Secondary narcolepsy is a rare sleep disorder that occurs due to brain damage, specifically to the hypothalamus region. This part of the brain regulates the sleep-wake cycle.

People with secondary narcolepsy experience the typical symptoms of narcolepsy. However, they may also have other neurological problems and sleep for long periods of time, sometimes for more than 10 hours a night.

This article provides an overview of secondary narcolepsy, including its causes, symptoms, diagnosis, and treatments.

A mattress leaning against a wall outside.Share on Pinterest
thenakedsnail/Getty Images

Secondary narcolepsy is a sleep disorder that occurs due to brain damage. It develops when the hypothalamus, which manages sleeping and waking, develops lesions. The hypothalamus is located deep inside the brain, near the brain stem.

This type of narcolepsy can occur after a traumatic brain injury (TBI). It can also happen due to damage from other injuries or medical conditions.

The symptoms of secondary narcolepsy are similar to other types of narcolepsy. However, they can be more severe, depending on the nature of the brain injury.

Common symptoms include:

In addition to these symptoms, people with secondary narcolepsy may have other neurological symptoms.

The cause of secondary narcolepsy is an injury to the hypothalamus. This may occur if a person has experienced a head injury, though other things can also cause damage to this region of the brain. They include:

These injuries disrupt the functioning of the hypothalamus, resulting in secondary narcolepsy symptoms.

Secondary narcolepsy occurs because of damage to the hypothalamus. Primary narcolepsy does not. Scientists are less sure what causes primary narcolepsy, though a combination of autoimmunity and genetics may play a role.

Doctors divide narcolepsy into two categories based on a person’s symptoms. People with type 1 narcolepsy have excessive sleepiness and episodes of sudden muscle weakness, or cataplexy. A person with this type may also have hallucinations, sleep paralysis, or insomnia.

Type 2 narcolepsy does not cause cataplexy and is often less severe than type 1.

People with secondary narcolepsy may have symptoms that more closely resemble type 1 or type 2.

When the condition is primary, there is no obvious brain damage. Instead, people with type 1 narcolepsy typically have a low level of a chemical known as hypocretin. This chemical helps to maintain wakefulness and regulates sleep-wake cycles.

Researchers believe primary narcolepsy with cataplexy may be the result of the immune system attacking healthy cells that make hypocretin, leading to a low level of the chemical. The cause of primary narcolepsy without cataplexy is unclear, as people with type 2 tend to have a typical hypocretin level.

The below table compares the symptoms of each type of narcolepsy:

Primary narcolepsy type 1Primary narcolepsy type 2Secondary narcolepsy
Symptomscataplexyno cataplexyvaries, though often includes additional symptoms
Severitymore severeoften less severeoften more severe
Hypocretin levellowoften typicalvaries

Doctors typically conduct a physical exam and review the person’s medical history to diagnose secondary narcolepsy.

They may use imaging studies, such as an MRI or CT scan, to detect the underlying cause of secondary narcolepsy and rule out other possible causes.

A doctor may also recommend polysomnography, or a sleep study, to measure the person’s sleep patterns and confirm their diagnosis. This involves spending the night in a laboratory, where doctors monitor brain activity and movement during sleep.

Secondary narcolepsy can look similar to other sleep disorders, such as primary narcolepsy or obstructive sleep apnea. Doctors may find it challenging to diagnose, and a person may wait years before they receive an accurate diagnosis.

If a person’s medical history and timeline of symptoms fit with this diagnosis, or they have distinctive symptoms that are not common in primary narcolepsy, a doctor may diagnose secondary narcolepsy.

Learn more about how doctors diagnose narcolepsy here.

Treatment for secondary narcolepsy may involve addressing the underlying cause of the disorder. This could include surgery to remove a tumor or medications to treat an infection. If there is a treatable underlying cause, the symptoms may resolve.

However, this is not always the case. If a person has a TBI with lasting effects, the symptoms may persist.

Doctors may recommend lifestyle changes and medications to manage the disorder. This could involve:

  • avoiding caffeine late in the day
  • stopping or reducing alcohol consumption
  • trying to stick to a consistent sleep schedule
  • reducing stress
  • getting regular exercise, though not in the hours before bedtime

Medications may vary depending on the person’s unique circumstances. Doctors may recommend sodium oxybate to those with cataplexy. They may also suggest certain antidepressants or stimulants.

Learn more about treatment options for narcolepsy.

Secondary narcolepsy is a sleep disorder that occurs when damage occurs in the hypothalamus, the area of the brain responsible for regulating sleep-wake cycles. This may occur following a TBI, stroke, tumor, or infection.

The main symptom is excessive daytime sleepiness. People may also experience sudden muscle weakness, hallucinations, sleep paralysis, and insomnia.

Diagnosis may involve imaging studies to look for underlying causes and sleep studies to evaluate sleep patterns.

Treatment for secondary narcolepsy may involve addressing the underlying cause and making lifestyle changes, such as avoiding caffeine and alcohol. Medications such as sodium oxybate, stimulants, or antidepressants may also help manage symptoms.