The full name of EEG is electro-encephalogram. Just as the ECG measures the electrical activity of the heart, the EEG test measures the electrical activity of the brain.
How is the EEG Test done?
- Before the test, the patient is asked to wash his hair, remove oil or shampoo, etc.
- At the time of the test, about 20 different electrodes are placed on the patient’s head with glue while lying down.
- These electrodes are connected by wire to a machine that takes the reading.
- This reading is printed out on a paper.
- The reading is taken by lying down with the patient relaxed and closed the eyes for some time. Then the reading is taken with the eyes open for some time. It is said to take a long deep breath in between or to take a rapid breath. Sometimes you can be asked to look towards bright light.
- Sometimes readings are taken even at bedtime.
When the EEG is released, the machine produces different waveforms on the paper. These waves are of 6-7 different types. They differ from each other in frequency, that is, each type has its own frequency.
There are 5 major waves of these:
- Delta wave: It is a wave of frequency 0.5 to 4 Hertz which is generated during deep sleep. This wave can also be seen during some types of epilepsy.
- Theta wave: It is a frequency wave of 4 to 7 Hertz which is generated during light sleep. Apart from this, it can also prevail in many diseases.
- Alpha wave: It is a frequency wave of 8 to 12 Hertz (8-12 Hertz) which can be seen while awake, especially when the eyes are closed and in a still state of mind. Its slowing down can be an indicator of disease.
- Sigma wave: It is a wave of frequency of 12 to 16 Hertz which can be seen during sleep.
- Beta wave: It is a wave of frequency of 13 to 30 Hertz (13-30 Hertz) which is seen in the modulus. These waves would arise while sleeping and even while awake. Some types of sleep medications can affect and change these.
Apart from these five major waves, there are other waves such as infra-slow or high-frequency or gamma etc.
Reasons to take the EEG Test:
- Epilepsy: Mostly EEG is done in patients with epilepsy. This helps in diagnosing epilepsy and estimating its severity. Many types of epilepsy have fewer external symptoms. In these, epilepsy can be identified only through EEG.
- Brain tumor: In many brain tumor patients, EEG is also used to check the effect of the tumor on the brain.
- Head injury: EEG of patients is also taken to evaluate the impact and extent of head injury.
- Sleep disorders: Many people have sleep disorders that make them unable to perform simple routine tasks. To detect such diseases, they are often tested in a sleep lab. EEG is also used in this test along with other instruments.
- EEG is used to see brain activity in coma patients. This can help determine the cause of the coma. Similarly, in stroke patients, doctors can also use EEG to examine the brain.
- Apart from this, EEG is also used to know the condition of the patient in ICU or to measure the depth of anesthesia during operation.
Advantages of EEG Test:
- There are many benefits to having an EEG. EEG is a less expensive technique than other imaging techniques such as MRI, CT scan, etc.
- Apart from this, there is no risk of getting any kind of radiation while doing EEG.
- EEG machines being small and mobile, can be brought to the patient, which is difficult with techniques like MRI, CT scan.
- Apart from this, the EEG is like a live feed that gives information about the electrical activity in the brain at the same time. In contrast, MRI, CT scan etc. give a picture of the time of the test, not a live feed.
Disadvantages of EEG:
- Like other lab tests, the EEG also has some drawbacks. The EEG does not capture the activity going on deep inside the brain. For this MRI, CT scan or PET scan is needed.
- It is also difficult to tell the focus or center of disease by EEG.
- Apart from this, the electrical activity of every part of the brain is not visible on the EEG.
- For all these reasons, EEG is used along with other lab tests such as MRI, CT scan or abdominal scan, etc.
The EEG test measures the electrical activity of the brain. Its readings are taken for 30-40 minutes by placing 20 different electrodes on the patient’s head while lying down. While leaving it, the machine generates different types of waveforms on the paper.
EEG is performed for a variety of reasons such as screening for epilepsy, brain tumours, testing for head trauma, estimating the effects of sleep disorders, and estimating brain activity in coma patients. An EEG is a less expensive and radiation-free live feed that is used in conjunction with the rest of the test.