Electroencephalogram

Information on EEG and it's application in healthcare.

1. EU501: BIOMEDICAL SIGNAL MEASUREMENT ELECTROENCEPHALOGRAM (EEG) PREPARED BY: THARSHINI ELANGOVAN 08DEU13F2031 SHALENI KAVIRAJAN 08DEU13F2013 LECTURER: PN IDA MARIA BT MOHD YUSOFF

2. INTRODUCTION Electroencephalography (EEG) - is a medical imaging technique that reads scalp electrical activity generated by brain structures. Electroencephalogram (EEG) - is defined as electrical activity of an alternating type recorded from the scalp surface after being picked up by metal electrodes & conductive media.

3. ELECTROENCEPHALOGRAM

4. FUNCTIONS OF EEG Diagnosis of epilepsy Monitor alertness, coma and brain death. Locate areas of damage in the brain following head injuries, stroke, tumor and etc. Control anesthesia depth. Investigate sleep disorder and physiology.

5. COMPONENTS OF EEG EEG machine consists of following components: i . Electrodes ii. Amplifiers iii. Filters iv. Recording unit Electrodes ECG Amplifier

6. PARTS OF EEG MACHINE EEG electrodes -> Small metal discs usually made of stainless, tin, god or silver covered with a silver chloride coating . -> Placed on the scalp in special positions. These positions are specified using the International 10/20 system. -> Each electrode site is labeled with a letter and a number . The letters refers to the area of brain underlying the electrode ( e.g ; F-Frontal lobe and T-Temporal lobe). Even numbers denote the right side of the head and odd numbers denote the left side of the head.

7. PARTS OF EEG MACHINE Electrode gel -> acts as a malleable extension of the electrode, so that the movement of the electrodes cables are less likely to produce artifacts. -> The gel maximizes skin contact and allows for a low- resistance recording through the skin. -> The electrolyte gel is injected into each cavity until a small amount out the hole in the mount. With a moderate amount of downward pressure , the syringe with the blunt needle is rapidly rocked back and forth.

8. HOW EEG IS DONE? Patient will be asked to lie on their back on a bed or table or relax in a chair with eyes closed. The EEG technologist will attach several flat metal discs (electrodes) to different places on patients’ head, using a sticky paste to hold the electrodes in place. A cap with fixed electrodes may be placed on the head instead of individual electrodes. In rare cases, these electrodes may be attached to the scalp with tiny needles . During the recording, patients have to lie with eyes closed and they are not allowed to talk to the technologist unless they need to do so . The recording may be stopped from time to time to allow patient to stretch and reposition themselves .

9. HOW EEG IS USED? EEG system covers all parts of brain by placing electrodes on all parts of brain.

10. ECG ACTIVITY The billions of nerve cells in human brain produce very small electrical signals that form patterns called brain waves. During an EEG, small electrodes and wires are attached to the head. The electrodes detect brain waves and the EEG machine amplifies the signals and records them in a wave pattern. An EEG measures electricity that produce by the brain; it does not measure thoughts or feelings, and it does not send any electricity into the brain.

11. ECG ACTIVITY EEG activity can be broken down into 4 distinct frequency bands: i . Beta activity > 13 Hz ii. Alpha activity 8 Hz-13 Hz iii. Theta activity 4 Hz-7 Hz iv. Delta activity < 4 Hz

12. ECG ACTIVITY TYPE OF BRAIN WAVE EXPLANATION BETA ACTIVITY Beta activity is a normal activity present when the eyes are open or closed. It tends to be seen in the channels recorded from the centre or front of the head. Some drugs will increase the amount of beta activity in the EEG. ALPHA ACTIVITY Alpha activity is also a normal activity when present in waking adults. It is mainly seen in the channels recorded from the back of the head. It is fairly symmetrical and has an amplitude of 40 µV to 100 µV. It is only seen when the eyes are closed and should disappear or reduce in amplitude when the eyes are open.

13. ECG ACTIVITY TYPE OF BRAIN WAVES EXPLANATION THETA ACTIVITY Theta activity can be classed as both a normal and abnormal activity depending on the age and state of the patient. In adults it is normal if the patient is drowsy. However it can also indicate brain dysfunction if it is seen in a patient who is alert and awake. In younger patients, theta activity may be the main activity seen in channels recorded from the back and central areas of the head. DELTA ACTIVITY Delta activity is only normal in an adult patient if they are in a moderate to deep sleep. If it is seen at any other time it would indicate brain dysfunction. Abnormal activity may be seen in all or some channels depending on the underlying brain problem.