Athetoid cerebral palsy (ACP) is also called dyskinetic cerebral palsy. It is caused by damage to the basal ganglia in a developing brain resulting from bilirubin encephalopathy (Kernicterus) and hypoxic-ischemic brain injury. It constitutes 25% of cases of cerebral palsy and is characterized by hypertonia as well as hypotonia .
ACP shows no racial predilection, however, it is more prevalent in male children, premature neonates, and children in poor living conditions. Diagnosis is usually made on clinical grounds supported by neuroimaging and other investigations .
Diagnosis is achieved by the patient history and neurological examination with further detail provided by neuroimaging, genetic testing, and metabolic screening.
Treatment is largely supportive and includes physical therapy, speech therapy, occupational therapy, and pharmacological therapy. Deep brain stimulation (DBS) is indicated in the failure of conservative treatment.
ACP results from damage to a developing brain  and is characterized by damage to the extrapyramidal tracts in the basal ganglia or cerebellum. The main cause of these lesions is hypoxic-ischemic encephalopathy and kernicterus .
Hypoxic-ischemic brain injury occurs basically as a result of hypoxia and insufficient blood perfusion. Lesions in this condition occurring in the putamen and thalamus are responsible for symptoms of cerebral palsy. Bilirubin encephalopathy is characterized by deposition of bilirubin in the central nervous system particularly the basal ganglia, the acoustic nucleus of the brainstem, and the ocular movement nucleus. The hallmark of the disease mechanism is bilirubin transport across the blood-brain barrier into the brain parenchyma. Effective and early treatment of hyperbilirubinemia in preterm infants are critical in reducing the occurrence of cerebral palsy.
Risk factors for ACP can be categorized based on the stage of the pregnancy into prenatal, perinatal, and postnatal. Prenatal risk factors include maternal illness, exposure to teratogenic agents, and chorioamnionitis. Perinatal risk factors include abruptio placentae, prolonged or obstructed labor, uterine rupture, postmaturity, instrumental delivery, and abnormal fetal presentation, and the postnatal risk factors include neonatal sepsis, neonatal meningitis, hyperbilirubinemia, childhood head injury (before the age of 3 years), and respiratory distress.
Cerebral palsy can be classified on the basis of its severity, motor dysfunction, and degree of involvement of the extremities. The Gross Motor Function Classification System (GMFCS) and the International Classification of Functioning, Disability and Health are evaluation systems for assessing the severity of cerebral palsy. On the basis of motor features, cerebral palsy can be classified into extrapyramidal and corticospinal depending on the pathways of the central nervous system that are damaged . Athetoid cerebral palsy is an extrapyramidal non-spastic form of cerebral palsy. Furthermore, non-spastic cerebral palsy can be classified into ataxic and dyskinetic, the latter being further classified into choreoathetoid and dystonic. The choreoathetoid form is characterized by focal involuntary movements usually limited to the face and the extremities, whereas the dystonic cerebral palsy is characterized by slow spasms which may be generalized.
A study involving 544 patients with cerebral palsy was done to analyze the epidemiology, clinical presentation, and etiology of cerebral palsy, it was shown that 65.1% of the patients were males and that most of the cases (91.4%) were of the spastic type. The spastic-type cases comprised of quadriplegia (34.9%), hemiplegia (28.7%), and diplegia (21.9%).
Mental retardation was observed in 47.2% of cases. Other presentation included speech difficulties in 37% of cases, visual impairments, convulsions, and hearing loss which all occurred in few patients.
Most of the cases resulted from brain insult in the natal period (43.8%), while the postnatal brain insult resulted in the least number of cases (7.7%), and prenatal insult accounted for 26.1% of cases. 77.6% of the cases had a single etiological factor, 14.5% cases had multiple etiological agents, while 7.9% cases were idiopathic .
