What common symptom characterizes cataplexy in narcolepsy?

The defining characteristic of cataplexy in narcolepsy is the sudden loss of muscle tone that occurs in response to strong emotions, such as laughter, anger, or surprise. This loss of muscle control can lead to varying degrees of physical collapse, ranging from slight weakness to complete body collapse while maintaining consciousness. Cataplexy is distinct in that it manifests during emotional experiences rather than being directly linked to sleep pressure, making it a unique and identifiable symptom of narcolepsy.

While the other symptoms listed are commonly associated with narcolepsy—such as irresistible sleep attacks, sleep paralysis, and hallucinations—they do not specifically describe cataplexy. Irresistible sleep attacks typically refer to the overwhelming need to sleep that can happen throughout the day. Sleep paralysis is characterized by the temporary inability to move or speak while falling asleep or waking up, and hallucinations often occur during the transition between sleep and wakefulness. These symptoms, while significant in narcolepsy, do not encompass the unique muscle tone loss that defines cataplexy.