An EEG is a test that detects electrical activity in the brain using sensors placed on the scalp. It is used to diagnose brain conditions like epilepsy and Alzheimer's. During an EEG, electrodes detect brain waves which are amplified and recorded. Abnormal brain wave patterns can indicate conditions affecting the electrical activity in the brain. A neurologist interprets the EEG results to look for normal and abnormal patterns to make a diagnosis.

1. Presented by – Dr. Ajay Singh

2. EEG is a medical device for analyzing the electrical
activity of the brain.
It can detect Epilepsy or Alzheimer's diseases.
Used in humans by Hans Berger in 1924.
The general mechanism is picking up the charge of
electrical potentials.
The neurons are negative (-) when they are at rest
and become positive (+) when they synapse.

3.  The EEG can record this change by electrodes "the signals are
transferred from the electrodes to the amplifiers because the power of
brain signal is very small.
 “Then processed signals are shown on a screen or printed on paper.
 “The neurologist can compare them with normal EEG recording.
 “It's a safe procedure *instructions will be given to the patient before
the procedure.

4. 1-Electrodes: Small metal discs usually made of stainless
steel, tin, gold or silver covered with a silver chloride coating.
 Placed on the scalp in special position these position is
specified using the international 10/20 system.
 Each electrode site is labeled with a letter and a number,
the letter refer to the area of brain underlying the electrode.
 Even numbers denote the right side of the head and odd
numbers denote the left side of the head.

5. 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 and transmit signals to the therapist computer.

6. 3 -Writing unit: The final link between the patient and a legible EEG
tracing is the writer. A pen-ink-paper system is employed.
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.
Note: The writing unit may be replaced by a digital screen in modern
EEG devices

7. The billions of nerve cells in The brain produce very small electrical
signals that form patterns called brain waves. During an EEG, small
electrodes and wires are attached to your head. The electrodes detect
your brain waves and the EEG machine amplifies the signals and
records them in a wave pattern on graph paper or a computer screen.

8. There are two types of EEGs, depending on where the signal
is taken in the head: scalp or intracranial.
 For the scalp EEG, small electrodes are placed on the scalp
with good mechanical and electrical contact.
 Special electrodes implanted in the brain during the surgery
result in intracranial EEG. On the other hand, the EEG
measured directly from the cortical surface using subdural
electrodes is called the electrocorticogram (ECoG).

9. 1. FREQUENCY
 Frequency refers to rhythmic repetitive activity (in Hz). The frequency of EEG activity
can have different properties including:
 Rhythmic. EEG activity consisting in waves of approximately constant frequency.
 Arrhythmic. EEG activity in which no stable rhythms are present.
 Dysrhythmic. Rhythms and/or patterns of EEG activity that characteristically appear
in patient groups or rarely or seen in healthy subjects.

10. 2. Voltage
 Voltage refers to the average voltage or peak voltage of EEG activity. Values are
dependent, in part, on the recording technique. Descriptive terms associated with EEG
voltage include:
 Attenuation (synonyms: suppression, depression). Reduction of amplitude of EEG activity
resulting from decreased voltage. When activity is attenuated by stimulation, it is said to
have been "blocked" or to show "blocking".
 Hypersynchrony. Seen as an increase in voltage and regularity of rhythmic activity, or
within the alpha, beta, or theta range. The term implies an increase in the number of
neural elements contributing to the rhythm. (Note: term is used in interpretative sense but
as a descriptor of change in the EEG).
 Paroxysmal. Activity that emerges from background with a rapid onset, reaching (usually)
quite high voltage and ending with an abrupt return to lower voltage activity. Though the
term does not directly imply abnormality, much abnormal activity is paroxysmal.

11. 3. Morphology
 Morphology refers to the shape of the waveform. The shape of a wave or an EEG
pattern is determined by the frequencies that combine to make up the waveform and
by their phase and voltage relationships. Wave patterns can be described as being:
 Monomorphic. Distinct EEG activity appearing to be composed of one dominant
activity
 Polymorphic. distinct EEG activity composed of multiple frequencies that combine to
form a complex waveform.
 Sinusoidal. Waves resembling sine waves. Monomorphic activity usually is
sinusoidal.
 Transient. An isolated wave or pattern that is distinctly different from background
activity.

