EEG is the process of recording the electrical activity in the brain by means of sensors called electrodes placed on the scalp. It helps us understand brain functions indirectly.
It is used in the diagnosis and follow-up of many diseases, especially epilepsy (such as coma, dementia, brain damage, infections, brain death). It is one of the first tests to be done in patients presenting with seizures.
EEG may not be abnormal in all patients with seizures, and abnormal EEG may be observed in individuals who do not have seizures or epilepsy. In this case, it may be necessary to repeat the EEG recording for certain periods or to record for longer periods.
During the EEG procedure, no electrical current is given to the patient, so no pain or discomfort is felt. It can be easily applied to individuals of all ages, including pregnant women. During the procedure, you will be asked to follow commands such as opening and closing your eyes, looking at a lamp placed in front of you intermittently (photic warning), and breathing deeply and rapidly for 3 minutes (hyperventilation). There is no medical drawback to taking EEG at frequent intervals or recording for a long time.
EEG examination; can be performed while awake in the form of a short-term “Routine EEG” , lasting about 30-45 minutes. It is known that abnormal electrical activities that do not appear in routine EEG can become active during sleep, and some epileptic seizures occur only during sleep. Terefore, a “Sleep-Awake EEG” with a longer duration (approximately 1.5 hours), which includes both sleep and awake states, can also be performed.
For an accurate recording with high quality, the hair should be washed the day before. If a sleep EEG examination is also requested, it may be necessary for the person to be sleepless for the specified periods the night before the recording, in order to sleep easily in the laboratory. In children, EEG is usually performed during sleep because it is difficult for them to adapt to the recording. For this reason, it is sometimes recommended for the child to sleep late the night before the examination and wake up early, or medication may be given before the recording.
It should be noted that, for accurate diagnosis and treatment, recording and interpretation of the EEG records should be performed by experts experienced in this field.
What is EEG?
Electroencephalogram (EEG)is a test used to evaluate the electrical activity in the brain. Brain cells communicate with each other through electrical impulses. An EEG can be used to help detect potential problems associated with this activity. An EEG tracks and records brain waves. Small flat metal discs called electrodes are attached to the scalp with wires.
The electrodes analyze the electrical impulses in the brain and send signals to a computer that records the results. The electrical impulses in an EEG recording look like wavy lines with peaks and valleys. These lines allow doctors to quickly assess whether there are abnormal signals. Any irregularities may be a sign of seizures or other brain disorders.
What is EEG Recording?
An EEG is used to detect problems in the electrical activity of the brain that may be associated with certain brain disorders.
The measurements given by an EEG are used to confirm or rule out various conditions, including below:
- Seizure disorders (such as epilepsy)
- Head injury
- Encephalitis (inflammation of the brain)
- Brain tumor
- Encephalopathy (disease that causes brain dysfunction)
- Memory problems
- Sleep disorders
When a person is in a coma, an EEG may be performed to determine the level of brain activity. The test can also be used to monitor activity during brain surgery. There are no risk associated with an EEG. The test is painless and safe. Some EEGs do not include lights or other stimuli. If an EEG does not produce any abnormalities, stimuli such as strobe lights, or rapid breathing may be added to help induce any abnormality.
When someone has epilepsy or another seizure disorder, the stimuli presented during the test (such as a flashing light) may cause a seizure. The technician performing the EEG is trained to safely manage any situation that might occur.
How is an EEG Taken?
An EEG measures the electrical impulsesin your brain by using several electrodes that are attached to your scalp. An electrode is a conductor through which an electric current enters or exits.
The electrodes transfer information from your brain to a machine that measures and records the data. Specialized technicians can apply EEGs at hospitals, doctor’s offices, and laboratories. The test usually takes 30 to 60 minutes to complete, and involves the following steps:
- You’ll lie down on your back in a reclining chair or on a bed.
- The technician will measure your head and mark where to place the electrodes.
- These spots are scrubbed with a special cream that helps the electrodes get a high-quality reading.
