eeg ppt defining all aspects of eeg and various type of waves seen in every epilepsy

Eeg presentation

1. EEG Dr Somasundaram pl Junior resident Department of paediatric Guide – Dr Roopal Khobragade

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)

3. Definition EEG is the record of electrical activity of brain( superficial layer i.e. the dendrites of pyramidal cells) by placing the electrodes on the scalp.

4. Role of EEG EEG is the most informative laboratory test in patients with epileptic seizures. It can play an important role in – Diagnosis of epilepsy Classification of epileptic seizure type and epilepsy syndromes Localization of epileptogenic zone Assessment of response to treatment Estimation of risk of seizure recurrence after discontinuation of antiepileptic medication Non convulsive status epilepticus Encephalitis and encephalopathy Coma

5. Sensitivity and specificity of routine EEG Routine EEG after 1 st unprovoked seizure In adults - has sensitivity of 17.3% and specificity of 94.7% In children - has sensitivity of 57.8% and specificity of 69.6%

6. Normal sleep Duration: 8 hr • NREM (75%): 1. Stage 1 (5%) 2. Stage 2 (45%) 3. Stage 3 (12%) 4. Stage 4 (13%). NREM stage 3&4 together k/a deep sleep(25% ) which is equivalent to duration of REM sleep. REM (25%)

7. 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 Dreaming Not remembered Remembered

8. As sleep progresses NREM sleep decreases & REM sleep increases

9. Arrangement of electrodes 4 Anatomincal Landmarks- Nasion-indentation between the forehead and the nose, Inion - a ridge at the midline over the occipital area, 2 Preauricular points - indentations just above the cartilage that covers the external ear openings. Occasionally, additional electrodes Sphenoidal Suboccipital

10. Electrodes F = frontal Fp = frontopolar T = temporal C = central P = parietal O = occipital A = auricular(ear electrode). Even numbers- right side. Odd numbers - left side. "z" points to midline.

11. International 10-20 system (Jasper 1958)

12. Alpha waves - 8-13 Hz Beta waves - >13 Hz Theta waves - 3.5-7.5 Hz Delta waves - 3 Hz or less

13. 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.

14. Different types of brain waves in normal EEG Rhythm Frequency (Hz) Amplitude (uV) Recording & Location Alpha( α ) 8 – 13 50 – 100 Adults, rest, eyes closed. Occipital region Beta( β ) 14 - 30 20 Adult, mental activity Frontal region Theta( θ ) 5 – 7 Above 50 Children, drowsy adult, emotional distress Occipital Delta( δ ) 2 – 4 Above 50 Children in sleep D T A B

15. Brain activity: EEG findings  Awake/ eyes open = Beta (frontal predominantly)  Try to sleep (awake)/ eyes closed = Alpha (occipital)  Relaxed with eyes closed : Alpha  Active mental concentration : Beta  Focussed attention : Gamma ( highest frequency wave , >30 Hz).

16. EEG protocol To be recorded in both awake & sleep In sleep- Many of epileptiform activity can be picked In awake- tells about background activity and tells about cerebral function Sleep EEG is often required among infants and tells about cerebral function. Sleep EEG requires 4 hours of sleep deprivation ( not needed routinely) – this activates epileptiform activity which may be missed in routine EEG. Sedation( if required) – triclofos (20-50mg/kg/dose) or melatonin(2-6mg/dose)

17. Activation procedure Sleep Sleep deprivation Hyperventilation- ask the child to take deep breath in & out. Useful in diagnosis of absence seizures. Photic stimulation (intermittent) – 3 to 30hz It is useful in diagnosis of photogenic epilepsies ( eg - JME, etc)

18. Eye opening and closing can enhance assessment of the posterior dominant rhythm Eye closure may demonstrate abnormal activity in certain forms of epilepsy ( eg , benign occipital epilepsy) Fatigue rather than sleep per se is a main trigger. Sleep deprivation is an important activator of focal epileptiform abnormalities. Hyperventilation is an activation procedure, it mainly influences absence seizures & generalized 3hz spike & wave discharge . We typically hyperventilate patients for 3 mins , if features s/o absence then we hyperventilate for 4 mins twice during EEG.

19. Hyperventilation in structural & vascular conditions Hyperventilation in structural & vascular conditions can show focal slowing. Hyperventilation results in hypocarbia and vasoconstriction Hence it should be cautiously used in case of known or suspected moya moya disease , vascular disorders , complete stroke and transient ischemic attacks . It is contraindicated in patients with significant cardiac disease , severe respiratory problems and sickle cell disease .

