26 Feb Narcolepsy
BASIC CONCEPTS
Sleep study used in Diagnosis: Multiple Sleep Latency Test (MSLT)
Narcolepsy is a sleep disorder with irresistible episodes of daytime sleepiness, often in conjunction with disturbed sleep at night, cataplexy, sleep paralysis, and hypnagogic and hypnopompic hallucinations.
Cataplexy is a sudden reduction or loss of muscle tone, triggered by strong emotions, while maintaining consciousness.
Hypnagogic hallucinations are vivid hallucinations at sleep onset and hypnopompic hallucinations are vivid hallucinations at awakening.
Sleep paralysis is a transient generalized inability to move or speak when falling asleep or awakening.
CLASSIFICATION
The International Classification of Sleep Disorders (ICSD-3) recognizes 2 forms of narcolepsy.
- Narcolepsy type 1 (NT1), formerly called narcolepsy with cataplexy, is characterized by:
Cataplexy very low levels (≤ 110 pg/mL) of hypocretin 1 (also called orexin A) in cerebrospinal fluid severe but highly selective loss of hypocretin neurons
- Narcolepsy type 2 (NT2), formerly called narcolepsy without cataplexy, is characterized by absence of cataplexy normal levels of hypocretin 1 in cerebrospinal fluid some loss of hypocretin neurons, reported in only 10%-30% of patients.
Narcolepsy usually presents in children, adolescents, and young adults (aged 10-20 years) peaking in the second decade with average time from onset of symptoms to diagnosis 5-15 years.
Patients with narcolepsy are reported to have deficits in vigilance and sustained attention with slower reaction times and increased error rates and experiencing difficulty in performing demanding, monotonous, and prolonged tasks.
Narcolepsy can increase the risk for motor vehicle accidents.
EVALUATION
Patients often report history of ≥ 1 of the following:
- Excessive daytime sleepiness (EDS) occurring almost daily for at least 3 months with gradual or sudden onset of persistent daytime sleepiness resulting in difficulty focusing and staying awake and in deficits of attention feeling of sleepiness waxing and waning throughout day episodes recurring daily or almost daily patients feeling refreshed after full night’s sleep or brief nap but sleepiness returning after 1-2 hours.
- Involuntary episodes of falling asleep, which can occur at school, work, while driving, or when sedentary, resulting in poor daytime functioning.
- Cataplexy, described as follows: most episodes are triggered by strong emotions (laughter, surprise, fear, anger); partial cataplexy is characterized by slurred speech and sagging face with complete episodes, patients may slump to the ground fully conscious, at least at the beginning of attack, and remain immobile; hearing and auditory comprehension is preserved during attacks; children with cataplexy can have long-lasting periods of low muscle tone with wobbly gait and perioral movements such as grimacing and tongue protrusion attacks end suddenly with return of muscle tone without mental confusion or amnesia
- Sleep paralysis, described as follows:
- Total incapacity to move that occurs when falling asleep or when transitioning from sleep into wakefulness.
- Temporary inability to perform voluntary acts but consciousness is maintained.
- Ends abruptly after mental effort or with external sensory stimulation.
- May be accompanied by sensation of inability to breathe and varied hallucinations
- Hypnagogic and hypnopompic hallucinations: occur spontaneously when the patient is falling asleep or awakening. They are characterized by dreamlike, vivid, often disturbing visual hallucinations (complex auditory hallucinations or fixed delusions are rare).
- disturbed nocturnal sleep with frequent awakenings and parasomnia.
- fatigue or lack of energy.
ACCURATE DIAGNOSIS
Should be established for excessive daytime sleepiness including a thorough evaluation of possible causes of excessive daytime sleepiness or stablish a differential diagnosis.
In patients suspected with narcolepsy type 1
Perform lab overnight polysomnography (PSG) to rule out other conditions and confirm diagnosis of narcolepsy
Consider performing multiple sleep latency test (MSLT) to confirm diagnosis
Consider cerebrospinal fluid (CSF) analysis of hypocretin 1 as alternative to PSG and MSLT for diagnosis of narcolepsy type 1
In patients suspected with narcolepsy type 2
Perform lab overnight PSG to rule out other conditions and confirm diagnosis of narcolepsy
Consider performing MSLT to confirm diagnosis
REFERENCES
National Library of Medicine, or “Vancouver style” (International Committee of Medical Journal Editors): DynaMed Plus [Internet]. Ipswich (MA): EBSCO Information Services. 1995 – . Record No. 116132, Narcolepsy; [updated 2018 Mar 09, cited place cited date here]; [about 29 screens]. Available from http://www.dynamed.com/login.aspx?direct=true&site=DynaMed&id=116132. Registration and login required.