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- 1. Normal and Sleep EEG DrArchana Kushwah Choithram Hospital & Research Centre ,Indore Guide Dr Vinod Rai Choithram Hospital & Research Centre ,Indore
- 2. Normal & SleepEEG Introduction Definition Descriptors of EEG activity Normal EEG (Wakeful adult) Normal Sleep EEG Normal EEG (Extremes of age) Activation procedures Artifacts Benign or normal EEG variants
- 3. Hans Berger (1873–1941)recorded the first human EEG in 1924 Brief History ● Vladimirovich (1912) ● first animal EEG study (dog) ● Cybulski (1914) ● first EEG recordings of induced seizures ● Berger (1924) ● first human EEG recordings ● 'invented' the term electroencephalogram (EEG) ● American EEG Society formed in 1947 ● Aserinsky & Kleitman (1953) ● first EEG recordings of REM sleep
- 4. INTRODUCTION (What, Where,How) What Electrical potential generated by summation of cortical nerve cell(Pyramidal cell) EPSP & IPSP: Not AP
- 5. INTRODUCTION (What, Where,How) Where Thalamic pacemaker cells in nucleus reticularis Thalamocortical neurons stimulated excitatory impulses to cortex.
- 6. INTRODUCTION (What, Where,How) How EEG is difference in voltage between 2 recording electrodes plotted over time.
- 8. Definition of normalEEG Normal EEG Absence of abnormal components No criteria for normal patterns Requires recognition of normal patterns at different ages and level of alertness Normal EEG does not always mean normal brain function. Abnormal EEG does not always mean abnormal brain function.
- 9. Descriptors of EEG Morphology Repetition Frequency Amplitude Distribution Phase relation Timing Persistence Reactivity
- 10. Descriptors : 1.Morphology Wave: difference of electrical potential between two recording electrodes Wave form : describes the shape of wave. Transient &/or paroxysm: stands out against the background
- 11. Descriptors : 2.Repitition Rhythmic Semi rhythmic Irregular polymorphic Descriptors : 3.Frequency Number of times a wave recurs in 1 sec. Slow waves < 8 Hz. Fast waves > 13 Hz.
- 12. Total verticaldistance of a wave. Measured in 𝜇𝑉 not in mm. Low< 20𝜇𝑉 :medium 20-50𝜇𝑉 :high >50𝜇𝑉 Changing the montage changes the voltage. Amplitude assymetry ~ confirmed by montage change. Descriptors : 4.Amplitude
- 13. Wide spread/diffuse/ generalised. Lateralized. Focal / localized. Multifocal epileptiform pattern 3 or more anatomically distinct areas generating epileptiform activity. In describing location electrode names should be used.(not head regions / brain areas) Descriptors : 5.Distribution
- 14. Descriptors : 6.Phaserelation Timing and polarity of components of waves in 1 or more channels. In phase (Troughs and peaks occur at same time in different channels) Out of phase (Troughs and peaks donot coincide) Phase reversal (peaks pointing in oppposite direction)
- 15. Descriptors : 7.Timing • Synchronous(same time) •Asynchronous • Independent • 5millisec and <time can be appreciated by digital instruments. 8.Persistence • How often a wave or pattern occurs during the recording. • Persistence index • High /moderate/ low • Sporadic / periodic 9.Reactivity • Changes produced by various maneuvers. • Opening or closing eyes • Hyperventilation • Photic stimulus • Sensory stimulus • Changes in level of alertness. • Movement
- 16. Normal EEG (wakefuladults) Alpha rhythm Beta rhythm Mu rhythm Lambda waves Vertex sharp transients Kappa rhythm Intermittent posterior theta rhythm Low voltage activity
- 17. Alpha rhythm Frequency ≥ 8 Hz & ≤ 13 Hz Distribution posterior head region Reactivity Blocked by eye opening and other alerting maneuver. Disappears in drowsiness and sleep
- 18. Alpha rhythm(frequency) 8-13Hz Nearly constant in a given individual throughout life(decline of 1 or more Hz is abnormal) Frequency in two hemisphere should be same difference of over 1 Hz is abnormal Hemisphere with lower frequency is abnormal. Squeak phenomenon Brief increase in frequency after eye closure followed by rapid deceleration to baseline frequency.
- 19. Alpha rhythm (distribution) Greatest amplitude and most persistent in occipital, posterior temporal and parietal areas. Alpha frequency activity restricted to FP1and FP2 is eye movement artifact until proven otherwise.
