EEG in Neuropsychiatry

Presentor- Dr. Kapil KulkarniModerator- Dr. J.P. Rawat

Jagjivan Ram Railway Hospital, Mumbai Central

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KAPIL S KULKARNI

What is EEG ?

• EEG (Electroencephalogram) refers to recording and analysis of electrical activity of brain recorded by amplifying voltage differences between electrodes placed on scalp or cerebral cortex .

• This electrical potential is produced by excitatory or inhibitory post synaptic electrical discharges from neuronal dendrites at cortical surfaces.

• Such neurons constitute only 5% of total neurons of the brain.

• Voltage recorded on EEG is only 10% of the voltage recorded on ECG due to high resistance of skull.

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Historical review

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RECORDINGS FROM ANIMAL BRAIN

• First person to record electrical

activity from animal brain in

1874.

RICHARD CATON , 18745

RECORDING FROM HUMAN BRAIN

• First recording from human

scalp in 1924.

• Report published in 1929

• Danis William started clinical

use to localize brain trauma

during ww II in oxford.

HANS BERGER 1924 6

Hans Berger 1835-1911: Human EEG

Prof of Psychiatry, University of Jena Germany, Removed from job in one day notice by the Nazis, committed suicide

Berger wave

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How EEG recording practically done?

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• Standard 10-20 International Electrode Placement System.

• Total 21 electrodes.

• Odd number left & even number on right side.

• Electrodes- Silver/gold/steel. • Fp1,2= prefrontal• F3,4=frontal• C3,4=central• P3,4=parietal• O1,2=occipital• F7,8=ant.-temporal

[placed on frontal bone]

• T3,4=mid-temporal• T5,6-=post.-

temporal• A1,2=ear, mastoid• Fz=Frontal midline• Cz=Central vertex• Pz=parietal midline

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SURFACE RECORDING

BRAIN

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2

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R

RE

CO

RD

ING

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• Montage refers to the particular combination of electrodes

examining at a particular point of time.

• When a single reference point is used for all electrodes

Referential montage.

• When several referential points are used for recording Bipolar

montage.

• In bipolar montage the electrodes form a chain passed side by side

or front to back.

MONTAGE

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REFERENCE MONTAGE • Connects active scalp electrodes and an inactive electrode placed away from the scalp e.g. on ear, nose or chin [Referenceelectrode]

– Disadvantage with ear-some brain activity

– Chin & nose-heart activity

• Useful for seeing amplitude of waves

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BIPOLAR MONTAGE• Connects two active

scalp electrodes• Each channel is

attached to two different electrodes

• Arrangement of channels in montages-– Anteriorly placed

electrodes on initial channels-helps see progression of waves

– Alternate left and right electrodes-helps compare the two sides

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• Electrodes- 21

• Sensitivity- 5-10 micro volts/mm ( avg 7)

• Paper speed – 3 cm/ sec ( adjustable)

• Length of recording – 2 min each montage

- 30 min awake record (10 min sleep)

• Activation – Hyperventilation – 3min + 1min

- Photic st -30 cm 10,15,20,30,40 Hz ,each in trains of 10 sec.

STANDARDS

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What are normal EEG waves?

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Normal EEG

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Found in normal eye closed EEG

Highly rhythmic

Frequency 8 to 13 HZ

Prominent in the posterior cortex

Mainly occipital , temporal and parietal cortex

NORMAL ALPHA WAVES

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NORMAL BETA WAVE

Frequent in normal

eye open EEG

EEG waves of >13 HZ

Usually of low voltage

Found in frontal and

central region

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Effect of eye closure

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NORMAL THETA WAVES

Small amount of sporadic and isolated activity found in normal awake state

Prominent in drowsy and sleep EEG tracing

EEG activity of 4 to 7 HZ

found in frontal and temporal region

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NORMAL DELTA ACTIVITY

Not present in normal awake EEG

Prominent in normal deeper stage of sleep.

A frequency of < 4 Hz.

