Electroencephalogram

Generality

The electroencephalogram is the completely safe and painless recording of the electrical activity of the brain and other parts of the brain.

Figure: Electroencephalography of a young patient. From the site: http://escola.britannica.com.br/

The acquisition of an electroencephalogram takes place during an examination called electroencephalography (EEG), which involves the application of about twenty electrodes to the patient's head, connected to an instrument called an electroencephalograph.
Doctors resort to electroencephalography in the presence or suspicion of neurological diseases, capable of altering the conduction of electrical signals within the brain.
The procedure does not require special preparation and is quite simple from a practical point of view. It usually lasts an hour, but if it is done while the patient is asleep, it can last for more than 3 hours.
The interpretation of an electroencephalogram is the responsibility of a physician experienced in neurophysiology.

What is the electroencephalogram?

The electroencephalogram is a recording of the electrical activity of the brain, which is graphically reproduced in a trace marked by different sections called waves.

To be obtained, the electroencephalogram requires the application of small electrodes on the head, connected to an electroencephalograph (sophisticated electronic instrument, capable of creating a trace of the recorded brain signals).

The examination with which the graphical representation of the brain's electrical activity is obtained is called electroencephalography (EEG).

ELECTRICAL ACTIVITY OF THE ENCEPHALUS

The brain (from enkefalos, all that is inside the head) can be divided into three parts: the brain (consisting of the telencephalon which overhangs the diencephalon), the cerebellum and the brainstem. These regions communicate with the rest of the body via nerve cells called neurons.
To communicate with each other and with other types of cells (for example with muscle cells), neurons use the ions present inside them or on their external surface. In fact, ions are positively or negatively charged particles which, when they undergo a quantitative variation, generate an electric current (ionic current).
The brain sends electrical signals and receives others. For example, it can send signals to limbs and muscles for their movement, while it can receive input from sensory organs to create "images" of the perceived world.
Both the sending and the reception of the signals take place thanks to a variation of the ionic quantities present inside the neurons

HISTORY OF EEG

The first human EEG dates back to 1924, thanks to the research and studies of a German physiologist and psychiatrist named Hans Berger (1873-1941).
Since then, several Anglo-Saxon scientists deepened the methodology launched by Berger and improved it. Not surprisingly, already in 1936, al Massachusetts General Hospital, the first electroencephalographic laboratory was built.
In the following years, the instrumentation was perfected more and more and, in 1953, it allowed the first description of the REM sleep phase (Aserinsky and Kleitman).
Since the 1980s, electroencephalography has become a very frequently used diagnostic procedure with more than reliable results.

When you do

The electroencephalogram is able to record the anomalies of the electrical activity that characterize certain diseases of the brain.
Therefore, doctors use electroencephalography when they suspect or need to monitor the following diseases:

• Epilepsy and seizures. The attacks (or seizures) of epilepsy are the signal of a "hyperactivity or a malfunction of the brain neurons. During a seizure, the epileptic individual can accuse loss of consciousness, sensory, psychic or motor alterations and violent spasms or contractions of the type convulsive skeletal muscle.
• Brain tumor. It is a mass of cells formed and grown in a completely abnormal way in an "area of ​​the brain". Brain tumors can be benign or malignant.
• Trauma to the head.
• Encephalopathies. A group of pathologies characterized by a "functional and / or structural anomaly of the brain".
• Encephalitis. It is inflammation of the brain, often caused by infectious agents.
• Stroke. This is a sudden loss of brain function, caused by an "insufficient blood supply to a" more or less extensive area of ​​the brain tissue. If the cause of the stroke is a narrowing of the blood vessels, it is called an ischemic stroke; if the responsible event is a vessel injury, it is called a hemorrhagic stroke.
• Sleep disorders. This category includes insomnia, hypersomnia, sleep-wake disorders, parasonies, obstructive sleep apnea syndrome, etc.
• Dementia. It is a disorder acquired in the course of life, which causes a partial or total loss of intellectual functions. Patients with dementia experience memory gaps, language problems, lack of abstraction, etc.
• Brain death. We speak of brain death when the brain of an individual, precisely the brainstem, ceases to perform any activity. Individuals in a state of brain death have permanently lost consciousness and any ability to respond to external stimuli.
• Coma. Prolonged state of unconsciousness which can be due to various causes, including: severe trauma to the head, brain tumor, stroke, alcohol or drug intoxication, diabetes, etc.

Attention: electroencephalography does not provide any information about an individual's IQ.

EEG AND EPILEPSY

Figure: EEG of an epileptic person. From the site: http://en.wikipedia.org/

Electroencephalography is one of the most suitable diagnostic tests in case of epilepsy.
In fact, thanks to an electroencephalogram, it is possible to identify the causes of an epileptic seizure and the electrical alterations that occur inside the brain, both during an attack and in normal conditions.
Furthermore, based on the characteristics of the resulting tracing, doctors can determine the exact type of epilepsy and the best therapeutic treatment to adopt.

