Narcolepsy Vs idiopathic hypersomnia-do we need to care?

Two half days a week I see patients in the sleep center. One of the reasons patients come to see me is for excessive daytime sleepiness (EDS). Patients may voice the above complaint in different ways. Some say [Dr. Sethi my biggest problem is that I feel sleepy during most of the day. I find it hard to concentrate at work or my mind feels “dull”]. Others may say they find it difficult to wake up in the morning in time for work or college. The history may be more worrisome: the patient may have fallen asleep while driving. So how does one differentiate between the various causes of EDS? In this post I shall touch on these very topics.

The various causes of EDS can be broadly listed as follows:

1. Untreated sleep disordered breathing: Obstructive sleep apnea (OSA), Central sleep apnea (CSA), Mixed sleep apnea (MSA).

2. Poor sleep hygiene

3. Circadian rhythm disorder: Delayed sleep phase syndrome (DSPS), Shift work disorder

4. Narcolepsy: primary and secondary

5. Idiopathic hypersomnia.

6. Medical disorders causing poor sleep at night.

Narcolepsy: is characterized by excessive sleepiness. It may or may not be associated with cataplexy. Cataplexy in simple terms refers to loss of muscle tone. Let me explain with the aid of an example. Let us assume a narcoleptic patient hears a joke. He starts laughing and suddenly experiences loss of muscle tone and finds himself on the ground. This sudden loss of muscle tone is referred to as cataplexy. Another example of cataplexy is a runner who collapses when the starter gun goes off. Narcolepsy is usually accompanied with sleep paralysis and vivid hallucinations which are reported either at onset of sleep or when the patient is about to wake up (that is around sleep-wake transitions). A point to note is that if the patient has cataplexy then the diagnosis of narcolepsy is easy to make. It is narcolepsy without cataplexy that is tough to diagnosis. A caveat to remember here is that not “everything” is cataplexy-so weakness in the knees if you have been laughing hard does not constitute cataplexy. Narcolepsy occurs due to the loss of hypocretin neurons in the lateral hypothalamus. So secondary narcolepsy may also occur if these neurons are damaged by a hypothalamic stroke or a hypothalamic tumor or by a infectious/ inflammatory process (limbic encephalitis). The clinical presentation of secondary narcolepsy though is different: example the history is of excessive sleepiness after a stroke or a tumor.

The diagnosis of narcolepsy is made on the basis of an overnight polysomnography (sleep study) which is done to rule out sleep disordered breathing (sleep apnea). One needs to make sure that the patient does not have untreated sleep apnea before the EDS can be attrbuted to narcolepsy. The patient also undergoes a test called multiple sleep latency test (MSLT). During the MSLT the mean sleep latency is calculated. In narcoleptics the mean sleep latency is usually less than 5 minutes and they also have sleep onset REMs (meaning they enter REM sleep as soon as they fal asleep). This is against what is seen in idiopathic hypersomnia which too has a short sleep latency but there is no sleep onset REMs.

The treatment of narcolepsy and idiopathic hypersomnia is virtually identical. The patient is usually prescribed stimulants such as Adderall, modafinil (Provigil) or Nuvigil.

In my next post I shall elaborate on this further.

Nitin Sethi, MD

Sleep apnea syndrome: how to identify it and what to do?

Sleep apnea syndrome or SAS is a relatively common sleep disorder. As the name suggests patients who have SAS have episodes of apnea during sleep (meaning they have episodes where in they stop breathing as they sleep). Usually patients who have sleep apnea are obese (overweight), have a large neckand snore during sleep. It is usually their sleeping partners who notice that the patient stops breathing during sleep. The patients themselves may not be aware of the fact that they stop breathing at night. They however do complain of feeling sleepy during the day (we refer to this as excessive daytime sleepiness or EDS) and of feeling tired and fatigued. Patients with SAS may frequently fall asleep while watching TV, sitting by themselves and reading or at times even while driving.

SAS has in the recent past gained more attention from the medical community. Studies have shown that patients who have SAS especially that which remains untreated have increased incidence of elevated blood pressure, coronary artery disease and even strokes. As these patients are overweight, this too adds to the risks of both CAD and strokes.

SAS can be of two types. Obstructive sleep apnea (OSA) and central sleep apnea (CSA). The difference between them is quite technical but clinically they both present in the same way.

So who all should be evaluated for SAS. A person who is overweight, has a thick short neck, who snores loudly at night and complains of feeling sleepy during the day should be evaluated for SAS. SAS can occur in children too but here the causes are slightly different. One important cause which needs to be ruled out in a child is enlarged tonsils or adenoids (enlarged tonsils and adenoids obstruct and narrow the air passages).  Some people may also have an enlarged tongue or their facial structure is such that the structures inside their mouth are all crowded. These patients too are predisposed to SAS.

Diagnosis of SAS: so how is the diagnosis of SAS made? Well a good clinical history and examination shall suggest the diagnosis to the doctor. To confirm and grade the degree of SAS we ask for what is called a sleep study. You come into the lab for an overnight sleep study. I call it a lab but it is more like a bedroom in your own house. We place electrodes on your head to look at your brain waves, electrodes to measure the air as it moves in and out of your nose, a device to detect when you snore, a device to detect if you have limb movements at night etc.  Then you are allowed to fall asleep and it is while you are asleep that we detect if you indeed do have apneic spells at night and we grade how severe your apnea is (there are standarized grading scales available for this purpose).

A report is generated and your doctor then tells you what kind of SAS you have: is it OSA or is it CSA and how severe it is.

 

Treatment of SAS: so you have SAS. What to do about it? Depending upon the severity of the SAS, the treatment varies. If it is mild, all your doctor may ask you to do is to try to lose weight and change the position in which you sleep (SAS is worse if you sleep on your back, as the tongue falls back obstructing the air passages, on the other hand if you sleep on your side, the tongue falls to one side and your air passage remains open). We actually tie a small tennis ball on the patients back so that he does not roll back onto his back. If the SAS is moderate to severe, your doctor may recommend what is called a CPAP machine. CPAP stands for continuous positive airway pressure. This is a small device which is placed besides the patient’s bed at night and through a tight fitting mask it blows air into the patients mouth and nose. This keeps the air passages patent preventing them from collapse and thus abolishes SAS. It takes time to get used to a CPAP machine as sometimes the mask is too tight and patients cannot sleep as the machine keeps making a little noise and blowing air into them. That said and done a CPAP machine is the treatment of choice for moderate to severe SAS. What pressure to set the machine at, is determined during the sleep study by the technician. We use the minimal pressure which would abolish all the apneic events.

Some surgical options are also available but these need to be discussed with your doctor. There is a specific subgroup of patients who gain benefit from surgery.

 

Nitin Sethi, MD