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
Editor's Recommendations
Most Read Articles
Dr. Melvin Wu, 01 Dec 2013

GPs can be crucial to identifying and helping codeine addicts get professional help to kick their habit.

Elvira Manzano, 01 Dec 2013

Neurogenesis, the birth of neurons or nerve cells in the hippocampus, continues during adulthood, new research suggests.

24 Aug 2016

Roshini Claire Anthony spoke with Adjunct Associate Professor Gamaliel Tan, head and senior orthopaedic consultant at Ng Teng Fong Hospital in Singapore, on how GPs can help diagnose and treat lower back pain.

Dr. Andrea Luk, Dr. Doris Chan, 13 Sep 2016

A 40-year-old woman who underwent recent resection of a nonfunctional pituitary macroadenoma and radiotherapy to the pituitary gland complained of excessive thirst, polydipsia and polyuria.