Chapter 28 - Paroxysmal Dyskinesias

Abstract

This chapter describes the main forms of paroxysmal dyskinesias (PxD), including paroxysmal kinesigenic dyskinesia (PKD), paroxysmal nonkinesigenic dyskinesia (PNKD), paroxysmal exercise-induced dyskinesia (PED), and nocturnal PxD/nocturnal hypnogenic dyskinesia (PHD) and reviews the episodic ataxias and some rare variants of PxD. With regard to etiology, PxD may be a primary disorder (often familial or sporadic) or due to an acquired (secondary) cause. PKD episodes are by definition triggered by sudden movement; the attacks are typically brief, lasting seconds. The clinical manifestation of PKD may exhibit dystonia, chorea, ballismus, or a combination of these. PKD attacks usually respond well to anticonvulsants, and carbamazepine is the drug of choice. PNKD has a longer duration compared with PKD and is not induced by sudden movement but by alcohol, coffee, or strong emotion. There is no consistent correlation between the duration and frequency of PNKD. PED is a rare form of paroxysmal movement disorder with a male-to-female ratio of 2:3. PED may be accompanied by migraine without aura or a combination of alternating hemiplegia, epilepsy, and ataxia. PHD is newly recognized, however, as a form of nocturnal frontal lobe epilepsy (NFLE), a distinct sleep-related syndrome characterized by nocturnal paroxysmal dyskinesias, very brief paroxysmal arousals, and prolonged somnambulism behavior. The chapter discusses the clinical aspects, pathophysiological mechanisms, genetics, treatment, and prognosis of PKD, PNKD, PED, and nocturnal PHD. Miscellaneous movement disorders occurring in bursts or as paroxysmal attacks are also discussed.