The incidence of narcolepsy is 0.2-1/1000 individuals. The first signs of narcolepsy (excessive daytime sleepiness) usually manifest in adolescence but are frequently unrecognized. Most patients are diagnosed as adults when cataplexy (sudden loss of voluntary muscle tone) occurs.
The classic tetrad of symptoms include
Excessive daytime sleepiness: Typically the patient complains of increased daytime sleepiness. In children this is typically ignored or considered secondary to poor sleep habits. This is usually the most debilitating of the features as the patient repeated naps or sleep phases during the day. In some cases the patient can have an automatic or semiautomatic behavior in which they appear to be continuing a task while in actual fact, they are asleep. The task usually does not get done appropriately.
Hypnagogic hallucinations: This is a condition in which the patient relates a history of having episodes wherein the patient goes to sleep, and promptly goes into a dream state, wakes up abruptly and has difficulty differentiating between wakefulness and dream events.
Sleep paralysis: In this condition, the patient has episodes in which they awake from sleep and are unable to move. The sensation typically only lasts a few seconds. Sleep paralysis is as a result of REM related atonia continuing into wakefulness, with an associated inability to move skeletal muscles
Cataplexy: This is a condition in which the patient has a sudden loss of muscle tone. It is typically associated with a strong emotional event (laughter, anger, happiness, extreme sadness). It may affect facial muscles and affect speech. There is no loss of consciousness.
A fifth manifestation is poor night time sleep: Patients with narcolepsy tend to report fragmented and poor night time sleep which runs counter to the fact that they have excessive daytime sleepiness
Several teenage patients with narcolepsy have mood disorders, mostly depression at the time of diagnosis. Occasionally patients are diagnosed following negative evaluations by cardiology and neurology for suspected seizures and near syncopal events.
- Idiopathic hypersomnia
- Bipolar disorder
- Unexplained falls
- Partial complex seizures
- Near syncopal attacks
- The patient is more likely to have:
- poor or falling school grades (>50%)
- Recurrent depression
- Obsessive thoughts
- Recurring suicidal thoughts
- Reduced job performance, earnings, promotions.
- Required psychotherapy
Cataplexy is diagnostic for narcolepsy in the presence of excessive daytime somnolence.
Multiple sleep latency test with 2 sleep onset REM episodes in a 4-5 nap series is also diagnostic or Early onset REM on an overnight polysomnography with 1 sleep onset REM on the MSLT done the following morning.
HLA typing alone does not confirm diagnosis in the absence of either cataplexy or a multiple sleep latency test and is not required for the diagnosis of narcolepsy
CSF hypocretin levels are helpful but not required for diagnosis.
Patients require an evaluation by a sleep specialist and this should include a full history and physical examination, completion of a subjective sleepiness scale (Epworth sleepiness scale), maintenance of sleep logs, and performance of an overnight sleep study and a multiple sleep latency test.
Multiple sleep latency test:
A multiple sleep latency test is used for the diagnosis of narcolepsy and for differentiation from idiopathic hypersomnia.
The test is done following a diagnostic sleep polysomnogram and involves 4-5 naps 2 hours apart.
The patient is allowed 20 minutes to fall asleep and 15 minutes to sleep if sleep is achieved.
Parameters recorded include:
Time of lights out
REM presence and latency
A sleep latency of < 8 mins is abnormal and < 5 minutes is pathologic. Between 8-10 minutes requires a correlation with patient functioning. > 10minutes is normal.
<2 sleep onset REM in 5 naps is normal.
2 or more sleep onset REM diagnostic for narcolepsy
Maintenance of wakefulness test:
A maintenance of wakefulness test is used to assess the efficacy of treatment of excessive daytime somnolence.
The test involves 4-5 sessions 2 hours apart.
The patient is placed in a chair in a dark and quiet room for 40 minutes and asked to stay awake
The treatment of narcolepsy must target the various facets of the condition
Improved sleep hygiene, addition of a daytime nap, education of all parties involved with the patient including, parents, teachers, supervisors.
Excessive daytime sleepiness management:
- Somnolytic agents: Modafinil (Provigil) 200-400mg/day, Armodafinil (Nuvigil) 150-250mg/day
- Psychostimulants: Amphetmine-Dextroamphetamine salts (Adderall, Adderall XR) 5-50mg/day, Methylphenidate (Ritalin). 5-50mg/day
- Sodium Oxybate (Xyrem) 4.5-9gm/night
- Sodium Oxybate (Xyrem) 4.5-9gm/night
- SSRI’s: Sertraline (Zoloft), Fluoxetine (Prozac) 10-80mg/day
- SNRI’s: Venlafaxine (Effexor) 75-375mg/day
- TCA’s: Clomipramine (Anafranil) 10-200mg/day, Protriptyline (Vivactil)