Sleep disorders encompass a wide range of conditions beyond the common categories of insomnia and sleep apnea. Parasomnias involve abnormal behaviors or experiences during sleep. Narcolepsy involves pathological sleepiness with REM sleep dysregulation. Restless legs syndrome and periodic limb movement disorder affect sleep through sensory and motor disturbances.

Person relaxing and sleeping peacefully in bed — Sleep disorders encompass over 80 recognized conditions including insomnia, sleep apnea, restless legs syndrome, parasomnias, and narcolepsy. Source: Unsplash.

Parasomnias

Parasomnias are undesirable physical experiences or behaviors that occur during entry into sleep, within sleep, or during arousal from sleep. They are classified by the sleep stage in which they occur.

NREM parasomnias occur during slow-wave sleep (N3) and typically in the first third of the night. They are more common in children (30% experience at least one episode) and usually resolve by adolescence. Episodes involve automatic behavior with no conscious awareness, unresponsiveness to external stimuli, and no dream recall (there may be fragmentary imagery but no full dream narrative). The patient is confused and disoriented if awakened during an episode. There is typically amnesia for the event the next morning.

Confusional arousals are the mildest NREM parasomnia — the individual sits up in bed, appears confused and disoriented, and may mumble or speak incoherently, with episodes lasting 5-15 minutes. They are most common in young children and usually resolve spontaneously.

Sleepwalking (somnambulism) involves getting out of bed and walking with reduced awareness. Complex behaviors may occur (opening doors, dressing, leaving the house, driving). The eyes are typically open with a blank stare. Sleepwalking is usually benign but can be dangerous — remove objects that could cause injury, secure doors and windows, avoid sleeping on upper bunk beds. Never wake a sleepwalker abruptly (this may cause extreme confusion or aggression) — gently guide them back to bed.

Sleep terrors (pavor nocturnus) involve sudden arousal from slow-wave sleep with a piercing scream or cry, intense fear (tachycardia, tachypnea, sweating, dilated pupils), inconsolability, and no dream recall. Episodes last 1-10 minutes. They are distinct from nightmares (which occur during REM sleep, involve vivid dream recall, and the person is fully alert upon waking). Sleep terrors peak at age 5-7 and typically resolve by adolescence.

Management of NREM parasomnias includes reassurance and safety precautions for mild, infrequent episodes. Scheduled awakening (waking the child 15-30 minutes before the typical episode time, then allowing them to return to sleep) is effective for frequent episodes. For severe or dangerous episodes, low-dose clonazepam (0.5-1 mg at bedtime) or tricyclic antidepressants are sometimes used. Identifying and treating triggers (sleep deprivation, stress, fever, alcohol, medications) is essential.

REM sleep behavior disorder involves loss of normal REM atonia, causing patients to act out their dreams physically. Patients may punch, kick, leap out of bed, or vocalize. The eyes remain closed. The patient can usually recall the dream content upon waking. RBD is strongly associated with neurodegenerative disorders — 50-80% of patients with idiopathic RBD develop a synucleinopathy (Parkinson disease, dementia with Lewy bodies, or multiple system atrophy) within 10-15 years. RBD can also be induced by medications (SSRIs, SNRIs) or associated with narcolepsy. Treatment: clonazepam 0.5-2 mg at bedtime (effective in 90% of patients — suppresses REM without eliminating atonia through GABAergic mechanisms) or melatonin 3-12 mg (safer alternative, especially in older adults with dementia risk). Safety precautions include removing sharp objects from the bedroom, padding corners, placing the mattress on the floor, and separating the bed partner if necessary.

Nightmare disorder involves recurrent, extended, highly dysphoric dreams that awaken the individual from REM sleep. The person is alert upon waking and can recall the detailed dream narrative. Nightmares are common in the general population (5-8% report frequent nightmares) and highly prevalent in PTSD (50-70%). Treatment: image rehearsal therapy (rehearsing a rescripted, non-threatening version of the dream during the day) reduces nightmare frequency and intensity. Prazosin (1-10 mg at bedtime) is effective for trauma-related nightmares.

Narcolepsy

Narcolepsy is a chronic neurologic disorder of hypocretin deficiency and REM sleep dysregulation characterized by excessive daytime sleepiness and REM sleep phenomena intruding into wakefulness.

Type 1 narcolepsy (narcolepsy with cataplexy) is caused by autoimmune destruction of hypocretin-producing neurons in the lateral hypothalamus. Hypocretin levels in cerebrospinal fluid are low (under 110 pg/mL). Associated with the HLA-DQB1*0602 haplotype (90% of type 1 patients). Type 2 narcolepsy (narcolepsy without cataplexy) has normal hypocretin levels and no known autoimmune basis.

