Nocturnal paroxysmal dystonia to sleep-related hypermotor epilepsy: A critical review.

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Sleep-related paroxysmal motor episodes (SPMEs) have been described by various names, including nocturnal paroxysmal dystonia, nocturnal frontal lobe epilepsy (NFLE), and sleep-related hypermotor epilepsy. The underlying pathophysiology has been debated over the years, with these episodes assumed to be a form of paroxysmal dystonia or parasomnia versus a form of epilepsy. In most studies published on SPMEs and their variants (paroxysmal arousals, nocturnal paroxysmal dystonia, and episodic nocturnal wanderings) in the early 1990s, the authors speculated on the pathophysiology but did not commit to one idea. It was not until the mid-1990s that epilepsy became the leading prospect. We performed a narrative review of the major articles that have described this syndrome in a chronological fashion. We identified three eras, 1972-1993, 1994-1998, and 1999 to the present, each era marked by a landmark study. Our critical review of these early studies shows that the neurophysiological data supporting epilepsy as the sole basis for all SPME cases is very weak. In 1994-1995, a familial pattern of this syndrome was described and the term autosomal dominant NFLE was coined, with the authors claiming that all their patients had a form of frontal lobe epilepsy. With the exception of a few reference cases, the neurophysiological evidence that all patients had frontal lobe epilepsy was very weak. Compared to articles published on surgical series of frontal lobe epilepsy, the percentage of SPME cases with positive interictal/ictal electroencephalograms remained very low, seriously questioning the epileptic basis of the syndrome. Our critical review and analysis of the published literature shows that the evidence presented in favor of SPMEs being a homogenous focal epilepsy syndrome is very weak. Neurologists must recognize that SPMEs could be a form of movement disorder, parasomnia, or epilepsy. We recommend a pragmatic semiology-based classification of these episodes using the four-dimensional classification system.