Narcolepsy is a rare brain condition that changes your body’s ability to regulate sleeping and waking, making you feel sleepy throughout the day while having uneven sleep at night. People with narcolepsy may quickly and unexpectedly fall into the grasp of sleep (called sleep attacks). These sleep attacks can happen in the middle of activities like eating, talking with others, or — very dangerously — driving.

For some people, it may take years to be properly diagnosed with narcolepsy. The main reason behind this holdup is that narcolepsy’s symptoms usually overlap with other conditions, such as sleep apnea, sleep deprivation, epilepsy, or depression. Plus, it can be challenging to differentiate between narcolepsy types and identify the specific condition you may have.

An electroencephalogram (EEG) can sometimes play a role in the diagnosis of narcolepsy. However, EEGs are not a routine test used to diagnose everyone with narcolepsy. This article explains how EEGs fit into the narcolepsy diagnosis and what to expect if this test is recommended by your health care provider.

The Basics of Diagnosing Narcolepsy

Diagnosing narcolepsy often involves a multistep approach. The first step includes a visit with your health care provider, during which they’ll review your medical history and symptoms and perform a physical exam. The most common symptom your health care provider will look for is excessive daytime sleepiness, which causes you to feel sleepy most of the day.

Other signs your health care provider may note are:

• Sudden muscle weakness and loss of muscle tone, called cataplexy
• A tendency to see or feel things that are not there when falling asleep or waking up, called hallucinations
• Sleep paralysis, which includes an inability to move just after waking up

If your health care provider suspects you have narcolepsy, they might send you for sleep studies. Sleep studies for narcolepsy include polysomnography and the multiple sleep latency test (MSLT).

Polysomnography is an overnight study that involves monitoring your body’s functions during sleep, including brain activity, eye movements, muscle activity, heart rate, and respiratory patterns. This test provides valuable insights into your sleeping habits and helps to rule out other sleep disorders, such as sleep apnea.

The Role of MSLT and EEG

The multiple sleep latency test is conducted during the daytime. During this test, you are given four to five nap opportunities. Health care providers assess your ability to fall asleep during the day. They also note how quickly you enter rapid eye movement (REM) sleep during naptime. These are significant aspects of diagnosing narcolepsy.

MSLT is more critical than other sleep tests for diagnosing the specific type of narcolepsy someone has. A diagnosis of narcolepsy type 1 (narcolepsy with cataplexy) is based on cataplexy, excessive daytime sleepiness seen on the MSLT, and low hypocretin levels. Hypocretin is a hormone that helps the body regulate sleep and is released in your cerebrospinal fluid, the liquid that surrounds your spinal cord and your brain.

People with narcolepsy type 2 will have similar results on the MSLT, but they don’t experience cataplexy and often have hypocretin levels in the normal range.

An EEG detects the electricity generated by your brain cells. During the procedure, electrodes — small circular metal pieces attached to thin wires — are placed on your scalp. The EEG records how your sleep changes when you take short naps during the MSLT. By carefully analyzing the EEG waves, doctors can detect some differences among people with narcolepsy types 1 and 2.

Understanding the EEG Process

If your doctor determines an EEG is necessary for your narcolepsy evaluation, knowing what to expect during the procedure can help ease your mind. Following are the steps involved in the EEG test.

Preparation for the Test

On the day of the test, make sure your hair is clean and dry. You should not use oils or gels on your hair before the test. You might have problems with EEG results if your hair is oily or sticky with hair products.

Electrode Placement During the Test

During the procedure, a trained technician will clean your scalp with alcohol wipes. They’ll measure and mark your head with a pencil to indicate where the electrodes should be placed. These areas on your head might be scrubbed with a gritty cream to clean the area and allow a better EEG reading.

From there, the technician will attach 10 to 20 electrodes to your head using a conductive gel. These electrodes will be connected by wires to a computer that will record the electrical activity of your brain as a graph.

Napping Periods

During the MSLT, you will be asked to nap several times throughout the day. During these naps, the EEG will continue to record your brain activity to monitor any changes in your sleep patterns, including REM sleep.

After the Test

Once the recording of your brain’s electrical activity is finished, the technician will detach the electrodes from your head. You might need to wash your hair to remove any remaining gel residue.

Is the EEG Test Painful?

The simple answer is no. You will not experience any pain during the EEG test. The EEG process is noninvasive. The electrodes do not create any sensations of pain in your head. If your scalp feels irritated while the technician is cleaning the electrode areas before the EEG, be sure to let them know.

Are There Any Side Effects of an EEG Test?

There are no side effects of an EEG test. You might notice some discoloration on your head where the electrodes were attached, due to irritation from the gel. This usually wears off within hours.

Speak With Your Doctor

It’s essential to communicate openly with your health care provider. Not everyone undergoing an evaluation for narcolepsy requires an EEG. An EEG is just one of the several tests for narcolepsy, and your doctor will determine if it’s the right step for you. Before undergoing the procedure, don’t hesitate to talk to your health care provider about any questions or concerns you might have about the EEG process. Understanding what to expect can help you feel more at ease.

Talk With Others Who Understand

MyNarcolepsyTeam is a social network for people with narcolepsy and their loved ones. On MyNarcolepsyTeam, more than 10,000 members come together to ask questions, give advice, and share their stories with others who understand life with narcolepsy.

Have you ever had an EEG to help diagnose narcolepsy? How did it go? Share your experience in the comments below, or start a conversation by posting on your Activities page.