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Narcolepsy is a chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep. People with narcolepsy often find it difficult to stay awake for long periods, regardless of the circumstances. This can lead to disruptions in daily activities.

History of Narcolepsy

Narcolepsy was first identified in the late 19th century. French neurologist Jean-Baptiste-Édouard Gélineau coined the term in 1880, combining the Greek words "narkē" (numbness) and "lepsis" (attack or seizure). Early descriptions focused on excessive daytime sleepiness and sudden muscle weakness (cataplexy), but the understanding of narcolepsy has evolved significantly since then.

Causes and Genetic Factors

  • Hypocretin Deficiency: Hypocretin (orexin) is a neurotransmitter that regulates wakefulness. Many people with narcolepsy, particularly type 1, have low levels of hypocretin due to the loss of neurons that produce it.

  • Genetic Component: While narcolepsy can run in families, it is not directly inherited in the way some genetic disorders are. Certain genetic variations, such as those in the HLA-DQB1 gene, increase susceptibility, but environmental factors are also crucial.

  • Autoimmune Hypothesis: It's believed that in some cases, the immune system mistakenly attacks hypocretin-producing cells, possibly triggered by infections or other environmental factors.

Symptoms

Excessive Daytime Sleepiness (EDS)

  • Description: A persistent, overwhelming sense of tiredness and an inability to stay awake during the day.
  • Impact: Can lead to lapses in attention and memory, affecting work, school, and daily activities.
  • Management: Short, scheduled naps can help alleviate symptoms temporarily.

Cataplexy

  • Description: Sudden, brief episodes of muscle weakness, often triggered by strong emotions.
  • Variability: Ranges from minor weakness, like drooping eyelids, to complete collapse.
  • Awareness: Individuals remain conscious during episodes.

Sleep Paralysis

  • Description: Temporary inability to move or speak while falling asleep or waking up.
  • Duration: Typically lasts a few seconds to a couple of minutes.
  • Experience: Can be frightening but is harmless.

Hypnagogic/Hypnopompic Hallucinations

  • Description: Vivid, often frightening hallucinations occurring at the transition between wakefulness and sleep.
  • Types: Can be visual, auditory, or tactile.
  • Context: Often occur with sleep paralysis.

Disrupted Nighttime Sleep

  • Description: Frequent awakenings, vivid dreams, and restless sleep.
  • Impact: Contributes to daytime sleepiness and fatigue.

Diagnosis

Polysomnogram (PSG)

Purpose: Conducted overnight to monitor sleep stages and detect abnormalities.

Parameters Monitored:

  • Brain Activity (EEG): Assesses sleep stages and detects unusual patterns.
  • Eye Movements (EOG): Helps identify REM sleep.
  • Muscle Activity (EMG): Detects muscle tone changes.
  • Heart Rate (ECG): Observes heart activity during sleep.
  • Breathing Patterns: Identifies potential breathing disruptions.

Multiple Sleep Latency Test (MSLT)

  • Purpose: Conducted the day after a PSG to assess daytime sleepiness.
  • Process: Consists of several short naps at two-hour intervals.

Measurements:

  • Sleep Onset Latency: Time taken to fall asleep.
  • REM Latency: Time between sleep onset and REM sleep initiation.

Treatment

Medications

  1. Stimulants:

  • Examples: Modafinil, armodafinil, methylphenidate.
  • Function: Promote wakefulness and reduce daytime sleepiness.

  1. Sodium Oxybate:

  • Function: Improves nighttime sleep quality and reduces cataplexy.
  • Administration: Taken in two doses, one at bedtime and another several hours later.

  1. Antidepressants:

  • Examples: SSRIs (e.g., fluoxetine), SNRIs (e.g., venlafaxine).
  • Function: Suppress REM sleep to manage cataplexy and related symptoms.

  1. Pitolisant and Solriamfetol:

  • Function: Target specific neurotransmitter systems to enhance wakefulness.

Lifestyle Modifications

  • Scheduled Naps: Regular, short naps can improve alertness.
  • Consistent Sleep Schedule: Helps stabilize the sleep-wake cycle.
  • Healthy Diet and Exercise: Supports overall health and sleep quality.
  • Avoidance of Alcohol and Caffeine: Reduces sleep disruption.

Treatment Duration

  • Ongoing Management: Narcolepsy is a lifelong condition, and treatment focuses on symptom control.
  • Regular Follow-ups: Necessary to adjust medications and strategies as needed for optimal symptom management.