A diagnosis of paroxysmal kinesigenic, non-kinesigenic, exertion-induced, or hypnogenic dyskinesia is based upon a thorough clinical evaluation including a complete physical and neurologic assessment; evaluation of characteristic symptoms with assessment of episode duration, frequency, and "trigger factors" or precipitants; and a careful patient and family history.
There is no definitive diagnostic test for these disorders. Certain blood tests, other laboratory studies, or neuroimaging or neurophysiologic studies may be conducted to eliminate similar disorders and to confirm or rule out underlying conditions that may result in secondary (symptomatic) paroxysmal dyskinesia. Such neuroimaging or neurophysiologic studies may include computerized tomography (CT) scanning or magnetic resonance imaging (MRI) to create detailed, cross-sectional images of certain bodily tissues and organs; electroencephalography (EEG) to detect or rule out potential seizure activity; or other techniques, such as specialized sleep studies (e.g., polysomnograms) in those with suspected paroxysmal hypnogenic dyskinesia to help evaluate the occurrence of nocturnal episodes of involuntary movement. However, experts indicate that neuroimaging studies (e.g., CT or MRI) typically are not helpful in those with idiopathic (familial or sporadic) paroxysmal dyskinesia.
The differential diagnosis of idiopathic paroxysmal kinesigenic dyskinesia (PKD) includes repeated seizures or epilepsy and hyperexplexia, also known as startle disease. Patients with hyperexplexia have an exaggerated startle response to unexpected stimuli. These heightened responses may cause stiffening and falling without loss of consciousness. Tetany, associated with hypocalcemia; may rarely mimic paroxysmal dyskinesias. It is characterized by muscular twitching and cramping; spasms at the wrist and ankle joints; spasmodic closure of the larynx, with an associated, high-pitched sound upon inhalation (stridor), and abnormal involuntary movements resembling chorea. The diagnosis of idiopathic, particularly sporadic, paroxysmal non-kinesigenic dyskinesia (PNKD) may include measures to help differentiate the condition from movement disorders in which symptoms have an emotional rather than an organic origin (psychogenic disease).
The differential diagnosis of paroxysmal hypnogenic dyskinesia should also include various forms of epilepsy. However, EEG findings may provide evidence of seizure activity arising from a specific region of the cerebral cortex.