What is it?
The Electroencephalogram (EEG) is a functional test designed to observe the brain’s electrical activity.
Electroencephalographic tests may include standard EEG, EEG with sleep test or polygraph EEG in neonates with digital equipment (Grass Telefactor).
Other tests that use EEG include:
- Ambulatory EEG (24-hour Holter EEG with up to 24-channel recorder.
- Ambulatory (home) sleep polygraph recording – installation of portable equipment in the clinic.
Possibility of examining EEG channels and classifying/quantifying sleep phases. - Multiple Sleep Latency Test It must be carried out in the clinic under permanent technical supervision.
It is important for diagnosing diseases that cause excessive daytime sleepiness, such as narcolepsy.
How is it done?
The EEG can be carried out with the patient awake or asleep, an indication that should be given by the patient’s attending physician.
When asleep, the patient is instructed to sleep for about half the time they usually do the day before the test, in order to obtain the recording during physiological sleep.
The sleep EEG lasts between one and a half and two hours.
The EEG in wakefulness (routine) lasts about an hour (total time including placing and removing the electrodes).
Ambulatory EEG (EEGamb) is an electroencephalogram carried out with an ambulatory (portable) recorder which is designed to record uninterruptedly for several hours – the usual standard is 24 hours of recording, with 19 electrodes.
The patient is connected to the recorder and can go home or to their usual work.
Preparation of the head by the technician takes longer as the electrodes are placed one by one with an appropriate glue.
The patient can and should maintain activities as close to normal as possible during the recording day(s).
The electrodes are removed in the laboratory at the end of the examination.
The EEGamb is usually carried out on patients who have already had a routine EEG or even an EEG with a sleep test carried out previously.
Your doctor will know which type of test is right for you.
O Sleep Polygraph Study or Polysomnography (PSG) is a special recording in which the brain’s electrical activity during sleep is studied, along with signs of breathing, heartbeat and oxygen saturation, among others needed to study the patient’s sleep.
PSG is indicated in cases of suspected sleep disorders, such as obstructive sleep apnea syndrome, restless legs syndrome and narcolepsy, among the most important.
It can be carried out on an outpatient basis, i.e. with a portable recorder making it easy for the patient to go to sleep in their own home, or in the clinic with a fixed recorder and under technical supervision and continuous video surveillance.
O Multiple Sleep Latency Test (MSLT) is a very complex type of sleep study in which we observe how easily the patient falls asleep every two hours in successive tests carried out exclusively in the diagnostic clinic.
Electroencephalographic, electrooculographic and electromyographic channels are recorded and data on sleep latencies are extracted.
It is an important test for diagnosing narcolepsy.
For which cases is it indicated?
The EEG is indicated in clinical situations in which there are alterations in consciousness, both sudden and short-lived, and more insidious and longer-lasting.
Where to do it?
The Electroencephalogram can be done at the NRD, at the following address: Avenida Columbano Bordalo Pinheiro, nº 11-B, r/c, 1070 – 060 Lisboa (Next to Praça de Espanha)