mang ppt_Introduction_To_EEG (1)

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about EEG characteristics in epilepsy

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Electroencephalography (EEG) In Epilepsy:

Electroencephalography (EEG) In Epilepsy Mangroo Kumar sahu MSc. Neuroscience 2012

Electroencephalography:

Electroencephalography 1st used in humans by Hans Berger in 1924 (the first report was published in 1929) A Graphical records of resultant electrical activity of cortical and subcortical neurons. A tracing of voltage fluctuations versus time recorded from electrodes placed over scalp in a specific array Represent fluctuating dendritic potentials from superficial cortical layers Required amplification

Types of EEG Recording:

Types of EEG Recording Routine analog, digital with computerized analysis & brain electrical activity mapping Long-term Monitoring

Routine EEG Techniques:

Routine EEG Techniques 20-min or longer sampling of brain activity but practically up to 15-18 min. Written out or recorded directly on magnetic tape or digitally by computer Cup, flat disc shaped gold or silver electrodes are applied according to 10-20 International system of electrode placement Montages: referential (monopolar), bipolar, changeable with digital recording

Montages:

Montages Referential-Involves active (scalp) and inactive electrodes placed(on the ear, nose or chin) Bipolar-Involve only active electrodes.

International 10-20 System of Electrode Placement:

International 10-20 System of Electrode Placement Established in 1958 Measure the circumference of head and accordingly electrodes are placed in10-20 Electrodes are spaced at 10% or 20% of distances between specified anatomic landmarks Left hemisphere-Odd number electrodes Right hemisphere-Even number electrodes Use 21 electrodes, but others can be added increase spatial resolution record from specific areas monitor other electrical activity (e.g. ECG, eye movements)

PowerPoint Presentation:

International 10-20 System of Electrode Placement

Activations:

Activations Routine Eye opening and closure Hyperventilation Intermittent photic stimulation 1, 5, 10, 15 & 20 Hz eyes open eyes closed eyes closure Optional Sleep deprivation Sedated sleep Specific methods of seizure precipitation video games visual patterns AED withdrawal

Strength and Advantages of EEG :

Strength and Advantages of EEG Is a measure of brain function; supplement neuroimaging studies Provides direct rather than indirect evidence of epileptic abnormality Provides best temporal resolution Provides some spatial or localization information Low cost Low morbidity Readily repeatable Portable / ambulatory

Limitations and Disadvantages Of EEG:

Limitations and Disadvantages Of EEG Detects cortical dysfunction but rarely discloses its etiology Relatively low sensitivity and specificity Subject to both electrical and physiologic artifacts Influenced by state of alertness, hypoglycemia, drugs Small or deep lesions might not produce an EEG abnormality Limited time sampling (for routine EEG) and spatial sampling

Analyzing EEG Activities:

Analyzing EEG Activities Morphology Distribution Frequency Amplitude Voltage Duration State of the patient Background from which activity is arising from Similarity or dissimilarity to the other ongoing background rhythms

EEG Interpretation:

EEG Interpretation Normal Lack of Abnormality Abnormal Non-epileptiform Patterns Epileptiform Patterns

Epileptiform Patterns on Scalp-recorded EEG:

Epileptiform Patterns on Scalp-recorded EEG Interictal Epileptiform Pattern Ictal Epileptiform pattern Electrographic Seizure Pattern Isomorphic seizure pattern Metamorphic seizure pattern

Criteria For Potentially Epileptogenic Transients:

Criteria For Potentially Epileptogenic Transients Clearly of cerebral and not artifactual origin Abnormal for the age and the state of the patient Have a significant epileptiform character

PowerPoint Presentation:

Sharp Transients

Physiologic Activities That Can Be Confused With Epileptiform Activities:

Physiologic Activities That Can Be Confused With Epileptiform Activities Vertex transients of light sleep Hypnagogic hypersynchrony Positive occipital sharp transients of sleep (POST) Mu rhythm Lambda waves Breach rhythms

PowerPoint Presentation:

Breech Rhythm

Benign characteristics Of Unknown Clinical Significance:

Benign characteristics Of Unknown Clinical Significance Benign epileptiform transients of sleep (small sharp spikes) 6- and 14-Hz positive spikes Wicket spikes Psychomotor variants (rhythmic mid-temporal theta discharge of drowsiness) Subclinical rhythmic EEG discharge of adults Phantom spike and wave

PowerPoint Presentation:

Small Sharp Spikes

PowerPoint Presentation:

Wicket Spikes FP1 – F7 F7 – T3 T3 – T5 T5 – O1 FP2 – F8 F8 –T4 T4 – T6 T6 – O2 FP1 – F3 F3 – C3 C3 – P3 P3 – O1 FP2 – F4 F4 – C4 C4 – P4 P4 – O2 Fz – Cz Cz – Pz EKG PHOT

Examples Of Inter-ictal Epileptiform Patterns:

Examples Of Inter- ictal Epileptiform Patterns Spikes Sharp waves Benign Epileptiform Discharges of Childhood Spike-and-wave complexes 3Hz Spike-and-wave complexes Slow spike-and-wave complexes Photo-paroxysmal response

Interictal Spikes / Sharp Waves:

Interictal Spikes / Sharp Waves Spikes (<70 msec in duration) or Sharp Waves (70-200 msec in duration) Usually surface negative; occasionally bipolar or only surface positive Monophasic, biphasic or polyphasic Occur alone or accompanied by an after-coming slow wave (usually surface negative and higher in amplitude than the spike or sharp wave) Occurs singly or in burst, lasting at most a few seconds Focal or generalized No clinical manifestation