In developed countries, there is a prevalence rate of 2-2.5 cases per 1000 live births . However, epidemiological data are not sufficient in developing countries, however, the prevalence rate is estimated at 1.5-5.6 cases per 1000 live births. Generally, the prevalence is significantly higher in preterm and very low birth weight infants  . Despite the advances in neonatal care and treatment of hyperbilirubinemia, the incidence of cerebral palsy has remained unchanged over the years.
Cerebral palsy shows no racial predilections. Furthermore, the male gender  and poor socioeconomic conditions  are key risk factors.
The critical stages of brain development in humans consist of several processes beginning with primary neurulation which occurs at the 3rd or 4th week of gestation to myelination of all the formed structures occurring from birth to several years after birth .
Certain studies have demonstrated an increased risk of ACP in children born before term (37-38 weeks) or post-term compared to children born at term . The underdevelopment and vulnerability of the brain in premature neonates make them susceptible to ACP. Furthermore, in term infants vascular insults to the brain occur in the distribution of the middle cerebral artery. Ischemic injuries to the term brain usually affect the watershed areas of the cortex such as the end zones of the major arteries of the brain and result in spastic quadriplegic CP. Ischemic insults can also affect the basal ganglia in term infants.
Before term, the distribution of the fetal cerebral circulation poses a risk of hypoperfusion of the periventricular white matter, which is the part of the brain most susceptible to metabolic and ischemic brain injury. The germinal matrix capillaries within the periventricular white matter carry a particularly high risk of damage from the hypoxic-ischemic brain injury because of their location between the end zones of the striate and thalamic arteries and because, being cerebral capillaries, they have a high demand for oxidative metabolism. Hypoperfusion of the periventricular white matter may result in periventricular leukomalacia and germinal matrix hemorrhage. The periventricular white matter contains nerve fibers which control motor activity and muscle tone, therefore, injuries to this area result in spastic diplegia, which involves a predominant spasticity and weakness of the lower limb muscles with or without less involvement of the upper limbs. Periventricular leukomalacia is symmetric and may cause unilateral symptoms in asymmetric periventricular white matter injury. This is described as asymmetric spastic diplegia. Periventricular hemorrhage-intraventricular hemorrhage has been classified into four grades of increasing severity including :
The clinical pattern and outcome of ACP depend on the sites of the brain affected by the insult. However, movement disorders occur in 50% of patients .
In athetoid cerebral palsy, patients present with slow, writhing movements of the hands, feet, arms, and legs. Occasionally, patients may present with abnormal facial expressions, difficulty feeding, and drooling. Typically, the movement disorders are worsened by emotional stress and activity. Symptoms resolve at rest. Furthermore, the patient exhibits agitation, restlessness, difficulty holding the body in place, jerkiness, and difficult mobility. Children with ACP would find difficulty writing and holding objects.
Patients also present with speech difficulties because of impaired control of the muscles of the tongue, vocal cords, and the accessory respiratory muscles.
Diagnosis is mainly clinical. A diagnosis can be made from a good history and neurological examination. The neurological examination includes motor and sensory examination of the limbs. Progressive mental deterioration should be further investigated, as it is not a feature of athetoid cerebral palsy.
A detailed history should indicate the presence of prenatal, perinatal, or postnatal risk factors for athetoid cerebral palsy in the patient. A history of neonatal seizures is also important as 25% of infants treated for neonatal seizures develop cerebral palsy. A family history of predisposing genetic and metabolic disease should be excluded as should a history of child abuse. A detailed history of the child's developmental milestones is also required and may be evaluated using the Denver II and Bayley III evaluation scores. Delayed motor milestones usually give a clue to the diagnosis. Delay in cognitive development occurs in 40% of patients.
Investigations are necessary for supporting a clinical diagnosis of athetoid cerebral palsy. Neuroimaging usually reveals periventricular leukomalacia, cerebral hemorrhage, and cystic lesions. The magnetic resonance imaging (MRI) of the brain is the preferred neuroimaging study and reveals abnormalities in 80% of cases. Brain MRI is recommended for all patients with a suspected diagnosis of athetoid cerebral palsy. Ultrasound and computed tomography (CT) scanning of the brain are less sensitive compared to MRI in detecting brain lesions in cerebral palsy.
