Electroencephalogram (EEG)

a report about electroencephalogram(EEG)
by: Ahmed Nazar

1. UNIVERSITY OF DUHOK
COLLEGE OF MEDICINE




Electroencephalography
(EEG)

Authors:
1.Ahmed Nazar Mustafa
2.Omed Xthr Habib
3.Alla Abdulrazaq mustafa
4.jaber Mahmud abdulrahman
5.Ahmed Thati Hassan


6.Azad Khalid Sulayman
7.Ayman Thsin Ibrahim
8.Payan Younes Mohammed
9.Aza Njiar Najeeb
10.Bizhar Ahmed Mohammed
Supervisor:
Dr. Gulistan Ahmed
Medical biophysics
April 20, 2018

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Table of Contents
1.INTRODUCTION ............................................................... 3
2.EEG instrumentation ....................................................... 4
2.1 EEG electrodes
 ........................................................ 4
2.2 Amplifier ................................................................... 6
2.3 Filters ........................................................................ 7
2.4 Writing unit .............................................................. 8
3.Mechanisim ..................................................................... 8
4.EEG Waveform ................................................................ 9
5.Why is an EEG performed? ............................................ 10
5.1 Medical use ............................................................ 10
5.2 Research ................................................................. 11
6.Risks of EEG ................................................................... 12
7.Preparation for EEG ....................................................... 13
8.During the EEG procedure: ............................................ 14
9.After EEG procedure: ..................................................... 15
10.EEG results: ................................................................. 16
11.CONCLUTION ............................................................... 17
12.Resources: ................................................................... 18

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1.Introduction

An EEG is a medical device used in order to analyze the
components of the brain and “detect problems in the
electrical activity of the brain”. It is also known as an
electroencephalogram. The first human EEG recording was
recorded by Hans Berger in 1924 after about thirty years of
being used by scientists on animals. The immediate
objective was to find out how an EEG worked and it's
primary functions so that it will be more familiar to those
around us who want to understand it better and/or need to
have this procedure.

People today have so many questions about an EEG test;
thus, it is immensely important for society today to
understand how an EEG works and how this machine is
helpful to patients and doctors in the medical industry.

Hence, the question, “Is an EEG an important device in the
medical world?” The answer is “Yes.” An EEG is a medical
device used to analyze the brain in order to detect problems
with/in the brain's electrical activity. Problems such as
Epilepsy and Alzheimer's disease are detected by the
electroencephalogram. Metal disks also known as
electrodes are placed onto the patients scalp in order to
receive the electrical activity clearly. As well, there could be
an electrode cap or net used in place of singular electrodes.
Without the aid of an EEG, many diseases/malfunctions in
the brain's electrical activity may not be diagnosed and
could lead to serious illness or even death.
The general mechanism, procedure, composition and
risks will be discussed briefly in hope to answer the common
questions that might be on reader’s head.

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2.EEG instrumentation

EEG machine consists of following components:
[Figure 1]
• Electrodes
• Amplifiers
• Filters

• writing unit

Figure 1

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2.1 EEG electrodes



• Small metal discs usually
made of stainless steel, tin,
gold or silver covered with a
silver chloride coating
[Figure 2].

• Placed on the scalp in
special positions. These
positions are specified using
the International 10/20
system [Figure 3].



• Each electrode site is
labeled with a letter and a
number [Figure 4]. The
letters refer 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





Figure 2
Figure 3
Figure 4

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Types of electrode placement
1. EEG electrodes placed separately on scalp [Figure 5].



2. EEG electrodes mounted as special band on head
[Figure 6].




2.2 Amplifier

It is an electronic device that increases the power of a
signal. It does this by taking energy from a power supply
and controlling the output to match the input signal shape
but with a larger amplitude. Human brainwave activity is
too subtle to read unless the signal is amplified. These
units available now usually connect through a USB port
Figure 5
Figure 6

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and transmit signals to the therapist computer. Older
units use a serial interface.


2.3 Filters

The use of filters in recording and displaying EEG data is
an indispensable tool in producing interpretable EEG
tracings. Without filters, many segments of EEG would be
essentially unreadable [figure 7]. The main benefit of
filters is that they can appear to “clean up” the EEG
tracing, making it easier to interpret and generally more
pleasing to the eye. Certain filter settings can also be
used to accentuate particular types of EEG activity.
Filters can, however, be used improperly, and at times
their use can lead to unintended consequences.












Figure 7

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2.4 Writing unit

The final link between the patient and a legible EEG
tracing is the writer. a pen-ink-paper system is employed
[Figure 8].
The speed of the paper mechanism should include 30
mm/s with at least the additional speeds of 15 mm and
60 mm/s selectable during operation.
The writing unit may be replaced by a digital screen in
modern EEG devices.