OTHER USES

Electroencephalography can also be useful for:

• Check if drug coma has been adequately induced.
  In other words, electroencephalography represents a tool for monitoring general anesthesia for patients voluntarily induced into a coma.
• Monitor, indirectly, cerebral perfusion during a "carotid endarterectomy.
  This surgery is performed to restore the patency of a "carotid artery occluded by an atherosclerotic plaque.
• Monitor the effects of amobarbital during the Wada test.
  The Wada test is used to check which cerebral hemisphere a certain cognitive function belongs to. It involves the injection, in one carotid artery at a time, of a sedative substance, called amobarbital.

Risks

The acquisition of an electroencephalogram does not cause any discomfort and does not endanger the patient in any way. Therefore, electroencephalography is a completely safe and painless examination.

Special case: the study of epilepsy may require that, during the electroencephalography, the individual under examination is voluntarily stimulated to suffer a seizure. This should not worry the patient, as he is surrounded by medical personnel ready to assist him in case of need .

Preparation

Electroencephalography does not require any particular preparation. In fact, it is sufficient for the patient to take care of:

• The evening before the exam, wash your hair and head thoroughly, avoiding applying gels, sprays or lotions to the scalp thereafter. This recommendation, to be observed until the end of the examination, is due to the fact that the use of certain products can make the application of the electrodes more difficult.
• On the day of the exam, avoid taking caffeinated drinks, as the latter alters the results of the procedure.

Some special cases

If the patient is under drug treatment, it is advisable to continue with the normal assumptions, unless the attending physician expressly forbids it.
Whether the analysis of brain activity during sleep is planned, the physician is likely to instruct the patient not to sleep (or sleep less hours) the night before the exam.
If a little sedation is planned before the procedure, the patient is invited to be assisted by a family member or friend, especially when returning home.

Procedure

The classic electroencephalographic examination is an outpatient procedure lasting a total of about 60 minutes.
Here is what happens in this time frame:

• A hospital technician measures the size of the patient's head and marks the exact points where to apply the electrodes. Generally, in these same points he also spreads a grainy cream, which serves to improve the quality of the future track.
• The same technician puts the patient in communication with the recording tool: first he attaches the electrodes to the marked points, then he connects the electrode cables to the electroencephalograph.
  The number of electrodes used is considerable (even more than 20), so much so that they cover all parts of the head.
• Once the connection has been made and the patient is relaxed (N.B: he can be lying down or sitting according to the purpose of the electroencephalography), the recording can begin.
• During the recording, the individual under examination may be asked to: close their eyes, perform simple mathematical calculations, read a paragraph of a book, look at a photo, breathe deeply for a few minutes and / or look into a very bright light. they are justified by the fact that their execution could make a fundamental contribution to the ongoing investigation.
• At the end of the recording, the technician turns off the EEG and detaches the electrodes from the patient's head, who can go home immediately.
  Results are usually available after a few days.

Depending on the purpose of the electroencephalography, the traditional procedure may undergo small variations. Below are three of the main variations.

Adhesive electrodes or headphones

The electrodes can be applied to the skin using a special adhesive, or they can be glued to a kind of cap.

EEG WITH ASLEEP PATIENT

Figure: example of a cap on which to apply the electrodes. From the site: http://en.wikipedia.org/

During sleep, brain activity undergoes significant changes compared to the waking phase. Therefore, the EEG traces will also be extremely different.
Doctors use EEG with the patient asleep when they suspect a sleep disorder or when the traditional EEG procedure has not provided significant results.
Remember that, in order to fall asleep more easily, the patient may be asked not to sleep the night before the recording.
The electroencephalographic examination of a sleeping individual could take up to three hours.

DYNAMIC EEG

Dynamic EEG is the recording of brain activity for at least one full day. It is particularly useful when it is not yet clear what exactly causes the brain changes.
During the examination, the patient can perform almost all normal daily activities, as the EEG is small in size and can be applied to clothing.
For the purposes of the investigation, it certainly does not help to lead a different life than usual (N.B: it is obvious that everything that could damage the recording device must be avoided).

EEG VIDEO

Video EEG is a dynamic EEG of several consecutive days, during which the patient is also constantly filmed in his daily activities.
It is widely practiced when the individual under examination is a child and suffers from epileptic seizures, as young subjects hardly know how to tell the doctor what triggers epilepsy attacks in them (N.B: this can also happen to adults).
Moreover, it finds application even when the information collected with the traditional EEG is very scarce.
Usually, the entire video EEG procedure takes place in a hospital room, built specifically to film what is happening inside.

Results

The reading and interpretation of the electroencephalogram is the responsibility of a physician specialized in neurophysiology. Neurophysiology is the branch of medicine that deals with analyzing the functioning of the entire nervous system, both central and peripheral.
Generally, the results of an "electroencephalography are available within a few days (maximum one week).
At the time of the withdrawal of the exams, there is also an interview between doctor and patient, during which the first will explain to the second what emerged from the registration.
Furthermore, the doctor-patient meeting represents a good opportunity for the individual examined to remove any doubts about his own situation. In this regard, it is good practice for the patient to be accompanied by a friend or family member, so that the latter reminds him of all the issues to be clarified and helps him in gathering the most important information provided by the attending physician.
Some of the classic questions to ask the doctor during the interview are:

• Based on the results, what are the next steps?
• Should the examination be repeated after some time?
• Is the electroencephalogram reliable or was there something that may have altered the final outcome?