EEG different waves, procedure and eeg patterns in diseases
- 1. EEG
- 2. Topics to discuss: 1.Normal sleep 2.Sleep cycle 3.Stages of sleep cycle 4.Electrophysiology of sleep 5.Abnormal EEG (seizure) 6.Abnormal EEG (non-epileptiform) 7.EEG in psychiatry.
- 3. Normal sleep • Duration: 8 hr • NREM (75%): 1.Stage 1 (5%) 2.Stage 2 (45%) 3.Stage 3 (12%) 4.Stage 4 (13%). Deep sleep equal to REM sleep in duration. • REM (25%). Deep sleep = REM sleep (in duration)
- 4. NREM (Orthodox) REM (Paradoxical) Brain activity Lower than awake Increased except muscle tone (muscle paralysis) Pulse, BP, respiration Lower than awake state few min to min variation (synchronized sleep) Higher than those in NREM & often more than awake & variable (desynchronized sleep) Body movement Involuntary & episodic Near total paralysis of skeletal muscles Temperature Homeothermic Thermoregulation altered (Poikilothermic), ↑Core body temperature Penile erection* Nil Occurs in almost every REM period* Dreaming Not remembered Remembered Purposeful & vivid (Lucid) Abstract & surreal *Presence of nocturnal/ early morning erections rules out organic cause of erectile dysfunction/
- 5. Night terror vs. Nightmare: Night terror Nightmare Not remembered (NREM) Remembered (REM) No memory Memory present Within few hours of bedtime Later in deep cycle Disoriented, confused Upset, scared Not consolable Comforted
- 6. • NREM disorders: 1. Walking in sleep/ Somnambulism: Mostly affects children 2. Somniloquy: Talking in sleep 3. Night terrors 4. Bruxism 5. Nocturnal enuresis. • REM disorders: 6. Nightmares 7. Narcolepsy 8. REM sleep behavioral disorders.
- 7. Kleine Levin syndrome Sleeping beauty syndrome Recurrent periods of prolonged sleep Intervening period of normal sleep Hypersomnia followed by hyperphagia (voracious eating) Social withdrawal Apathy Irritability.
- 8. Sleep cycle Sleep latency = (Point where we intend to sleep) to (Point where we get sleep) Dark portion: REM Time taken for first REM to come: REM latency time which is equal to 90
- 9. Decreased REM latency is seen in: 1. Narcolepsy 2. Depression. As sleep progresses, NREM decreases and REM increases.
- 11. EEG Electrode placement: • Odd electrode is left •Even electrode is right Example: • O1O3 -> Left occipital • O2O4 -> Right occipital.
- 12. International 10-20 system (Jasper 1958)
- 13. Waves of EEG Wave Frequency (Hz) Alpha 8-13 Beta 13-30 Theta 4-8 Delta 0.5-4 Delta is slowest, beta is fastest. Downward is positive deflection.
- 14. Waves of EEG One liners: Beta is recorded over frontal & parietal region Alpha is recorded over occipital region Theta is seen in children & sleeping adults Delta is seen in infants & sleeping adults.
- 15. Brain activity: EEG findings Awake/ eyes open = Beta (frontal predominantly) Try to sleep (awake)/ eyes closed = Alpha (occipital) Relaxed with eyes closed: Alpha • Step 1 NREM = Vertex waves (Theta) • Stage 2 NREM = Sleep spindles & K complexes • Deep sleep (stage 3 & 4 NREM): Delta wave • REM sleep: Fast/ mixed frequency waves - Saw tooth Active mental concentration: Beta Focussed attention: Gamma (highest frequency wave, >30 Hz).
- 16. Stage 1 NREM: Vertex/ Theta (Lightest stage of sleep)
- 17. Stage 2 NREM: oSleep spindles & K complexes oLargest % of sleep oDisorder: Bruxism.
- 18. Delta: 20-50% -> Stage 3 Delta: >50% -> Stage 4 o Deepest sleep o Decreases with age o Most relaxed stage o Disorders: Night terror, Sleep walking and enuresis.
- 19. REM sleep o Burst activity o No EMG (due to muscle paralysis) o Penile erection + o Muscle atonia o ↑Pulse, Respiration o Peak at 5-6 AM o Saw tooth waves o Most of the deaths due to cardiac problems.
- 21. • Properties of a normal EEG: 1.In adults who are awake, EEG shows mostly alpha (eyes closed) & beta (eyes open) waves 2.The two sides of the brain show similar patterns of electrical activity 3.There are no abnormal bursts of electrical activity & no slow brain waves.
