An electroencephalogram (EEG) is a test used to detect abnormalities related to electrical activity of the brain. This procedure tracks and records brain wave patterns.
Small metal discs with thin wires (electrodes) are placed on the scalp, and then send signals to a computer to record the results. Normal electrical activity in the brain makes a recognizable pattern. Through an EEG, doctors can look for abnormal patterns that indicate seizures and other problems.
Why is an EEG Done?
The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG.
Patients with lesions of the brain, which can result from tumours or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion.
The test can also be used to diagnose other disorders that influence brain activity, such as Alzheimer's disease, certain psychoses, and a sleep disorder called narcolepsy.
The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures.
There may be other reasons for your doctor to recommend an EEG.
Results of EEG
Abnormal results on an EEG test may be due to:
- Abnormal bleeding (haemorrhage)
- An abnormal structure in the brain (such as a brain tumour)
- Tissue death due to a blockage in blood flow (cerebral infarction)
- Drug or alcohol abuse
- Head injury
- Migraines (in some cases)
- Seizure disorder (such as epilepsy)
- Sleep disorder (such as narcolepsy)
- Swelling of the brain (oedema)
The EEG has been used for many years and is considered a safe procedure. The test causes no discomfort. The electrodes only record activity and do not produce any sensation. In addition, there is no risk of getting an electric shock.
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