- 20. Alpha rhythm (reactivity) Blocked by eye opening, sudden alerting, attention to visual and other stimuli, mental concentration. Bancaud phenomenon Unilateral blocking of alpha rhythm indicates presence of abnormality of non reactive hemisphere. Paradoxical alpha rhythm Alpha rhythm appears on eye opening and disappears on eye closure in drowsy patient. Partial alerting response
- 21. Alpha rhythm Phaserelation Often not in phase Amplitude Commonly more on right side Left side should be at least 50% of right. Asymmetry depends on occipital bone thickness.(not on handedness) Alpha variants Slow alpha variant ~3.5-6.5 Hz: admixture with normal alpha: blocks as alpha. Fast alpha variant ~ 16-20Hz: blocks as alpha. Physiological purpose Possibly integrated with visual system function.
- 22. Beta rhythm Frequency Over 13 Hz Upper beta range ~ gamma range Distribution and reactivity Frontal MC Blocked by movement / intention to move/tactile stimulus (opposite hemisphere) Widespread Not blocked by any stimulus Posterior (fast alpha) Accentuates in Drowsiness and stage 1 sleep. Excess medication (BDZ & Barbiturate)
- 23. Beta rhythm Amplitude Assymetry ~> 35% is abnormal Breach rhythm Localised increase in beta activity in skull defect areas. Physiological significance Possibly integrated with S/M function of the brain. Almost always a good prognostic sign.
- 24. Mu rhythm Wicket/comb/arceaurhythm <5% EEG: young adults 7-11Hz For few seconds in central or centroparietal area(difference from alpha by blocking) At different times on both sides Intermittent & asymmetrical : persistent asymmetry on same side is abnormal Facilitated when scanning visual images. Blocked by ~ voluntary/ reflex/passive movement/intention to move /tactile stimuli. Physiological significance Somatosensory process associated with movement.
- 25. Lambda rhythm Sawtooth shaped Positive polarity Occipital Appears on looking at images containing visual details. 100-250 millisecond duration,< 50microvolt Resembles POST in shape and distribution. Accompanied by eye movement & eye blink artifact. Neither presence nor absence is abnormal Asymmetry is abnormal
- 26. Vertex sharp transients(V waves) Single, negative polarity Maximal over vertex extends to F,P,T area. Common in normal sleep Wakeful adults Sudden loud noise/startle/percussions of hands or feet. >2 times /sec, bilateral synchronous
- 27. Kappa rhythm Bursts of very lowamplitude of alpha or theta frequency In temporal lobe engaged in mental activity. Normal posterior theta rhythm Slow alpha variant Rhythmic slow waves of 4-5 Hz Blocking & distribution same as alpha. Low voltage EEG No activity over 20 microV More common in advancing age / tense subjects. < 10microV abnormal <2 microV electrocerebral inactivity(brain dead)
- 28. Normal sleep EEG(adults) Elements of normal sleep activity Slow waves Positive occipital sharp transients Vertex sharp transients Sleep spindles K complexes Sleep stages Sleep cycle
- 29. Slow waves Moreprominent posteriorly. Less persistent, more asynchronous, low amplitude, fast frequency in light sleep than deep.
- 30. POSTS Triangular waves in occipitalarea 4-6Hz. Mono /bi phasic Lambdoid waves (Shape & distribution) Prominent lambda waves are associted with more POSTS & photic driving responses.
- 31. Sleep spindles 12-14Hz Duration >0.5 sec Maximum over central After 2 years simultaneous and symmetrical K COMPLEX Resembles v wave in distribution , reactivity and polarity >0.5 sec Less sharply contoured
- 32. Stages of sleep StageW • Slowing • Predominance of alpha • Prominent beta in drug induced • SEM (first EEG sign of drowsiness) Stage 1 • Disappearance of alpha(30 sec Epoch ~ < 50% alpha) • Paradoxical alpha • Slow waves
- 33. Sleep stage 2 Sleep spindles K complexes Slow waves continue POSTS often persists V wave often persist
- 34. Sleep stage 3& 4 Stage 3 • 20-50% of 30 sec Epoch contains • Waves of 2Hz or < • Waves of <75 microV • In C3-A1 or C4-A2 • K complexes / sleep spindles/POSTs Stage 4 • >50% • K complexes blend with slow waves • Spindles & POSTs rare • After 55 yr~ St 3& 4 rare(only amplitude criteria apllied)
- 35. REM sleep >50% of a 30 sec Epoch contains Low voltage EEG Prominent theta wave Rapid eye movt. Reduced muscle tone Resemble stage 1 but no v wave Saw tooth wave Alpha frequency ~1- 2 Hz Appearance of REM in routine EEG is pathological.
