Neurological Disorders: Narcolepsy
What is this condition?
Narcolepsy is a neurological disorder and is characterized by recurrent episodes irresistible sleeping during the awake-periods like day time. It is subcategorized under the sleep disorders.
Who gets this disease?
Narcolepsy is not uncommon however it is definitely under diagnosed. Patients are sometimes considered as lazy, depressed etc. It affects all races, gender and ethnicities. It usually begins to manifest around the teen-age and young adulthood.
What causes it?
Based on the current knowledge this appears to be an autoimmune disorder. And it also seems to be a genetically linked disease, but some environmental factors might be required for the disease to manifest.
Studies have shown that a protein in the brain called as Orexin (Hypocretin) is absent or deficient in these patients. This protein is related with the sleep regulation.
How does the patient present?
The following are the important manifestations of this condition;
• Irresistible episodes of sleep during awake period
• Hypnagogic hallucinations
• Sleep attacks
The first symptom mentioned above is the most characteristic one for this disease. Patients may fall asleep wherever they are, even while driving. Scary agree? Yes indeed, serious accidents and death can occur due to this disease. It is also embarrassing to fall asleep when the patient is with somebody else like in the office, school etc. It can affect patient’s personal, social and professional functioning.
Cataplexy is characterized by recurrent episodes where patient suddenly loses the muscle tone and collapse to the ground without loss of consciousness. The episodes may be precipitated when there is some kind of intense emotional thinking. Minor episodes occur too where patient may develop partial or focal weakness of muscles like dropping of the jaw etc.
Hypnagogic hallucinations are kinds of vivid hallucinations that usually occur while patient falls to sleep or when come out of sleep.
Sleep attack usually happens when patient wakes up in the morning or falls to sleep in the night. During the attack patient is awake but cannot move, speak or perform any motor activities. It will continue for some time then suddenly patient becomes normal.
What are the conditions that mimic narcolepsy?
• OSA (obstructive sleep apnea)
• Idiopathic hypersomnia (excessive daytime sleep, cause unknown)
• Neurodegenerative conditions (e.g. prion diseases) etc.
Sleep laboratory studies:
Once a clinical suspicion of this condition arises then a polysomnography (sleep study) will be done. The following day after the night time sleep study patient will undergo another neurology test called as MSLT (multiple Sleep Latency Test).
Doctor who interprets this study will be looking for abnormally shortened REM (rapid eye movement) sleep latency. Normally REM sleep is attained around 90 minutes after you begin seeping. But with this condition it is palpably shortened (<8 to 10 minutes).
Orexin (hypocretin) estimation in the CSF (cerebrospinal fluid):
Majority of the patients with narcolepsy the concentration of this chemical substance is
Undetectable in the CSF and it is a very useful test.
HLA-DQB1*0602 is another test to be considered although its usefulness is less as compared to orexin or sleep study.
A neurologist is frequently involved in the care of these patients. There is no cure for this condition at this moment & the following medications are generally used;
• Stimulants like Methylphenidate (Ritalin), amphetamines, caffeine, modafinil (provigil) etc
• Sodium Oxybate (especially for cataplexy attacks)
• Patients with poorly controlled conditions need adjustment in their professional life including driving precautions etc.
Narcolepsy to Neurology Articles
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