A 7-year-old boy is brought to the pediatric neurology clinic by his mother, who reports that he has had 2 episodes of facial twitching and drooling that occurred at night while sleeping over the past 3 months. During these episodes, he was unable to speak clearly but remained aware of his surroundings. Neurological examination and developmental assessment are completely normal. An awake EEG shows normal background activity. The EEG during sleep reveals the pattern marked **A** in the diagram — high-amplitude diphasic sharp waves over the centrotemporal regions with a horizontal dipole, bilateral and independent. What is the most likely diagnosis?