Prevalence of nocturnal frontal lobe epilepsy in the adult population of Bologna and Modena, Emilia-Romagna region, Italy

Study Objectives: To estimate the prevalence of nocturnal frontal lobe epilepsy (NFLE) in the adults of two areas of the Emilia-Romagna region (northeast Italy) and to describe the clinical features from a population-based perspective.
Design: Population-based retrospective cohort study including adults with NFLE.
Setting: Two areas of the Emilia-Romagna region: the city of Bologna (330,901 adult residents) and five districts of the province of Modena (424,007). Prevalence day: December 31, 2010.
Participants: Patients with NFLE collected from multiple databases of neurologic hub centers of the districts involved. Diagnostic criteria: clinical history of sleep related bizarre motor attacks and videopolysomnographic recording confirming the typical features of NFLE. Inclusion criteria for prevalence calculation: residence in one of the two geographic areas on the prevalence day and an "active" or "in remission with treatment" form of NFLE.
Measurements and Results: Six subjects from Bologna and eight from Modena were included. Crude prevalence (per 100,000 residents) was 1.8 (95% confidence interval 0.7-4.0) in Bologna and 1.9 (0.8-3.7) in Modena. Similarly, the main clinical features were consistent: onset during adolescence (median age 11-13 y), mainly hyperkinetic seizures, nonlesional form in more than two-thirds of cases, an active form of epilepsy in more than two-thirds of cases. A family history of epilepsy was reported only for two patients.
Conclusions: This epidemiologic study establishes that nocturnal frontal lobe epilepsy is a rare epileptic condition, fulfilling the definition for rare disease. Because of methodological limitations of our case ascertainment, the estimates we disclose must be considered the minimum prevalence.