As a result, the uncontrollable writhing motions witnessed with athetosis deal with the over-activity of synapses within the basal ganglia. Neonatal jaundice
Neonatal jaundice is the other chief complication that leads to the basal ganglia damage associated with this condition. Jaundice is caused by hyperbilirubinemia, or abnormally high levels of bilirubin in the blood. Bilirubin is usually bound to albumin immediately and sent to the liver. However, in neonatal jaundice, the concentration of bilirubin overwhelms that of albumin and some of the bilirubin remains unconjugated and can enter the brain through the blood–brain barrier. Normally bilirubin would not be able to diffuse across the blood–brain barrier, but in infants, the barrier is immature and has higher permeability. Bilirubin is toxic as it prevents the phosphorylation of many proteins, including synapsin I which binds vesicles in the presynaptic terminal. Therefore, it directly inhibits the exocytosis of neurotransmitters and severely hinders the synapses it affects. In autopsies of children who suffered from neonatal jaundice, chronic changes of neuronal loss, gliosis and demyelination were observed in the basal ganglia and more specifically within the globus pallidus. Thalamic stroke
Another study was done where the onset of athetoid movement followed a thalamic stroke. The thalamus is part of a pathway that is involved with the cortical feedback loop in which signals from the cortex are relayed through the striatum, pallidus and thalamus before making it back to the cortex. The striatum receives excitatory inputs from the cortex and inhibits the pallidum.
A component of this is the finding that most often the symptoms that involve athetosis occur as a part of choreoathetosis as opposed to athetosis alone.It is also noteworthy that the presence of athetosis in cerebral palsy (as well as other conditions) causes a significant increase in a persons basal resting metabolic rate. It has been observed that those who have cerebral palsy with athetosis require approximately 500 more Calories per day than their non-cerebral palsy non-athetoid counterpart. Pseudoathetosis
Pseudoathetosis is a movement disorder, very similar to athetosis, in which the symptoms are not differentiable from those of actual athetosis, however the underlying cause is different. While actual athetosis is caused by damage to the brain, specifically in the basal ganglia, pseudoathetosis is caused by the loss of proprioception. The loss in proprioception is caused by damage to the area between the primary somatosensory cortex and the muscle spindles and joint receptors. Additionally, when observing an MRI, it can be seen that in the brain of a pseudoathetoid patient, lesions on the brain are not seen in the basal ganglia, the area that is oftentimes the cause of athetosis. Social implications
Athetosis is characterized as a symptom that is present in many forms of central nervous system disorders that affect the body movement coordination, such as cerebral palsy. Children may struggle to engage in social communication, since the poor coordination of the tongue and mouth muscles can reduce their speech ability and hinder their social interaction to a greater degree.