Narcolepsy and hypersomnolence — branching viva

Opening — framing the problem

The examiner begins: a ten-year-old has three months of irresistible daytime sleepiness and, when he laughs hard, his knees buckle and his head drops while he stays fully aware. Talk me through your reasoning. ^{[1] [2]}

I would frame this as narcolepsy type 1 until proven otherwise, because the pairing of new, irresistible daytime sleepiness with emotion-triggered loss of muscle tone and preserved consciousness is the clinical signature of cataplexy, which is nearly specific for narcolepsy type 1. The rapid weight gain points to the hypothalamic involvement seen in paediatric narcolepsy. ^{[2] [7]}