3. Mansoura University Hospitals
EEG Teaching Courses
Tamer Belal, MD ,PHD
Lecturer of Neurology
Mansoura University Hospitals

4. Uses of ambulatory EEG
Evaluation of interictal epileptiform activity
Documentation of seizures of which patients are unaware
Evaluation of response to therapy
Evaluation of nocturnal or sleep-related events
Evaluation of suspected pseudoseizures
Evaluation of syncope

5. Uses of ambulatory EEG

7. Normal EEG waves

8. Normal EEG waves Delta 0-4 Theta 4-8 Alpha 8-13 (5-100uv) Type
Frequency (Hz)
Location
Normally
Pathologically
Delta
0-4
frontally in adults, posteriorly in children;
high amplitude waves
adults slow wave sleep (deep sleep)
in babies
Has been found during some continuous attention tasks
subcortical lesions
diffuse lesions
Metabolic encephalopathy hydrocephalus
deep midline lesions
Theta
4-8
Found in locations not related to task at hand
young children
drowsiness or arousal in older children and adults
Associated with inhibition of elicited responses (has been found to spike in situations where a person is actively trying to repress a response or action)
focal subcortical lesions
metabolic encephalopathy
deep midline disorders
some instances of hydrocephalus
Alpha
8-13
(5-100uv)
posterior regions of head, both sides, higher in amplitude on non-dominant side. Central sites (c3-c4) at rest
Relaxed/reflecting
Closing the eyes
Also associated with inhibition control, seemingly with the purpose of timing inhibitory activity in different locations across the brain.
Attenuated by eye opening, attention and mental effort (Alpha block)
Alpha Coma (unresponsive)
Paradoxical alpha
Interside differences˃50% (lt)
Unilateral failure of the alpha rhythm to attenuate
reflects an ipsilateral abnormality (Bancaud’s phenomenon

9. Normal EEG waves Beta ˃13-30 ˂35uv Gamma 30-100+ Mu 8-13 Type
Frequency (Hz)
Location
Normally
Pathologically
Beta
˃13-30
˂35uv
both sides, symmetrical distribution, most evident frontally; low amplitude waves
alert/working
active, busy or anxious thinking, active concentration
Benzodiazepines
Gamma
Somatosensory cortex
Displays during cross-modal sensory processing (perception that combines two different senses, such as sound and sight)
Also is shown during short term memory matching of recognized objects, sounds, or tactile sensations
A decrease in gamma band activity may be associated with cognitive decline, especially when related the theta band; however, this has not been proven for use as a clinical diagnostic measurement yet Mu
8-13
Sensorimotor cortex
Cz and Pz
Shows rest state motor neurons
During wakefulness
Attenuated by contraction of contralateral muscles
When persistent, unreactive, and associated with focal slowing, mu like frequencies are abnormal
Mu suppression could indicate that motor mirror neurons are working. Deficits in Mu suppression, and thus in mirror neurons, might play a role in autism

10. Normal EEG waves

11. Electrodes
Recording System
Electrodes Board
Electrodes
Selector
Switches
Filters
Amplifier
Chart Drive
Power supply

12. Recording System

13. Sleep and EEG

14. EEG and states of Arousal

15. The 5 principles of localization
Rule 1
Widely placed electrodes record larger voltages than closely placed electrodes
The potential recorded from the pair having one electrode at F will be greater than the potential recorded from the pair having neither electrodes at F
Rule 2
The further away the dipole is from the surface of the scalp the smaller will be the potential observed at the surface, inter-electrode distance being constant
Rule 3
Phase reversal is really an instrumental one and no true phase reversal. The reversal results from the fact that the shared electrodes goes to opposing inputs and hence causes the opposite deflection to occur
Rule 4
Rule 5
If two Electrodes are equidistant from the focus, no voltage will be recorded between them (Cancellation)

16. The 5 principles of localization
Widely placed electrodes record larger voltages than closely placed electrodes
The potential recorded from the pair having one electrode at F will be greater than the potential recorded from the pair having neither electrodes at F
The further away the dipole is from the surface of the scalp the smaller will be the potential observed at the surface, inter-electrode distance being constant
Phase reversal is really an instrumental one and no true phase reversal. The reversal results from the fact that the shared electrodes goes to opposing inputs and hence causes the opposite deflection to occur
If two Electrodes are equidistant from the focus, no voltage will be recorded between them (Cancellation)

17. The 5 principles of localization

18. Commonly seen localization patterns
A Phase reversal observed in a line of referentially connected electrodes is a true phase reversal . The longer the deflection associated with a particular focus of activity, the closer is the electrode to the focus
Contamination results from a significantly active F included in the reference electrode.