20. Normal pattern seen in hyperventilation High amplitude rhythmic slowing may occur during hyperventilation and clinically mimic an absence seizure & should not be considered as an ictal pattern.

21. Photic stimulation Intermittent photic stimulation is primarily an activator of generalized spike wave or polyspike wave – seen in idiopathic generalized or myoclonic epilepsies. Generalized spike wave discharge that outlasts the duration of photic stimulation is a genetic pattern and may be seen in individuals with no history of epileptic seizures. Hence photosensitivity should be interpreted appropriately and should not result in inappropriate management with AEDs. A spike wave discharge that outlasts the duration of the photic stimulation or is associated with clinical signs such as myoclonic or absence seizure, is a photoconvulsive response & is clearly abnormal pattern.

22. Posterior dominant rythm When the patient is relaxed with eyes closed, the background is usually characterized by posteriorly dominant alpha rhythm, aka posterior dominant rythm

23. Reactivity EEG reactivity refers to a change in the EEG background activity in response to external stimuli. on eye closure , evolution of alpha dominant rhythm in occipital region In focal cerebral lesions, the posterior predominant frequency may show unilateral impairment of reactivity to eye opening ( Bancaud phenomenon ) or alerting. Lesions do not need to be in the occipital lobes to produce these abnormalities of EEG reactivity

24. Bancaud phenomenon Failure of alpha rhythm to accentuate even after eye opening, indicates ipsilateral focal lesion of any lobe ( not specific to occipital lobe )

25. Normal patterns Upto age of 4 months , the presence of sharp transients , which are seen in many neonates without history of seizures and correlate poorly with epileptic seizures or outcome. A posterior dominant rhythm first appears at the age of 3 months, and is 3hz in the alert state. Evolution of posterior dominant rhythm Age Hz 4 months 4 12 months 6 3 years 8 10 years 10-12

26. By 3 years of age, the posterior dominant rhythm reaches alpha frequency. It is best seen with eyes closed and in a relaxed state. It is blocked by attention . Eg ; eye opening or mental effort.

27. Stages of sleep & their patterns 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 waves

28. Stages of sleep EEG pattern Somatic or Behavioral changes Alert Alpha activity on eye closed Desynchronization on eye opening Respond to verbal commands I (Drowsiness) Alpha dropout & appearance of vertex waves & theta. Reduced HR & RR II (Light sleep) Sleep spindles, vertex sharp waves & K-complexes Reduced HR & RR III ( Deep Sleep) Much slow background K-complexes Reduced HR & RR

29. IV (very deep sleep) Synchronous delta waves, some K-complexes Reduced HR & RR REM sleep (paradoxical sleep) Desynchronization with faster frequencies HR, BP & RR irregular Marked hypotonia Rapid eye movement 50 – 60 /min. Dreaming threshold of arousal

30. • Stage 1 NREM: Vertex/ Theta (Lightest stage of sleep)

31. • Stage 2 NREM : o Sleep spindles & K complexes o Largest % of sleep

32. K complex- characteristic biphasi c Negative-positive waves lasting more Than 0.5 seconds. Large-amplitude delta frequency waves, sometimes with a sharp apex. They can occur throughout the brain and more prominent in the bifrontal regions. Usually symmetric , they occur each time the patient is aroused partially from sleep. Sometimes followed by runs of generalized rhythmic theta waves- an arousal burst . K complex

33. Sleep spindles Sleep spindles- spindle shaped rhythmic waves which gradually increase & then decrease in amplitude, lasts around 0.5 to 3 sec & generated every 3-6 sec Groups of waves during many sleep stages, especially in stage 2. Frequencies in the upper levels of alpha or lower levels of beta . Lasting for a second or less, they increase in amplitude initially and then decrease slowly. They usually are symmetric and are most obvious in the parasagittal regions .

34. Delta: 20-50% - > Stage 3 • Delta: >50% -> Stage 4 o Deepest sleep o Decreases with age o Most relaxed stage

35. REM Sleep Burst activity No EMG (due to muscle paralysis) Penile erection + Muscle atonia ↑ Pulse, Respiration Peak at 5-6 AM Saw tooth waves

36. Changes in brain waves during different stages of sleep & wakefulness

37. Sleep Spindle K - complex

38. EEG Artifacts Biological artifacts Eye artifacts (including eyeball, ocular muscles and eyelid) ECG artifacts EMG artifacts Glossokinetic artifacts (minor tongue movements) External artifacts Movement by the patient settling of the electrodes Poor grounding of the EEG electrodes the presence of an IV drip

39. Artifact- eye blink

40. Muscle activity

41. Amplitude abnormalities Amplitude differences need to be interpreted with caution since isolated differences in amplitude may occur as a normal finding. Alpha rhythm may be increased in amplitude on one side, most often the right , by as much as a 2:1 ratio . Less commonly, the alpha rhythm of the left hemisphere is increased by as much as a 3:2 ratio . More pronounced differences in background amplitude are abnormal.