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NORMAL GAMMA WAVE

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Amplitude

• Measured: peak to peak

• Expressed as range i.e 40-50μv

• Depends on

– Inter electrode distance

– Type of montage

– Type of recording

• surface (10-100 μv)

• Depth 500-1500 μv

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Referral (Ipsilateral ear) Bipolar

EFFECT OF MONTAGE ON AMPLITUDE

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• Hyperventilation - causes cortical hypocapnia-> cerebral vasoconstriction and hypoxia -> may allow epileptic foci to become evident

• Photic stimulation - a strobe light flashing at 8-15 Hz is used to capture the occipital α frequency - α frequency adjusts to match that of the strobe - may allow epileptic foci to be seen and may even induce epileptic seizures, as may a flickering television screen

• Sleep deprivation.• Sleep EEG

ACTIVATION

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• Depth electrodes

• Ambulatory (24-hour) EEG

• Q-EEG/BEAM/Brain Mapping/rEEG

Multichannel recording of eyes-closed, resting EEG - visuallyedited & a sample of artifact-free data, analyzed, using theFast Fourier Transform (FFT) to quantify the power at eachfrequency of the EEG averaged across the entire sample,known as the power spectrum.

QEEG findings are then compared to a normative database

This database consists of brain map recordings of severalhundred healthy individuals

Comparisons are displayed as Z scores, which representstandard deviations from the norm.

EEG TECHNIQUES

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• Absolute power

This refers to the amount of activity within a specific frequencyband of brain waves

• Relative power

This refers to the relative amount of activity within a specificfrequency band compared to all the other frequency bands

• Coherence

Measure of synchronization between activity in two channels

• Symmetry

Ratio of power in each band between a symmetrical pair of

electrodes29

LORETA (Low Resolution Electromagnetic Tomography) -Complex mathematical calculations to construct a visual imageof the 3D electrical activity of deep parts of the brain fromsurface electrical measures

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EEG techniques (continued..)

• Video EEG/Video telemetry- Simultaneous recording of brain

activity on an EEG and behavior on tape or digital video

• ERP - An event-related potential (ERP) is any stereotyped

electrophysiological response to an internal or external

stimulus.

• Polysomnography – Simultaneous recording of EEG, muscle

tone, oculogram, respiration.

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• Non-invasive

• Low cost

ADVANTAGES OF EEG

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What are normal EEG changes according to age ?

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• At birth up to 6 months – 4 Hz (Delta)

• 6-12 months – 6 Hz (Theta)

• 1-3 yrs – 8 Hz (Alfa coming in)

• 3-11 yrs – 12 Hz (Maturation of Alfa)

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What are normal EEG changes in sleep?

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• Sleep uncovers epileptiform activities.

• Normal sleep activities also simulates abnormal activities.

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• NREM sleep

– Stage I- Drowsiness

– Stage II- Light sleep

– Stage III- Deep sleep

– Stage IV- Very deep sleep

• REM sleep (paradoxical sleep)

SLEEP STAGES

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SLEEP CHANGES EEG CHANGES

• NREM

• Stage1-Drowsiness - Alpha drop out,vertex waves, POSTS.

• Stage 2-Light sleep - Spindle,vertex wave, K-complex, theta activity.

• Stage 3-Deep sleep – Slow wave sleep,K- complexes, Delta activity starts.

• Stage 4-Very deep sleep - Much slowing ,some K complexes, delta activity.

• REM sleep - Desynchronization with fast frequencies.

