Athetoid Cerebral Palsy
Athetoid cerebral palsy, also known as dyskinetic cerebral palsy, is a subtype of cerebral palsy (CP). Cerebral palsy is a group of non-progressive, permanent disorders that causes limitation of activity by affecting the developing motor control circuit. These non-progressive disturbances result from insults during fetal development or in the infant's brain. Cerebral palsy as a group is the most common cause of childhood disability.
Dyskinetic cerebral palsy is the second most common subtype of cerebral palsy, comprising of around 12 to 14% of patients who are affected, the most common being the spastic subtype.  Athetoid cerebral palsy is defined by abnormal postures and movements. These abnormalities are due to impaired muscle tone, impaired movement control, and impaired coordination. These abnormalities can be described by detailing the typical movements themselves, such as dystonic, extrapyramidal, choreoathetotic, choreoathetoid, or athetoid cerebral palsy.
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Unlike spastic CP, which is more commonly associated with preterm delivery or prolonged moderate-intensity hypoxic events resulting in periventricular leukomalacia and diffuse white matter injury, dyskinetic CP (DCP) is associated with basal ganglia and thalamic injuries. These injuries are usually seen with brief but profound hypoxic insults. Patients with dyskinetic CP are more commonly term infants versus those with spastic CP.
Another common cause is neonatal hyperbilirubinemia induced kernicterus as there is bilirubin deposition in the basal ganglia. As kernicterus has become less common because of preventive strategies in hyperbilirubinemia, there has been a decrease in the incidence of DCP. Additionally, any insults such as intracranial hemorrhage, stroke, or cerebral infection to the basal ganglia and thalamus can result in dyskinetic CP.
Cerebral palsy overall is the most common cause of childhood disability, occurring in 1.5 to 2.5 per 1000 live births. The most common subtype of cerebral palsy is the spastic type, which further divides into spastic diplegia, spastic hemiplegia, and spastic quadriplegia types.
Dyskinetic or athetoid type cerebral palsy, which we are discussing in this article, makes up 12% to 14% of the cerebral palsy cases overall. This calculates to around 1.8 to 3.5 cases per 10000 live births for dyskinetic cerebral palsy. The least common subtype of cerebral palsy is the ataxic subtype, making up 4% to 13% of the total cases of cerebral palsy.
As mentioned previously, dyskinetic cerebral palsy occurs more commonly in term infants compared to the spastic subtype, which is more common and has a higher association with preterm birth.
History and Physical
Dyskinetic cerebral palsy, like all forms of cerebral palsy, is a clinical diagnosis. The history should identify risk factors for athetoid cerebral palsy, such as perinatal asphyxia or severe hyperbilirubinemia in the perinatal period. Other parts of the history that are important include detailed history regarding the prenatal and perinatal period as well as developmental history, which is important as patients with dyskinetic cerebral palsy will have motor and other developmental delays. Family history can help determine if other neurological or movement disorders should be considered as a differential diagnosis. Questions should also focus on finding comorbidities associated with dyskinetic cerebral palsy. Non-motor comorbidities can be more common in dyskinetic cerebral palsy than spastic subtype. These include intellectual impairment, which can be severe, speech problems, and epilepsy. Other common comorbidities include weight loss, poor feeding, and sleep and respiratory disturbances. Musculoskeletal deformities are also common.
The physical exam is an important part of evaluating a patient with dyskinetic cerebral palsy. It is important, especially in identifying the disease as the dyskinetic subtype versus the other subtypes of cerebral palsy. The subtypes are characterized by the distribution as well as the tone of the abnormal musculature.
Common clinical findings in dyskinetic cerebral palsy include the following:
In early infancy: Delayed motor development, reduced spontaneous movements, variable tone with movements while hypotonic at rest, and persistence of primitive reflexes.
By age 2 to 3: Involuntary movements are more apparent along with abnormal posturing. This includes head being persistently turned to one side, extension in the supine position, flexion, and shoulder retraction while prone.
The involuntary movements can be characterized by the type of movements they are. Within dyskinetic cerebral palsy, there is choreathetotic CP, which consists of chorea and athetosis. Chorea involves irregular and rapid contractions of muscles, including those of the face, proximal extremities, and toes and fingers. Athetosis involves slow, writhing movements of the distal extremities. These movements can be induced or worsened by emotions, stress, and illness. Dystonic CP consists of repetitive and patterned movements that are sustained, such as twisting of the limbs and trunk. These movements can be slow or fast. There is a sudden increase in tone that occurs during movement or with emotions.
Other than the clinical history and physical exam, as mentioned above, neuroimaging is helpful in the assessment of athetoid cerebral palsy. 70% of patients with dyskinetic cerebral palsy have lesions found on magnetic resonance imaging (MRI) of the brain in the basal ganglia or thalamus. Few patients have scans that look normal. Other lesions can be found, as well. In those with kernicterus, lesions in the globus pallidus are usually seen.
There are also clinical scales and assessment tools to help measure the severity of dystonia and choreoathetosis, which are often complex and hard to measure. These include several measurement scales, such as the Barry-Albright Dystonia Rating scale, Burke-Fahn-Marsden Dystonia Rating scale (BFMS), and the Dyskinesia Impairment scale. These scales can help evaluate the severity of dystonia in dyskinetic cerebral palsy. These scales have limitations in dyskinetic cerebral palsy as there is no measurement for choreoathetosis. This is resolved in the Dyskinesia Impairment Scale (DIS), which was made specifically for the assessment of patients with dyskinetic cerebral palsy. DIS and BFMS are often used for outcome measurements in interventions such as deep brain stimulation.
