What Is a QEEG?

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  • Written By: Andrew Kirmayer
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 04 October 2019
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Quantitative electroencephalography (QEEG) is a medical diagnostic test that is used to measure electrical brain activity as well as an individual’s brain function. During the procedure, 19 sensors are placed on the head, often as part of a device known as a Lycra cap. Each sensor on the cap is located in a pre-determined position according to scientific standards. A cable links this cap to a computer which processes the data to analyze various brainwaves as well as create a graphical map of brain activity.

During the QEEG, technicians make sure the patient is comfortable once all the equipment is connected. Data is recorded while the patient’s eyes are open and closed, while they read, and as they try to solve math problems. The results are compared with standard patterns of brain activity for people in the same age group as the person being tested.

Brain waves are measured according to their frequency bands. Of the 19 that are typically assessed by the QEEG, some of the main frequencies are Delta, Theta, Alpha, Beta1, Beta2, Beta3, High Beta, and Gamma. Certain wave patterns indicate a sleep state, as well as coma, brain infection, or epileptic activity. Such activity measurements, which have been studied since the 1930s, can be used to diagnose Attention Deficit Hyperactivity Disorder (ADHD) as well, but the diagnostic tool does not provide information on the physical structure of the brain.


The end result of a QEEG is a graphical report that can be anywhere from 12 to as much as 30 pages long. This report describes the test process, patient, and the normal and abnormal results that show up. Electrical measurements from all 19 regions are detailed and compared to one another. A QEEG brain map is generated and arranges the waveform data into a topographical perspective, which includes colors to depict the amplitude of electrical activity detected from different brain regions.

A QEEG does not involve any invasive procedures on the patient, nor does it cause pain. The analysis and mapping take a couple of hours. Using the data produced by the diagnostic tool, technicians and physicians can identify a variety of injuries and neurological disorders, such as depression, addictions, and obsessive compulsive disorder. The part of the brain affected and the variation of the readings from normal can help determine what medications, at what doses, and which treatments may be necessary.


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