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ALFA DRIFTING INTO THETA STAGE I

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• In deep drowsiness, stage I (may persist during stage II & III)

• 50-80% in normal adults

• Location – occipital

• Monophasic, triangular

• 1Hz (4-6 Hz rare)

POSITIVE OCCIPITAL SHARP TRANSIENT OF SLEEP(POSTS)

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POSTS during Stage I sleep

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Drowsiness/ drop out alpha & POSTS

Sleep Awake 43

• 12-14Hz, slowed with ↑sleep

• Waxing & waning

• Location: fronto cental

• Origin: Deep frontal & thalamus

SLEEP SPINDLES

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• Positive followed by large negative wave

• May precede or follow smaller waves of opposite polarity

• Maximum at vertex may extend to frontal & parietal region

• Bilaterally synchronous

• Appear by 5month, prominent in youth

• Not suppressed by focal lesion

VERTEX SHARP WAVES

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Sleep spindle/Vertex sharp wave

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• Stage II-IV sleep

• Frontocentral

• Initial sharp (biphasic)→ slow (1000ms) → fast activities

• Appear by 5months of age

K- COMPLEX

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K- Complex/ sleep spindle

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Arousal rhythm

Series of K- complex

Normal awake pattern

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Arousal in moderate sleep

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Stage II or III sleep

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What are common variations in EEG ?

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AWAY FROM NORMALITY

WAVE EEG

AMPLITUDE SPIKES / SHARP WAVES

RHYTHM SLOW / FAST / PERIODIC DISCHARGES

COMMON IS THE PERMUTATION AND COMBINATION OF THE TWO

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ABNORMAL ACTIVITES

• Spike • Sharp waves • Spike – and – wave complexes• Slow spike – and – wave complexes• 3-Hz spike – and – wave complexes• Polyspikes• Photoparoxysmal response

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SPIKES

It is a transient discharge , clearly distinguished from thebackground activity , having pointed peak and duration of 20to 70 m sec. in conventional paper speed.

The main component is generally negative and amplitude isvariable.

The after coming slow wave is surface negative and depictlong hyper polarization.

Positive waves are common in in depth recording.

Spikes increased after seizure , but not increased prior toseizure (Gotman 1984)

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MORPHOLOGY OF SPIKES

Morphologically spikes are of mainly three types:

Mono-phasic

Bi-phasic

Tri-phasic

Poly-phasic

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ROLANDIC SPIKES

Misnomer as the total duration is more than 70 m sec

Appears as isolated spikes in centrotemoral region.

In BCECTS

The entire complex consists of 80 to 120 ms

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SHARP WAVES

• Sharp waves are defined as transient discharges clearlydistinguished from background activity having pointed peakand at conventional paper speed it has a duration of 70 – 200m sec.

• The main component is usually negative with ascendingcomponent is sharp but descending component is slow.

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SPIKE AND WAVE COMPLEX

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3 Hz SPIKE n WAVE

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POLYSPIKES

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SLOW WAVES

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• Abnormal

• Spike : < 70 ms

• Sharp waves : 70 – 200 ms

• Slow waves : > 200 ms

• Alone or in combination

• Focal, multifocal, hemigeneralized, generalized

• Infrequent to continuous

• Periodic

PAROXYSMAL ACTIVITY

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PAROXYSMAL EEG ACTIVITY

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What are clinical uses of EEG ?

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ABRUPT LOSS OF VOLTAGE DUE TO DESYNCHRONYSATIONTHERE IS 20 – 40 HZ FAST ACTIVITY

1 - 3 SEC

APPROXIMATELY 10 HZ SPIKE WAVE WITH HIGH AMPLITUDE

APROXIMALTELY 10 SEC

FREQUENCY SLOWS DOWN AND COME TO DELTA RANGE

ONCE 4 HZ REACHED THEN SLOW WAVES INTERUPT THE RECURRING RHYTHM

IT FOLLOWS THE POST ICTAL FLATNESS

GRADUALLY DETA , ALPHA THE BETA RANGE WAVES RETURNS

GENERALIZED TONIC CLONIC SEIZURE

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GENERALIZED TONIC CLONIC SEIZURE

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ABSENCE SEIZURE

Characteristics are 3 HZ spike wave complex

Appears and goes of abruptly on normal background activity

Maximum at frontal and midline region

Starts at 4 HZ then slows down to 3.5 HZ then up to 2.5 Z

Hyperventilation precipitate such attacks

Paroxysm of more than 5 sec leads to clinical seizure 69

SIMPLE PARTIAL SEIZURE

• Consciousness is fully preserved.

