Paroxysmal movement disorders and epilepsy

The diagnosis of paroxysmal events is standard fare for the clinical neurologist. Amid the throngs of patients with seizures, migraine, or syncope appear rarities such as paroxysmal movement disorders (PMD). Broadly, PMD are divided into the episodic ataxias and the paroxysmal dyskinesias. In the past, PMD were often diagnosed as seizures. The clinical recognition that PMD are distinct from the epilepsies has been challenged by new clinical and molecular genetic observations, such as those of Swoboda et al. in this issue of Neurology.1

Why are PMD generally regarded as distinct from epilepsies? Epilepsies are characterized by the paroxysmal occurrence of specific, usually brief, stereotyped events, which may evolve into, or be associated with, tonic-clonic seizures, and are usually accompanied by interictal epileptiform discharges on EEG. Epileptic seizures are associated with characteristic ictal discharges on clinical EEG and abnormal hypersynchronous discharges of cortical neuronal aggregates at a microphysiologic level. In contrast, PMD have stereotyped motor events that resemble the persistent movement disorders, do …