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some facts and definitions

EEG (Electroencephalogram)

According to North Shore LIJ, an EEG (electro-ence-phalo-gram) is a brain wave test. It detects abnormal brain wave or electrical activities. EEG tests are used to determine brain disorders like epilepsy, lesions, Alzheimer’s, narcolepsy.etc. This procedure is done by applying electrodes that consists of small metal disks with wires that are pasted onto the scalp. Among the basic waveforms, there are alpha, beta, theta and delta rhythms. 

The alpha wave occurs at a frequency of 8 to 12 cycles per second in a regular rhythm. Alpha waves only occur when you are awake but have your eyes closed. 

The beta wave occurs 13 to 30 cycles per second. Beta waves are associated with anxiety, depression or the use of sedatives. 

The theta waves occur 4 to 7 cycles per second which are common in children and young adults. 

Delta waves occur 0.5 to 3.5 cycles per second and these waves only occur in young children when they are asleep. 


Yes, there are wires on your scalp but fear not! Coming from experience, EEG’s are safe. There are no risks of getting an electrical shock. However, there can be risks depending on your medical condition. Hypoglycemia (low blood sugar) due to fasting, certain medications like sedatives, oily hair or hairspray can interfere with the reading of the EEG test. 

When taking an EEG test, the doctor, nurse or EEG technician will ask you to sit in a a chair or lie on a bed. They will attach 16 to 25 electrodes to your scalp. You will be asked to close your eyes, relax and stay still. The only uncomfortable part of the EEG test is that once they begin recording your brain wave activity, you must stay still throughout the test. After a while of recording your brain activity while you are at rest, you will also be asked to take a deep breath rapidly for three minutes and or you may be exposed to a bright light.

EEG tests usually take 45 minutes to two hours. 

After the procedure is done, the EEG technician will remove the electrodes and remove the paste by using warm water. Your scalp may be somewhat itchy or irritated from the paste where the electrodes were placed. 

North Shore LIJ: EEG

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