Inter-ictal Epileptiform Patterns:

Inter-ictal Epileptiform Patterns Idiopathic Epilepsies Partial / Focal Benign focal epilepsy of childhood w ith centrotemporal spikes Benign focal epilepsy of childhood w ith occipital spikes Generalized 3 Hz spike-and-wave Polyspikes Atypical spike-and-wave Symptomatic Epilepsies Partial / Focal Temporal Frontal Centro-parietal Occipital M idline Generalized Hypsarrhythmia Slow spike-and-wave Paroxysmal fast activity Multiple independent spike foci

PowerPoint Presentation:

3 Hz Spike & Wave Complexes

PowerPoint Presentation:

3 Hz Spike & Wave Complexes

PowerPoint Presentation:

Polyspikes

PowerPoint Presentation:

Polyspikes & Wave

PowerPoint Presentation:

Slow Spike & Wave Complexes

PowerPoint Presentation:

Fp1 – F7 F7 – T3 T3 – T5 T5 – O1 Fp2 – F8 F8 – T4 T4 – T6 T6 – O2 Fp1 – F3 F3 – C3 C3 – P3 P3 – O1 Fp2 – F4 F4 – C4 C4 – P4 P4 – O2 Fz – Cz Cz – Pz T1 – T2 A1 – A2 EKG Photic Benign Epileptiform Discharges of Childhood

PowerPoint Presentation:

Sharp Wave, Regional, Left Temporal

PowerPoint Presentation:

Sharp Wave, Regional, Right Frontal

PowerPoint Presentation:

Sharp Wave, Regional, Right Posterior Temporal

PowerPoint Presentation:

Sharp Wave, Regional, Central Vertex

Normal EEG In People With Epilepsy:

Normal EEG In People With Epilepsy Sahu, 2012 49 of 88 patients(children and adolescents) with Focal seizure have normal EEG 6 of 14 patients(children and adolescents) with generalized shows normal EEG Holmes, 1986 25% of 24 paediatric patients with documented seizures on long-term monitoring had no IEDs first and only EEG abnormalities recorded was complex partial seizures Patients with well-documented seizures may have normal EEGs

Factors Responsible For Detection Of Epileptiform Discharges :

Factors Responsible For Detection Of Epileptiform Discharges Characteristic of Generator Source Voltage of cortical discharge which is directly related to size/area of cortex involved in generation of synchronous activity Distance between electrodes and the generator source Orientation of dipole Sampling Time Activation

Factors Which Modify Spike Frequency:

Factors Which Modify Spike Frequency Sleep Photic stimulation Hyperventilation Temporal relation to a seizure Age of patient Effect of anticonvulsant withdrawal

Recording of Focal Interictal Spikes:

Recording of Focal Interictal Spikes Yield of recording focal interictal spikes increases during NREM sleep, especially stage 3/4 after sleep deprivation after seizures during long-term monitoring ? using supplementary electrodes (e.g. sphenoidal) Occurrence of focal interictal spikes is not affected by increasing or decreasing the AED dosages or level by hyperventilation or photic stimulation before seizures

Routine EEG Concluding Remarks:

Routine EEG Concluding Remarks EEG is the most valuable tool in the evaluation of patients with a seizure disorder Interpretation of clinical significance of EEG abnormality(ies) can only be made by a physician who is evaluating the patient’s history and physical findings has an understanding of the benefits and limitations of EEG recording

Epileptiform Patterns on Scalp-recorded EEG:

Epileptiform Patterns on Scalp-recorded EEG Interictal Epileptiform Pattern Electrographic Seizure Pattern Isomorphic seizure pattern Metamorphic seizure pattern

Electrographic Seizure Pattern:

Electrographic Seizure Pattern Rhythmic repetition of components that may or may not have an epileptiform morphology Lasting more than several seconds When this pattern produce clinical symptoms and/or signs, it is called a clinical electrographic seizure discharge When it does not produce clinical symptoms, it is called a subclinical electrographic seizure discharge

Isomorphic Seizure Pattern:

Isomorphic Seizure Pattern Ends as it begins, without progressing through multiple phases into a postictal phase Ictal morphology is usually similar to interictal epileptiform patterns Differ only in having greater rhythmicity, duration, spatial extent and amplitude Almost exclusively seen in generalized seizures Prototype: 3/s spike-and-wave complexes

Metamorphic Seizure Pattern:

Metamorphic Seizure Pattern Ends differently from its beginning, commonly progressing through 2 or more different ictal phases into a postictal state Ictal morphology can also be dissimilar to interictal epileptiform patterns Ictal morphology may consist of smooth sinusoidal rhythms and has no spike or sharp wave Seen both in generalized seizures and focal seizures

PowerPoint Presentation:

Seizure, Regional, Left Temporal

PowerPoint Presentation:

Seizure, Generalized

ICTAL EEG:

ICTAL EEG Always abnormal in generalized seizures Almost invariably abnormal during a partial seizures especially with loss of consciousness Might be normal for simple partial seizures Should be correlated with behavioral changes

Long-term EEG Monitoring:

Long-term EEG Monitoring In- or out-patient setting Methods Prolonged Conventional Ambulatory With video recording of behavior analog, digital Telemetered EEG recording radio, cable

Video/EEG Monitoring:

Video/EEG Monitoring To obtain a prolonged interictal EEG sample To record habitual seizures or spells To make precise EEG / behavioral correlation To classify seizures (e.g. absence vs. complex partial) To localize epileptogenic focus, especially in epilepsy surgery candidates To quantify seizures when they occur frequently Evaluate seizure precipitants

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