Athetosis is a symptom characterized by slow, involuntary, convoluted, writhing movements of the fingers, hands, toes, and feet and in some cases, arms, legs, neck and tongue. Movements typical of athetosis are sometimes called athetoid movements. Lesions to the brain are most often the direct cause of the symptoms, particularly to the
corpus striatum. This symptom does not occur alone and is often accompanied by the symptoms of cerebral palsy, as it is often a result of this physical disability. Treatments for athetosis are not very effective, and in most cases are simply aimed at managing the uncontrollable movement, rather than the cause itself.
Signs and symptoms
Athetosis can vary from mild to severe motor dysfunction; it is generally characterized by unbalanced, involuntary movements of muscle and a difficulty maintaining a symmetrical posture. The associated motor dysfunction can be restricted to a part of the body or present throughout the body, depending on the individual and the severity of the symptom. One of the pronounced signs can be observed in the extremities in particular, as the writhing, convoluted movement of the digits. Athetosis is caused by lesions in several brain areas such as the hippocampus and the motor thalamus, as well as the corpus striatum; However, a less-studied consequence of the resulting hypoxia is its effect on the concentrations of the neurotransmitter dopamine within the synapses of neurons in the basal ganglia. Hypoxia leads to an increase in the extracellular dopamine levels and therefore, an increase in the activity of the dopaminergic neurons. Furthermore, this increase in extracellular concentration is not caused by an increase in the neurotransmitter synthesis, but instead on inhibiting its reuptake back into the neurons and glial cells. Therefore, there is an increased dopaminergic effect as dopamine remains in the synapse at higher concentrations leading to additional post-synaptic response. 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. The striatum receives excitatory inputs from the cortex and inhibits the pallidum. By doing so it frees the thalamus from pallidal inhibition allowing the thalamus to send excitatory outputs to the cortex. Therefore, the lesions to the thalamus or any other part of this feedback loop can result in movement disorders as they can alter the reactivity of one towards the other.
Drugs can also be used in the treatment of athetosis, however their collective effectiveness is not very convincing. There is not a single drug that is a standard among treatment. Many different medicines can be used, including:
- trihexyphenidyl
- benzatropine
- Curare, Patients who undergo surgical treatment to relieve the athetosis often see significant improvement in the control of their limbs and digits. Considering the etiology of both disorders are fairly similar, it comes as no surprise that chorea and athetosis can and usually do occur together in a condition called choreoathetosis.
Cerebral palsy
Athetosis is a commonly occurring symptom in the disease cerebral palsy. Of all people with the disease, between 16% and 25%
It is also noteworthy that the presence of athetosis in cerebral palsy (as well as other conditions) causes a significant increase in a person's 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. 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. The caregivers of the affected children are encouraged to closely monitor their nutrition and growth and to provide them with hearing aids in order to relieve their symptoms as well as support their academic plans. A growing number of patients is shown to benefit from communication devices such as shorthand typing programs and computer speech devices, as well as simple picture boards. Patients are also inclined to associate themselves with people who tend not to be engaged in physical activities, according to the September 2008 issue of "Journal of Physical Activity and Health".
History
The first noted case of athetosis was discovered by W. A. Hammond and described in his book Diseases of the Nervous System in 1871. In his initial description of athetosis, the extent of the uncontrolled movement was limited to the fingers and toes. In association with this, he noted that the patients' calves and forearms were oftentimes flexed and that movements were generally slow. Over the period of time leading into the late 20th century, the definition of athetosis was expanded to include movements of the neck, tongue, face, and even the trunk. Along with the expansion of the symptoms came the recognition that it was a part of many medical conditions, including cerebral palsy and stroke.
An additional possible treatment option for those afflicted with the symptom is neurostimulation. Studies have begun, and in cerebral palsy patients affected with dystonia-choreoathetosis, it has been demonstrated that neurostimulation has been an effective treatment in lessening symptoms in patients. There has not been a tremendous amount of experimentation, though, in this as a possible treatment option.
See also
- Chorea
- Dyskinesia
- Dystonia
- Pupillary athetosis