12. 4. Synchrony
 Synchrony refers to the simultaneous appearance of rhythmic or morphologically
distinct patterns over different regions of the head, either on the same side (unilateral)
or both sides (bilateral).
5. Periodicity
 Periodicity refers to the distribution of patterns or elements in time (e.g., the
appearance of a particular EEG activity at more or less regular intervals). The activity
may be generalized, focal or lateralized.

13. ELECTRODE POSITIONING
(10/20 SYSTEM)
 The standardized placement of scalp electrodes
for a classical EEG recording has become
common since the adoption of the 10/20 system.
The essence of this system is the distance in
percentages of the 10/20 range between Nasion-
Inion and fixed points. These points are marked
as the Frontal pole (Fp), Central (C), Parietal (P),
occipital (O), and Temporal (T). The midline
electrodes are marked with a subscript z, which
stands for zero. The odd numbers are used as
subscript for points over the left hemisphere, and
even numbers over the right.

14. 10/20 System of electrode placement

15.  Montage means the placement of the electrodes. The EEG can be monitored with
either a bipolar montage or a referential one. Bipolar means that you have two
electrodes per one channel, so you have a reference electrode for each channel. The
referential montage means that you have a common reference electrode for all the
channels.
Bipolar montage: Each waveform in the EEG represents the difference in voltage between
two adjacent electrodes, e.g. ‘F3-C3’ represents the difference in voltage between channel F3
and neighbouring channel C3. This is repeated across the whole scalp through the entire
array of electrodes.

16.  Reference montage: Each waveform in the EEG represents the difference in voltage
between a specific active electrode and a designated reference electrode. There is no
standard position for the reference, but usually a midline electrode is chosen so as not
to bias the signal in any one hemisphere. Other popular reference signals include an
average signal from electrodes placed on each ear lobe or mastoid.
• Average Reference montage: Activity from all electrodes is measured, summed and
then averaged. The resulting signal is then used as a reference electrode and acts as
input 2 of the amplifier. The use can specify which electrodes are to be included in this
calculation.

17. The patient should ask his healthcare provider to tell them what they
should do before the test-
 The patient will be asked to sign a consent form that gives him/her
permission to do the procedure.
 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 health care provider of all medicines
(prescription and over-the counter and herbal supplements that they
are taking.

18.  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.
 The patient must avoid fasting the night before the day of the procedure
low blood sugar may influence the results.

19.  A standard noninvasive EEG takes about 1 hour. The patient will be positioned on a
padded bed or table.
 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.
 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.

20.  A. After the test is complete, the technician will remove the electrodes.
 B. The patient will be instructed when to resume any medications.
 C. 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).
 D. 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.
 E. These precautions do not necessarily apply to the person who was not on any
seizure medication prior to the EEG.
 F. The doctor or technician will tell the patient when and how they will learn the results
of their EEG.

21. Attenuated during movement
Seen during alertness,
active concentration
Relaxation, closing of the
eyes
Control of inhibition
Drowsiness, meditation,
action inhibition
Continuous attention, slow
wave sleep
• Mu (8 – 13 Hz):
Rest state motor neurons
• Gamma (30 – 100+ Hz):
Cross-modal sensory
processing, short-term
perceptual memory
can characteristically be broken down into
different frequency bands

22. In the Medical Field -
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
 encephalopathy (disease that causes brain dysfunction)
 memory problems
 sleep disorder
And also When someone is in a coma, an EEG may he performed to determine the
level of brain activity. The test can also be used to monitor activity during brain surgery.

23. 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. BUT In rare
instances, an EEG can cause seizures in a person with a seizure disorder. This is due
to the flushing lights of the deep breathing that may be involved during the test.
AND ALSO Other risks may be present. Certain factors or conditions may interfere with
the reading of an EEG test. These include:
A. caused Low blood sugar (hypoglycemia by fasting).
B. Body or eye movement during the tests.
C. Lights, especially bright or flashing ones
D. Drinks containing caffeine, such as coffee and cola
E. Oily hair or the presence of hair spray

24.  When the EEG is finished, the results are interpreted by a neurologist, 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.

25.  Although the diagnoses of 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.
 This means that sometime the EEG is described as 'abnormal' but does
not specify the abnormality or disease.
 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.

26. THANK YOU