This circuit is part of the motor control circuit in the brain, making it a reasonable place for abnormality in a movement disorder, but again, researchers are still unsure of the role these differences they found play in the disease pathology. Diffusion tensor imaging
Diffusion tensor imaging (DTI) displays physical alterations in the brain that may not be seen on regular MRI. In one study researchers found that some of the patients had abnormalities in their thalamus. However, this does not prove that all patients have abnormalities in their thalamus. Other cases are cited, including a patient who developed a similar paroxysmal dyskinesia after a thalamic infarction, implicating that an abnormality in the thalamus of individuals could contribute to PKD. It is not fully known, however, what role a thalamic abnormality plays in the disease pathophysiology. Diagnosis
Paroxysmal kinesigenic dyskinesia is diagnosed using a strict set of guidelines. These criteria were studied and confirmed by Bruno et al. in a study of 121 individuals with PKD. The age at onset is between 1 and 20 years old. The attacks of involuntary movements last less than one minute and have a known trigger, usually a sudden voluntary movement. For example, if a PKD patient stands up or begins walking after being sedentary for a period of time, or a person goes from a walk to a run, it can trigger an attack. Persons with PKD do not lose consciousness during attacks and have a full memory of the entire attack.
The genes typically code for proteins known to be involved in synaptic transmission, ion channels or ion transporters. The first gene to be identified was the PRRT2 gene on chromosome 16, found in 2011 to be the cause of the disease in some patients. The mutations in this gene included a nonsense mutation identified in the genome of one family and an insertion mutation identified in the genome of another family. Researchers found PRRT2 mutations in 10 of 29 sporadic cases affected with PKD, thus suggests PRRT2 is the gene mutated in a subset of PKD and PKD is genetically heterogeneous. Later reports have identified the genes SCN8A, CHRNA4, and SLC16A2 as further causes of PKD. Pathophysiology
The pathophysiology of PKD is not fully explained. A few mechanisms have been suggested thus far:

GABA dysregulation
Abnormal breakdown of dopamine in the basal ganglia
Dysfunction of the substantia nigra
A form of epilepsyMultiple methods are being used to study the potential brain abnormalities of individuals with PKD compared with “normal” individuals. These methods include SPECT studies, fMRI studies, and diffusion tensor imaging. The main problem with many of the studies concerned with the pathophysiology of the disorder is the small sample size. Because the studies normally only include about 7-10 patients with PKD, the results cannot be generalized to the entire population of patients. However, the studies do bring up possibilities for further study.