What is a sleep study or a polysomnography  ?

The sleep study, also called polysomonography, is a clinical test used to diagnose and evaluate treatment for the disorders of your sleep. This study may record different variables out of your body while you are asleep, including: brain waves, heart rate, the oxygen level in your blood, your breathing, snoring level and sometimes eye and leg movements. The study may be done at sleep centers or at home. 




How is the sleep study done?

The sleep study that we indicate as a neurology clinic is done at home, the recording is made during two nights, the following image is the equipment that we use:

We will educate you in terms of how to set up the equipment for the testing. Here is a video with the instructions for the setting up: Patient Instructions Video.

Why is the sleep study done?

Since the sleep study monitors the stages and cycles of your sleep, it may identify when these patterns are disrupted and the cause.

The sleep study is recommended by your doctor if he suspects you may having one of the following:

  • Obstructive sleep apnea. In this condition stoping and starting of your breathing (apneas) occurs while you are asleep.

  • Periodic limb movement disorder and restless legs syndrome. In these disorder you may experience discomfort and involuntary movement of your legs while sleeping. 

  • Narcolepsy. This condition is likely If you experience overwhelming daytime drowsiness and sudden attacks of sleep.

  • REM sleep behavior disorder. This condition involves acting out dreams as you sleep and may be an early indicator or Parkinson Disease.

What results should I expect of this test?

The measurements recorded during polysomnography provide a great deal of information about your sleep patterns. For example:

  • Brain waves and eye movements during sleep can help your doctor assess your sleep stages and identify disruptions in the stages that may occur due to sleep disorders such as narcolepsy and REM sleep behavior disorder.

  • Heart and breathing rate changes and changes in blood oxygen that are abnormal during sleep may suggest sleep apnea.

  • Frequent leg movements that disrupt your sleep may indicate periodic limb movement disorder.

  • Unusual movements or behaviors during sleep may be signs of REM sleep behavior disorder or another sleep disorder.

The following image is an example of the information collected during your home sleep study. You may notice the graphs for some of the oxygen level of your blood, the sleep cycle and its stages and the level of snoring,

At a follow-up appointment, your doctor reviews the results with you. Based on the data gathered, your doctor will discuss any treatment or further evaluation that you may need.


Before we continue, what is the normal pattern of sleep?

The normal sleep is divided in several sleep stages, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. NREM sleep is subdivided in three stages, 1, 2 and, 3, where the most remarkable one is slow-wave sleep  or deep sleep (phase 3).

During NREM sleep, your brain waves, as recorded by electroencephalography (EEG), slow down considerably.

Your eyes don't move back and forth rapidly during NREM, in contrast to later stages of sleep. After an hour or two of NREM sleep, your brain activity picks up again, and rapid eye movement (REM) sleep begins. Most dreaming occurs during REM sleep. You normally go through multiple sleep cycles a night, cycling between NREM and REM sleep in about 90 minutes. Sleep disorders can disturb this sleep process.


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