narcolepsy
NARCOLEPSY

Narcolepsy is a chronic neurologic sleep disorder wherein the patient have excessive daytime sleepiness and rapid eye movement sleep is dysregulated.

It affects 1 in 1000 individuals, with prevalence of about 0.04% of general population.
The exact cause remains unclear.
Studies suggest a combination of genetic predisposition, abnormal neurotransmitter functioning and abnormal immune modulation.
Symptoms include excessive daytime sleepiness, cataplexy, sleep paralysis, sleep-related hallucinations, automatic behavior, fragmented nocturnal sleep and insomnia.

Definition

  • Narcolepsy is a chronic neurologic sleep disorder, affecting 1 in 2000 individuals, with prevalence of about 0.04% of general population
  • Onset at any age, but usually within the first 2 decades of life with mean age of onset of 16
    • Rare onset at older adults
  • Affects both gender but with slight preponderance in males

Etiology

  • Exact cause of narcolepsy remains unclear
  • Studies suggest a combination of genetic predisposition, abnormal neurotransmitter functioning, & abnormal immune modulation
    • Variation on human leukocyte antigen (HLA) genes, specifically HLA-DR2 & DQB1*0602, on chromosome 6
    • Decreased production of hypocretin secondary to an autoimmune response caused by the HLA abnormalities
      • Hypocretin is a neurotransmitter involved in the regulation of appetite, energy, homeostasis, & sleeping patterns
    • Hypoactive monoaminergic system
  • There are current observations of an association of group A streptococcal throat & H1N1 infections

Signs and Symptoms

Excessive daytime sleepiness

  • Present in all narcoleptic patients
  • Primary symptom of narcolepsy
  • Strong, almost irresistible urge to fall asleep, nod or doze off at inappropriate times whether in sedentary situations or during physically demanding activities
  • Patients feel sleep-deprived & have chronic daytime fatigue
  • Sleep episodes can occur several times a day & may last from a few seconds to several minutes
  • Patients wake up feeling refreshed after the sleep episode
  • There is a refractory period of 1 to several hours before the next episode occurs

Cataplexy

  • Seen in more than half of narcoleptic patients
  • An abrupt & reversible partial or generalized loss of bilateral voluntary muscle tone
  • May not appear until weeks or months after onset of excessive daytime sleepiness
  • Usually a response to strong emotion (eg laughter, anger, fear)
  • Manifestations depend on the muscles affected (eg diplopia, blurred vision, head drooping, sagging jaw, facial sagging, dysarthria, knee buckling, sensation of weakness to partial or complete paralysis)
  • Patient remains conscious & aware of surroundings during the cataplexy attack
  • Duration of attack is variable lasting for 30 seconds to 2 minutes
  • Its presence strongly suggests the diagnosis of narcolepsy
  • Pathognomonic sign for narcolepsy

Sleep paralysis

  • Occurs in 33% of narcoleptic patients
  • Inability to move while falling asleep or during awakening (eg suddenly unable to move the extremities, speak, or even breathe deeply)
  • Patient is fully aware of what is happening during the attack & can recall the events clearly
  • Brief & benign episodes lasting for a few minutes & resolves spontaneously
  • Often associated with hypnagogic hallucinations

Sleep-related hallucinations

  • Abnormal vivid auditory or visual hallucinations that occur while falling asleep (hypnagogic hallucinations) or during awakening (hypnopompic hallucinations)
  • Usually unpleasant experience associated with fear, major threat, or feeling of dying
  • Combined elements of dream sleep & consciousness & are often bizarre or disturbing to the patients
  • Tactile or multisensory hallucinations may also occur

Other symptoms

  • Automatic behavior
    • Absent-minded behavior or speech which is nonsensical & often not remembered by the patient because of extreme sleeping
  • Fragmented nocturnal sleep (eg frequent awakenings during the night/disturbed nighttime sleep)
  • Insomnia
  • Vivid, bizarre & delusional dreams or may have nightmares
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