19. Commonly seen localization patterns
(A) Bipolar montage demonstrating phase reversal and (B) referential
montage demonstrating absolute voltage.

20. Commonly seen localization patterns
EEG demonstrating bipolar (A) and reference (B) montages to illustrate a left anterior temporal sharp wave.

21. Commonly seen localization patterns
The rules governing polarity and convention relative to “pen”deflection. When input 1 is negative the deflection is up.

22. EEG Reading
Both the background activity and the changes that appear in the features of the tracing are described in the following terms
Frequency: fast, slow, monomorphic, polymorphic or periodic
Amplitude :low ˂20uv, Medium 20-5-uv, high˃50uv
Attenuation and blocking, suppression , paroxysmal
Wave shape (morphology) : transients (sharp, spike) or complex, monomorphic , polymorphic
Symmetry (synchrony)
Location : focal , generalized or lateralized
Continuity : continuous or intermittent
Reactivity

23. Writing the EEG report Two parts
1- Actual description f the EEG findings and their interpretation
2- Clinical correlation that render the report meaningful
Brief history of the clinical findings today
Mention what the referring physician hope to find out
Descriptive details regarding the testing situation
Describe the state of the patient
Describe the EEG ( just descriptive)
Impression : normal or abnormal and define abnormality
Attempt to correlate the EEG with clinical picture
Suggest further study if needed

24. Writing the EEG report
The EEG was recorded with the standard system of electrode placement. The patient was awake and cooperative.
EEG Report : Background activity comprises of alpha activity 9-10 c/s, which is symmetrical in the occipital leads and spreading anteriorly interspersed with fast beta activity. No paroxysmal activity seen. Hyperventilation and photic stimulation is non-contributory.
IMPRESSION: Normal record. No epileptiform activity seen. Clinical correlation advised.
Note: A normal EEG does not rule out the diagnosis of epilepsy, as epileptiform discharges may be paroxysmal.

25. Abnormal EEG Patterns Abnormality of background rhythm
Abnormal sleep patterns
Abnormal slow activity:
Generalized intermittent slow activity
Focal and lateralized intermittent slow activity
Persistent slow activity
Paroxysmal epileptogenic abnormalities
Inter-ictal epileptiform discharges( focal, generalized)
Ictal
Secondary bilateral synchrony
Epileptiform patterns of doubtful significance
Abnormal periodic paroxysmal patterns
Generalized periodic paroxysmal patterns
SSPE,CJD,Herpes S E, suppression patterns, Triphasic waves
Lateralized periodic paroxysmal patterns
PLEDS,BPLEDS

26. The Normal EEG Patterns
Alpha rythm
Alpha frequency
Normal 10-Hz alpha rhythm “blocked” by eye opening and returning on eye closure. Note the faster frequency immediately on eye closure (“squeak”).

27. The Normal EEG Patterns
Note the prominent left central mu rhythm during eye opening (Mu rhythm)

28. The Normal EEG Patterns
Breach rhythm in the right temporal region (maximal at T4) following craniotomy for temporal lobectomy

29. The Normal EEG Patterns
Normal frontocentral theta rhythm in an 18-year-old patient while awake.

30. The Normal EEG Patterns
Bi-occipital lambda waves in a 28-year-old patient with dizziness.
Notice the frequent “scanning” eye movement artifact in the F7 and T8 derivations.

31. The Normal EEG Patterns
Intermittent left mid-temporal delta during transition to drowsiness in a normal 84-year-old patient evaluated for syncope

32. The Normal EEG Patterns
NORMAL SLEEP ARCHITECTURE
POSTS appearing in the lower three channels in a bipolar circle montage demonstrating positive polarity in the occipital region during sleep.
Notice the surface negative vertex waves maximal at Cz

33. The Normal EEG Patterns
NORMAL SLEEP ARCHITECTURE
Stage 2 sleep with prominent sleep spindles and POSTs

34. The Normal EEG Patterns
NORMAL SLEEP ARCHITECTURE
Slow-wave sleep. Note the intermittent POSTs and sleep spindles against the continuous delta background

35. The Normal EEG Patterns
NORMAL SLEEP ARCHITECTURE
REM sleep with rapid eye movements associated with lateral rectus spikes is noted at the F7 and F8 derivations

36. The Normal EEG Patterns ACTIVATION PROCEDURES
Normal build-up during hyperventilation

37. The Normal EEG Patterns ACTIVATION PROCEDURES
Normal 10-Hz alpha rhythm “blocked” by eye opening and returning on eye closure. Note the faster frequency immediately on eye closure (“squeak”).

38. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
Rhythmic temporal theta bursts of drowsiness.
Note the sharply contoured morphology.

39. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
Central theta (maximal at Cz) seen during the awake state in a 35-year-old patient with migraine headaches

40. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
A 6-Hz (phantom) spike-wave burst with frontal predominance in the 5th second of this EEG in an awake patient with temporal lobe epilepsy.

41. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
Fourteen- and 6-Hz positive bursts maximal in the T6 electrode derivation in a linked-ears reference montage. Note the downward deflection and prominent 14-Hz frequency

42. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
A right benign Epileptiform transients of sleep (BETS) in the temporal region during stage 2 sleep. Note the higher amplitude in the T1 and T2 channel with a longer interelectrode distance

43. The Normal EEG Patterns
BENIGN VARIANTS OF UNCERTAIN SIGNIFICANCE
Wicket waves maximal at T3 and T4

44. Normal EEG Variants 

45. Normal EEG Variants 
Refer to waves that are rare or unusual but not generally abnormal. They may be unusual in shape or in distribution.
They can include
wave mixtures that can appear unusual and can confuse the casual reader (for example, wave harmonics)
Artifacts or electrical disturbances from structures that are not in or part of the brain and do not affect the brain or its function but appear in the EEG tracing

46. Normal EEG Variants 
Odd-Looking Waveforms
Psychomotor variant (rhythmic harmonic theta)
Mu (rhythm en arceau or wicket rhythm, arciform rhythm )
14- and 6-Hz waves
Small sharp spikes of sleep (SSS) , benign epileptiform transients of sleep (BETS). posterior occipital transients of sleep POSTS
6-Hz spike and wave (phantom spike and wave)
Wicket spikes
Subclinical rhythmic EEG discharges in adults
Rhythmic midline theta

47. Normal EEG Variants 
Odd-Looking Waveforms
Psychomotor variant (rhythmic harmonic theta)
Asymmetrical runs of theta or delta activity primarily in the mid-temporal regions, lasting for a few seconds or as long as 30-45
occurs in 0.5% to 2.0% of selected normal adults and consists of bursts or runs of 5- to 7-Hz theta waves that may appear sharp, flat, or notched in appearance
It starts suddenly on 1 side and lasts for several seconds before terminating suddenly. This behavior resembles a seizure discharge, hence the name "psychomotor variant."
Generally considered benign, this waveform does not correlate with seizure disorder. It is best seen on a prolonged EEG and tends to be more common in children and young people

48. Normal EEG Variants 
Odd-Looking Waveforms
Psychomotor variant (rhythmic harmonic theta)
Rhythmic temporal theta bursts of drowsiness. Note the sharply contoured morphology.

49. Normal EEG Variants 
Odd-Looking Waveforms
Mu (rhythm en arceau or wicket rhythm, arciform rhythm )
This waveform is recognized easily and has no pathological significance. The naive may not recognize it and assume it to be abnormal
The mu waveform occurs in the central regions in the awake patient. It is seen best if a bone defect underlies the electrodes
It can be markedly asymmetrical
Often in the alpha range frequency, it has rounded positive aspects on 1 side and sharpened negative aspects on the other
It is not blocked by eye opening
It becomes obvious when the alpha disappears (ie, alpha blocking).
Associated with fast activity, mu has a frequency about half that of fast activity.
The most classical feature of mu waveform is that it blocks with motor activity of the contralateral body (or the thought of such movement).

50. Odd-Looking Waveforms
Normal EEG Variants 
Odd-Looking Waveforms
14- and 6-Hz waves
The 2 frequencies are intimately intertwined and the complexes occur in bursts.
They generally are thought to be clinically insignificant.
They occur in healthy children and adolescents. Some claim that they are best seen in referential recordings during sleep
Small sharp spikes of sleep (SSS)
This waveform also is known as benign epileptiform transients of sleep (BETS).
These sharp, small waves occur on 1 or both sides (often asynchronously), especially in the temporal and frontal regions.
Rarely seen in children, they are seen most often in adults and the elderly
They can occur in epileptic patients but often are seen in healthy individuals. They can be regarded as a probable normal variant

51. Odd-Looking Waveforms
Normal EEG Variants 
Odd-Looking Waveforms
6-Hz spike and wave (phantom spike and wave)
These occur as bursts of miniature spike and wave complexes or runs of such complexes at 6 Hz rather than the usual 2-4 Hz.
Their significance is debated, but generally those occurring in the posterior head regions are regarded as benign
Seen at all ages (but especially in adults), they often are confused with 14- and 6-Hz waves and may merge into them
The anterior variety are regarded by some as consistent with epilepsy, but further studies are needed to confirm this
Wicket spikes
Almost exclusively in adults
Like wicket rhythm, (rounded aspects to 1 side and sharp points to the other, giving the appearance of spikes or sharp waves
distinguished by their morphology and at times by their defined background rhythms, which are harmonizing.
Can be seen either in wakefulness or sleep in the anterior or temporal head regions.

