At greywhite junction post ictal The Frequencies EEG contd B What does the EEG

At greywhite junction post ictal the frequencies eeg

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? At grey/white junction; post-ictalThe Frequencies
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EEG cont,dB. What does the EEG tell us?1- General health of the brain“Vital signs”EncephalopathyFocal pathology2- Epilepsy -are there seizure activity?Ictal activityInterictal activityWith or without specific provocation
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EEG cont,d1. General health of the brain1a. “Vital signs”Posterior basic rhythmBackground fast activityBackground slow activitySleep activitySigns from various sleep stagesArousals from sleepNearly all have age-appropriate norms
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normalL parasagRTL TR parasag MID
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FP1-F7F7-T3T3-T5T5-O1FP2-F8F8-T4T4-T6T6-O2FP1-F3F3-C3C3-P3P3-O1FP2-F4F4-C4C4-P4P4-O21 sec100µVRhythmic temporal theta bursts of drowsiness
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Spindles
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POSTS
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EEG cont,d1b. EncephalopathyMetabolic (e.g., triphasic waves)Infectious (e.g., meningitis)Toxic (e.g., drug overdose)Anoxia/hypoxiaEEG: usually generalized findings (e.g., diffuse loss of normal background activity)
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EEG cont,d1c. Focal pathology – e.g. Tumor, Stroke, Bleeds, fluid collections, etcCertain infections (e.g., HSV encephalitis)Malformations of cortical developmentBrain injuryDegenerative disordersEEG: focal slowing or loss of fast activity; may see focal spikes or sharp waves
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EEG cont,d2. Epilepsy- seizure disorders Ictal activityoGeneralized vs. focal seizure patternsInterictal activityoSpikes, sharp waves, hypsarrhythmiaProvocative maneuversoSleepoHyperventilationoIntermittent photic stimulationClarification/ Classification of seizure disorders/status
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EEG demonstrating a couplet of left anterior temporal spike-and-slow waves.
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POLYSPIKE WAVE
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Evoked potentials/ Event Related Potentials.
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EPsreflect neurophysiological processing along the pathways from sensation to primary sensory cortex EPs develop 1–150 milliseconds after presentation of the stimulus used to evoke themthe exact timing (latency) of the EP after stimulus delivery dependent on the location of its neural generators along the processing pathway in which it is evoked
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Filter & AmplifyAverage across Trials & IndividualsCollapsed to form a “Grand Average” Or mean of meansElectrical activity at the onset of a stimulus recorded
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Single Trial: 100ms visual stimulusAverage of 200 trials to same stimulusERP derived from EEG
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  • Fall '19
  • Evoked potential, Electroencephalography, Event-related potential, Motor unit

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