What is a sleep disorder?
Sleepiness is common in the general population, and even more common among people with epilepsy, but sleep disorders are frequently missed. Sleep disorders are medical conditions that cause specific problems with sleep.
- Examples of different sleep disorders are obstructive sleep apnea, narcolepsy, insufficient sleep syndrome, periodic limb movements, and nocturnal seizures.
- Tiredness during the day is a symptom of nearly all sleep disorders, but many practitioners attribute consistent tiredness in epilepsy to an unavoidable effect of anti-seizure medication and don’t think about the possibility of a sleep disorder.
- Studies of epilepsy patients with sleep disorders show that their sleep disorders are, generally, treatable conditions. In one series, obstructive sleep apnea was found in 71% of epilepsy patients referred for a sleep study.
- Sleep disorders are often overlooked in epilepsy patients, and sometimes polysomnography (also called an overnight sleep test) is required for diagnosis.
Types of Sleep Disorders
Obstructive sleep apnea is one of the most common and most important sleep disorders, because of the possible serious consequences. It is probably present in at least 3% of the general population but has been reported in up to 40% of middle aged men.
- It is characterized by repetitive episodes of complete or partial airway obstruction.
- The most common complaints are excessive daytime sleepiness and frequent awakenings, but there can also be associated bruxism (grinding of teeth), dry mouth on awakening, morning headaches, erectile dysfunction, memory deficits, and snoring.
- Upper airway obstruction in sleep apnea usually occurs between the epiglottis and the soft palate. As muscle tone decreases during non-REM and particularly REM sleep, the potential for obstruction increases.
- Obesity of the upper body can also contribute to the disease.
- Treatment options include continuous positive airway pressure (CPAP), oral appliances for repositioning of the airway, surgery (uvulopalatopharyngoplasty, reducing the tissue in the throat and improving airflow), and conservative treatments (sleep positioning, weight loss).
Restless Legs Syndrome (RLS)
Periodic limb movements and restless legs syndrome are both relatively common conditions. The incidence of restless legs syndrome is between 2.5% and 15%. Periodic limb movements occur in about 5% of young adults, however the prevalence may be as high as 44% in patients over age 64. These two disorders often occur together and have many characteristics in common, thus are discussed together.
- Periodic limb movements consist of repetitive cycles of rhythmic movements, usually occurring in one or both legs but sometimes involving the arms. Patients are unaware of the movements but may report frequent awakenings.
- The history from a bed partner may be of jerking movements in sleep, therefore potentially resulting in confusion with epilepsy. On closer questioning, however, the movements are not clonic, are typically limited to a single limb, and occur many times during the night at regular intervals. Most commonly, they occur in clusters every 5-90 seconds with each movement lasting 0.5 to 5 seconds.
- Restless legs syndrome is usually characterized by an itching or burning sensation in the legs which occurs when the patient is relaxed, particularly when trying to go to sleep. This is followed by movement of the legs with relief of the sensation. The movement can be suppressed voluntarily however typically the urge to move becomes overwhelming. Many patients need to actually walk to stop the sensation.
- As opposed to periodic limb movements, restless legs syndrome becomes manifest during wakefulness or drowsiness as opposed to sleep. The result, however, is that the patient is unable to sleep and it results in daytime drowsiness.
- Similar to periodic limb movements, however, a description of irresistible shaking of the legs could be confused with epilepsy; a major difference is that restless legs syndrome can be suppressed voluntarily while an epileptic seizure cannot be suppressed.
- Kidney problems are an important cause of restless legs syndrome, and prevalence may be as high as 40%. Other important associated conditions include iron deficiency anemia, pregnancy, peripheral neuropathy, and drugs (neuroleptics, caffeine).
- Treatment of both conditions begins with a search for underlying cause. Either condition can be asymptomatic, but if associated drowsiness requires pharmacological treatment, dopaminergic agents (carbidopa/levodopa, bromocriptine), benzodiazepines (clonazepam), opioids (codeine), and carbamazepine may be recommended by a sleep specialist.
