What is Polysomnography (PSG)?

It is the recording of several parameters while you sleep that gives a full assessment of how you sleep. It is an important test to determine sleep disorders. A Polysomnography (PSG) looks at your sleep staging via electroencephalography (EEG), body movements via electromyography (EMG), eye movement via electrooculography (EOG), heart rate via electrocardiography (ECG) air flow, respiratory effort, oxygen saturation, snoring, body position and video recording. These electrodes are placed by a trained sleep technologist and the results are interpreted by a sleep physician.

What kind of sleep disorders does a polysomnography (PSG) diagnose?

A PSG helps determine the type and severity of sleep apnea. Sleep apnea can also be diagnosed via a simplified PSG known an a cardiorespiratory polygraphy. A PSG is recommended for those patients that don’t fit all the known characteristics of a patient with moderate to severe sleep apnea. A patient may present with excessive daytime sleepiness, and sleep apnea, but may also suffer from underlying sleep disorders.

Periodic limb movement disorder (PLMD) is where a patient moves his/her legs in a repetitive fashion throughout the night that may affect his/her daytime sleepiness. A PSG in needed to confirm the amount and type of leg movements seen to ascertain a proper diagnosis. A patient medical history will help a physician understand the cause of PLMD if that is not noted on the PSG.

Bruxism is a sleep disorder where excessive grinding of the teeth can lead to both tooth wear and daytime fatigue. In a polysomnography, grinding can be heard on recording and seen in the EMG channels.

REM sleep parasomnias, REM sleep behavior disorder (RBD) is where there is abnormal movements noted during REM sleep. No movements should be seen during REM sleep because a patient enters a state where all the muscles relax (muscle atonia). Due to this further relaxation of muscles, sleep apnea may present more severely in this sleep stage. A patient may lash out due to responding to dream activity. If a patient awakens after an episode, they may remember the dream action.

The following video shows REM sleep behavior disorder.

When is a Polysomnography not needed?

Some sleep disorders can be determined via a detailed patient history and a sleep questionnaire. It is important to let you sleep technologist know everything in your medical history, this may effect your diagnosis.

Restless legs syndrome (RLS) is a sleep disorder where patients have the uncontrollable urge to move their limbs. A PSG is only performed if the patient has other issues with their sleep. Many people with RLS, do also present with PLMD.

Certain types of insomnia may not warrant a PSG. A medical history and consultation with a physician will determine if a PSG is necessary.

Certain parasomnias, like sleep terrors and sleep walking can be determined via patient family history. A PSG is performed dependant on the severity of symptoms.

What test is best for you?

Your family physician can best determine what needs to be done. A consultation with a sleep specialist may be required before any sleep testing is performed. The filling out of medical forms and questionnaires is invaluable when it comes to helping the sleep specialist determine the diagnosis. A sleep technologist observes and ensures proper recording of the polysomnography parameters. Any information missed on questionnaires should be divulged to the sleep technologist to help with your diagnosis.

There are more sleep disorders not mentioned in this article. Calling a sleep clinic can be your first step in determining how to get sleep testing and questions about all things sleep.