EEG in neurology and psychiatry

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  1. 1. EEG in Neuropsychiatry Presentor- Dr. Kapil Kulkarni Moderator- Dr. J.P. Rawat Jagjivan Ram Railway Hospital, Mumbai Central
  3. 3. What is EEG ? EEG (Electroencephalogram) refers to recording and analysis of electrical activity of brain recorded by amplifying voltage differences between electrodes placed on scalp or cerebral cortex . This electrical potential is produced by excitatory or inhibitory post synaptic electrical discharges from neuronal dendrites at cortical surfaces. Such neurons constitute only 5% of total neurons of the brain. Voltage recorded on EEG is only 10% of the voltage recorded on ECG due to high resistance of skull. 3
  4. 4. Historical review 4
  5. 5. RECORDINGS FROM ANIMAL BRAIN First person to record electrical activity from animal brain in 1874. RICHARD CATON , 1874 5
  6. 6. RECORDING FROM HUMAN BRAIN First recording from human scalp in 1924. Report published in 1929 Danis William started clinical use to localize brain trauma during ww II in oxford. HANS BERGER 1924 6
  7. 7. Hans Berger 1835-1911: Human EEG Prof of Psychiatry, University of Jena Germany, Removed from job in one day notice by the Nazis, committed suicide Berger wave 7
  8. 8. How EEG recording practically done? 8
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  10. 10. Standard 10-20 International Electrode Placement System. Total 21 electrodes. Odd number left & even number on right side. Electrodes- Silver/gold/steel. Fp1,2= prefrontal F3,4=frontal C3,4=central P3,4=parietal O1,2=occipital F7,8=ant.-temporal [placed on frontal bone] T3,4=mid-temporal T5,6-=post.- temporal A1,2=ear, mastoid Fz=Frontal midline Cz=Central vertex Pz=parietal midline 10
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  13. 13. Montage refers to the particular combination of electrodes examining at a particular point of time. When a single reference point is used for all electrodes Referential montage. When several referential points are used for recording Bipolar montage. In bipolar montage the electrodes form a chain passed side by side or front to back. MONTAGE 13
  14. 14. REFERENCE MONTAGE Connects active scalp electrodes and an inactive electrode placed away from the scalp e.g. on ear, nose or chin [Reference electrode] Disadvantage with ear- some brain activity Chin & nose- heart activity Useful for seeing amplitude of waves 14
  15. 15. BIPOLAR MONTAGE Connects two active scalp electrodes Each channel is attached to two different electrodes Arrangement of channels in montages- Anteriorly placed electrodes on initial channels- helps see progression of waves Alternate left and right electrodes- helps compare the two sides 15
  16. 16. Electrodes- 21 Sensitivity- 5-10 micro volts/mm ( avg 7) Paper speed 3 cm/ sec ( adjustable) Length of recording 2 min each montage - 30 min awake record (10 min sleep) Activation Hyperventilation 3min + 1min - Photic st -30 cm 10,15,20,30,40 Hz ,each in trains of 10 sec. STANDARDS 16
  17. 17. What are normal EEG waves? 17
  18. 18. Normal EEG 18
  19. 19. Found in normal eye closed EEG Highly rhythmic Frequency 8 to 13 HZ Prominent in the posterior cortex Mainly occipital , temporal and parietal cortex NORMAL ALPHA WAVES 19
  20. 20. NORMAL BETA WAVE Frequent in normal eye open EEG EEG waves of >13 HZ Usually of low voltage Found in frontal and central region 20
  21. 21. Effect of eye closure 21
  22. 22. NORMAL THETA WAVES Small amount of sporadic and isolated activity found in normal awake state Prominent in drowsy and sleep EEG tracing EEG activity of 4 to 7 HZ found in frontal and temporal region 22
  23. 23. NORMAL DELTA ACTIVITY Not present in normal awake EEG Prominent in normal deeper stage of sleep. A frequency of < 4 Hz. 23
  24. 24. NORMAL GAMMA WAVE 24
  25. 25. Amplitude Measured: peak to peak Expressed as range i.e 40-50v Depends on Inter electrode distance Type of montage Type of recording surface (10-100 v) Depth 500-1500 v 25
  26. 26. Referral (Ipsilateral ear) Bipolar EFFECT OF MONTAGE ON AMPLITUDE 26
  27. 27. Hyperventilation - causes cortical hypocapnia-> cerebral vasoconstriction and hypoxia -> may allow epileptic foci to become evident Photic stimulation - a strobe light flashing at 8-15 Hz is used to capture the occipital frequency - frequency adjusts to match that of the strobe - may allow epileptic foci to be seen and may even induce epileptic seizures, as may a flickering television screen Sleep deprivation. Sleep EEG ACTIVATION 27