3.Mechanisim

The billions of nerve cells in 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
Figure 8

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detect brain waves and the EEG machine amplifies
the signals and records them in a wave pattern on
graph paper or a computer screen.

4.EEG Waveform

EEG waveforms are generally classified according to
their frequency, amplitude, and shape, as well as the
sites on the scalp at which they are recorded. The most
familiar classification uses EEG waveform frequency (eg,
alpha, beta, theta, and delta) [Figure 9] [Table 1].

Figure 9
One way that scientists study EEG recordings is by
looking at different waves in the EEG. These waves do
not move across the body, but occur as changes in the
signal at one place over time. They are studied using
mathematical techniques for separating a signal into
different frequencies. The slowest waves are called delta,
and they occur at 1 to 4 cycles per second. Delta occurs
in sleep and during anesthesia. The next frequency is
Table 1

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called theta, and it occurs at 4 to 8 cycles per second.
Theta is seen when a person is trying to keep many
different things, such as numbers or words, in memory. It
is also seen when a person is drowsy. After theta comes
alpha, a wave occurring at 8 to 12 cycles per second.
Alpha is seen over the back of the head when a person
has his or her eyes shut. It is also seen when a person is
resting or meditating. Faster than alpha is beta, a wave
that occurs at 12 to 30 cycles per second. It is seen when
a person is getting ready to move or no longer resting. It
is also seen when a person takes benzodiazepine drugs.
Finally, gamma is the fastest wave seen in EEG,
occurring at 30 to 100 cycles per second. It is seen when
a person is thinking or paying attention to something.

5.Why is an EEG performed?

5.1 Medical use
An EEG is used to detect problems in the electrical
activity of the brain that may be associated with certain
brain disorders. The measurements given by an EEG are
used to confirm or rule out various conditions, including:
• seizure disorders (such as epilepsy)
• head injury
• encephalitis (inflammation of the brain)
• brain tumor

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• encephalopathy (disease that causes brain
dysfunction)
• memory problems
• sleep disorders
• stroke
• dementia
When someone is in a coma, an EEG may be performed
to determine the level of brain activity. The test can also
be used to monitor activity during brain surgery.
5.2 Research

EEG may be used in scientific research to understand
how the brain functions. However, several other methods
to study brain function exist such as, functional magnetic
resonance imaging (fMRI), positron emission
tomography, magnetoencephalography (MEG), nuclear
magnetic resonance
spectroscopy, electrocorticography, single-photon
emission computed tomography, near-infrared
spectroscopy (NIRS), and event-related optical
signal (EROS). Electroencephalography (EEG) has
excellent temporal resolution, low cost and no real safety
restrictions, but poor spatial resolution and high noise.

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6.Risks of EEG

The EEG has been used for many years and is
considered a safe procedure. The test causes no
discomfort. The electrodes record activity. They do not
produce any sensation. In addition, there is no risk
of getting an electric shock.
In rare instances, an EEG can cause seizures in a person
with a seizure disorder. This is due to the flashing lights
or the deep breathing that may be involved during the
test. If you do get a seizure, your healthcare provider will
treat it immediately.
Other risks may be present, depending on your specific
medical condition. Be sure to discuss any concerns with
your healthcare provider before the procedure.
Certain factors or conditions may interfere with the
reading of an EEG test. These include:
• Low blood sugar (hypoglycemia) caused by fasting
• Body or eye movement during the tests (but this will
rarely, if ever, significantly interfere with the
interpretation of the test)
• Lights, especially bright or flashing ones
• Certain medicines, such as sedatives
• Drinks containing caffeine, such as coffee and cola
• Oily hair or the presence of hair spray

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7.Preparation for EEG

The patient should ask his healthcare provider to tell them
what they should do before the test. Below is a list of
common steps that the patient may be asked to do.
• the healthcare provider will explain the procedure
and the patient can ask his questions.
• The patient will be asked to sign a consent form that
gives him/her permission to do the procedure. the
form must be read carefully and the patient should
ask questions if something is not clear.
• The patient must wash his/her hair with shampoo,
but conditioner must not be used the night before the
test.
• The patient must Tell his/her healthcare provider of
all medicines (prescription and over-the-counter) and
herbal supplements that they are taking.
• The patient must Discontinue using medicines that
may interfere with the test if the healthcare provider
has directed him/her to do so.
• The patient must Avoid consuming any food or
drinks containing caffeine for 8 to 12 hours before
the test.
• If the patient is having a sleep EEG, he or she may
be asked to stay awake the night before the exam.

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• The patient must Avoid fasting the night before or the
day of the procedure. Low blood sugar may influence
the results.

