Abnormal EEG brain in neurological disease

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10 – 20 system

Bipolar montage

Records the difference between two Active scalp electrodes

Referential montage

Active scalp electrodeInactive scalp / ear electrode : A1 , A2

Reference / Bipolar montage

Polarity

If the voltage input from electrode 2 is relatively “ positive ” compared to electrode 1 ,

then the pen will deflect “ up ”If electrode 2 is relatively “ negative ”

compared to electrode 1 , then the pen will deflect “ down ”

If electrode 1 equal to electrode 2 , then the pen stay “ baseline ”

Different Montage : Polarity

EEG interpretation

Identify background rhythms ( frequency ) Alpha 8 -13 Hz Beta 13 – 40 Hz Theta 4 – 8 Hz Delta < 4 Hz Mu 7 – 11 Hz Sleep stage ( awake , NREM , REM )

Identify any abnormal patterns Slow patterns

Diffusely , Focally Symmetry , Asymmetry

Paroxysms Spike , spike and wave complex , sharp wave Triphasic waves PLEDs ( Periodic lateralizing epileptiform discharges )

Localize those abnormal patterns Maximum amplitude ( Referential montage ) Phase reversal / Reciprocal changes ( Bipolar montage )

Background rhythm / frequency

Sleep stage : Background

Epilepsy

Factor lowering seizure threshold

Common ◦Sleep deprivation , ◦ Alcohol withdrawal , ◦ Television flicker , ◦ Systemic infection , Head trauma , ◦ Recreational drugs , antiepileptic drug , ◦ Menstruation

Occasional ◦ Dehydration , ◦ Barbiturate / Benzodiazepine withdrawal ,

◦Hyperventilation ,

◦Flashing lights , ◦ Diet and missed meals , ◦ Specific reflex trigger , ◦ Stress , Intense exercise

Activation tecniques ( EEG )

Rountine electroencephalograms◦Hyperventilation◦Photic stimulation◦Sleep-deprivation

Prolonged ambulatory recording

Video – EEG telemetry

Magnetoencephalography : Research

Seizure

Epileptiform discharge / Spike

Focal seizure : spike ( phase reversal )

Herpes simple encephalitisPLEDs ( Periodic lateralizing epileptiform discharges )

Ictal EEG : Spike and waves complexs

Generalized seizure

Absence seizure3 Hz spike and wave complexs

Syndrome of epilepsy

Syndrome of epilepsy

CJD – Mad cow diseaseDiffused slow pattern : encephalopathy

Prion encephalitisTriphasic waves

Severe dementiaTriphasic waves : degenerative disease

Encephalopathy

Comatose

Brain death

Sleep or Death

Sleep Spindle

Sleep spindle / K complex

Sleep

Sleep Lab / Polysomnography

Hypnogram

Eye Blink Artifact

Artifact