What is Narcolepsy?
The exact cause of narcolepsy is not known. An abnormality in the chemistry regulating sleep and wakefulness in the brain is suspected, but not proven. Both genetic and environmental factors are believed to play a role in the development of this disorder.
All patients experience excessive daytime sleepiness (sleep attacks and persistent daytime drowsiness). Sleep attacks are short periods of sleep that occur many times a day, regardless of the amount or quality of sleep the night before.
They are often described as irresistible and may occur with or without warning when a person is driving, working, eating, talking, or engaging in any other activity. Most patients also experience persistent daytime drowsiness. Excessive daytime sleepiness is usually the first symptom of narcolepsy and often the most difficult symptom to control.
The severity of excessive daytime sleepiness varies; some patients may have many sleep attacks each day and others only one or two sleep attacks per day.
Cataplexy refers to sudden, brief episodes of muscle weakness or paralysis triggered by strong emotions such anger, laughter, surprise or anticipation. Just as nighttime REM (rapid eye movement) sleep is normally accompanied by skeletal muscle paralysis and strong emotions (dreaming); an intense emotion during the waking period can trigger instantaneous muscle weakness or paralysis. Although unable to move, the person remains conscious.
For some people, any strong emotion may trigger cataplexy, while others react to only certain specific emotions. Although most patients experience cataplexy, some patients never develop this symptom.
Hypnagogoic hallucinations are vivid, often frightening, dream-like images that occur when dozing or when falling asleep. Sometimes these images are so vivid that they are difficult to distinguish from reality.
Sleep paralysis refers to a temporary paralysis upon falling asleep or waking up. Episodes may last only a few seconds to minutes.
Frequent awakenings at night are common, but are not the cause of excessive daytime sleepiness in patients with narcolepsy.
How is Narcolepsy Diagnosed?
An overnight stay in a sleep laboratory is necessary to rule out other conditions such as sleep apnea, periodic leg syndrome, and upper airway resistance syndrome that cause can excessive daytime sleepiness.
A daytime nap study will be performed the next day to evaluate the severity of daytime sleepiness. A blood test is neither necessary or sufficient to make the diagnosis of narcolepsy.
How is Narcolepsy Treated?
There is no known cure for narcolepsy, but symptoms can be managed with medications. Stimulant medications are used to control sleep attacks and excessive daytime sleepiness. Since patients respond differently to different stimulants, if one drug causes side effects or fails to relieve excessive daytime sleepiness, a different compound should be tried. Some patients may also find that short, frequent naps help relieve daytime sleepiness, and all patients are encouraged to avoid sleep deprivation. Stimulant medications are no substitute for adequate sleep at night.
At present, there is no evidence that dietary adjustments, nutritional supplements, or exercise will improve daytime alertness. Caffeine and over-the-counter drugs have not been shown to be effective and are not recommended.
Small doses of antidepressant medications and other drugs that suppress REM sleep may be used to control cataplexy. Not all patients with cataplexy require medication. Some have infrequent episodes and others learn to avoid situations that trigger cataplexy. Although disrupted night time sleep is usually not treated, some patients may be treated with short-acting hypnotic medications or sedating antidepressants.
Unfortunately, improving night-time sleep in narcoleptic patients rarely improves their ability to stay awake during the day.
Medications used to manage Excessive Daytime Sleepiness
Name of Medication Usual Daily Dose Notes dextroamphetamine-sulfate (Dexadrine®, Dextrostat®, Dexadrine-SR®) 5-100 mg Variable duration of action, depending on whether using regular form or SR (sustained release) form of medication. Schedule II medication in the US, limited number of tablets can be prescribed at one time and prescription cannot be refilled.
Methamphetamine-HCl (Desoxyn®) 5-100 mg More potent than dextroamphetamine. Schedule II medication in the US, limited number of tablets can be prescribed at one time and prescription cannot be refilled. Methylphenidate-HCL (Ritalin, Ritalin-SR®) 10-100 mg Most frequently prescribed stimulant for treatment of narcolepsy in the US. Less potent than dextroamphetamine or methamphetamine.
Variable duration of action, depending on whether using regular form or SR (sustained release) form of medication. Can be used in combination with other stimulants. Schedule II medication in the US, limited number of tablets can be prescribed at one time and prescription cannot be refilled.
Modafinil (Provigil®) 200-800 mg Lower potency than dextroamphetamine or methamphetamine, fewest side effects of stimulant medications. Long duration of action. Schedule IV medication in the US, prescription can be refilled for up to six months without a new prescription. pemoline (Cylert®) 37.5-300 mg Less potent than other medications used to control daytime sleepiness.
Long duration of action. Schedule IV medication in the US, prescription can be refilled for up to six months without a new prescription. Can cause liver damage, patients taking this medication should have blood drawn regularly to evaluate their liver function.
Medications used to manage Cataplexy.
Name of Medication Usual Daily Dose Notes clonipramine (Anafranil®) 25-150 mg Very effective against cataplexy, used more frequently in Europe desimpramine (Norpramin®, Pertofran®) 25-100 mg More anticholinergic effects (dry mouth, blurred vision, constipation) than impramine fluoxetine (Prozac®) 20-60 mg Fewer side effects than other clonipramine, disimpramine, and impramine.
Less weight gain than with other antidepressants. May need higher doses to control cataplexy Impramine (Jaminime®, Tofranil®) 10-100 mg Some anticholinergic effects (dry mouth, blurred vision, constipation) than clonipramine, and desimpramine Protriptyline (Triptil®, Vivactil®) 5-60 mg Anticholinergic effects (dry mouth, blurred vision, and constipation) at high doses. Mild stimulant.
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