Paroxysmal kinesigenic choreoathetosis (PKC) also called paroxysmal kinesigenic dyskinesia (PKD) is a hyperkinetic movement disorder characterized by attacks of involuntary movements, which are triggered by sudden voluntary movements. The number of attacks can increase during puberty and decrease in a persons 20s to 30s. Involuntary movements can take many forms such as ballism, chorea or dystonia and usually only affect one side of the body or one limb in particular. This rare disorder only affects about 1 in 150,000 people, with PKD accounting for 86.8% of all the types of paroxysmal dyskinesias, and occurs more often in males than females. There are two types of PKD, primary and secondary. Primary PKD can be further broken down into familial and sporadic. Familial PKD, which means the individual has a family history of the disorder, is more common, but sporadic cases are also seen. Secondary PKD can be caused by many other medical conditions such as multiple sclerosis (MS), stroke, pseudohypoparathyroidism, hypocalcemia, hypoglycemia, hyperglycemia, central nervous system trauma, or peripheral nervous system trauma. PKD has also been linked with infantile convulsions and choreoathetosis (ICCA) syndrome, in which patients have afebrile seizures during infancy (benign familial infantile epilepsy) and then develop paroxysmal choreoathetosis later in life. This phenomenon is actually quite common, with about 42% of individuals with PKD reporting a history of afebrile seizures as a child. Genetics
Paroxysmal kinesigenic dyskinesias are often inherited in an autosomal dominant fashion and several genes have now been identified where mutations can cause this disease.
SPECT studies
In a study by Joo et al., the researchers performed interictal studies, meaning they scanned the patients brain between attacks to find an underlying abnormality, rather than ictal scans, which look at the abnormalities that present themselves during an attack. The researchers found interictally decreased cerebral blood flow in the posterior parts of the bilateral caudate nucleus. However, the literature does state that although this could be a cause of PKD, it could also be a result of PKD. Another SPECT study showed an increase in the cerebral blood flow in the left posterior thalamus in a PKD patient during an attack. The researchers also subtracted the ictal from the postictal scans, and saw increased blood flow in the thalamus. They ultimately suggested that hyperactive blood flow in this area could be causing the pathophysiology of PKD. This study, however, was only performed on one patient, and would need to be replicated many more times in order to be generalized to the population of PKD patients. Other SPECT studies have been cited showing hyperactivity in the basal ganglia. fMRI studies
In a study by Zhou et al., the researchers performed fMRI studies on PKD patients, and analyzed the differences between the amplitude low frequency fluctuations (ALFF) of the patients. They found that the left postcentral gyrus and the bilateral putamen had increased ALFF in PKD patients. The researchers concluded that the hyperactivity in these regions suggested that there is a dysfunction in the basal ganglia-thalamo-cortical circuit in PKD.