- 36. Sleep cycle Eachcycle~ all stages NREM & REM: 4-7 cycles /sleep 1st cycle shortest: later 80-120 min. :REM sleep ~ appears 70-90 min after onset of sleep. Young adults: 30-50% stage 2; 20-40% stage 3&4: 5-10% stage 1 REM sleep: 25% in young adults & 20% in 5th decade.
- 37. EEG of elderly(>60years) Alpha rhythm Frequency, persistence, reactivity &voltage ↓ Beta activity More prominent : incidence & amplitude↑ Sporadic general slow waves More common than young adults. Intermittent temporal slow waves Especially on lt. side < 1% of waking record should be delta range < 10% in theta range(Arrena et al) Sleep Fairly prominent slow waves Sleep depth and consolidation reduced(St 3,4↓ 𝑡𝑜 < 10% ) REM sleep ↓ to < 20%
- 38. EEG of prematureage to 19 years Maturation of EEG parallels anatomical & physiological development of brain EEG of neonate is a function of actual age of brain Conception age (CA)= gestational age + legal age Always try to record normal active newborns immediately after feeding(quiet wakefulness)
- 39. CA< 29 wks Tracediscontinue Interhemispheric synchrony Delta brush pattern
- 40. EEG of prematureage to 19 years CA~ 29-32 wks Lowest Interhemispheric synchrony Temporal theta burst(temporal saw tooth wave) Highly useful for estimating CA
- 41. EEG of prematureage to 19 years CA~ 32-34 wks Multifocal sharp transients ; abundant delta brush EEG reactivity starts.
- 42. EEG of prematureage to 19 years CA ~ 34-37 wks Frontal sharp transients/ mono rhythmic frontal slowing Trace alternans(delta brush & multifocal sharp transietns ↓) Inter hemisheric synchrony ↓ Activity Moyene. CA ~ 38 -42 wks Similar to full term 4 basic pattern Low voltage irregular (wakeful & active sleep) Mixed vol (wakeful & transitional sleep) High vol. slow Trace alternans
- 43. EEG of prematureage to 19 years Full term to 3 month Precursor of alpha rhythm~ 3-4 Hz Sleep spindles appear Asymmetry up to 8 months ; beyond 2 yr asyym. Is abnormal. Trace alternans / multifocal sharp transient disppear. Interhemispheric synchrony 100% Reaction to tactile and auditory + Lamba waves
- 44. EEG of prematureage to 19 years 3 months – 1 year Wakefulness~ BGA – theta & delta range Occipital rhythm Drowsiness Hypnogogic hypersynchrony Sleep Starts to resemble adult Cone / O waves Sleep spindles appears at 3-6 mnt; assym. up to 8 mnt. V waves & k complex ~ 3-6 mnt.
- 45. EEG of prematureage to 19 years 1-19 YEARS Gradually becomes same as adult Alpha frequency gradually increases. Slow waves more prominent up to 4 years. Posterior slow waves of youth Most common at 8-14 years Hypnogogic hypersynchrony rare after 12 years SEM appears at 10 years. 14-6 Hz burst more common than adults. POST begin to appear.
- 46. Activation procedures Hyperventilation Sleep deprivation Photic stimulation Others Pattern or video game sensitivity Auditory stimuli Reading Eye opening /closing and mental concentration Tactile stimulation Drugs
- 49. Artifacts Physiological Blinking and eyemovements Muscle artifact Movement artifact ECG Pulse wave artifact Skin potential Movements of tongue and oropharyngeal structures Dental restoration Non physiological External electrical interference Internal electrical malfunctioning of recording system
- 58. Benign or normalEEG variants Rhythmical patterns RMTD/RTTD Alpha variants SREDA Midline theta rhythm Frontal arousal rhythm Benign patterns with epileptiform morphology 14 & 6 Hz positive burst(Ctenoids) Small sharp spikes(SSS) 6 Hz spike and wave bursts(Phantom) Wicket spikes Breach rhythm.
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- 65. Reference Fisch &Spehlmann’s EEG primer: 3rd edition: Elsevier 2009 Current pratice clinical EEG : 3rd edition : Pedley: liipincot williamson & wilkin 2003