The FLEP scale in diagnosing nocturnal frontal lobe epilepsy, NREM and REM parasomnias: Data from a tertiary sleep and epilepsy unit

Abstract

To test the usefulness of the FLEP scale in diagnosing nocturnal frontal lobe epilepsy (NFLE), arousal parasomnias, and REM sleep behavior disorder (RBD). The FLEP scale was applied to 71 subjects (60 male; 11 female; aged 54 +/- 21) referred to an outpatient's sleep and epilepsy unit for diagnostic assessment of nocturnal motor-behavioral episodes, which turned to be arousal parasomnias (11 subjects), NFLE (14 subjects), or idiopathic RBD (46 subjects), based on the findings of in-lab full night video polysomnography with extended EEG montages. The sensitivity of the scale as a diagnostic test for NFLE was 71.4%, the specificity 100%, the positive predictive value 100%, and the negative predictive value 91.1%. The FLEP scale gave an incorrect diagnosis in 4/71 (5.6%) of the cases, namely NFLE patients with episodes of nocturnal wandering, and uncertain diagnostic indications in 22/71 subjects (30.9%). The FLEP scale shows high positive and negative predictive values in diagnosing NFLE versus arousal parasomnias and RBD. However, the scale is associated with a real risk of misdiagnosis in some patients and gives uncertain indications in about one-third of cases, mainly RBD. Our investigation highlights the inadequacy of some of the items in the scale. The item investigating wandering, as presently formulated, may be unable to distinguish nocturnal wandering from sleepwalking. The items about "recall" and "clustering" of the events throughout the night may increase the likelihood of mistaking RBD for seizures. Further testing of the reliability of the FLEP scale items appears to be needed.