Additionally, serial plain radiographs of the hips and spine are necessary to monitor hip subluxation and spinal deformities respectively which may be concomitant congenital malformations. Serial X-rays are indicated in children older than 3 years.
Coagulation screening may be necessary especially in hemiplegic patients with unilateral hemisphere infarction.
In cases where a familial risk factor is suspected and in patients with concomitant abnormal morphological features such as hypertelorism, flat nasal bridge, low-set ears, and abnormal skin creases which indicate genetic syndromes, genetic testing may be necessary. Additionally, metabolic screening is important in cases where inborn errors of metabolism are suspected.
The management of athetoid cerebral palsy is mainly supportive and involves physical therapy, occupational therapy, speech therapy, and pharmacologic therapy. Physical therapy is instituted upon diagnosis and aims to improve mobility, range of motion, posture, and quality of life. Occupational therapy is aimed at supporting affected children with daily activities such as feeding, bathing, grooming, handwriting, and pencil grasp, and playing.
Speech therapy provides measures to aid patient with oral motor skills, restore speech, and provide alternate communication aids such as sign language.
Medications which are recommended include baclofen and tetrabenazine. Baclofen is a gamma-aminobutyric acid (GABA) agonist which inhibits excitatory impulse neurotransmission, thereby reducing muscle tone and the frequency of muscle spasms. Tetrabenazine is a drug used in the treatment of Huntington's disease and is effective for treating chorea.
DBS is recommended if pharmacological treatment fails to resolve the symptoms. It is associated with significant improvement in symptoms. DBS involves placing electrodes in the brain and sending electric impulses through them to the adjacent nuclei. DBS usually focuses on the globus pallidus.
Athetoid cerebral palsy is largely unpreventable, however, certain measures may reduce the incidence. These include antenatal maternal vaccination against the diseases which cause brain injuries such as rubella, regular antenatal visits, and fetal evaluation, and measures to prevent head injuries in children.
Movement of the arms and legs and the body as a whole is coordinated and controlled by a complex network of structures within the brain including the basal ganglia and cerebellum. Athetoid cerebral palsy results from damage to the basal ganglia by toxic agents such as excess bilirubin (a breakdown product of hemoglobin) and poor blood supply and oxygenation to the brain.
The condition in which bilirubin is too much in the blood is called hyperbilirubinemia. When it gets too much to cause brain damage, it is referred to as bilirubin encephalopathy or kernicterus. Damage to the brain due to poor oxygenation and blood supply is another common cause.
The risk factors for these insults to the brain include maternal illness during pregnancy, abnormal presentation of the baby in the uterus, exposure of the fetus to toxic agents such as drugs, prolonged labor, obstructed labor, placental tears, neonatal sepsis, and neonatal meningitis.
Athetoid cerebral palsy presents with movement disorders such that the child cannot hold the arms and legs still, causing difficulties walking, writing, and holding objects. Other symptoms include difficulty talking and eating because of the affected facial muscles and muscles involved in chewing.
The condition is commoner among male children and children living in poor social conditions.
Doctors can make a diagnosis of athetoid cerebral palsy by examining the child and taking a history of the child's birth, first few months of life, and the antenatal period. However, investigations such as a magnetic resonance imaging of the brain may be necessary to provide information about the damage done to the brain. Sometimes, the predisposing disease may be a genetic disease, so genetic testing may be necessary.
Treatment is largely supportive and involves physical therapy, speech therapy, occupational therapy, and administration of certain drugs which reduces the involuntary contraction of the muscles. Physical therapy serves to relax the muscles and make them more flexible, while occupational therapy seeks to enable the child to handle daily activities.