Treatment / Management
Management of dyskinetic CP centers around the management of symptoms and aims at improvement in the quality of life for the patient. This involves the management of dystonia and choreoathetosis, as well as helping with associated pain, disability, and discomfort. There is also a focus on the treatment of comorbidities that are non-motor. These comorbidities include epilepsy and depression. Other issues include ensuring optimal nutrition, possibilities of contractures, and orthopedic complications. Management of symptoms and all aspects of dyskinetic cerebral palsy should be done from an interprofessional team approach. This team often includes clinicians, as well as therapists and behavioral health specialists. As mentioned previously, intervention focuses on decreasing disability burden and maximizing quality of life.
There are medications that are often used in the treatment of dyskinetic cerebral palsy; however, most of them show low efficacy. The most commonly used drug in DCP is oral baclofen, a GABA-B agonist. Trihexyphenidyl is often used for dystonia. Efficacy for both of these drugs in DCP is, however, low. Adverse effects include the possibility of worsened choreoathetosis. This can occur when dystonia is reduced as dystonia masks the expression of choreoathetosis. Medications that are often used as an attempt to manage movement symptoms are below.
For dystonia: dopamine agonists (levodopa), anticholinergics (trihexyphenidyl, benztropine), benzodiazepine receptor agonists (diazepam, clonazepam), GABA-B receptor agonist (baclofen), monoamine blockers (tetrabenazine), and voltage-gated sodium channel blockers (carbamazepine).
An alternative that is sometimes used instead of oral medication, which generally has low efficacy with more side effects, is intrathecal baclofen. It can be administered at a lower dosage and with fewer side effects. There have been studies demonstrating a decrease in dystonia.
Deep brain stimulation (DBS) has been used increasingly in those with dyskinetic cerebral palsy. It is often used to decrease dystonia. Though it does decrease dystonia in those with DCP, there is less benefit in quality of life and functionality compared to that seen in patients with primary (inherited) dystonia.
Botulinum toxin is another treatment often used in the management of dystonia in DCP. There is some evidence that it decreases pain and dystonia in those with DCP However, as with DBS, there is more evidence of its therapeutic value in those with primary dystonia.
Differential diagnoses include movement disorders, neuromuscular disorders, neurodegenerative disorders, and inborn errors of metabolism. The predominant differential is based on other disorders with dystonia and/or chorea. This includes disorders such as:
The life span of patients with cerebral palsy depends on the severity of disability as well as complications. Those who are more severely disabled will usually have reduced life expectancy versus those who are less severely disabled. There is a higher amount of early death in patients with dyskinetic CP than the other subtypes of CP, due to the increased amounts of complications and disability in comparison. As with other types of CP, the most common cause of death is respiratory failure secondary to pneumonia and aspiration.
For dyskinetic CP, there often is more severe motor impairment than other forms of CP. Patients with DCP often score higher on the gross motor function classification system (GMFCS) and manual ability classification system (MACS). There is a correlation between the amount of dystonia with disability level, more so than choreoathetosis.
Many complications can exist with cerebral palsy, including intellectual disability, epilepsy, speech and hearing issues, orthopedic disorders, neurobehavioral disorders, and sleep disturbances.
In dyskinetic CP, as the motor impairments are more severe than other types of cerebral palsy as well as the characteristic involuntary movements, there are complications associated specifically with the severe motor impairments. This includes being underweight. Despite patients with dyskinetic CP usually being born with normal birth weights, many will be underweight on follow up, and this is thought secondary to involuntary movement leading to higher energy expenditure as well as combined with poor feeding and dysphagia, which are other complications. Patients with DCP also are less likely to be able to be independent of a caregiver given the severity of the motor impairments as well as increased comorbidities, which is highlighted below.
Non-motor complications of DCP include severe intellectual impairment, language disability, epilepsy, as well as a combination of these, which can occur in more than half of the patients with DCP. Other complications include visual and hearing impairments, pain, and musculoskeletal deformities. Mental health problems, including depression, are also common. The most common cause of death in DCP patients is from respiratory comorbidities, which are aspiration and pneumonia, leading to respiratory failure.
Deterrence and Patient Education
Dyskinetic or athetoid cerebral palsy is a subtype of cerebral palsy that is caused by a brain injury that occurs during late pregnancy or the early birth period. Dyskinetic cerebral palsy is marked by abnormal posturing, tone, and involuntary movements. Increased risk factors for dyskinetic cerebral palsy include brain injury and lack of oxygen during birth as well as kernicterus, which is marked by increased bilirubin.
Dyskinetic cerebral palsy is the second most common subtype of cerebral palsy after spastic cerebral palsy. Cerebral palsy overall is the most common childhood disability cause. The diagnosis of dyskinetic CP is made clinically through taking a history, performing a physical exam, as well as neuroimaging. The goal of treatment and management is aimed at improved functional outcomes and increased quality of life. This is best achieved through an interprofessional team approach.
Enhancing Healthcare Team Outcomes
Early diagnosis of dyskinetic cerebral palsy by clinicians can help patients be referred to the proper resources earlier, possibly improving functional outcomes, reducing disease burden, and reducing caregiver burden by increasing support and resources. As the aim of treatment and management focus on improved quality of life and managing comorbidities, therapy plays a large role in the treatment of patients. Rehabilitation exercises with physical and occupational therapists, as well as with speech and language therapists are important in improving patient functional levels and preventing worsened complications.
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