Sleep disorders

(I) Cataplexy and narcolepsy: Excessive daytime sleepiness, including episodes of irresistible sleepiness combined with sudden muscle weakness are the hallmark signs of narcolepsy. The sudden muscle weakness seen in narcolepsy may be elicited by strong emotion or surprise. Symptoms are narcoleptic sleep attacks, cataplexy, sleep paralysis, hypnagogic hallucinations (at the beginning of sleep), hypnopompic hallucinations (upon awakening) disturbed night sleep and automatic behavior. Onset of the disorder is mostly in adolescence. Sleep attacks can happen in inappropriate circumstances like while talking, walking, sitting etc. and last for about 30 mins. It affects school and work performance. Cataplexy is the sudden loss of tone in voluntary muscles, triggered by anger, rage, laughter etc. with complete return of consciousness in a few seconds to minutes. Secondary causes of narcolepsy-cataplexy are strokes, encephalitis, midbrain tumors, cerebral trauma etc.

(II) Idiopathic hypersomnia: It presents with excessive daytime sleepiness and either normal or prolonged nighttime sleep. Sleep is not refreshing. There is no history of snoring, cataplexy or nighttime awakenings.

(III) Insomnia: It is the most common sleep disorder. Patients present with difficulty initiating and maintaining sleep. Early morning awakening, excessive daytime sleepiness and functional impairment is seen. Patients have symptoms more than 3-4 times/week for more than a month. Primary insomnia is idiopathic. Secondary insomnia is seen due to acute stress, alcohol or drug abuse, psychiatric disorders etc.

(IV) Circadian rhythm sleep-wake disorder: They are caused by disturbances in the body clock and sleep-wake cycle due to jet lag, night shifts, diseases like Alzheimer’s, Parkinson’s disease, head trauma or encephalitis. It causes insomnia, excessive sleepiness, malaise, irritability, depression and increased risk of cardiovascular and metabolic disorders.

(V) Primary sleep terror disorder and nightmares: Sleep Terrors happen in NREM sleep. It is seen in young kids aged 5-7 years. They are characterized by sudden arousal from sleep, intense fear, screaming or crying, autonomic manifestations like tachycardia, tachypnea, sweating and amnesia of the event on waking up. They are often precipitated by sleep deprivation, fatigue and sedative-hypnotics. Sleepwalking is sometimes associated.

Nightmares occur during REM sleep and are commonly seen in children. They are characterized by frightening dreams, followed by awakening from sleep and vivid memory of the event. They can be precipitated by medications such as antiparkinsonian drugs, beta blockers and anticholinergics.

(VI) Sleepwalking or somnambulism: It is seen in slow wave sleep. It is more common in children aged 5-12 years, and is sometimes seen in adults. Motor activity like walking around the house, driving, eating or rarely, acts of violence may be associated with sleepwalking. There is no memory of the event. Sleep deprivation often precipitates sleepwalking.

(VI) REM sleep behavior disorder: It is a disorder seen in elderly individuals, in REM sleep, characterized by abnormal motor activities during sleep such as acting out dreams, violent behavior etc. It is seen more commonly in neurodegenerative disorders like Parkinson’s disease, Lewy body dementia, supranuclear palsy etc. It may sometimes be caused by drugs like SSRIs, TCAs, anticholinergics and by alcohol. Reduced presynaptic dopamine transporter and postsynaptic D2 receptors have been found in this disorder.

(VII) Restless legs syndrome or RLS: RLS is characterized by an unpleasant “creeping” sensation, often feeling like it is originating in the lower legs, but often associated with aches and pains throughout the legs. This often causes difficulty initiating sleep and is relieved by movement of the leg, such as walking or kicking. Abnormalities in the neurotransmitter dopamine have often been associated with RLS.

(VIII) Obstructive sleep apnea: It is characterized by recurrent episodes of upper airway collapse during sleep, resulting in airway obstruction and apnea-hypopnea. It is more common in obese, middle-aged males and in postmenopausal females. It presents with snoring, daytime sleepiness, choking, shaking or jerking in sleep and daytime sleep attacks when the individual is relaxing. It may lead to hypertension, polycythemia, cardiac arrhythmias, metabolic syndrome, impotence, headaches and heart failure.