• EEG shows

» Spikes over the involved cortex

» Wide spread desynchronisaton , more or less theta and delta activity.

» Uninvolved regions shows normal EEG pattern

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SIMPLE PARTIAL SEIZURE

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COMPLEX PARTIAL SEIZURE

•EEG is variable

•Nasopharyngeal and sphenoiddal electrode is helpful in recording

•Temporal spikes are common.

•The EEG may show 4Hz flat topped waves and 6 Hz flat-topped waves

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JAPANESE ENCEPHALITIS

It include the diminution of electrical activity

Slow waves are important the changes are not characteristic

It depicts the severity of the illness

Improvement occurs with the corresponding improvement of the EEG

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HEPATIC ENCEPHALOPATHY

Stage consciousness EEG

I Alert Normal

II Drowsy Slow alpha , poorly developed K-complex and sleep spindle

III Stupor Theta activity , absence of sleep pattern

IV Coma Tri-phasic wave

V Deep coma Delta wave

VI Deep coma Flat EEG74

EEG of a case of hepatic encephalopathy after vaproate toxicity , fig1 shows diffuse slowing of activity , fig 2 shows improvement after treatment ( curtsy – international journal of neurology Feb’ 09)

EEG OF HEPATIC ENCEPHALOPATHY

Fig 1 Fig 2

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DELIRIUM TREMENS

Beta predominance with spares normal alpha during acute florid stage

Persistent delta with little beta and alpha

During recovery the first to predominant beta with spares alpha

Those who exhibits persistent theta suggests residual brain damage.Beta prominence in the EEG

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PERIODIC DISCHARGE

• Periodic discharges are of high amplitude and it may me spikeor sharp waves and the duration may exceeds 150 m sec andrecurring at periodic interval.

• It may be the most important EEG finding for ongoing CNSdisease or some CNS infections.

• Morphology me be specific for the disease-

• Burst suppression

• Repetitive sharp waves

• Periodic triphasic

• Focal periodic

• Generalized periodic slow waves

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SSPE

Occurs in a minor percentage of cases of measles virus infection.

1. Periodic discharge dominates the picture.

2. Duration of 0.5 – 3 sec

3. Average of 500 mic volt

4. Every 4 – 16 sec interval

5. Giant slow waves

6. Discharges are mixed

7. Prominent in the vertex

8. There may be accompanying myoclonus

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EEG OF SSPE

0.5-3

4-16 sec

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CREUZFELDT – JAKOB DISEASE

• It is a prion disease.

• The EEG characteristics are as follows:

– In the first stage there is non specific change in the EEG

– In the 2nd stage patient developed

1. Periodic tri-phasic / bi-phasic complexes

2. Duration of 100-300 m.sec

3. Reparation every 0.5 to 2 sec

4. It is most prominent in anterior region

5. Later stages slow waves become prominent

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CREUZFELDT – JAKOB DISEASE

0.5-2

100-300ms

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HERPES SIMPLEX ENCEPHALITIS

• The EEG finding of HSE is highly suggestive (but not pathogomonic).

• EEG shows-

• Early stage there is focal or lateralized polymorphic delta activity on same side.

• Slow wave later involve frontotemporal region.

• Sharp slow wave recurring at every 1-5 sec interval.

• The complex comprises of upto1000ms.

• Usually appears with in 2 to 15 days but may appear after 30 days.

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HERPES SIMPLEX ENCEPHALITIS

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CEREBRAL ANOXIA

On flat back ground generalized synchronous repetitive simple or compound sharp waves.

Associated with myoclonus.

Occurs with a burst and suppression burst pattern.