- The technician will put a sticky gel adhesive on 16 to 25 electrodes, and attach them to spots on your scalp.
Once the test begins, the electrodes send electrical impulse data from your brain to the recording machine. This machine converts the electrical impulses into visual patterns that appear on a screen. A computer records these waves.
The technician may ask you to do certain things while the test is in progress.
- They may ask you to lie still,
- close your eyes,
- take a deep breathe, or look at stimuli (such as a flashing light or a picture).
After the test is complete, the technician will remove the electrodes from your scalp. During the test, very little electricity passes between the electrodes and your skin, so you will not feel any discomfort.
In some cases, EEG with a longer duration may be required. These EEGs are performed to capture seizure activity and use accompanying video. Even if the seizure does not occur during the test, the EEG may show abnormalities. However, it does not always show past abnormalities related to seizure.
For Which Diseases Is EEG Taken?
EEG is the recording of the electrical functioning of the brain. EEG is performed in the diagnosis and follow-up of epilepsy. However, EEG is also applied in brain inflammation diseases, nervous diseases, and in the investigation of headaches. EEG tests are also performed for tic disorders, learning disorders, dissociative disorders, and eating disorders. People with sexual identity disorders and personality disorders are also asked to take an EEG test.
Why is EEG Requested?
EEG is known as the writing of electrical functions produced by brain nerve cells in the form of brain waves. The normal functioning of the brain is impaired in many nervous diseases, especially epilepsy. EEG, on the other hand, detects the location of these disorders with brain waves and enables the acquisition of detailed information. EEG is commonly used to diagnose epilepsy disease.
Where Can I Have an EEG Taken?
EEG is taken during the diagnosis of nervous diseases, especially epilepsy. Therefore, EEG should be taken by neurology specialists. It can be taken while the patient is asleep or awake. In the meantime, the patient’s hair must be clean. Hence, the most accurate result can be obtained. In short, since EEG is used in the measurement of electrical activities, it is commonly used in neurology and neurophysiology departments.
How Long Does the EEG Take?
EEG recording is usually a process made during a scheduled appointment. Therefore, unless there is a case of emergency, you must be in the EEG appointment at the time given to you. This diagnostic test is carried out in different durations according to the method of examination
- A routine EEG recording lasts for an average of 30 minutes.
- If both sleep and awake states are examined, the EEG recording lasts about 1 or 1 and a half hours.
- In some cases, a 3-4 hour examination described as short-term sleep is carried out.
- However, if an asleep state between 7 to 9 hours all night seems necessary, the EEG recording is applied during a night’s sleep.
- In some necessary situations, this process may take up to 24 hours.
- Indeed, if EEG is made for epilepsy surgery, this process can take days.
- EEG recording in infants and children is a much more important and valuable case. Therefore, especially when EEG is recorded in infants, at least 1-hour continuous sleep is expected, and if found necessary after this process, the EEG recording continues in the awake state.
What To Do Before An EEG Test
EEG is the most reliable and healthy diagnostic method, with no proven side effects, that can be applied to almost everyone including infants. There are certain things to do before the EEG test:
- There is no comprehensive pre-preparation in adults for EEG. But it is important to wash the hair a day before. Hair products such as a gel or spray should not be used.
- If the person is hungry, blood sugar may fall. A fall in blood sugar can cause irregularities in the EEG. Therefore, if there is no emergency, the person is expected to be full before the EEG test.
- If a Sleep EEG is to be recorded, the patient is asked to remain asleep for a long time. For this, you will be expected to remain sleepless for a long time before the EEG recording. Hence, you may be asked to stay awake for about 24 hours before EEG.
- If sleep EEG is the preferred method, you must bring an outfit you feel comfortable with.
- If there is no emergency and you are not required to take an EEG test immediately, you should not consume sleep medicines, sedatives, alcohol, coffee before EEG.
- If the examinations are to be made to the children, especially to babies, their immobilization is more difficult than adults. Therefore, the children need to be completely sleepless before EEG.