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Normal Adult EEG
Ppt by Dr Husain
| Term | Definition |
|---|---|
| Alpha rhythm (PDR) | Predominant activity noted in occipital region during relaxed wakefulness 8 – 13 Hz; normal 8.5 Hz or greater Frequency constant, except: – Drowsiness – Alpha squeak Reactivity – blocks with eye opening, stimulation Amp asymmetry can be up to 50% |
| Spread of PDR | Can project to temp and central leads W/ ear ref, temp alpha can appear in frontal Morphology may be peaked at top or bottom; apiculate alpha Must be differentiated from epileptiform spikes – Does not disrupt background – Disappears with drowsiness |
| Mu | Arch shaped, 8 – 11 Hz over central regions Asymmetric and asynchronous Seen best when PDR blocked by EO Blocks when pt moves (or thinks of moving) contra limb Paradoxical mu appears w limb mmnt Decreases w age Apiculate phase can resemble spikes |
| Lambda | Sawtooth shaped, + waves in occipital region When scanning complex image Often accompany eye blink artifact Duration 160 -250 ms, amp < 50 µV Usually synchronous, though can be asymmetric Seen in young individuals, decrease with age |
| Vertex Waves | Surface neg, biphasic discharges max over vertex (Cz) Can project to Fz, Pz, parasagittal leads Can occur in runs and accompanies other sleep architecture Loud alerting noise can induce Amp decreases w age Occasionally asymmetric, resembling spikes |
| POSTS | Monophasic, triangular + waves Occipital as trains or single wave N1 % N2 Usually synchronous, can occur independently Looks like lambda When of high amplitude, can resemble spikes |
| HV normal response | Normal response is gradually increasing theta, then delta Finally continuous, gen delta Starts frontal in adults Subsides 60 – 90 sec after HV More prominent in younger pts & ppl w low blood sugar Differentiate from FIRDA/slowing - gradual spread |
| HV abnormal response | Generalized spike and wave discharges – Focal spikes – Lateralized slowing • Differentiate normal vs. spikes – Gradual build-up – Memory testing normal – Only seen during HV |
| RMTD | 5 – 7 Hz in temp area, relaxed wakefulness or drowsiness Can be sharp, flat topped, or notched Monomorphic, doesn't evolve Bilaterally or independently AKA psychomotor variant & rhythmic midtemp discharge Differentiate from spikes/seizure discharge |
| Midline Theta Rhythm | 4 – 7 Hz discharge most prominent over Cz but spreading to parasagittal Relaxed wakefulness and drowsiness Variable reactivity to eye opening and limb movement Originally thought to be associated with epilepsy, now considered a normal variant |
| Subclinical Rhythmic Electrographic Discharge in Adults (SREDA) | Uncommon rhythmic discharge in older adults Relaxed wakefulness or drowsiness 20 – 40 seconds, up to mins Gen discharge, can be prominent focally Onset w monomorphic sharps or high amp delta interrupting bckgrnd Uncertain clinical sig, not epilepsy |
| Small Sharp Spikes (aka BETS) | Mono or biphasic spikes w amp < 50 µV < 50 ms May have after going dip in background but not prominent slow wave N1, N2 Complex polarity, oblique dipole extending over both hemispheres Differentiate from spikes |
| 14 and 6 Hz Positive Burst | 0.5 – 1 second runs of + sharps Bursts can be13 – 17 Hz or 6 – 7 Hz Widespread field, best over temp Bt spiky phase is rounded neg phase Drowsiness & light sleep, mostly in teens & young adults Best in ref |
| 6 Hz Spike and Wave Bursts | 5 – 7 Hz (mostly 6), bilaterally synchronous bursts of spike and slow waves Spike often of low amp (phantom spike and wave) and buried in slow wave Bursts last 1 – 2 seconds Drowsiness and light sleep, mostly in teens and young adults |
| FOLD 6 Hz Spike and Wave Bursts | female, occipital, low amplitude, drowsy – Benign variant |
| WHAM 6 Hz Spike and Wave Bursts | wake, high amplitude, anterior, male – More often associated with epilepsy |
| Wicket spikes | Sharps between 90 – 150 ms duration, < 200 µV amp In trains or isolated; isolated wicket spikes identified by comparing to train Seen in drowsiness and light sleep Occur independently in both temporal regions Differentiate from epileptiform spikes |
| Eye movements | Eye electrically charged, cornea positive compared to retina When eye (cornea) moves upward, positive deflection in frontal leads Eye deflections asymmetric, unless electrodes asymmetric or unilateral enucleation |
Created by:
emmahagen