Clinical Pearl Series from Yale-G First Aid: Crush USMLE Step 2CK & Step 3 by Yale Gong, MD, Sr. Medical Advisor at www.medicine.net (Copyrighted)
Sleep-Wake Disorders
Sleep-wake disorders are very common in our daily lives. They carry varieties of causes, which may be physiologic-functional or pathological.
Normal Sleep
Two major stages
1. Nonrapid eye movement sleep (NREM): Characterized by slowing of the EEG rhythms, high muscle tone, and absence of eye movements and thought activity. In this stage the brain is inactive while the body is active. It consists of 4 sub-stages:
Stage-1: EEG shows alpha and theta waves. Stage-2 (45%, longest): Kappa (k)-complex and sleep spindles. Stage-3: Delta-waves (slowest, “slow wave sleep”). Stage-4: Continuation of delta-waves.
2. Rapid eye movement sleep (REM): 25%, with aroused EEG patterns (sawtooth waves), sexual arousal, rapid eye movements, generalized muscle atony, and dreams (nightmares). In this stage, the brain is active and the body is inactive.
Changes in sleep patterns from infancy to old age
Total sleep time and REM percentage decrease. Stages 3 and 4 tend to vanish.
Changes in neurotransmitters during sleep
There are increased 5-HT (serotonin) and ACh, and decreased NE (noradrenaline) and DA (dopamine).
Sleep disorders are very common. The International Classification of Sleep Disorders (ICSD-3) and DSM-5 have the following similar categories of sleep disorders:
1. Insomnia (disorder); 2. Breath-related sleep disorders (Sleep-related breathing disorders); 3. Hypersomnolence disorder and central disorders of hypersomnolence; 4. Narcolepsy; 5. Parasomnias; 6. Sleep-related movement disorders; 7. Circadian rhythm sleep-wake disorders; 8. Others.
It’s a disorder characterized by difficulties in initiating or maintaining sleep followed by frequent yawning and tiredness during the day, not due to physical or mental causes. It commonly affects up to 30% of the population at the level of functioning and is exacerbated by anxiety. It must be present > 3 times/week for 1 month for diagnosis. Acute or transient insomnia is usually due to psychological stress or travel over time zones. Chronic causes can be various from psychiatric, medical, medicinal, and primary.
Treatment
1. Good sleep hygiene techniques: Establish regular sleep schedule; avoid daytime naps, evening stimulation (including CNS stimulants, alcohol). Treat underlying cause if possible.
2. If it fails, try benzodiazepines (short-term—triazolam; intermediate—estazolam, lorazepam, temazepam; long-acting—flurazepam, quazepam), non-BZD (zolpidem), melatonin agonist (ramelteon), or diphenhydramine shortly (< 2-3 weeks).
Breath-related Sleep Disorders (Sleep-related Breathing Disorders)
These are characterized by abnormal respiration during sleep, occurring in both adults and children. There are four major types: (1) Central sleep apnea syndrome; (2) Obstructive sleep apnea (hypopnea) syndrome; (3) Sleep related hypoventilation disorder; (4) Sleep related hypoxemia disorder.
They can be further divided according to their etiology.
Sleep apnea syndrome is a disorder with cessation of airflow at the nose or mouth during sleep. These apneic episodes usually last longer than 10 sec/each, characterized by a loud snore followed by a heavy pause. During the apneic episodes, O2 saturation decreases, and pulmonary pressures increase. It’s considered pathologic if it’s more than 5 episodes/hour or > 30 episodes per night. It may be associated with depression and daytime sleepiness. Risk factors include obesity, family history, alcohol or sedative intake, hypothyroidism, and structural abnormalities.
Clinical features, subtypes, and diagnosis
1. Mostly seen in obese, middle-aged males. Patient usually presents with somnolence with loud snoring and apnea during the day or at night, accompanied with dry mouth, fatigue, and headache. Spouse complains of being interfered during the night. Patient may develop arrhythmias, hypoxemia, pulmonary hypertension and sudden death (especially infant and elderly).
2. Central sleep apnea (CSA): There is no central respiratory effort during the pause in breathing. After the episode of apnea, breathing may be faster (hyperpnea) for a period of time as a respiratory compensation. CSA can be primary (idiopathic) or secondary (mostly associated with Cheyne-Stokes breathing).
3. Obstructive sleep apnea/hypopnea (OSA, 95%): OSA is characterized by repetitive, intermittent episodes of airflow reduction (hypopnea) or cessation (apnea) due to upper airway collapse during sleep, including adult type and pediatric type. The airway collapse is due to muscle atonia in oropharynx or nasal, tongue, or tonsil obstruction. Each apneic period usually lasts 20 to 30 seconds and results in hypoxia, which arouses the patient from sleep. This occurs multiple times overnight.
4. Diagnosis: Sleep test (by polysomnography) is the most accurate means of diagnosis. It can record decreased O2 saturation and distinguish OSA from CSA, seizures, etc.
Treatment
1. CSA: Try to target underlying cause. (1) Continuous positive airway pressure (CPAP) is usually tried first (especially with Cheyne-Stokes breathing). (2) If failed, adaptive servo-ventilation (ASV) can be attempted. (3) If both CPAP and ASV are failed, bi-level positive airway pressure (BPAP) is tried with a backup respiratory rate. (4) If these cannot be tolerated, medications (acetazolamide, zolpidem, or triazolam) can be tried (if no risk factors for respiratory depression).
2. OSA: (1) Mild to moderate cases: patient education and behavior therapy—weight and tongue fat reduction (for obese people), avoidance of alcohol/sedatives intake and supine position during sleep.