Insomnia and daytime sleepiness are extremely common. According to a survey by the National Sleep Foundation in 2001, 7% of Americans have drowsiness sufficient to interfere with normal activities on a daily basis, and another 14% experience this at least several times a week. Drowsiness can have serious health consequences as well; 1% of respondents in this same poll reported having automobile accidents because of falling asleep while driving. Sleep disorders are often not reported to physicians and are typically not a part of a routine evaluation.
- Insomnia can consist of difficulty falling asleep, difficulty staying asleep, or both.
- There are many causes, but the most common are psychophysiological insomnia, primary insomnia. Insomnia also occurs commonly in the setting of medical and psychiatric illness.
- Depression and anxiety, both more common in patients with epilepsy, are frequently associated with insomnia. In this case, the best treatment is the treatment of the underlying condition although choice of sleeping drugs (if needed) can be influenced by coexisting problems.
- The treatment of insomnia depends on the underlying cause. For short term insomnia (due to relocation or stress) no treatment may be required. Short acting sleeping agents can be used, the most common of which are zolpidem (Ambien), zaleplon (Sonata), and eszopiclone (Lunesta). Zaleplon is very short acting; so short in fact that patients can take another dose during the night and still wake up refreshed. Eszopiclone lasts longer than zolpidem, so may be better for people who wake up during the night, but is more likely to still be in the system the next morning with drowsiness. Benzodiazepines are also used commonly, although their tendency to disrupt sleep structure and the development of tolerance make these drugs less desirable. Most commonly used are temazepam (Restoril) and estazolam (Prosom). Rebound insomnia (worse sleep when stopping the drug) is more common with these. A number of antidepressant drugs can also be used for sleep. In general, the more sedating drugs (such as trazadone (Desyrel) taken at bedtime can be helpful even in the absence of depression.
Other common sleep disorders
Many other sleep disorders exist, including “parasomnias” consisting of abnormal sleep phenomenon occurring either during sleep or wakefulness. These disorders do not always significantly disrupt sleep, but can be confusing in that some can have the appearance of a seizure. Parasomnias are described here.
These typically occur in non-REM sleep, especially in the deeper stages (slow wave sleep). All are more common in children, and occur more frequently whenever sleep is deeper (such as after sleep deprivation).
- Confusional arousals (“sleep drunkenness”) consists of confusion, sometimes accompanied by stumbling and slurring, on awakening and can last for several minutes. Sometimes there will be no memory of the awakening whatsoever.
- Sleep terrors consist of sudden awakening, often accompanied by screaming and a brief, frightening image. In this case the person may also be confused and disoriented for several minutes.
- Sleepwalking is also considered a disorder of arousal.
Sleep-wake transition disorders
These disorders usually occur as the person is falling asleep or waking up. Examples include:
- Sleep starts (sudden sometimes violent jerking on falling asleep) and sleep talking (“somniloquy”).
- Head banging (rhythmic movement disorder) is relatively common in young children and consists of rocking or banging movements as the child is falling asleep; these can sometimes be fairly violent.
- Teeth grinding (bruxism) can cause problems with sleep if it results in frequent awakenings. It also damages the teeth; a mouth guard used at night can prevent this.
- Bedwetting (sleep enuresis) is common in children and usually of no long term consequence.
- Snoring can occur in the absence of sleep apnea (“primary snoring”); this may not be a problem for the sleeper if he or she is not awakened by it, but can disrupt the sleep of bed partners.
Parasomnias associated with REM sleep
These generally consist of behaviors occurring during REM sleep that normally happen while awake, or a disruption of normal processes during REM sleep.
- Sleep paralysis occurs when the normal paralysis present during REM persists into wakefulness. It is usually brief and resolves spontaneously, but can be frightening. Similarly, hypnic hallucinations are dream images that persist into wakefulness. Both can occur in normal people occasionally, particularly when sleep deprived, but also are common in narcolepsy.
- Cataplexy is the sudden onset of paralysis (as occurs in REM sleep) when the person is fully awake. For reasons that are not well understood, this seems to occur in the presence of strong emotion (laughter or fear). This phenomenon also occurs in narcolepsy.
- Finally, REM sleep behavior disorder consists of the absence of normal paralysis during REM sleep. Because muscles remain functional, these patients can move about as they dream, sometimes leaving the room or (if the dream is frightening) having aggressive behavior that can result in injury.
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