Although unable to move, the person remains conscious. For some people, any strong emotion may trigger cataplexy, while others react to only certain specific emotions. Although most patients experience cataplexy, some patients never develop this symptom. Hypnagogoic hallucinations are vivid, often frightening, dream-like images that occur when dozing or when falling asleep. Sometimes these images are so vivid that they are difficult to distinguish from reality.
Sleep paralysis refers to a temporary paralysis upon falling asleep or waking up.
Episodes may last only a few seconds to minutes. Frequent awakenings at night are common, but are not the cause of excessive daytime sleepiness in patients with narcolepsy. An overnight stay in a sleep laboratory is necessary to rule out other conditions such as sleep apnea, periodic leg syndrome, and upper airway resistance syndrome that cause can excessive daytime sleepiness. A daytime nap study will be performed the next day to evaluate the severity of daytime sleepiness. A blood test is neither necessary or sufficient to make the diagnosis of narcolepsy.