  28. 28. Depth electrodes Ambulatory (24-hour) EEG Q-EEG/BEAM/Brain Mapping/rEEG Multichannel recording of eyes-closed, resting EEG - visually edited & a sample of artifact-free data, analyzed, using the Fast Fourier Transform (FFT) to quantify the power at each frequency of the EEG averaged across the entire sample, known as the power spectrum. QEEG findings are then compared to a normative database This database consists of brain map recordings of several hundred healthy individuals Comparisons are displayed as Z scores, which represent standard deviations from the norm. EEG TECHNIQUES 28
  29. 29. Absolute power This refers to the amount of activity within a specific frequency band of brain waves Relative power This refers to the relative amount of activity within a specific frequency band compared to all the other frequency bands Coherence Measure of synchronization between activity in two channels Symmetry Ratio of power in each band between a symmetrical pair of electrodes 29
  30. 30. LORETA (Low Resolution Electromagnetic Tomography) - Complex mathematical calculations to construct a visual image of the 3D electrical activity of deep parts of the brain from surface electrical measures 30
  31. 31. EEG techniques (continued..) Video EEG/Video telemetry- Simultaneous recording of brain activity on an EEG and behavior on tape or digital video ERP - An event-related potential (ERP) is any stereotyped electrophysiological response to an internal or external stimulus. Polysomnography Simultaneous recording of EEG, muscle tone, oculogram, respiration. 31
  32. 32. Non-invasive Low cost ADVANTAGES OF EEG 32
  33. 33. What are normal EEG changes according to age ? 33
  34. 34. At birth up to 6 months 4 Hz (Delta) 6-12 months 6 Hz (Theta) 1-3 yrs 8 Hz (Alfa coming in) 3-11 yrs 12 Hz (Maturation of Alfa) 34
  35. 35. What are normal EEG changes in sleep? 35
  36. 36. Sleep uncovers epileptiform activities. Normal sleep activities also simulates abnormal activities. 36
  37. 37. NREM sleep Stage I- Drowsiness Stage II- Light sleep Stage III- Deep sleep Stage IV- Very deep sleep REM sleep (paradoxical sleep) SLEEP STAGES 37
  38. 38. SLEEP CHANGES EEG CHANGES NREM Stage1-Drowsiness - Alpha drop out,vertex waves, POSTS. Stage 2-Light sleep - Spindle,vertex wave, K-complex, theta activity. Stage 3-Deep sleep Slow wave sleep,K- complexes, Delta activity starts. Stage 4-Very deep sleep - Much slowing ,some K complexes, delta activity. REM sleep - Desynchronization with fast frequencies. 38
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  41. 41. In deep drowsiness, stage I (may persist during stage II & III) 50-80% in normal adults Location occipital Monophasic, triangular 1Hz (4-6 Hz rare) POSITIVE OCCIPITAL SHARP TRANSIENT OF SLEEP (POSTS) 41
  42. 42. POSTS during Stage I sleep 42
  43. 43. Drowsiness/ drop out alpha & POSTS Sleep Awake 43
  44. 44. 12-14Hz, slowed with sleep Waxing & waning Location: fronto cental Origin: Deep frontal & thalamus SLEEP SPINDLES 44
  45. 45. Positive followed by large negative wave May precede or follow smaller waves of opposite polarity Maximum at vertex may extend to frontal & parietal region Bilaterally synchronous Appear by 5month, prominent in youth Not suppressed by focal lesion VERTEX SHARP WAVES 45
  46. 46. Sleep spindle/Vertex sharp wave 46
  47. 47. Stage II-IV sleep Frontocentral Initial sharp (biphasic) slow (1000ms) fast activities Appear by 5months of age K- COMPLEX 47
  48. 48. K- Complex/ sleep spindle 48
  49. 49. Arousal rhythm Series of K- complex Normal awake pattern 49
  50. 50. Arousal in moderate sleep 50
  51. 51. Stage II or III sleep 51
  52. 52. What are common variations in EEG ? 52
  54. 54. ABNORMAL ACTIVITES Spike Sharp waves Spike and wave complexes Slow spike and wave complexes 3-Hz spike and wave complexes Polyspikes Photoparoxysmal response 54
  55. 55. SPIKES It is a transient discharge , clearly distinguished from the background activity , having pointed peak and duration of 20 to 70 m sec. in conventional paper speed. The main component is generally negative and amplitude is variable. The after coming slow wave is surface negative and depict long hyper polarization. Positive waves are common in in depth recording. Spikes increased after seizure , but not increased prior to seizure (Gotman 1984) 55
  56. 56. MORPHOLOGY OF SPIKES Morphologically spikes are of mainly three types: Mono-phasic Bi-phasic Tri-phasic Poly-phasic 56
  57. 57. ROLANDIC SPIKES Misnomer as the total duration is more than 70 m sec Appears as isolated spikes in centrotemoral region. In BCECTS The entire complex consists of 80 to 120 ms 57
  58. 58. SHARP WAVES Sharp waves are defined as transient discharges clearly distinguish