There are several diagnostic tests that we use to make the diagnosis of narcolepsy. The first is simply a clinical history hearing the patient’s story and seeing what symptoms they have. After that, we look at the Epworth sleepiness scale score. What that is is a simple quiz. And the patient’s asked a few questions. How sleepy are they if they’re sitting in reading or after lunch or on a drive as a passenger for an hour without a break. So they have several clinical scenarios and they score themselves. I’m not sleeping at all. I’m a little sleepy, I’m moderately sleepy. I’m very sleepy. We add up the score and the higher the score, the more likely they are to be excessively sleepy or abnormally sleepy. So what we’d like is a nice low score, meaning that we’re well rested, but a score above 10 out of 24 is already abnormal.
Narcoleptics on average, have high scores like 17 or 18 out of 24. And they may answer positively to falling asleep at a stoplight or sitting and talking to some someone. So the first thing, the Epworth sleepiness scale score gives us a sense quantifies how sleepy they are during the day and how they function as a result. The next thing that we do is order a polysomnogram. This is a sleep study, which measures four things. We look at the brain waves to make sure there’s no seizure activity going on, but it also tells us when the patient’s awake during the night and what stage one, two, three, or REM sleep they’re in. We know that patients with narcolepsy have extra REM density. They dream more than the average person and that their dream has come very early into the night cycle. Not just 90 minutes after falling asleep, but even a few minutes or a few moments after falling asleep. We also look at their heart rate and rhythm their muscle activities and their breathing. But the biggest thing about that sleep study is their sleep cycles and how much dreams they have.