Michael J. Thorpy, MD: After we’ve assessed the patient’s sleep-wake pattern, what are the symptoms we want to look for in narcolepsy?
Alon Y. Avidan, MD, MPH: This is the 1 condition where, besides excessive daytime sleepiness, hypersomnolence as the sine qua non of the disease, you cannot really make a diagnosis without daytime sleepiness as a fundamental symptom. Besides daytime sleepiness, there are at least 4 or 5 other symptoms that I think are useful for clinicians to appraise. The first and foremost is cataplexy. Cataplexy is really a unique condition that patients often describe as a gradual loss of muscle tone that is triggered when they hear a funny joke or they get surprised. Usually, positive emotions tend to bring on this episode. Patients may have a sagging of their jaw, or may slur their speech, or may even find that it’s hard to maintain their posture or muscle tone. And it goes on fairly gradually for maybe a few seconds up to a minute. It typically does not last for more than a minute. Cataplexy is really what helps differentiate between the 2 types of narcolepsy, which is something we’ll go into in a little bit.
Michael J. Thorpy, MD: How easy is it for physicians to recognize that somebody has cataplexy? Or can it be quite difficult?
Alon Y. Avidan, MD, MPH: It is extremely difficult, and I’ll tell you why. I’m just curious, among everyone here, how many of you have witnessed cataplexy in your patients?
Michael J. Thorpy, MD: I think all of us have, because we’re dealing with this commonly. But I would say that most physicians have never seen it.
Alon Y. Avidan, MD, MPH: Most physicians have not, and I actually surveyed on this topic not too long ago. In a group of 50, 1 person had actually witnessed it. So it’s hard to validate. It’s hard to corroborate. Patients don’t present with cataplexy when they come in to see you. If you see it, it’s really helpful, but it requires validation. And things that can look like cataplexy are often not cataplexy. I think this is really the critical point of validating what the patient perceives as being abnormal.
Michael J. Thorpy, MD: How about in children, Kiran? Is cataplexy different in children as compared to adults?
Kiran Maski, MD, MPH: Yes. So a subset of children with narcolepsy can have what’s called static cataplexy, which is not triggered by emotion. They just look like they’re hypotonic. Their face looks droopy. Their eyes may be partially closed. Their mouth may be hanging open. They may even have what looks somewhat like an ataxic gait, but their neurologic exam is normal. It’s a unique presentation in children. And to add to your point, I’ve found that having parents bring in videos of events that they believe to be cataplexy can be very helpful.
Michael J. Thorpy, MD: What about the other symptoms, Alon, besides cataplexy?
Alon Y. Avidan, MD, MPH: Besides cataplexy, the next symptom to look for is sleep paralysis. Sleep paralysis is described as the inability to move—almost complete paralysis with the exception of breathing and eye movements—that typically occurs at the offset of sleep when the patient wakes up. It’s rather disruptive and disturbing to the patient. Often, they are quite anxious because of it. The good thing is that it goes away within a few minutes. Now, sleep paralysis is not unique to narcolepsy. Certainly, we have isolated sleep paralysis as a parasomnia, as an abnormal behavior, or as a sensory phenomenon during sleep or sleep-wake transition. But it is common in sleep deprivation, and it’s common, very common, in narcolepsy.
There are also some hypnagogic and hypnopompic hallucinations in narcolepsy. The hypnopompic occur as visually disruptive hallucinations when the patient wakes up. The hypnagogic hallucinations occur when the patient transitions into sleep. They are not typical dream-like experiences that you and I probably experience, but they’re rather abrupt onset into REM [rapid eye movement] sleep. And the experiences are rather visually disturbing to the patient.
Besides the hallucinatory experiences, sleep paralysis, and cataplexy, 1 of the fundamental issues that occurs in narcolepsy, which is related indirectly to the orexin hypocretin deficiency, is that besides the inability to maintain wakefulness in the day, there is inability to maintain sleep during the night. So insomnia, severe disrupted sleep onset, and sleep maintenance insomnia are very common in narcolepsy. You would think otherwise. You would think that those individuals would fall asleep and sleep soundly during the night, but it’s quite the opposite.
Michael J. Thorpy, MD: So this is really a 24-hours-a-day disorder, right? Patients have the sleepiness and the cataplexy during the daytime, but then they have these abnormal REM sleep phenomena and disrupted sleep at night. You rightly mentioned that sleep paralysis is more common upon awaking in the morning. But if you get it at the beginning of the night, is that more specific for narcolepsy?
Alon Y. Avidan, MD, MPH: I believe there are some studies that demonstrate that sleep paralysis at the onset of sleep is more specific to the narcolepsy phenotype as opposed to sleep paralysis in the setting of sleep deprivation that usually occurs in the morning.
Michael J. Thorpy, MD: Right. Typically, we don’t have REM sleep at the beginning of the night in normal individuals, do we? But we do have it at the end of the night. So if sleep is disrupted, we may be more likely to get that sleep paralysis when we wake up in the morning. But if you get abnormal REM at night, and you get sleep paralysis or hallucinations as you’re falling asleep at night, that really is a little bit more indicative of narcolepsy.
OK. Thank you very much Alon.