Narcolepsy
Last reviewed: 23.04.2024
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Narcolepsy is characterized by pathological daytime drowsiness, often combined with episodes of sudden loss of muscle tone (cataplexy), sleep paralysis and hypnagogic phenomena.
The diagnosis is based on the results of polysomnography and a multiple sleep latency test. For treatment modafinil and various stimulants are used.
[Causes of narcolepsy
The cause of narcolepsy is unknown. Narcolepsy is largely associated with certain HLA-haplotypes, and in children with narcolepsy, an increased (40 times) risk of the disease, indicating a genetic cause. At the same time, the twins' concordance rate is low (25%), which testifies to the important role of external factors. In animals and most people with narcolepsy, there is a deficiency of the neuropeptide of hypocretin-1 in the CSF, which suggests the HLA-associated autoimmune destruction of hypocretin-containing neurons in the lateral parts of the hypothalamus. Narcolepsy is equally affected by men and women.
In narcolepsy there is a disregulation of periodicity and control of the fast sleep phase (with BDG), i.e. Changing the structure of sleep. The phase of sleep with the BDG "invades" both during periods of wakefulness and during periods of transition from wakefulness to sleep. Many symptoms of narcolepsy are manifested by a sharp loss of muscle tone and vivid dreams that characterize a quick sleep.
Symptoms of narcolepsy
The main symptoms are pathological daytime sleepiness (PDS), cataplexy, hypnagogic hallucinations and insomnia; approximately 10% of patients have all 4 symptoms. Disturbances of a night dream are characteristic also. Symptoms usually debut in adolescents or young people, usually without any previous illnesses, although the appearance of narcolepsy is sometimes associated with illness, stress or a period of sleep deprivation. After the debut, narcolepsy becomes a lifelong disease, without affecting life expectancy.
Pathological daytime sleepiness may develop at any time. The number of attacks during the day can vary significantly; Attacks can be rare and numerous, their duration ranges from several minutes to several hours. The ability of the patient to resist falling asleep is very limited, although it is not more difficult to awaken him during a narcoleptic attack than in a normal sleep. Attacks often occur in a monotonous situation (for example, reading, watching TV, at a meeting), contributing to falling asleep and a healthy person, but in contrast, the patient can fall asleep and in an environment that requires increased attention (for example, while driving, talking , letters, meals). Possible attacks of sleep - sudden repeated attacks of sleep. The patient may feel cheerful after awakening, but after a few minutes may fall asleep again. Night sleep is fragmented, often interrupted by bright, frightening dreams, and does not bring satisfaction. The result is poor performance and productivity, impaired interpersonal relationships, poor concentration, lack of motivation, depression, a significant decrease in the quality of life and an increased risk of injury (especially due to traffic accidents).
Cataplexy is characterized by sudden muscle weakness or paralysis without loss of consciousness caused by sudden-with an element of surprise-emotional reactions such as anger, fear, joy or surprise. Weakness can be limited only to one of the limbs (for example, the patient suddenly drops the fishing rod when the fish is caught), or be generalized, when the patient, suddenly becoming angry or laughing heartily, falls down like a scapegoat. The loss of muscle tone in such episodes resembles the phenomenon observed in the fast sleep phase (with BDG). Cataplexy occurs in about 3/4 of the patients.
Sleep paralysis is a brief episode of muscle weakness that sometimes occurs at the time of falling asleep or awakening, during which the patient is unable to produce any voluntary movement. At this point the patient can embrace fear. Such episodes resemble the inhibition of motor activity during the fast sleep phase (with BDG). Sleep paralysis occurs in about 1/4 of patients, and sometimes in healthy children and adults.
Hypnagogic phenomena are unusually bright auditory or visual illusions or hallucinations that occur when you fall asleep or, more rarely, on waking. They somewhat resemble bright dreams that arise during the fast sleep phase (with the BDG). Hypnagogic phenomena occur in about 1/3 of patients, and are also common among healthy young children and are sometimes found in healthy adults.
Diagnosis of narcolepsy
The diagnosis is put on average 10 years after the onset of the disease. In patients with pathological daytime drowsiness, the presence of cataplexy allows us to presume narcolepsy. Diagnostic significance is represented by the results of nocturnal polysomnography and a multiple sleep latency test (MTLS). Diagnostic criteria of narcolepsy are the recording of the sleep phase in at least 2 out of 5 episodes of daytime sleep, and the shortening of the latent sleep time to 5 minutes in the absence of other disorders according to the results of night polysomnography. The results of the wake-up maintenance test are not diagnostic, but help to evaluate the effectiveness of the treatment.
According to the history and physical examination, it is possible to suspect other potential causes of chronic hypersomnia; CT or MRI of the brain and clinical blood and urine tests help confirm the diagnosis. The causes of chronic hypersomnia can be tumors of the hypothalamus or upper parts of the brain stem, increased intracranial pressure, certain types of encephalitis, as well as hypothyroidism, hyperglycemia, hypoglycemia, anemia, uremia, hypercapnia, hypercalcemia, hepatic insufficiency, epileptic seizures and multiple sclerosis. Acute, relatively short-term hypersomnia usually accompanies acute systemic diseases, such as influenza.
The Klein-Levin syndrome is a very rare disease affecting young people, characterized by episodic hypersomnia and polyphagia. Etiology is unclear, but may include an autoimmune reaction to infection.
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Treatment of narcolepsy
Single episodes of carotid paralysis or hypnagogic phenomena with mild pathological daytime drowsiness do not require special treatment. In other cases, prescribe stimulants. It is recommended that strict sleep hygiene is maintained, with a sufficiently long night and short daytime sleep (less than 30 minutes, usually after lunch) at the same time each day.
With mild or moderate drowsiness, modafinil, a long-acting drug, is effective. The mechanism of action is unclear, but the drug is not a stimulant. Typically, modafinil is prescribed for 100-200 mg orally in the morning. According to the indications, the dose may be increased to 400 mg, but in some cases a significantly higher dose is required. If the effect of the drug is not enough until the evening, at 12: 00-13: 00 you can take a second small dose (100 mg), mindful of the potential risk of disturbing night sleep. Side effects of modafinil are nausea and headache, which can be smoothened if you start with low doses and gradually bring them to the desired values.
In the ineffectiveness of modafinil, amphetamine derivatives are assigned instead of or together with modafinil. Methylphenidate can be more effective at doses from 5 mg 2 times / day to 20 mg 3 times / day inwards, which differs from modafinil by a faster onset of therapeutic action. Methamphetamine is prescribed for 5-20 mg 2 times / day inward, dextroamphetamine 5-20 mg 2-3 times / day inside; as long-acting drugs in most cases they are effective with a single dose per day. Possible side effects include agitation, arterial hypertension, tachycardia and mood changes (manic reactions). All stimulants have an increased risk of dependence. Pemoline, with a lower potential for dependence than amphetamines, is rarely used due to hepatotoxicity and the need for regular monitoring of liver function. According to the indications, the anorexigent drug mazindol is prescribed (2-8 mg orally 1 time / day).
Tricyclic antidepressants (especially imipramine, clomipramine and protriptyline) and MAO inhibitors are effective in the treatment of cataplexy, carotid paralysis and hypnagogic phenomena. Clomipramine 25-150 mg (by mouth 1 time / day in the morning) is the most effective anti-cataract medication. A new anti-cataract drug Na oxybate (list A, due to the risk of dependence and drug addiction) is prescribed at 2.75-4.5 grams orally twice during the night.