8.During the EEG procedure:
A standard noninvasive EEG takes about 1 hour. The
patient will be positioned on a padded bed or table, or in
a comfortable chair. To measure the electrical activity in
various parts of the brain, a nurse or EEG technician will
attach 16 to 20 electrodes to the scalp. The brain
generates electrical impulses that these electrodes will
pick up. To improve the conduction of these impulses to
the electrodes, a gel will be applied to them. Then a
temporary glue will be used to attach them to the skin.
No pain will be involved.
The electrodes only gather the impulses given off by the
brain and do not transmit any stimulus to the brain. The
technician may tell the patient to breathe slowly or quickly
and may use visual stimuli such as flashing lights to see
what happens in the brain when the patient sees these
things. The brain's electrical activity is recorded
continuously throughout the exam on special EEG paper.
• Sleep EEG: During a specialized sleep EEG, the
patient will be placed in a room that encourages
relaxation and asked to fall asleep while the brain's

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electrical activity is recorded. The sleep EEG will last
about 2 to 3 hours.
• Ambulatory EEG: During a specialized ambulatory
(moving from place to place, walking) EEG, the
electrodes are placed on the patient's scalp and
attached to a portable cassette recorder. The patient
will be allowed to go home and resume normal
activities while the EEG continuously records. The
ambulatory EEG typically lasts 24 hours.

9.After EEG procedure:
After the test is complete, the technician will remove the
electrodes. The patient will be instructed when to resume
any medications. The patient generally will be ready to go
home immediately following the test. No recovery time is
required. Because the patient may be at risk for a seizure
(especially if their medication has been withheld prior to
the EEG), they should have someone take them home,
and they should not drive. The patient should avoid
activities that may harm them if a seizure occurs, until
they have resumed their seizure medication for an
adequate length of time. These precautions do not
necessarily apply to the person who was not on any
seizure medication prior to the EEG.
The doctor or technician will tell the patient when and how
they will learn the results of their EEG. Probably the

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patient will either get a telephone call or have an office
visit. If the patient has not learned the test results within
2 to 3 weeks and doesn't yet have a follow up
appointment, call the doctor.

10.EEG results:

When the EEG is finished, the results are interpreted by
a neurologist (a doctor who specializes in the nervous
system). The EEG records the brain waves from various
locations in the brain. Each area produces a different
brain wave strip for the neurologist to interpret.
When examining the recordings, the neurologist looks for
certain patterns that represent problems in a particular
area of the brain.
For example, certain types of seizures have specific brain
wave patterns that the trained neurologist recognizes.
Likewise, a normal brain has a specific brain wave pattern
that the trained neurologist recognizes.
The neurologist must look at all recorded tracings, decide
what is normal and what is not, and determine what the
abnormal tracings represent.
The neurologist forwards the EEG results to the doctor
who ordered the test, and the patient is then notified as
arranged.

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11.Conclution

The aim of this paper was to give a simple idea about any
information associated with EEG. Although the diagnoses
od disease through EEG may seem simple to the reader,
but it is not as simple as it seems, because in many
diseases such as seizure, it does not cause a typical
pattern on EEG, it just causes a change in the EEG
(although there are some diseases that have a typical
EEG pattern associated with them). This means that
sometime the EEG is described as ‘abnormal’ but does
not specify the abnormality or disease, for example, some
people have ‘abnormal’ EEGs but do not have epilepsy.
Also, many people who have epilepsy will only have
‘abnormal’ activity on the EEG if they have a seizure at
the time the test is happening. This is why having an EEG
cannot diagnose epilepsy, and that is why EEGs are used
alongside other tests and investigations.
In general EEG is the best method to diagnose a disease
and it is better than its alternatives for many reasons, and
there are almost no low-cost alternatives to EEG. fMRI is
noisy and expensive, fNIRS is non-invasive and can be
used with children. But the equipment and training to use
it is expensive. You can't look at deep structures either.so
EEG is currently the best of its type.

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12.Resources:

• David Ficker, MD, Maureen Gartner, RN:
Electroencephalography. “https://mayfieldclinic.com/pe-
eeg.htm”.
• Diamond Vrocher III, MD: Electroencephalography
(EEG).
“https://www.emedicinehealth.com/electroencephalograp
hy_eeg/article_em.htm#electroencephalography_eeg_intr
oduction”. April 20, 2018.
• Epilepsy Society: A Closer Look at EEG.
“https://www.epilepsysociety.org.uk/closer-look-
eeg#.WttoVWaB00o”. April 20, 2018.
• Jasper HH (1958): Report of the Committee on Methods
of Clinical Examination in
Electroencephalography. Electroenceph. Clin.
Neurophysiol. 10: 370-1
• Peter W. How to write an EEG report. 2013; 80(1
Suppl 1): S43–S46.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3590
044/