- 22. Activation procedures 1.Intermittent photic stimulation 2.Hyperventilation (used in absence seizures) 3.Sleep & sleep deprivation 4.Special forms of stimulus: Visual/ auditory/ olfactory/ drugs (pro-epileptic).
- 23. Abnormal EEG • It is of 2 types: 1.Epileptiform 2.Non- epileptiform.
- 24. Abnormal EEG (Epileptiform discharges) • It is of 3 types: 1.Spike waves: <70 ms 2.Sharp waves: 70-200 ms 3.Slow waves: >200 ms. o <1/3rd of 200 ms: Spike o 1/3rd - Full of 200 ms: Sharp o >200 ms: Slow.
- 26. • Similarly, spike waves can be: 1.Monophasic 2.Biphasic 3.Triphasic 4.Polyphasic.
- 27. Polyspikes
- 28. Slow waves
- 29. Spike and wave discharge • A spike followed by a wave Spike and wave Types: Slow spike & wave (1.5-2 Hz) Lennox-Gastaut syndrome (LGS) 3 Hz spike & wave Absence seizure Fast spike & wave (4-6 Hz) Myoclonus (poly spike & wave)
- 30. Slow spike & wave in a patient with LGS
- 31. Generalized burst (3 Hz: Absence seizure) 3.5 Hz spike & slow wave in Juvenile myoclonic epilepsy.
- 32. Spike & dome in absence seizure
- 33. Fast poly spike & wave in a patient with Juvenile myoclonic epilepsy
- 34. Generalized vs partial seizure Partial: Present on one side Generalized: Present on both side.
- 35. Common EEG abnormalities MC EEG abnormality: Diffuse slowing of background rhythms (Reference: Kaplan) Triphasic wave: Seen in Toxic metabolic encephalopathies (Ex: Hepatic encephalopathy) Periodic lateralising epileptiform discharges (PLED) Periodic triphasic complexes (sharp waves): Commonly seen in: Creutzfeldt Jakob disease (CJD) Rapidly progressive dementia + Myoclonus.
- 36. Non-epileptiform EEG/ Periodic discharges • Characteristics: 1. Periodic discharges of high amplitude 2. May be spike or sharp 3. Recurring at periodic interval 4. Most important EEG finding for an ongoing CNS disease or CNS infection. 5. There are 4 types of periodic discharges: I. Burst suppression II.Repetitive sharp waves III.Periodic triphasic waves IV.Generalized periodic waves.
- 37. MCQs on periodic discharge 1. CJD: Periodic triphasic complexes (sharp waves) 2. SSPE: Periodic giant waves 3. Herpes encephalitis: Periodic lateralising epileptiform discharges (PLED) 4. Burst suppression: Cerebral anoxia * (Burst pattern: Absence seizure).
- 38. CJD (Periodic triphasic / sharp waves, Interval: 0.5-2 sec)
- 39. S S P E (Periodic giant waves, interval: 4-16 sec.)
- 40. Herpes encephalitis (PLED, present in one sided fronto-temporal lobe)
- 41. Burst suppression (Burst followed by suppression)
- 42. Hepatic encephalopathy Stage Consciousness EEG I Alert Normal II Drowsy Slow alpha, poorly developed k complex & sleep spindle III Stupor Theta activity, FIRDA*, absence of sleep pattern IV Coma Triphasic wave V Deep coma Delta wave VI Deep coma Flat EEG *Frontal intermittent rhythmic delta activity.
- 43. EEG in psychiatry slowing: except alcohol & BZD/ sedative withdrawal Deliriu m (fast) Dementi a slowing: EEG of Alzheimer disease, CJD: Characteristic triphasic sharp wave complexes Schizophrenia: Abnormal EEG, the most frequent abnormality is presence of low amplitude epileptiform activity (nonspecific).
- 44. Delirium tremens Alcohol withdrawal Beta prominence in the EEG Chaotic, very fast EEG.
- 45. Hypsarrhythmi a Consists of diffuse giant waves (high voltage, >400 mV) with a chaotic background of irregular, multifocal spikes and sharp waves Very little synchrony between the cerebral hemispheres Seen in WEST syndrome/ infantile spasm
- 46. EEG one liners Epileptiform: 3 Hz spike & wave: Absence seizure Poly spike & wave: Juvenile myoclonic epilepsy Slow spike & wave: Lennox-Gastaut syndrome. Non-epileptiform/ Periodic discharge: PLED: Herpes Burst suppression: Cerebral anoxia Periodic giant waves: SSPE
- 47. Thank you