42. Markedly diminished amplitude on one side- Abnormalities of cortical gray matter With excess fluid between the cortex and recording electrodes. Ischemic stroke with gray matter involvement Subdural hematoma Sturge-Weber syndrome.

43. Frequency abnormalities Alterations in frequency typically are most useful in the assessment of diffuse rather than focal cerebral disturbances . The EEG background frequency of the 2 hemispheres should be within 1 Hertz (Hz). Any greater difference is indicative of a lateralized EEG abnormality on the side with the slower background

44. Abnormal EEG • It is of 2 types: 1. Epileptiform 2. Non-epileptiform

45. 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<1/3 rd of 200 ms : Spike o > 1/3rd - Full of 200 ms : Sharp o >200 ms : Slow.

46. Similarly, spike waves can be: 1. Monophasic 2. Biphasic 3. Triphasic 4. Polyphasic.

47. Spike, generalized . High amplitude and the aftergoing background suppression and slow wave.

48. Spike, generalized . Significant spikes usually are followed by a slow wave,. Generalized spikes are typically maximal frontally. This is typical of the primary (ie, idiopathic, genetic) epilepsies. .

49. 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)

50. Slow spike-wave complexes (SWC). In addition to being slower, this is also less monomorphic than the 3-Hz SWC- the Lennox-Gastaut type.

51. Generalized burst (3 Hz: Absence seizure)

52. Fast poly spike & wave in a patient with Juvenile myoclonic epilepsy ( polyspike , generalized)

53. Polyspike, generalized. Aftergoing slow wave -typically juvenile myoclonic epilepsy

54. GTCS VS PARTIAL

55. Common EEG abnormalities MC EEG abnormality: Diffuse slowing of background rhythms Triphasic wave : Seen in Toxic metabolic encephalopathies (Ex: Hepatic encephalopathy) Periodic lateralising epileptiform discharges (PLED) Periodic triphasic complexes (sharp waves): Commonly seen in crutzfeld Jacob disease

56. Breach rhythm Asymmetric increase of EEG activity over skull defect ( Rt. Fronto-central region)

57. Background slowing Mild diffuse cortical dysfunction

58. Intermittent slowing- Generalized

59. Intermittent slowing regional-pathologic

60. Continuous slowing regional-pathologic

61. 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.

62. 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).

63. CJD (Periodic triphasic / sharp waves, Interval: 0.5-2 sec)

64. Herpes encephalitis ( PLED , present in one sided fronto -temporal lobe) Periodic – 1/sec at a regular interval Lateralising - involves one side Epileptiform discharges- high amplitude waves which are separated by other low amplitude waves

65. Burst suppression (Burst followed by suppression)

66. Hypsarrhythmia Consists of diffuse giant waves (high voltage, >400 mV) with a chaotic background of irregular, multifocal spikes and sharp waves

67. Encephalitis and encephalopathy Frequency of alpha rhythm slows-even before consciousness is altered Slow alpha rhythm intermixed with sporadic theta activity Slower theta activity become generalized and less reactive to external stimuli Slowing into delta range

68. Severe, generalized, slow-wave abnormality in a 10 year- old boy with encephalitis

69. SSPE showing a hypsarrythmia pattern with periods of flattening

70. Sharp and slow wave complexes recurring every 6 seconds :SSPE

71. Encephalopathic patterns in uremia - shows continuous theta and delta activity

72. EEG in coma Classification system for coma GRADES OF COMA FEATURES Grade 1 Regular alpha & some theta Grade 2 Predominant theta Grade 3 Widespread delta or some spindle coma Grade 4 Burst suppression pattern/alpha coma Grade 5 Flat

73. Alpha coma EEG pattern in alpha frequency predominantly in frontal region, non reactive to any external stimuli – seen in comatosed patients

74. Spindle coma Generalized high-voltage delta activity with sleep spindles superimposed . Spindles are more widespread than normal sleep, although similar morphology . Has better prognosis when compared to alpha coma.