Brief description on recording of EEG

1. ELECTROENCEPHALOGRAM
EEG

2. INTRODUCTION
• Hans Berger
• Record spontaneous electrical activity of the
brain taken from the scalp surface
• Graded or summated post synaptic potentials
• ELECTROCORTICOGRAM- Recorded from pial
surface brain

3. TECHNIQUE
• BIPOLAR
• Record of potential
difference between a
pair of scalp electrode
• UNIPOLAR
• Potential variation
between one active
electrode and indifferent
electrode placed some
where else on the body

4. LOCATIO OF ELECTRODES
International 10-20%
system (MONTREAL
METHOD)
Whole area of scalp is
then divided into
various points on basis
of lines passing
through and above
the described points

5. EEG RECORDING MODES
• Montage: Method of combining electrode
position
• Predetermined combination format Ka Pattern

6. EEG WAVES
• Frequency- 8-13 Hz
• Amplitude- 50-100 Microvolt
• Location – Parito-occipital area of scalp
• Disappear during sleep

7. DECREASE
• OLD AGE
• LOW BLOOD GLUCOSE
• LOW BODY TEMPERATURE
• LOW ADRENAL
GLUCOCORTICOIDS
• SLEEP
INCREASE
• HIGH BLOOD GLUCOSE
LEVEL
• INCREASE BODY
TEMPERATURE
• ALERTING STATE

8. ALPHA
BLOCK/AROUSAL/ALERTING
STATE
Waves are attenuated
and replaced by fast,
irregular low
amplitude waves
Seen when person
opens eyes
Involve in mental
activity
Any form of
stimulation is applied

9. BETA WAVES
FREQUENCY- 14-30 Hz
AMPLITUDE- 5-10
MICROVOLTS
LOCATION- PARIETAL
AND FRONTAL REGION
SEEN-
TENSION & CNS
ACTIVATION
AROUSAL RESPONSE
INFANTS
BARBITURATES

10. THETA WAVES
FREQUENCY- 4-7Hz
Duration-10 microvolts
Location- temporal and
parietal region
Seen-
Adults
Emotional stress(
disappointments and
frustration)
In crying children

11. DELTA WAVES
FREQUENCY- 4Hz
Amplitude- 20-200
microvolt
Occurs in cortex
independent of activities in
lower region of brain
Can be produced by
overbreathing
Seen:
Deep Sleep
Infancy
Serious brain damage

12. ABNORMAL EEG
• EPILEPSY: Uncontrolled excessive activity of
either part or all of CNS
• TYPES:
GRAND MAL EPILEPSY
PETIT MAL EPILEPSY
FOCAL EPILEPSY

13. GRAND MAL EPILEPSY
Extreme neural discharge in
cerebral cortex, deeper parts
of cerebrum and even in brain
stem
Tonic clonic seizures
Often bites his tongue
Breathing becomes difficult
May urinate and defecate
last for few min(3-4 min)
Post seizure depression
Sleep for hours after attack
Waves are of high voltage,
frequency discharge over
entire cortex

14. • Initiates by strong emotional stimuli, alkalosis,
drugs, fever, loud noises, flashes of light
• Stops due to neuronal fatigue or active
inhibition of neurons

15. PETIT MAL
EPLIEPSY/ABSENCE
SYNDROME
Thalamo cortical brain
activity
3-30 sec of
unconsciousness and
return to consciousness .
Appear late childhood and
disappear by age of 30
Waves are of Spike and
dome pattern
Results from inhibitory
thalamic reticular neuron
and excitatory
thalamocortical and
corticothalamic neurons

16. FOCAL SEIZURE OR JACKSONIAN
EPILEPSY
• Scar tissue, tumor, destroyed brain area,
congenital deranged local circuitry
• Gradually recruit adjacent areas of cortex into
epileptic discharge zone
• Progresses to muscle contraction of opposite
side of body mostly to the mouth region and
towards the legs

17. PSYCOMOTOR SEIZURE
CAUSE
1. Short period of amnesia
2. Attack of abnormal rage
3. Sudden anxity,fear,
discomfort
4. Incoherent speech
Involve limbic portion such as
hippocampus, amygdala,
septum and portion of
temporal cortex
EEG shows low frequency
rectangular wave with
frequency between 2-4 /
sec and superinposed
14/sec wave

18. COMA
• Permanent state of sleep from which subject
cannot be aroused
• Produced by blocking the connection between
RAS and thalamus
• Sensory pathway stimulation can produce
desynchronized EEG

19. TUMORS
• No wave form is seen at the site of tumor
• But slow waves are generated in the
surrounding parts
• Deep tumor have high amplitude slow waves

20. BRAIN DEATH
• EEG wave form is flat