The five core symptoms (the narcolepsy pentad) include excessive daytime sleepiness (universal) — irresistible sleep attacks with refreshing short naps; cataplexy (60-75% of type 1) — sudden bilateral loss of muscle tone triggered by strong emotions (laughter, surprise, anger), ranging from slight facial droop to complete collapse, with preserved consciousness; hypnagogic/hypnopompic hallucinations (40-60%) — vivid, often frightening dream-like experiences at sleep onset or upon awakening; sleep paralysis (30-50%) — inability to move or speak for seconds to minutes upon falling asleep or waking, often accompanied by hallucinations; and fragmented nighttime sleep (50-80%) — frequent awakenings and poor sleep quality despite excessive daytime sleepiness.

⚠ Clinical Correlation

Diagnosis requires polysomnography (to rule out other causes of sleepiness) followed by a multiple sleep latency test (MSLT). The MSLT measures the tendency to fall asleep in quiet conditions: five 20-minute nap opportunities at 2-hour intervals. Mean sleep latency under 8 minutes plus 2 or more sleep-onset REM periods (SOREMPs) is diagnostic. CSF hypocretin measurement (less than 110 pg/mL) confirms type 1. Treatment: modafinil or armodafinil (first-line for daytime sleepiness — promotes wakefulness without the abuse potential of amphetamines), amphetamine/stimulants (dextroamphetamine, methylphenidate — second-line), sodium oxybate (gamma-hydroxybutyrate, GHB) — improves nighttime sleep and reduces cataplexy and daytime sleepiness, approved for both type 1 and type 2, highly controlled. Cataplexy treatment: venlafaxine (SNRI — suppresses REM sleep and cataplexy), sodium oxybate, or pitolisant (histamine H3 receptor inverse agonist — promotes wakefulness and reduces cataplexy). Scheduled naps (15-20 minutes, 2-3 times daily) are an important behavioral strategy.

Restless Legs Syndrome

RLS (Willis-Ekbom disease) is a sensorimotor disorder characterized by an irresistible urge to move the legs, usually accompanied by uncomfortable sensations (creeping, crawling, pulling, aching, tingling, burning). Symptoms begin or worsen during rest or inactivity; are partially or totally relieved by movement (walking, stretching, jiggling legs); occur predominantly in the evening or night; and are not explained solely by another medical or behavioral condition (iron deficiency, pregnancy, neuropathy, medications making RLS worse).

RLS affects 5-10% of adults (2-3% moderate to severe). It is familial in 50-60% of cases (autosomal dominant pattern with variable penetrance, associated with BTBD9, MEIS1, and MAP2K5 gene variants). Secondary causes include iron deficiency (serum ferritin under 75 ng/mL — first step in evaluation), pregnancy (20-30% of pregnant women, especially third trimester, resolves after delivery), end-stage renal disease (20-40% of dialysis patients), and medications (antihistamines, SSRIs, SNRIs, antipsychotics, dopamine antagonists, caffeine, alcohol, nicotine).

Treatment: the first step is checking and correcting iron deficiency (ferritin target over 75 ng/mL). Mild to moderate RLS can be treated with non-pharmacologic approaches (avoid alcohol, caffeine, and nicotine before bed; moderate exercise; stretching; massage; hot or cold packs; compression stockings). First-line pharmacotherapy for moderate to severe RLS is alpha-2-delta ligands: gabapentin (300-1,800 mg) or pregabalin (75-300 mg), taken 1-2 hours before bedtime. These are effective and do not cause augmentation (worsening of symptoms with treatment, the main problem with dopamine agonists). Dopamine agonists (pramipexole, ropinirole, rotigotine patch) were previously first-line but are now second-line due to high risk of augmentation (50-80% over 5-10 years). Augmentation: symptoms occur earlier in the day, spread to other body parts, increase in intensity, and occur at lower doses. Iron therapy (oral or IV) is used for those with low ferritin even without anemia.

Periodic Limb Movement Disorder

PLMD involves repetitive, stereotypic limb movements during sleep (typically leg flexion at the hip and knee, with dorsiflexion of the great toe). Movements last 0.5-5 seconds and occur every 5-90 seconds. The periodic limb movement index (PLMI) is the number of movements per hour of sleep. A PLMI over 15 in adults is considered elevated. PLMD is diagnosed when PLMs are present with sleep disturbance (insomnia or hypersomnia) that is not explained by another sleep disorder. PLMs are present in 80-90% of RLS patients, but most people with PLMs do not have RLS. Treatment is the same as RLS (low-dose gabapentin or pregabalin, and avoidance of aggravating medications). Isolated PLMs without sleep disturbance do not require treatment.

Summary

NREM parasomnias (sleepwalking, sleep terrors, confusional arousals) occur during slow-wave sleep, are common in children, and are managed with safety measures and scheduled awakenings. REM behavior disorder involves loss of REM atonia with dream enactment — it predicts neurodegenerative disease in older adults and is treated with clonazepam or melatonin. Narcolepsy type 1 is caused by hypocretin neuron loss and treated with modafinil, sodium oxybate, and venlafaxine. RLS is a sensorimotor disorder treated by correcting iron deficiency and using gabapentinoids as first-line. Dopamine agonists are second-line due to augmentation risk.