How to Diagnose Narcolepsy

Narcolepsy patients experience excessive drowsiness and frequent attacks of sleep during the day. This affects normal daytime activities like school, work, social life etc. This chronic sleep disorder is related to the nervous system and is not a mental illness. It is the second most common cause of intense daytime sleepiness; the first being sleep apnea.

Besides excessive sleepiness, patients suffering from narcolepsy show symptoms like sudden loss of muscle tone, sleep paralysis, and dream-like hallucinations. The incidence of patients having all the symptoms is very low. Also, narcolepsy symptoms are not specific to it.

There are other medical conditions like sleep apnea, depression, bacterial/ viral infections, and chronic illnesses, that disturb regular sleep patterns producing similar symptoms. This makes its diagnosis difficult by simply looking at the symptoms. Therefore, diagnostic tests are used to confirm this disorder in patients.

The first step towards diagnosis of narcolepsy is a thorough physical examination of the patient. The doctor will inquire about the patient's personal and family's medical history, to figure out if there have been any cases of narcolepsy in the family earlier. Certain blood tests are also done to rule out other causes that can result in similar symptoms.

The patient may also be asked to maintain a sleep log for a few weeks, so that his sleep pattern and alertness can be analyzed. He may also be asked to wear an actigraph which is capable of measuring how much and when a person sleeps. The next step involves a few narcolepsy-specific tests that are carried out to confirm the disorder in the patient.

This test basically involves filling up a questionnaire by the patient. The doctor gives a questionnaire to the patient and asks him to answer eight questions using a scale from zero to three. This helps in analyzing the chances of the patient falling asleep during daytime activities like reading, watching television, sitting etc.

Maximum score of the questionnaire is 24. If the patient's score ranges between 0-10, it indicates normal daytime sleepiness. Any score above 10 or specifically, 18 and above, indicates high daytime sleepiness. Patients with such high scores are then prescribed further tests for diagnosis.

A polysomnography is carried out by sleep specialists who know how to conduct this test. The patient needs to stay overnight at a sleep center to undergo this study. In this test, the patient is required to sleep at night, with a number of electrodes and bands placed on different parts of the body.

Electrodes are placed on the face and scalp, and above the lip. Bands are placed around the chest and abdomen. An oxygen sensor is attached to a finger and other sensors are attached to the person's legs. 

Once the study begins, the following body functions are monitored -

• Brain waves
• Muscle tone
• Heart rate
• Movements in the abdomen and chest
• Airflow through nose and mouth
• Oxygen levels of the blood

During and after the test, the sleep specialist analyzes the test results and finally reports the findings.

This test is usually carried out the next day after the polysomnography is done. Again, electrodes are attached to various body parts of the patient and he is asked to take four or five, 20-minute naps after every 2 hours during daytime. The sleep-pattern is then recorded by the electrodes, mainly concentrating on the Rapid Eye Movement (REM) stage.

A normal person enters the REM stage only after 80-100 minutes of sleep, while a person with narcolepsy enters this stage within 20 minutes. The time taken to fall asleep is also monitored. A person with narcolepsy takes not more than five minutes to fall asleep in comparison to a healthy person who needs at least 10-15 minutes for the same.

This test is inaccurate, as it sometimes gives positive results even in healthy people. Narcolepsy is linked to an antigen. The doctor may prescribe this test to check the presence of this antigen in the patient's blood. Symptoms of narcolepsy are triggered by the presence of this antigen, as the body starts producing antibodies to protect itself from it.

Apart from these tests, the cerebrospinal fluid is sometimes tested for orexin and hypocretin levels, to confirm narcolepsy in patients. If a person feels excessively sleepy during the day, falls asleep while carrying out daily activities, faces difficulty in moving after waking up, and/ or is unable to hold up his/her head due to weakness in neck muscles.

It is better to go for narcolepsy screening. This problem may not appear severe, but imagine falling asleep while walking or driving, which can be dangerous. Currently, there is no cure for narcolepsy. But, identifying symptoms at the right time can help manage them so that the effect of this disorder on one's daily life can be minimized to a large extent.