52. Odd-Looking Waveforms
Normal EEG Variants 
Odd-Looking Waveforms
Subclinical rhythmic EEG discharges in adults
SREDA consists of theta rhythm occurring in a widespread manner, maximal over the parietal and posterior temporal regions, and lasting for a few seconds to a minute without clinical signs or symptoms.
It is described as "not evolving" and appears quite stable for its duration.
Mechanism of SREDA is not understood, represent a benign EEG phenomenon that distinguished from seizure discharges
Another unusual variant (delta rhythm as well as notched waveforms with a frontal distribution and a more prolonged duration that even includes sleep(FRIDA)
Rhythmic midline theta
Rhythm maximal at the midline, most prominently at Cz
It has a frequency of 5-7 Hz and typically has an arciform, spiky, mu like appearance
Waxes and wanes, can appear during wakefulness or drowsiness, and is usually reactive to eye opening or limb movement

53. Normal EEG Variants 
Artifacts
Forehead, jaw, and eyelid muscle movements homotor variant (rhythmic harmonic theta)
Tongue and eyes have their own dipole electric chargeu (rhythm en arceau or wicket rhythm)
Sweating produces electrical disturbances by shorting electrode pairs.
Other sources of artifacts include ambient electrical waves from respirators, intravenous pump machines, televisions, and other electrical equipment.

54. Normal EEG Variants 
Artifacts
Many are recognized by their characteristic appearance on the tracing, but others are identified by direct inspection and reported by the technologist or identified on the video tracing in video-EEG recording.
Artifacts show great variation because of their protean origin.
They may be single waves or recurrent waves (eg, intravenous infusion running), while others are prolonged disturbances (eg, sweating).

55. Artifact produced by tongue movement
EEG artifact of eye blinking.
Example of EEG chewing artifact

56. Normal EEG Variants 
Artifacts
The following can be regarded as clinically insignificant
Chewing produces spurious spike and wave runs in the frontal and temporal regions from the temporalis muscles
Sweating produces very slow waves, because the salt solution shorts out pairs of adjacent electrodes
Eye movements occur with blinking and result from the electrical charge of the eye itself (see image below). They are frontal. Nystagmus also produces artifactual waves
ECG and pulse motion produce unusual waveforms. ECG produces small spikes that are recurrent and are especially evident in the monopolar montages.

57. Normal EEG Variants 
Artifacts
The following can be regarded as clinically insignificant
Tremor and movement of the head or body may cause electrodes to move
Electrode pops or movements can produce sudden, recurrent, or continuous electrical waves
Electrical fields result from electrical devices and televisions.
ICU special waveforms may result from respirator-induced movements, intravenous drips and drip pumps, electrical fields, or cautery in the operating room or emergency department.

58. Normal EEG Variants 
Harmonics
EEG is a complex summation of many frequencies
Different frequencies sometimes add to or cancel each other, creating odd waveforms or fluctuations of waveforms
Pseudospikes or pseudoslow waves may be seen with intermixing of waves.
Many fascinating patterns have been generated by mixing artificially created computer-generated frequencies.
These waveforms have the significance of the basic waveforms that underlie the patterns.

59. Central theta (maximal at Cz) seen during the awake state in a 35-year-old patient with migraine headaches

60. A 6-Hz (phantom) spike-wave burst with frontal predominance in the 5th second of this EEG in an awake patient with temporal lobe epilepsy.

61. Fourteen- and 6-Hz positive bursts maximal in the T6 electrode
derivation in a linked-ears reference montage. Note the downward
deflection and prominent 14-Hz frequency.

62. A right benign epileptiform transients of sleep (BETS) in the temporal region during stage 2 sleep. Note the higher amplitude in the T1 and
T2 channel with a longer interelectrode distance.

63. Wicket waves maximal at T3 and T4.

64. SREDA in a 73-year-old patient during hyperventilation (HV)
SREDA in a 73-year-old patient during hyperventilation (HV). No clinical signs were present.

65. Thank you