Generality
The electroencephalogram is a 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: //escola.britannica.com.br/
The acquisition of an electroencephalogram occurs during an examination called electroencephalography (EEG), which involves the application on the patient's head of about twenty electrodes, connected to an instrument called an electroencephalograph.
Doctors use electroencephalography in the presence of the presence or suspicion of neurological diseases, capable of altering the conduction of electrical signals inside the brain.
The procedure does not require special preparation and is quite simple from a practical point of view. It generally lasts an hour, but if it is done while the patient is sleeping it can last for more than 3 hours.
The interpretation of an electroencephalogram is the responsibility of a doctor experienced in neurophysiology.
What is the electroencephalogram?
The electroencephalogram is a recording of the electrical activity of the encephalon, which is graphically reproduced in a path 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 cerebral electrical activity is obtained is called electroencephalography ( EEG ).
ELECTRICAL ACTIVITY OF THE ENVIRONMENT
The encephalon (from enkefalos, everything that is inside the head) can be divided into three parts: the brain (consisting of the telencephalon above 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 ions present within them or on their outer surface. Ions, in fact, are particles of positive or negative charge which, when they undergo a quantitative change, generate an electric current (ion current).
The brain sends electrical signals and receives others. For example, it can send signals to the limbs and muscles, for their movement, while it can receive input from the sensory organs to create "images" of the perceived world.
Both sending and receiving signals take place thanks to a variation of the ionic quantities present inside the neurons
HISTORY OF ELECTROENCEPHALOGRAPHY
The first human electroencephalogram dates back to 1924, thanks to the research and studies of a German physiologist and psychiatrist named Hans Berger (1873-1941).
Since then, several scientists of Anglo-Saxon origin have studied the method launched by Berger and improved it. Not by chance, already in 1936, at Massachusetts General Hospital, the first electroencephalographic laboratory was built.
In the following years, the instrumentation was perfected more and more and, in 1953, allowed the first description of the REM phase of sleep (Aserinsky and Kleitman).
Since the 1980s, electroencephalography has become a diagnostic procedure used very frequently and with more than reliable results.
When you run
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 have to monitor the following diseases:
- Epilepsy and seizures . Epilepsy attacks (or seizures) are a sign of hyperactivity or malfunction of brain neurons. During a crisis, the epileptic individual can experience loss of consciousness, sensory, psychic or motor alterations and violent convulsive spasms or contractions of the skeletal musculature.
- Brain tumor . It is a mass of cells formed and increased in a completely anomalous way in an area of the brain. Brain tumors can be benign or malignant.
- Head trauma .
- Encephalopathies . Group of pathologies characterized by a functional and / or structural abnormality 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 supply of blood to a more or less extensive area of brain tissue. If the cause of the stroke is a narrowing of the blood vessels, it is called an ischemic stroke; if instead the responsible event is a vasal lesion, we speak of hemorrhagic stroke.
- Sleep disorders . Insomnia, hypersomnias, sleep-wake disorders, parasites, obstructive sleep apnea syndrome, etc. belong to this category.
- Dementia . It is a disorder acquired during life, which causes a partial or total loss of intellectual functions. Patients with dementia experience memory gaps, speech problems, lack of abstraction, etc.
- Brain death . There is talk of brain death when the brain of an individual, precisely the brain stem, ceases to perform any activity. Individuals with brain death have permanently lost consciousness and any ability to respond to external stimuli.
- Coma . State of prolonged unconsciousness which may be due to various causes, including: severe head trauma, brain tumor, stroke, alcohol or drug poisoning, diabetes etc.
Attention: electroencephalography does not provide any information about an individual's IQ.
ELECTROENCEPHALOGRAPHY AND EPILEPSY
Figure: Electroencephalogram of an epileptic person. From the site: //en.wikipedia.org/
Electroencephalography is one of the most indicated 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 route, doctors can determine the exact type of epilepsy and the best therapeutic treatment to be adopted.
OTHER USES
Electroencephalography can also be useful for:
- Check whether the pharmacological coma has been induced adequately.