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FOCAL BRAIN LESIONS

• The types of EEG abnormality in focal brain lesions are:

– Abnormal background rhythm

– Focal absence of neuronal activity tumor area

– Burst suppression pattern abutting area

– Continuous slow wave most distal zone

– Arrhythmic focal hemispheric or generalized delta activity

– Less than 4 HZ delta activity

– Continuous or sporadic

– Destructive lesions abscess, hematoma are associated

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FOCAL BRAIN LESION

– Intermittent rhythmic slow activity:

– It may be of theta or delta range

– Independently or mixed

– Infra-tentorial, supra-tentorial or peri-ventricular tumor.

– Epileptiform activity

– Focal in onset

– Localized hemispheric lesion

–Often accompanied by slowing of activity

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FOCAL BRAIN LESION

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DEGENERATIVE DISEASE

• The EEG change in the degenerative disease is non specific.

• There was no consistent difference between cortical or sub-cortical dementia.

• But sub-cortical dementia shows more normal EEG

• Multi-infract condition may show some lateralizing sign.

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DEGENERATIVE DISEASE

• Alzheimer's disease:• Initially there was irregular theta activity

• Later become prominent back ground activity

• Lastly delta activity become prominent

• Fronto-temporal dementia :• EEG remains persistently normal

• Quantitative analysis showed some abnormality

• Huntingtons disease:• > 10 µv beta activity is characteristic

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EEG OF A CASE OF ALZHEIMERS DISEASE

EEG of Alzheimer's disease showing irregular theta activity. 90

What is role of EEG in psychiatry ?

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SCHIZOPHRENIA

• S-EEG findings in schizophrenia is non specific

Widespread slow activity

Diffuse Dysrhythmia

Spikes or spike-wave complex

• Q- EEG abnormality -extensively examined:

Extensive slow wave rhythm preponderance

Delta activity anterior brain region

Theta activity posterior brain region

Beta activity with small increase in amplitude

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MOOD DISORDER

• Most of the studies suggests-

• Increased beta / alpha power

• Asymmetric increase in alpha / beta activity in left

frontal region

• Less alpha power and higher EEG findings are seen in

subclinical and depressed patients relatives.

• Recently Q-EEG used as the predictor for

antidepressant response.

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ANTISOCIAL AND BORDERLINE PERSOANLITY DISORDER

• Antisocial personality disorder:

• Frequently associated with organic brain pathology.

• Abnormal behavior is frequently but non specific EEG changes.

• Borderline personality disorder:

• A number of patients subsequently diagnosed as complex partial seizure.

• 40 – 80 % have back ground slowing of activity.

• ¼ th of cases have 6 to 14 / sec spike activity might be the correlate of episodic impulsive activity.

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ATTENTION DEFICIT HYPERACTIVITY DISORDER

• 1/3rd had EEG abnormality.

• Pediatric Neurology reports Epiletiform discharges in ADHD patients.

• Q-EEG showed increased activity in Frontal region.

• But confounding factors denote that learning disability also shows similar result.

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CONTROVERSIAL WAVE FORMS RELEVANT TO PSYCHIATRY

• Fourteen and six per second positive spike:– Age related change in wave form ,

– some psychiatric phenomena are though to be associated,

– etiology presumed to be closed Bain injury or infection.

• Rhythmic mid temporal discharges:– 1/3rd to ½ patient showed rhythmic mid temporal

discharges

– Associated with anxiety and somatization.

– Some studies demonstrate behavioral discontrol and autonomic phenomena.

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CONTROVERSIAL WAVE FORMS RELEVANT TO PSYCHIATRY

• Benign Epiletiform transients of sleep:

• Low-voltage sharp negative or biphasic waves

• some time alternate between right to left hemisphere.

• Associated with vegetative symptoms.

• Six per second spike and wave:

• Also called phantom wave

• Low amplitude waves difficult to recognize

• Associated with impulsivity and vegetative symptoms.

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Take Home Message

EEG is simple, noninvasive and inexpensive investigation.

It can be used for screening as well as predicting outcome of many neurological and psychiatric disorders.

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Thank You 99

Hypsarrthemia in Infantile Spasm

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