Electroencephalography Written Report

Comprehensive Written Report
Electroencephalogram (EEG)

EEG

Electroencephalogram records electrical potentials generated by nerve cells in the cerebral cortex. It is a test or record of brain activity produced by electroencephalography. Encephalography is any of various techniques for recording the structure or electrical activity of the brain.
Electroencephalography (EEG) is typically a non-invasive (however invasive electrodes are often used in specific applications) method to record electrical activity of the brain along the scalp. EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain.[1] In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time,[1] as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus on the spectral content of EEG, that is, the type of neural oscillations that can be observed in EEG signals.
EEG is most often used to diagnose epilepsy, which causes abnormalities in EEG readings.[2] It is also used to diagnosesleep disorders, coma, encephalopathies, and brain death. EEG used to be a first-line method of diagnosis for tumors, strokeand other focal brain disorders,[3] but this use has decreased with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis, especially when millisecond-range temporal resolution (not possible with CT or MRI) is required.

Derivatives of the EEG technique include evoked potentials (EP), which involves averaging the EEG activity time-locked to the presentation of a stimulus of some sort (visual, somatosensory, or auditory). Event-related potentials (ERPs) refer to averaged EEG responses that are time-locked to more complex processing of stimuli; this technique is used in cognitive science, cognitive psychology, and psychophysiological research.

Brain

Light, sound and odors, for example, are transformed by our sensory organs into a code made of series of electrical impulses that travel along neurons from the body to the brain. Information about the onset and the intensity of a stimulus is thought to be sent to the brain by the timing and frequency of these electrical impulses. How information is sorted by the brain has been an open question. The group discovered that different neurons in the brain are dedicated to respond to specific portions of the information.

The History of EEG

Hans Berger is the EEG pioneer. He's the first one to observe alpha waves called Berger waves in 1924.
The discovery of electroencephalography (EEG) in 1929 by the German psychiatrist Hans Berger was a historical breakthrough providing a new neurologic and psychiatric diagnostic tool at the time, especially considering the lack of all those now available in daily practice (EP, CT, MRI, DSA, etc.) without which the making of neurologic diagnosis and planning neurosurgical operative procedures would now be unconceivable.His method involved inserting silver wires under the patient's scalp, one at the front head and one at the back. Later he used silver foil electrodes attached to the head by a rubber bandage. He used double-coil Siemens recording galvanometer, which allowed him to record electrical voltages as small as one ten thousandth of a volt. The resulting output, up to three seconds duration, was then photographed by an assistant.
Listed below is the timeline of the development of EEG:
In 1929, Hans Berger
Recorded brain activity from the closed skull
Reported brain activity changes according to the functional state of the brain
In 1957, Gray Walter
Made recordings with large numbers of electrodes
Visualized brain activity with the toposcope
Showed that brain rhythms change according to the mental task demanded
William Grey Walter, neurophysiologist and robotician, brain waves and EEG topography, 1930s. Walter produced his own versions of Berger's machine with improved capabilities, which allowed it to detect a variety of brain wave types ranging from the high speed alpha waves to the slow delta waves observed during sleep.
He was the first to determine by triangulation the surface location of the strongest alpha waves within the occipital lobe (alpha waves originate from the thalamus deep within the brain).

