Hello friends!!
This is the third one in the four-post series on Narcolepsy. Let's commence.
Diagnosing a not so common disorder, that too neurological
is quite tricky. The greatest difficulty is separating it from the normal
daytime and postprandial sleepiness of most people. Admit it, most of us feel
like sleeping in the afternoon period after lunch, especially while reclining
in the sofa, while watching television or in the theatres watching matinee
shows. :p
What distinguishes the typical
narcoleptic attack from commonplace postprandial drowsiness and napping is the
frequent occurrence of the former(2 to 6 times everyday), their irresistibility,
and their occurrence in unusual situations, as while eating, standing, or
carrying on a conversation.
Excessive daytime sleepiness can also be present with heart
failure, hypothyroidism, use of antihistaminics, alcohol intake, head trauma,
certain brain tumours like craniopharyngioma etc.
Overnight polysomnography followed by a standardized
multiple sleep latency test can exclude other causes of excessive daytime
sleepiness like obstructive sleep apnea. In the test, the patient is given 5
opportunities to nap at 2 hour intervals in a day
.
If there are more than 2
Sleep-onset REM periods and a mean sleep latency of less than 8 minutes, it
strongly suggests narcolepsy.
Actually, in Narcolepsy, there is characteristic
reversal in the order of the two states of sleep, with REM (rather than NREM)
phase occurring at the onset of sleep
attacks. And the sleep latency is nothing but the interval between the point
when an individual tries to sleep and the point of onset of sleep with the
respective EEG patterns.
Measurement of hypocretin(orexin) levels in the CSF may help
establish the diagnosis; a level lower than 110pg/ml is diagnostic of
narcolepsy.
Cataplexy must also be distinguished from syncope, drop
attacks and atonic seizures. In atonic seizures, there is temporary loss of
consciousness, while in narcolepsy consciousness is perfectly preserved.
That's all! Do go through the other posts in this series.
Role of Orexins in Narcolepsy
Clinical features of Narcolepsy
Treatment of Narcolepsy
-VM
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