Narcolepsy - Causes

Causes

The exact cause of narcolepsy is not known, however, lack of production of Hypocretin - a sleep-regulating chemical in the brain has been implicated.

Narcolepsy is a brain disorder caused by the brain's inability to regulate sleep-wake cycles normally.

A sleep cycle is defined by a segment of non-rapid eye movement (NREM) sleep that comprises of four stages followed by a period of rapid eye movement (REM) sleep. A classic sleep cycle begins with NREM sleep which lasts about 100 - 110 minutes. It is followed by REM sleep which lasts about 80 - 100 minutes.

REM sleep is accompanied by bursts of Rapid Eye Movements and during this phase there is heightened brain activity associated with temporary paralysis of the muscles that control posture and body movements. REM sleep is otherwise referred to as the dream sleep as most of our dreams occur during this phase of sleep and the temporary muscle paralysis that occurs during this phase is a protective mechanism so that we do not act out our dreams.

Groups of neurons from specific regions in the brain interact to bring about the transition from NREM to REM. For most adults, a normal night's sleep lasts about 8 hours with four to six separate sleep cycles.

In the case of narcoleptic individuals the brain is not able to regulate the smooth transition of the sleep wake cycles, resulting in the patients directly entering REM without experiencing NREM. Researchers have discovered abnormalities in parts of the brain involved in regulating REM sleep.

Research continues to understand what causes this change in narcolepsy. The current hypothesis on narcolepsy implicates interplay between genetic and environmental causes. Some of the causative factors are listed below:

• Brain Chemicals:

Scientists believe that people with narcolepsy who begin to feel drowsy and then drop instantly into "dream sleep" may have imbalances in certain brain chemicals important in regulating sleep.In this regard, hypocretin, is a significant sleep regulating chemical that causes people to wake up and stay awake. It is now believed that the cells that produce the hypocretin chemical are destroyed or the cells, even if present, are unable to produce the chemical.

Hypocretin is found to be inadequate in victims of narcolepsy. A spinal tap from patients with nacrolepsy would reveal vary low levels of hypocretin in comparision to normal individuals.

• Abnormal gene:

Research continues to focus on an abnormal hypocretin gene that could possibly be responsible for narcolepsy. It has also highlighted the presence of different forms of the same gene in the region of chromosome 6 which may have a link with narcolepsy.

• Immune system:

It has been postulated that the body's immune system may be involved in mistakenly attacking hypocretin-producing cells in the brain (Autoimmune Disorder).

References:

1. Narcolepsy Fact Sheet - (http://www.ninds.nih.gov/disorders/narcolepsy/detail_narcolepsy.htm)
2. Narcolepsy - (http://www.mayoclinic.com/health/narcolepsy/DS00345)
3. About Narcolepsy - (http://en.wikipedia.org/wiki/Narcolepsy)