Parts of an EEG machine

Electrodes
Electrodes are placed on the scalp in special positions. There are two systems of electrode placement. These are:
10-20 International System – 21 electrodes
10-10 International System – 64 electrodes
Electrodes are placed on the scalp in special positions are identified by the recorders
who measures the head using International 10-20 System.
Flat electrodes whether disposable self-adhesive stickies or reusable flat electrodes can better retain the consistency of the conductive material in contact with the electrode. So, the flat lead should allow for more consistent recording quality for a longer periods of time. But, again, this should be tested per facility to compare the options. Some flat electrodes take some time to "get used to" and may require slight adjustments in application techniques. Additionally, some flat electrodes are significantly more comfortable for the patient and have shown to cause less skin irritations than some cup designs.
Cup designed electrodes can be maximized for their potential with a good covering placed over the cup to help keep the paste in place longer; but the flat designs offer patient comfort and some skin benefits as well. And especially with pediatrics the comfort and skin integrity issue is probably more prominent than in an adult facility.
There are two different types of EEG signals depending on where the signal is taken in the head: scalp or intracranial. For scalp EEG, electrodes are placed on the scalp with good mechanical and electrical contact. In intracranial EEG, the EEG signal is obtained by special electrodes implanted on the brain surface during the surgery
Electrode Montages
They are pattern of connections between the electrodes and the recording channels. There are two basic types of EEG montages, these are referential montage and bipolar montage. Referential Montage is where each channel represents the difference between a certain electrode and a designated reference electrode. There is no standard position for this reference; it is, however, at a different position than the "recording" electrodes. Whereas in Bipolar Montage, the potential difference is measured between two active electrodes
Bipolar montage
Each channel (waveform) represents the difference between two adjacent electrodes. The entire montage consists of a series of these channels. For example, the channel "Fp1-F3" represents the difference in voltage between the Fp1 electrode and the F3 electrode. The next channel in the montage, "F3-C3," represents the voltage difference between F3 and C3, and so on through the entire array of electrodes.
Referential montage
Each channel represents the difference between a certain electrode and a designated reference electrode. There is no standard position for this reference; it is, however, at a different position than the "recording" electrodes. Midline positions are often used because they do not amplify the signal in one hemisphere vs. the other. Another popular reference is "linked ears," which is a physical or mathematical average of electrodes attached to both earlobes or mastoids.

EEG Amplifiers

They amplify the voltage between the active electrode and the reference (typically 1,000–100,000 times, or 60–100 dB of voltage gain). In analog EEG, the signal is then filtered (next paragraph), and the EEG signal is output as the deflection of pens as paper passes underneath.

Filter

This is where filtering occurs. Filtering, an operation that results in zero amplitude for the waves at frequencies that we don't want to contribute to the final waveform.







Recording Unit

The recording unit of the EEG is where brain waves are being monitored. It includes computer with equipment connected to the electrodes. The computer has software for the brainwave's graphical user interface. The GUI has every patient's general information like age and name.

EEG Examination

Practices during an EEG Examination:
You may be asked to breathe deeply and rapidly (hyperventilate). Usually you will take 20 breaths a minute for 3 minutes.
You may be asked to look at a bright, flashing light called a strobe. This is called photic or stroboscopic stimulation.
You may be asked to go to sleep. If you can't fall asleep, you may be given a sedative to help you fall asleep. If an EEG is being done to check a sleep problem, an all-night recording of your brain's electrical activity may be done.
An EEG takes 1 to 2 hours. After the test, you may do your normal activities.




Dangers

Dangers of EEG:
An electroencephalogram (EEG) is a very safe test. The electrical activity of your brain is recorded, but at no time is any electrical current put into your body. An EEG should not be confused with electroshock (electroconvulsive) therapy.
If you have a seizure disorder such as epilepsy, a seizure may be triggered by the flashing lights or by hyperventilation. If this occurs, the technologist is trained to take care of you during the seizure.

Applications of EEG

EEG functions:
Diagnose epilepsy and see what type of seizures is occurring. EEG is the most useful and important test in confirming a diagnosis of epilepsy.
Check for problems with loss of consciousness or dementia.
Help find out a person's chance of recovery after a change in consciousness.
Study and sleep disorders, such as narcolepsy.
Watch brain activity while a person is receiving general anesthesia during brain surgery.
Help find out if a person has a physical problem (problems in the brain, spinal cord, or nervous system) or a mental health problem.

Proposed Advancement

Disorders like epilepsy are unpredictable. It could appear anytime. Some patients
cannot afford EEG examination fee. Others who can afford the examination are confined in the hospital and as a result, they cannot do their daily routines.
What we propose is a portable EEG with graphical user interface (Java). The proposal includes electrodes connected to smartphones. Through Java programmed GUI, the patient or even his guardian can monitor the patient's brain electrical impulses from time to time. The results can then be printed and presented to the doctor to evaluate the results.