In other words, electroencephalography is a tool for monitoring general anesthesia, for patients who are voluntarily induced into coma.
- Indirectly monitor cerebral perfusion during a carotid endarterectomy .
This surgery is practiced 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 verify which cerebral hemisphere is responsible for a specific cognitive function. It involves the injection, into a 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 in any way endanger the patient. Therefore, electroencephalography is a completely safe and painless examination.
Special case: the study of epilepsy may require that, during electroencephalography, the individual under examination is voluntarily stimulated to suffer a crisis. This does not have to worry the patient, as he is surrounded by medical personnel ready to assist him in case of need.
Preparation
Electroencephalography does not require special preparation. In fact, it is sufficient for the patient to take care of:
- The evening before the exam, thoroughly wash the hair and the head, avoiding from that moment on to apply gels, sprays or scalp lotions. 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 caffeine- based drinks, as the latter alters the results of the procedure.
Some special cases
If the patient is under pharmacological treatment, it is a good idea to continue with normal hiring, unless the treating doctor specifically forbids it.
If brain activity analysis is planned during sleep, it is likely that the doctor will request the patient not to sleep (or sleep less hours) the night before the exam.
If a small sedation is required before the procedure, the patient is invited to be assisted by a family member or friend, especially when they return home.
Procedure
The classic electroencephalographic examination is an outpatient procedure with a total duration of about 60 minutes.
Here's what happens in this time frame:
- A hospital technician measures the size of the patient's head and marks the precise points in which to apply the electrodes. Generally, in these same points it also spreads a granular cream, which serves to improve the quality of the future layout.
- The same technician puts the patient in communication with the recording instrument: 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 the parts of the head a little.
- Once the connection has been made and the patient is relaxed (NB: he can be relaxed or seated according to the purpose of electroencephalography), he can start recording.
- During the recording, the individual under examination may be invited to: close his eyes, perform simple mathematical calculations, read a paragraph in a book, look at a photo, breathe deeply for a few minutes and / or watch a very intense light. These requests 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 electroencephalograph and detaches the electrodes from the patient's head, which can immediately return home.
Generally, results are available after a few days.
Depending on the purpose of electroencephalography, the traditional procedure may undergo small variations. Below are three of the main variants.
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 SLEEPING PATIENT
Figure: example of a cap on which to apply the electrodes. From the site: //en.wikipedia.org/
During sleep, the encephalic activity undergoes considerable changes compared to the waking phase. Therefore, also the EEG tracks will be extremely different.
Doctors use EEG with the sleeping patient when they suspect a sleep disorder or when the traditional EEG procedure has not provided significant results.
Remember that, to fall asleep more easily, the patient could be asked not to sleep the night before the registration.
The electroencephalographic examination of a sleeping individual could last even longer than three hours.
DYNAMIC EEG
The dynamic EEG is the recording of brain activity for at least a full day. It is particularly useful when it is not yet clear what exactly causes brain alterations.
During the examination, the patient can perform almost all normal daily activities, as the electroencephalograph is small and applicable to clothing.
For the purposes of the investigation, it is certainly not useful to make a life different from the usual (NB: it is obvious that we must avoid everything that could damage the recorder).
VIDEO EEG
EEG video 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 report to the doctor what triggers epilepsy attacks in them (NB: this can also happen to adults).
Moreover, it is also applied when the information gathered with the traditional EEG is very scarce.
Usually, the entire EEG video procedure takes place in a hospital room, built specifically to film what happens inside.
Results
The reading and interpretation of the electroencephalogram belong to a doctor specialized in neurophysiology . Neurophysiology is the branch of medicine that deals with analyzing the functioning of the entire nervous system, both central and peripheral.
In general, the results of an electroencephalography are available within a few days (maximum one week).
At the time of exam collection, there is also an interview between doctor and patient, during which the former 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 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 questions 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 findings, what are the next steps?
- Should we repeat the exam after some time?
- Is the electroencephalogram reliable or was there something that may have altered the final outcome?
