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Electroencephalogram (EEG) is the recording of electrical activity of the brain


Published: Jun 04, 2013

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In translation from its Greek roots, Electroencephalogram (EEG) means electro — electrical, encephalo — brain and gram(ma) — picture.

An electroencephalogram (EEG) is the recording of electrical activity of the brain, similar to the ECG (electrocardiogram) where recording electrodes are placed on the chest to capture the electrical activity of the heart. By placing electrodes on the scalp and amplifying the activity, an electrical brain picture is recorded. This picture may be normal but in specific disease processes, distinct abnormal patterns may be generated indicating seizure or tendency to have a seizure.

A routine EEG recording lasts about an hour with preparation time lasting about the first 20 minutes of that hour. The procedure is painless but requires patience. The electrodes are placed on the scalp with a conductive gel or paste, usually after preparing the scalp area with a light skin prep gel to reduce artifact. During the recording, activation procedures are used that may induce abnormal activity that might not otherwise be seen. These procedures include fast breathing also known as hyperventilation (HV), photic-stimulation (flashing a strobe light in front of the eyes), eye closure, mental activity, and sleep deprivation (lack of sleep).

The main application of the EEG is in the diagnosis and monitoring of epilepsy but is also used in the diagnosis of patients who are suspected of having various problems which may be non-epileptic in nature, including neurological problems (brain tumors, strokes, degenerative, metabolic or toxic brain disorders or infections), psychiatric disorders and movement disorders.

A seizure can mimic many disorders simply because depending on where in the brain the abnormal electrical discharges are occurring, an individual will present with symptoms related to the functioning of that area, which means that any sudden, unexpected change in behavior be it motor, sensory (touch, vision or hearing), learning, psychic or emotional can be due to seizure.

Imagine your baby developing sudden jerky movements, your child suddenly and unexpectedly passing out, your spouse having staring episodes and ignoring you, a sudden drop in academic performance or strange bizarre behavior in grandmother.

These may all be due to various problems but can all be caused by seizure activity.

Although EEGs are designed to assist in diagnosis and monitoring of treatment of seizures it is extremely useful in eliminating non-epileptic events. There are different types of EEGs with use in different situations such as:

• Routine EEG: A 20 to 40 minute recording of the resting brain activity performed while the patient is awake, drowsy and/or asleep.  Total testing time is one to 1.5 hours.

• Sleep-deprived EEG: An EEG that is also recorded for approximately 30 to 45 minutes, after the patient has been deprived of sleep for at least 24 hours.

• Prolonged EEG: A one to five hour extended EEG recording is used specifically to capture typical episodes that are concerning such as unusual occurrences such as jerks, twitching, bedwetting, staring, uncontrollable shaking, drooling from the mouth or strange behavior. This type of EEG can be extended to days if necessary provided episodes are occurring frequently enough and there is a good chance of capturing it while brain waves are being recorded.

• Video EEG: An EEG recorded while the patient is being filmed.  This provides clear correlation of the physical and brain activity. If there is an unusual occurrence such as staring or body movements, we can evaluate the brain function and the video in real time, to see if there is any correlation.

• Ambulatory EEG: A 24 to 48 hour EEG recording which can be extended for much longer, in which the patient wears a monitor at home. The ambulatory EEG unit is a small piece of equipment that is connected to the scalp electrodes and brain waves continuously. This is similar to the Holter monitor used by cardiologists to record heart beats when suspecting heart problems. The ambulatory EEG allows for complete mobility of the patient and is used to evaluate episodes that are frequent or that may occur in specific environments. It can also be used to monitor medication effects and behavior changes. It cannot however be taken into the shower. A routine EEG must precede this study.

If you or a family member develops a sudden, unexpected event and believe that a seizure is a possibility then discuss with your doctor about obtaining the appropriate EEG. Accurate diagnosis is essential for appropriate treatment and despite misconceptions by the general public that modern tests (such as MRI and CT scans) reveal everything any good doctor will tell you that accurate diagnosis is based predominantly on a thorough history and a good clinical examination. Tests are tools utilized to help to either confirm or negate the clinical diagnosis and should never be applied in a shotgun approach, which is neither efficient nor cost-effective.

EEGs are very cost-effective when considering that if the wrong diagnosis is made, this can mean that an individual is placed on unnecessary medications for years with possible side effects or alternatively not placed on appropriate seizure medication and is at risk for catastrophic events. Remember that seizures can indeed kill.

• Arona Aranha is an EEG technician.



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