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Electroencephalogram (EEG)The EEG, electroencephalogram, or EEG, is a test that is used to study the functioning of the central nervous system, specifically the activity of the cortex of the brain. It essentially consists of using special electrodes register the electrical currents that form in the brain neurons, and that are the basis of the functioning of the nervous system. Thanks to it can be diagnosed alterations of brain electrical activity that suggests diseases such as epilepsy, narcolepsy or dementia, among many others. It is also an essential test to certify a death in a patient in a coma.
Since the 19th century were already performed experiments in which will detect electrical currents in the brain of monkeys, but was needed to open the skull for your study. Eventually, the electrodes improved and already detected brain activity through the skull. In 1920 the German doctor Hans Berger began his studies of electroencephalography in humans, which meant a revolution in the field of Neurology and Psychiatry.
This test may identify normal and pathological cerebral activity rhythms. Normal electrical waves depend on the State of wakefulness or sleep. Waves which are typically are:
- Vigil: Alpha rhythms, delta, beta and thetha.
- Dream: activity REM and non-REM (which is divided into 4 phases).
- Stimulus: alterations of the rhythms of the past when Visual, sound, painful or sensory stimuli.
When doing an electroencephalogram (EEG)Electroencephalogram (EEG) is a test that is used when the following conditions are suspected:
Epilepsy: this disease appears when a group of neurons begin to generate nerve impulses of an uncontrolled manner that spread throughout the brain. That leads to a seizure which can be detected with the realization of an electroencephalogram.
Dementia: dementia is a clinical diagnosis, every time described more alterations encefalograficas that help to classify them and so you can adjust to the best treatment that delay their advance.
Brain damage: the brain can occur for many reasons. Among the most common are strokes (or strokes) and head injuries. In those cases, there would be a part of brain without electrical activity that would be in the electroencephalogram.
Encephalopathies: encephalopathies are different from other brain diseases that in this case the brain is healthy, but there are external agents that modify its activity. We may find ourselves brain diseases, metabolic, toxic, inflammatory, etc. All of them can have manifestations on the electroencephalogram.
Psychiatric disorders: is used as a complementary test to qualify better psychiatric alterations of each patient. The EEG is also used in research to find a relationship between the biological basis of each disease and the psychological picture.
Coma and brain death: the electroencephalogram can help differentiate between these two States. In both cases the person is unconscious but breathing and their heart beats. In coma there is brain activity, but in brain death (is not what is known as 'flat electroencephalogram').
Preparation for the electroencephalogram (EEG)If they are going to perform an electroencephalogram (EEG) these are the issues that you must take into account before introducing you to the test:
Duration: electroencephalogram takes about 20-30 minutes. The only extra time would be the preparation and collection after the test. Sometimes must be an electroencephalogram during sleep (as in polysomnography), by proving it can last a night.
Income: the electroencephalogram can be in a hospital, with a unit of neurophysiology, without requiring the patient admission, so you will be able to test and then go back to your normal life.
Is necessary to be accompanied?: do not need to be accompanied.
Drugs: don't need to take any prior medication. You should tell your doctor all the medicines taken regularly and will decide which suspend or maintain, especially if you take drugs for epilepsy, psychiatric illnesses, antiarrhythmics, relaxing sedative or muscle.
Food: it is not necessary to remain in fasting prior to testing or after. You can not drink drinks with caffeine between 12-8 hours before the test (coffee or energy drinks).
Clothes: you can go to the quote from the test with the same clothes every day. The night before you will have to wash your head with your usual shampoo, but you should avoid conditioners, masks or other cosmetic products.
Documents: is essential to bring with you the steering wheel which shows the performance of this test. You have to carry the health insurance card and medical history on diseases to study, if you have them, although the doctor will already have it with him. It can give you a document after the test, keep it.
Pregnancy and breast-feeding: the electroencephalogram is not contraindicated in pregnancy or lactation. Although it is important that your health care provider know that you're pregnant, because some biological constants are altered for itself during these stages.
Contraindications: is considered a safe test and has no absolute contraindications. However, it recommended caution in an EEG performed in people with severe seizures, since they may be triggered easily during the test.
How is the electroencephalogram (EEG)First, the doctor will assess whether it may be useful to perform the electroencephalogram (EEG) and if so will quote you one day for the test and you will explain the basic measures that you need to know to put you to the test. Avoid drinks with caffeine (coffee, Coca Cola, energy drinks...) 12-8 hours before the test, and the day before its realization do not use conditioner, hair gel or other hair cosmetics in the area of the body that you go to study.
When you arrive at the hospital and go to the room where you someterás to the EEG ask you that you sit in a Chair. Then placed the electrodes in her head, which are adhesive patches that are glued to the scalp. They are between 16 and 25 sensors, for concerned it the entire head. So well they conduct electrical impulses used a hair gel, so hair is very viscous after the test, but it solves no problems after washing it. All electrodes have a cable that terminates in an oscilloscope that records all the electrical signals.
Once placed all the electrodes, they ask you that relax and remain seated with your eyes closed. Throughout the test you will be monitored by the physician or the technician electroencephalogram, may not stay in the room and go to an adjoining room with a window, thus will not affect the test. While you're relaxing resting brain electrical activity will be recorded.
To detect the brain electrical activity corresponding to external stimuli, they will make different simple sensory experiences . For example, to see what the response to Visual stimuli you illuminated with a flashlight several times, to sound stimuli used a beep that will vary in intensity and tone, and to the sensory stimulus directly touched parts of your body with different textures. Another stimulus that is frequently used is breathing fast and deep for a few seconds, this manoeuvre can trigger mild epileptic seizures in some people and modifies the brain electrical activity.
Once the test completes one electrode will be one. They will leave you a paper or cloth to remove excess gel thickness, although you will have to wash your hair later at home. Then you may have to wait until you give you the results, although not come analyzed by the doctor because you'll need more time.
Complications of the electroencephalogram (EEG)The electroencephalogram is a very little invasive test and does not usually pose any risk for people who are subjected to it. Some complications that have been described in relationship to it is that some of the electrodes can irritate the skin in people who have it especially sensitive, something not very common.
When you study the cerebral electrical activity against external stimuli can be triggered seizures in individuals predisposed to them. This is normal and in many cases are looking that they happen to be able to study, but in people with a history of very serious crises should assess whether it is worth the risk of appearing a new crisis.
Results of electroencephalogram (EEG)During the realization of the electroencephalogram (EEG) electrodes different capture electrical signals that are stored in a memory. At the same time that the test you can see these measurements, but it is virtually impossible to analyze them because it takes time and dedication to study the different parameters simultaneously.
The neurophysiologist or neurologist will analyze the pattern of electric waves recorded on the electroencephalogram. It is set in several parameters such as frequency, amplitude, and the morphology of the same. The frequency is the number of times that a wave is repeated in time, the width is the distance between the maximum and minimum point of the wave, and morphology is seen with the way that each type of wave. With those data can differentiate the rhythms alpha, beta, REM, caused by stimuli, etc.
You can go to pick up the medical specialist who sent you the test, results of electroencephalogram (EEG) will normally be a neurologist. On that date it explain the alterations that have been throughout the study. It may necessary to perform more tests that require further diagnosis, such as a CT scan or an MRI. After all, your health care provider explain your illness and what treatment options, among which will recommend you the most suitable option.