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| NARCOLEPSY |
 | Complaint of sleepiness or sudden muscle weakness |
| Recurrent daytime naps or lapses into sleep that occur almost daily |
|
| Overview |
| Male = female |
| Prevalence: about 1 in 4000 in North America and Europe (Hublin et al
1994) |
| Onset: 20 to 40 years old, rarely before age 5 or after age
60. |
| Polysomnography: short sleep latency, short REM sleep latency. |
| Multiple Sleep latency test: sleep latency < 5 minutes; 2 or more
sleep-onset REM periods. |
|
| Clinical symptoms |
| Excessive sleepiness:
 | Most common initial symptom |
| Sleepiness is similar to those caused by sleep
deprivation: most apparent in boring, sedentary situations and is partially relieved
by movement. |
| No amount of nighttime or daytime sleep produces
full alertness. |
|
| Cataplexy:
| Episodic weakness without altered consciousness lasting seconds to
minutes. |
| Precipitated by excitement or emotion: may occur several times daily or
less than once per month. |
| Laughter is the most common precipitant. Anger, embarrassment, excitement, and other forms of emotion also can
induce it. |
| Severe attacks produce complete paralysis of striated muscles, but
respiratory muscles are spared. |
| Twitching around the face or eyelids may accompany the weakness. |
| Milder attacks are common: sagging of the face, eyelids, or jaw;
dysarthria; momentary head drop; buckling of the knees; or even just a sensation of
weakness. |
| Consciousness is preserved at the onset but prolonged episodes may be
associated with auditory, visual, or tactile hallucinations and may lead directly into REM
sleep. |
| Cataplexy usually develops within a few months or years of the onset of
sleepiness, about 10-15% do not have cataplexy until 10-40 years after the onset of
sleepiness. |
|
| Sleep paralysis: last a few seconds or minutes of inability to move
during sleep onset or upon awakening -- occurs in the majority of narcoleptics. |
| Hypnagogic hallucinations: occur during transitions between sleep and
wakefulness and may accompany sleep paralysis or occur independently.
| Visual dreamlike hallucinations: someone standing over the bed,
threatening to enter the house is common. |
| Differ from dreams because some awareness of the surroundings is
preserved. |
|
| Memory problem: up to 50% of patients, probably caused by drowsiness with impaired attention and concentration. |
| Diplopia and blurred vision, also common complaints, are probably due to
failure of fusion induced by drowsiness. |
|
| Differential
Diagnosis |
| Idiopathic hypersomnia:
| a related variant |
| Excessive sleepiness: prolonged sleep periods and long unrefreshing naps |
| Not accociated with REM sleep abnormalities or cataplexy |
| Polysomnography: sleep latency < 10 min; normal REM sleep latency; normal or prolonged sleep |
| MSLT: sleep latency < 10 minutes; < 2 sleep-onset REM periods |
|
| Excessive daytime sleepiness (hypersomnia)
| Sleep apnea syndrome (including upper airway resistance syndrome) |
| Periodic limb movement disorder |
| Insufficient sleep syndrome |
| Circadian rhythm disorders |
| Sedating medications |
| Withdrawal from stimulants |
| Organic hypersomnias due to thalamic infarction, encephalitis, encephalopathy,
tumor. |
| Idiopathic hypersomnia |
| Pseudo-hypersomnia
 | Fatigue, tiredness, apathy, or weakness associated with medical and psychiatric disorders |
| Malingering (to obtain stimulants) |
|
|
| Short onset REM sleep periods
| Sleep apnea syndrome |
| Endogenous depression |
| Circadian rhythm disorders |
| Drug or alcohol withdrawal |
| Structural brain lesions |
| Periodic limb movement disorder |
|
|
| Management |
| Patient and family education |
| Importance of good sleep hygiene. |
| One to three 10-60 minute naps daily |
| Risks associated with sleepiness while driving and in the workplace |
| Adequate sleep at night is important, sleep deprivation aggravate
symptoms. |
|
| Medications for sleepiness |
|
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| Medications for cataplexy and sleep paralysis. |
| Tricyclic antidepressants: Effective in about 80% of patients. Tolerance
may develop requiring gradual withdrawal followed by a two-week drug holiday to restore
efficacy. Abrupt withdrawal can lead to a rebound increase in cataplexy, or even status
cataplecticus lasting for several hours or days.
| Protriptyline (Vivactil) 5-30 mg qd |
| Imipramine (Tofranil) 50-200 mg qd |
| Clomipramine (Anafranil) 10-200 mg qd |
| Nortriptyline (Pamelor) 50-200 mg qd |
|
| Fluoxetine (Prozac) 20- 80 mg qd |
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| Further reading & references |
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