Increased frequency of arousal parasomnias in families with nocturnal frontal lobe epilepsy: a common mechanism?

PURPOSE: Retrospective observations disclosed an overlap between parasomnias and nocturnal frontal lobe epilepsy (NFLE) not only in patients but also in their relatives, suggesting a possible common pathogenetic mechanism. This study aimed to verify whether relatives of patients with NFLE have a higher frequency of parasomnias, namely arousal disorders, and thereby shed light on the still unknown pathophysiologic mechanisms underlying NFLE.

METHODS

We undertook a case-control family study in which we recruited NFLE probands and healthy controls, matched for age, sex, education, and geographic origin. At least four relatives were included for each proband and control. Each subject underwent a standardized interview, with application of the International Classification of Sleep Disorders-Revised (ICSD-R 2001) minimal criteria to diagnose the lifetime prevalence of the main parasomnias.

RESULTS

Four hundred fifty-eight individuals were recruited: 33 NFLE probands, 200 relatives of probands, 31 controls, and 194 control relatives. All NFLE probands but one have sporadic NFLE. The lifetime prevalence of the following parasomnias differed in proband relatives versus control relatives: arousal disorders [odds ratio (OR) 4.7, 95% confidence interval (CI) 2.0-11.6; p < 0.001] and nightmares (OR 2.6, 95% CI 1.6-4.2; p < 0.001) were more frequent among NFLE proband relatives. In the secondary analysis comparing NFLE probands to controls, arousal disorders (OR 6.3, 95% CI 1.3-31.7; p = 0.023) and bruxism (OR 5.4, 95% CI 1.3-21.7; p = 0.017) were more frequent among NFLE probands.

DISCUSSION: The higher frequency of arousal disorders in NFLE families suggests an intrinsic link between parasomnias and NFLE and an abnormal (possibly cholinergic) arousal system as a common pathophysiologic mechanism.