(2) Severe OSAHS (>20 apneic episodes with arterial oxygen desaturations) —continuous (fixed) positive airway pressure (CPAP) is the main therapy, which can prevent occlusion of the upper pharynx. If not tolerated, BPAP is an option. If this fails, uvulopalatopharyngoplasty (to remove redundant tissue in oropharynx) or an upper airway stimulation system may be tried.
(3) Children—surgery for tonsillar/adenoidal hypertrophy.
Central Disorders of Hypersomnolence and Hypersomnolence Disorder
These disorders refer to excessive daytime sleepiness that is not due to disturbed sleep or misaligned circadian rhythms. In ICSD-3, Central Disorders of Hypersomnolence include narcolepsy type 1 and type 2, idiopathic hypersomnia, and Kleine-Levin syndrome (KLS, recurrent hypersomnia). KLS is a rare disorder that starts during adolescence and has a male gender preference. The patients have recurrent episodes of hypersomnia, which are often associated with compulsive overeating and hypersexuality.
I．Hypersomnolence Disorder
It is characterised by excessive daytime sleepiness that is not due to medical or mental conditions, drugs, poor sleep hygiene, insufficient sleep, or narcolepsy. It occurs at least three times per week for at least 3 months and causes significant distress or impairment in social or occupational functioning. This disorder is less well-defined and lack of REM sleep and other features of narcolepsy.
Treatment
Psychostimulants (methylphenidate or amphetamine) is the choice of treatment. SSRIs may be helpful in some patients.
Also known as hypnolepsy, it is a chronic neurological disorder involving the loss of the brain’s ability to regulate sleep-wake cycles normally, characterized by excessive daytime sleepiness and abnormalities of REM sleep for more than 3 months, causing significant impairment in social or occupational functioning. It’s an inherited disorder of variable penetrance. REM sleep usually occurs in less than 5 min. Patients feel refreshed upon awakening.
Clinical features and diagnosis
1. Involuntary “sleep attacks”: Most common symptoms—frequent irresistible sleeping at any time of day (during any activity) that lasts several min, refreshed upon awakening, and falling asleep quickly at night.
2. Cataplexy (70%)—pathognomonic sign: Sudden loss of muscle tone, which may have been precipitated by a loud noise or intense emotion.
3. Hypnagogic and hypnopompic hallucinations: Dreaming while awaking; it occurs as the patient is going to sleep and is waking up from sleep, respectively.
4. Sleep paralysis: Patient cannot move when waking up.
Treatment
1. Forced naps at a regular time of day is usually helpful.
2. A psychostimulant (methylphenidate or amphetamine) is the main medical treatment. TCAs can be used if cataplexy is present. Pitolisant, a novel oral histamine H3 receptor inverse agonist, is used in narcolepsy patients with poor response or tolerate to other medications. Oxybate salts, a lower sodium mixed-salt formulation of gamma hydroxybutyrate is for narcolepsy with cataplexy.
Parasomnias are undesirable physical events (movements, behaviors) or experiences (emotions, perceptions, dreams) that occur during entry into sleep, within sleep, or during arousals from sleep. The behaviors can be complex and appear purposeful; however, the patient is not consciously aware of the behavior. The sub-category includes:
(1) NREM related parasomnias: they are disorders of arousal including confusional arousals, sleepwalking, sleep terrors, and sleep related eating disorder.
(2) REM related parasomnias: involve the intrusion of the features of REM sleep into wakefulness (e.g., sleep paralysis), exaggeration of the features of REM sleep (e.g., nightmare disorder), etc.
(3) Other parasomnias without specific relationship to sleep stage: exploding head syndrome, sleep related hallucinations, sleep enuresis, and drug-associated parasomnias.
Nightmare (disorder): It occurs commonly in 50% of the population. Patient can remember the event upon awakening. It increases during times of stress. There is no special therapy required but adjustment of stress.
Night terror: Awakened by scream or intense anxiety. Patient usually has no memory of the event the following day. It’s more common in boys and with family history. No special treatment is needed. If severe, limited use of benzodiazepines (BZD, BZs) may be considered.
Sleepwalking: It occurs during stage 3-4 of sleep, with sequencing behaviors during sleep without full consciousness; ends in waking embarrassment without remembering anything. It’s more common in young boys and may be associated with neurologic diseases. Treatment: First assure patient’s safety. If it occurs frequently, give BZs to suppress stage 3-4 sleep.
Sleep-related Movement Disorders
These are characterized by simple, stereotypic movements that disturb sleep and cause related symptoms (daytime sleepiness, fatigue, etc.). Patients may or may not be aware of the movements.
The classic disorders include restless legs syndrome, periodic limb movement disorder, sleep related leg cramps, sleep related bruxism (teeth grinding), and sleep related rhythmic movement disorder.
Circadian Rhythm Sleep-Wake Disorder
It’s characterized by chronic or recurrent sleep disturbance due to misalignment between the environment and an individual’s sleep-wake cycle. People with the disorder are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks. The quality of their sleep is usually normal. There are several types of circadian rhythm disorders:
1. Shift work disorder and jet lag disorder are the most common types, although most of these cases do not come to medical attention.
2. Delayed sleep-wake phase disorder is characterized by sleep and wake times that are habitually delayed compared to conventional times, more common in a younger patient.
3. Advanced sleep-wake phase disorder is characterized by sleep and wake times that are habitually early compared to conventional time, more common in the elderly.
4. Irregular sleep-wake rhythm disorder is characterized by lack of a clearly defined circadian rhythm of sleep and wake. This disorder is commonly associated with developmental disorders in children and with neurodegenerative diseases such as Alzheimer disease, Parkinson disease, and Huntington disease.
Treatment
1. Jet-lag disorder: It usually resolves in 2-7 days without treatment.
2. Shift-work disorder: Light therapy may help.
3. Delayed sleep-phase disorder: Taking oral melatonin 30 min before bedtime may help.
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