COMMON SLEEP DISORDERS
Narcolepsy Or Excessive Day time sleep:
Narcolepsy is a clinical syndrome of daytime sleepiness, cataplexy (sudden bilateral loss of muscle tone), hypnagogic hallucinations, and sleep paralysis. Only one-third of patients will have all of these classical findings.
EPIDEMIOLOGY: People with narcolepsy are typically classified as having either narcolepsy type 1 (narcolepsy with cataplexy) or narcolepsy type 2 (narcolepsy without cataplexy). Narcolepsy type 1 is estimated to have a prevalence of 25 to 50 per 100,000 people, the incidence rate is highest in the second decade, and the disorder is equally common in men and women. There are definite cases of familial clustering. The risk of narcolepsy in first-degree relatives of patients is 10–40 times higher than in the general population. The onset is frequently associated with nonspecific environmental factors, such as head trauma, stroke, and change in the sleep-wake cycle. Moreover, recent studies have shown an association between streptococcal infection and HIN1 vaccination. Most people with narcolepsy are DQB1*0602 positive but this finding is not specific because the haplotype also occurs in 30 percent of healthy Americans.
ETIOLOGY: Narcolepsy Type 1 results from the loss of the neuropeptides orexin (hypocretin), which is a dorsolateral hypothalamic neuropeptide that function in the promotion of wakefulness and in regulating the sleep-wake cycles, and its deficiency could lead to malfunctioning of these systems excessive daytime sleepiness.
Secondary narcolepsy: lesions of the posterior hypothalamus and midbrain can cause narcolepsy. Tumors, vascular malformations, and strokes have all been reported to cause secondary narcolepsy, most likely due to direct injury to the orexin neurons or their projections
Clinical presentation:
1-Daytime sleepiness: all patients with narcolepsy have chronic sleepiness. They are prone to fall asleep throughout the day, often at inappropriate times. The sleepiness may be so severe that patients with narcolepsy can doze off with little warning; these episodes are commonly referred to as "sleep attacks." Sleepiness associated with narcolepsy usually improves temporarily after a brief nap, and most patients feel rested when they awake in the morning.
2-Cataplexy: it is emotionally triggered transient muscle weakness. Most episodes are triggered by strong emotions such as laughter, joking, excitement, anger, or grief in some individuals. Cataplexy develops within three to five years of the onset of sleepiness in 60 percent of people with narcolepsy. Muscle weakness is often partial, affecting the face, neck, and knees. Severe episodes can induce bilateral weakness or paralysis, causing the patient to collapse. Sometimes, the weakness can have an atypical appearance with facial tremor, or tongue protrusion, especially in children. Consciousness remains intact during cataplexy, and the weakness usually resolves in less than two minutes.
3-Hypnagogic hallucinations: these are vivid, often frightening visual, tactile, or auditory hallucinations that occur as the patient is falling asleep. They probably result from a mixture of wakefulness and the dreaming of rapid eye movement (REM) sleep. Hypnopompic hallucinations are similar hallucinations that occur upon awakening; they can also occur in narcolepsy but are less common.
4-Sleep paralysis: Sleep paralysis is the complete inability to move for one or two minutes immediately after awakening. It may also occur just before falling asleep. Episodes of sleep paralysis can be frightening because the immobility may be accompanied by hypnopompic hallucinations or a sensation of suffocation. Sleep paralysis can be distinguished from cataplexy because sleep paralysis occurs upon awakening, while cataplexy is triggered by positive emotions. Episodes of sleep paralysis are common in patients with narcolepsy but are not specific to the diagnosis. Hypnagogic hallucinations and sleep paralysis can also occur as isolated phenomena, often precipitated by insufficient sleep, circadian rhythm sleep disorders, obstructive sleep apnea, and anxiety. They can also occur as a rebound phenomenon in patients who abruptly stop taking REM sleep-suppressing substances (eg, alcohol, amphetamines, and antidepressants)
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