There are two classifications for narcolepsy in international diagnosis: Narcolepsy with cataplexy and narcolepsy without cataplexy. Both of these disorders share the primary narcolepsy symptom: Excessive Daytime Sleepiness (EDS). This is the symptom that defines narcolepsy. It is this symptom that narcolepsy testing is looking for.
Excessive Daytime Sleepiness
Excessive Daytime Sleepiness (EDS) is exactly what it sounds like. The patient experiences not just being tired or the feeling of exhaustion, but the desire to sleep that is so strong it becomes need. People with EDS often find themselves falling asleep at inappropriate times. There is little sympathy for a student that falls asleep during a lecture or an employee that sleeps on the job. These episodes can cause embarrassment for patients and lead to complications like depression and self-medication with illegal stimulants.
Cataplexy is suffered by approximately seventy percent of narcolepsy patients. Cataplexy is the experience of sudden and uncontrollable loss of muscle tone. When a person experiences cataplexy, they lose control of muscle function.
This can be so slight that it is not noticed, lasting for a few short seconds an example of a simple cataplexy episode would be the momentary drooping eyelid. It most commonly affects the face, around the eyes or the slackening of the jaw. It can also be a very serious event. A severe cataplexy episode can leave a patient completely collapsed with no control for a period that can last for over an hour.
It is believed in scientific circles that cataplexy is a form of REM function. During REM sleep, muscles lose tone and go slack. The biggest difference between normal REM sleep and Cataplexy is that the person who is experiencing it is completely alert. Being awake and unable to move can be a terrifying experience, especially the first time it is experienced.
Other Common Narcolepsy Symptoms
Although less common than EDS or cataplexy, there are two other symptoms that are associated with narcolepsy. Sleep paralysis and hallucinations occur often enough in narcolepsy patients to merit notice.
Sleep Paralysis Although they are not related, the behavior of sleep paralysis and cataplexy are similar. Sleep paralysis is experienced in the twilight between wake and sleep. Like cataplexy, it is believed to be a displaced part of REM sleep. The subject experiences paralysis during this time, but they have not lost consciousness. This can be as frightening as cataplexy, especially since it is often associated with hallucinations.
Hallucinations are a common symptom of narcolepsy. They occur either with or independent of other symptoms. Again, these waking dreams, these hallucinations are believed to be displaced aspects of REM sleep. They can be dark and sinister and when experienced during sleep paralysis, they have historically been mistaken for possessions or out of body experiences.
Sleep paralysis and hallucinations are not exclusively narcolepsy symptoms, neither are they experienced by every narcolepsy patient. In fact, it is exceedingly rare that any one patient would have all of these symptoms.
Using the Nocturnal Polysomnogram and Multiple Sleep Latency Test, narcolepsy is determined by the sleep cycles and the details they give.
First, the patient spends the night at the sleep center. They are monitored through the night for abnormal patterns, snoring, or apnea- anything that may explain the excessive daytime sleepiness that the patient experiences are carefully recorded.
During the test, an electroencephalogram or EEG monitors the patients and coupled with video surveillance an accurate record of nocturnal behavior is made. Some of the things that will be determined are how long it takes the patient to fall asleep and the onsets and duration of REM sleep is also recorded. This is a very important factor in determining the diagnosis of narcolepsy.
Multiple Sleep Latency Test
The next day, the patient stays at the clinic. The MSLT is done during this time. For this narcolepsy test, the patient spends the day at the clinic and during their stay; they will have five, 20 minute, scheduled naps that are set two hours apart throughout the day. During the naps, the patient is settled into a comfortable room that is made as sedate and sleeps inducing as possible. During this time, the time it takes to fall asleep and the presence or absence of REM sleep are carefully scrutinized as it is by these things that the doctor will decide if the patient suffers from narcolepsy.
An event that is uncommon in normal sleepers but often happens with narcolepsy patients is SOREM or Sleep Onset REM. The diagnosis of narcolepsy takes several recorded events. First is that it should take an average of eight minutes for the subject to fall asleep on average through the five naps. Then there needs to be either two occurrences of SOREM or even one occurrence of REM at any point within the 20 minute naps.
Even though it is the accepted standard, some experts criticize the MSLT as a diagnostic tool for narcolepsy as there are several other sleep disorders such as sleep apnea, shift work Sleep disorder, and periodic limb movement disorder, that can cause multiple SOREMS on a MSLT. However, with a lack of a better standard for testing, narcolepsy is diagnosed by history, Nocturnal Polysomnogram and the Multiple Sleep Latency Test.
The Role of Hypocretin in Cataplexy
Narcolepsy with the symptom of cataplexy earned itself its own diagnosis because it has its very own bio-marker. The protein hypocretin-1 is found in the hypothalamus. In patients with the diagnosis of Narcolepsy with cataplexy, over 90% had a significant reduction in the levels of hypocretin-1. This deficiency is an important discovery into the cause, treatment and possible the future cures for narcolepsy with cataplexy.
Approximately 20-40% of non-cataplectic, narcolepsy patients show a low level of hypocretin-1. So it is not a good indicator of narcolepsy in general and the presence of the deficiency in cataplectic indicates a separate pathology for the two.
Testing for hypocretin-1 deficiency is a difficult process that involves removing some of the spinal fluid. Because this procedure is both painful and potentially dangerous, it is not a common diagnostic tool. This kind of testing is left for laboratory work and scientific studies.
Perhaps the most used and most reliable testing for narcolepsy and the only one widely used for cataplexy is a detailed medical history. Often a doctor will have a patient journal to record symptoms and episodes. Family and personal medical histories are carefully compiled and scrutinized as well.