic-ischemic encephalopathy (HIE). Events such as placental complications or severe blood pressure drops can lead to this deprivation. Because the basal ganglia are highly sensitive to oxygen changes, they are vulnerable to damage during acute incidents. Other causes include brain infections like meningitis or a stroke affecting deep brain structures.
Characteristics of Involuntary Movement
The involuntary movements that define Athetoid CP are collectively known as dyskinesia, which can manifest in three primary forms. Athetosis describes slow, continuous, writhing movements, particularly noticeable in the hands, arms, feet, and legs. These movements prevent the limbs from maintaining a stable, fixed position.
A second type is chorea, which presents as brief, irregular, and rapid movements that often appear jerky or dance-like. A combination of athetosis and chorea is frequently observed and referred to as choreoathetosis.
The third movement pattern is dystonia, characterized by sustained or intermittent muscle contractions that cause repetitive twisting movements and abnormal posturing of the limbs or trunk. These dystonic movements often lead to awkward, fixed positions that can cause discomfort.
These uncontrolled motions severely interfere with daily life, intensifying when the person attempts purposeful movement or experiences emotional stress. Fine motor skills, such as writing or using utensils, are significantly impaired. The face and tongue muscles are also frequently affected, leading to difficulty with feeding, drooling, and a speech disorder known as dysarthria. Dysarthria makes it challenging to articulate words clearly because the involuntary movements disrupt precise muscular control.
Diagnosis and Management Approaches
Diagnosis involves careful clinical observation and review of developmental milestones. Healthcare providers look for the characteristic pattern of fluctuating muscle tone and involuntary movements, which typically become apparent between 18 months and two years of age. Imaging studies, such as MRI or CT scans, are often used to visualize damage to the basal ganglia region. These scans also help rule out other neurological conditions causing similar movement disorders.
Management of Athetoid CP is a lifelong, multidisciplinary effort focused on maximizing function and independence. Physical therapy (PT) improves strength, flexibility, and range of motion to counter fluctuating tone and involuntary contractions. Occupational therapy (OT) helps individuals develop adaptive strategies for self-care and daily activities, such as dressing and eating. Speech therapy addresses dysarthria and feeding difficulties, improving communication and swallow function.
Medications help control the severity of involuntary movements and muscle tone issues. Muscle relaxants (like baclofen or diazepam) and anticholinergic agents (such as trihexyphenidyl) may be used to reduce contractions and spasms. For severe, localized dystonia, botulinum toxin injections can temporarily relax specific overactive muscles. Advanced interventions like deep brain stimulation (DBS) may also be considered to modulate abnormal signals originating from the basal ganglia.