No abstract available. Article truncated after first page. Which of the following is the most helpful in differentiating nocturnal frontal lobe epilepsy (NFLE) from non-rapid eye movement (NREM) arousal parasomnias? 1. Onset during rapid eye movement (REM) sleep. 2. Arousal preceding the event. 3. Stereotypy. 4. Concomitant presence of sleep apnea.