From nocturnal frontal lobe epilepsy to Sleep-Related Hypermotor Epilepsy: A 35-year diagnostic challenge

Nocturnal frontal lobe epilepsy (NFLE) is a focal epilepsy with seizures arising mainly during sleep and characterized by complex, often bizarre, motor behavior or sustained dystonic posturing. First described in 1981, it was initially considered a motor disorder of sleep and was named nocturnal paroxysmal dystonia (NPD). The unusual seizure semiology, onset during sleep, and often uninformative scalp EEG and brain MRI make it difficult to distinguish NPD attacks from other non-epileptic nocturnal paroxysmal events, namely parasomnias. The long-debated epileptic origin of the condition was finally demonstrated in 1990 and the term NFLE introduced. Even though many aspects of parasomnias and NFLE have been clarified in the last two decades, the differential diagnosis remains a challenge for clinicians. To address controversial issues and define the diagnostic criteria for NFLE, a Consensus Conference was held in Bologna, Italy in 2014. Major points of agreement emerged on: (i) the relationship of the seizures with sleep and not with the circadian pattern of seizure occurrence; (ii) the possible extrafrontal origin of hypermotor seizures, without substantial differences in seizure semiology. In the wake of the Consensus, the syndrome was renamed Sleep-Related Hypermotor Epilepsy (SHE).