Key opinion leaders discuss symptoms associated with narcolepsy such as cataplexy, hallucinations, sleep paralysis, and excessive daytime sleepiness (EDS).
Phyllis Zee, MD, PhD: We have talk about how narcolepsy is often an overlooked diagnosis in patients who experience excessive daytime sleepiness. What are some of the symptoms of narcolepsy that we should be recognizing?
Alon Avidan, MD, MPH: The cardinal symptoms of narcolepsy include the following: irresistible, excessive, pathologic sleepiness that does not go away. From the moment the patient wakes up until they go to sleep, they experience a severe sleepiness in the form of sleep attacks. They may also experience what we conceptualize as an intrusion of rapid eye movement [REM] sleep into wakefulness. The prime example, the sine qua non pathognomonic sign that we all think about is cataplexy.
Cataplexy is the abnormal loss of muscle tone that is temporarily associated with an emotional sensation, which is typically laughter or when a patient hears a joke. It can also occur, probably less commonly, when the patient is in a state of fear or stress. such as when they are surprised, when they are angry, and even during sex. This is temporary, and it can be partial or it can be complete. The sudden loss of muscle tone can affect the jaw. The people who may observe it may not recognize that a patient is having cataplexy, but the patient may have a temporary arrest of speech. In more complete and severe forms, there is an unbuckling of the knees where a patient falls to the ground. Cataplexy is often missed. It is often missed because physicians and clinicians may not observe it, and the patient may not know that they are having cataplexy. When it is present, it is often a strong sign of type 1 narcolepsy, which we will be discussing a bit later.
However, some of the other features that we must not lose sight of include the fact that patients may have abnormal hallucinations or dream-like experiences. When the patient falls asleep, these hallucinations are called hypnagogic hallucinations, or when the patient wakes up, they are called hypnopompic hallucinations. These are bizarre, vivid, dreamlike experiences as well as the persistence of a muscle atonia that characterizes REM sleep. The persistence occurs when the patient is trying to wake up while still in REM sleep, and they feel completely paralyzed. The only thing they can do is breathe and probably move their eyes, but everything else is paralyzed. What is interesting is that sleep paralysis is not specific to narcolepsy: We have heard of patients who experience sleep paralysis simply because they are sleep deprived. The cardinal issue is to differentiate narcolepsy from other causes of daytime sleepiness that can manifest.
Phyllis Zee, MD, PhD: I agree. As you said, cataplexy is 1 of the important things to identify because it can be subtle. It could be a weakening of the patient’s jaw muscles or slurring of their speech. Because it is so pathognomonic, it is really important to recognize that, no question about it. Do patients with narcolepsy have to have all these associated symptoms other than excessive daytime sleepiness?
Alon Avidan, MD, MPH: No. People with narcolepsy may have certain attributes, and the presence or the absence of these signs helps us differentiate between type 1 and type 2 narcolepsy.
Phyllis Zee, MD, PhD: Let's talk about that. Let's talk about type 1 and type 2 narcolepsy.
Alon Avidan, MD, MPH: Sure.
Phyllis Zee, MD, PhD: As you said earlier, type 1 narcolepsy is patients who have cataplexy, which is why it is so important to identify that, whereas type 2 narcolepsy is differentiated by those who do not have cataplexy. We will go into the diagnostic criteria a bit later. In addition to those types, we also see patients with disturbed nocturnal sleep, which is something we do not tend to think about in patients with narcolepsy because we think that they are sleepy all the time.
From a neurology standpoint, which is curious, the other thing is that these are kinds of stereotypical behaviors. Even during the day, because the patients are sleeping, it is almost like sleepwalking. Those could be REM sleep phenomena intruding into wakefulness and vice versa as well.
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Transcript Edited for Clarity