Learning to Describe EEG
Step 1: Reviewing Normal Adult EEG
Pickie4Education.com
Electroencephalography (EEG): An introductory Text by AES
https://www.ncbi.nlm.nih.gov/books/NBK390342/
Britton JW, Frey LC, Hopp JLet al., authors; St. Louis EK, Frey LC, editors. Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants [Internet]. Chicago: American Epilepsy Society; 2016. An Orderly Approach to EEG Analysis: Visual Inspection of the Background and Pattern Recognition. Available from: https://www.ncbi.nlm.nih.gov/books/NBK390342/
Favorite Resource
ACNS Guideline 14- Steps & Tools
https://www.acns.org/pdf/guidelines/Guideline-14-pocket-version.pdf
https://www.acns.org/UserFiles/file/Guideline14.StandardizedCriticalCareEEGTerminology.pdf
https://www.acns.org/research/critical-care-eeg-monitoring-research-consortium-ccemrc/education
ACNS Defines Background EEG
ACNS Guideline 14 clearly defines expected characteristics of background EEG
Must have information
Reviewing EEG without these is like…
Traveling a new city without GPS, a map, or a guide
Can it be done?
Of course
Should it be done?
NO
Why is that information critical?
Montage – orientation of leads in relation to one another defines normal vs abnormal.
Skull defects determine electrode placement, asymmetries, breech rhythm, modifications to placement
Normal for a 4-year-old is not normal for a 40-year-old.
This Photo by Unknown Author is licensed under CC BY-SA
Background
Example A
Example B
Can you describe these without knowing the montage, skull defects, age and state of the patient? Sure. But should you? NO!
Describing EEG: Normal Adult EEG
Background
Example A
Example B
Both: longitudinal bipolar
NOT the same layout!
Background
Example A
Example B
Both: longitudinal bipolar
NOT the same layout!
NO Midline!
Background
Example A
Example B
Both: longitudinal bipolar
NOT the same layout!
Background
Example A
Example B
Both: longitudinal bipolar
NOT the same layout!
Now that you are oriented to montage
Determine: skull defects, age, state
Now you are ready to look at details.
Normal Adult EEG: Background
Synchrony
Symmetry
Anterior to posterior gradient
Organized
What do these terms mean?
Synchrony: left & right hemispheres moving together
Symmetry: frequency & amplitude left to right is similar
Anterior to posterior gradient- is there a noticeable difference frontal to occipital frequency & amplitude
Organized- are there differences in regions of the brain and do the overall appearances remain regionalized
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Left
Right
Midline
Left
Right
SCALE
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Left
Right
Midline
Left
Right
SCALE
Synchrony – are things occurring at the same time left to right?
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Left
Right
Midline
Left
Right
SCALE
**Technically for symmetry- you must evaluate in referential montage! ACNS Guidelines!
Symmetry: is amplitude & frequency similar L-R?
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Posterior
Anterior
SCALE
Posterior
Anterior
Anterior to posterior gradient- is there an increase in amplitude and decrease in frequency frontal to occipital?
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Left
Right
Midline
Left
Right
SCALE
Organization – Do regions have their own patterns or do patterns cross into other neighborhoods?
Background
Example B
Synchrony
Symmetry
Anterior to posterior gradient
Organized
By comparison:
The first 3 seconds have:
NO gradient
Too synchronous
Exactly symmetrical
Too organized
Background
Example A
Synchrony
Symmetry
Anterior to posterior gradient
Organized
Continuous, symmetrical, synchronous, well organized EEG with slightly higher amplitude right than left, clear anterior to posterior gradient.
Normal Adult EEG: Features
PDR: posterior dominant rhythm
Frequency- relative and absolute
Amplitude- relative and absolute
Topography
Morphology
Occurrence
Polarity
Frequencies
This Photo by Unknown Author is licensed under CC BY-SA
Necessary components!!
PDR
Aka ALPHA
Posterior dominant rhythm
Measure at fastest frequency, highest amplitude, compare left to right
Frequency- how many wave cycles per second?
Measured both:
Absolute cycles per second
And
Relative L>R and anterior to posterior
Amplitude- how high baseline to peak is the waveform at its highest
Topography-
Where on the cortex is the waveform located?
Frontal, Central, Parietal, Temporal, Occipital, Midline
Occurrence- how often does the pattern occur?
ACNS Guidelines very clear definitions!
Normal Adult EEG: Stages
https://www.ncbi.nlm.nih.gov/books/NBK390354/pdf/Bookshelf_NBK390354.pdf
EEG Atlas
All of the following slides are from this text.
When looking at EEG what steps do we take?
1) Identify Montage
When looking at EEG what steps do we take?
1) Identify Montage
2) Identify display settings
When looking at EEG what steps do we take?
1) Identify Montage
2) Identify display settings
3) Identify age of patient
When looking at EEG what steps do we take?
1) Identify Montage
2) Identify display settings
3) Identify age of patient
4) Identify prominent features (FAtmop)
GAME TIME
WHAT IS THE MOST NOTABLE FEATURE?
HOW DO YOU KNOW?
WHAT ELSE CAN YOU IDENTIFY?
What is the most notable feature?
A) large deflection in channels 1 and 5
B) robust sinusoidal activity in channels 4 and 8
C) low voltage activity in channels 2-3 and 5-6
What is the most notable feature?
B) sinusoidal activity in 4 and 8
What is that activity?
How do you know?
What is the most notable feature?
B) sinusoidal activity in 4 and 8
What is that activity?
How do you know?
What is the most prominent feature?
A) low voltage activity
B) deflections in channels 1, 5, 9
C) sinusoidal activity in channels 9, 11, 13, 14
What is the most prominent feature?
A) low voltage activity
B) deflections in channels 1, 5, 9
C) sinusoidal activity in channels 9, 11, 13, 14
What is the most prominent feature?
A) low voltage activity
B) deflections in channels 1, 5, 9
C) sinusoidal activity in channels 9, 11, 13, 14
What is the most prominent feature?
A) large deflections in channels 1, 5, 9, 13, 17?
B) sharply contoured activity in the posterior channels
C) generalized low voltage beta
What is the most prominent feature?
A) large deflections in channels 1, 5, 9, 13, 17?
B) sharply contoured activity in the posterior channels
C) generalized low voltage beta
What is the most prominent feature?
B) sharply contoured activity in the posterior channels
How do you know?
What is the large deflection in the anterior leads?
Describe the low voltage beta.
What change occurs to cause the abrupt activity here?
A) patient wakes up
B) patient has a seizure
C) photic stimulation has begun
What change occurs to cause the abrupt activity here?
C) photic stimulation has begun
How do you know?
What change happens here?
A) patient becomes post ictal
B) patient is becoming drowsy
C) patient is waking up
What change happens here?
A) patient becomes post ictal
B) patient is becoming drowsy
C) patient is waking up
What change happens here?
B) patient is becoming drowsy
How do you know?
What change happens here?
A) Wake
B) Sleep
C) Abnormal periodic discharges
What change happens here?
A) Wake
B) Sleep
C) Abnormal periodic discharges
What change happens here?
A) awake
B) asleep
C) Lateralized periodic discharges
What change happens here?
A) awake
B) asleep
C) Lateralized periodic discharges
Extra Helps from the book
https://www.ncbi.nlm.nih.gov/books/NBK390354/pdf/Bookshelf_NBK390354.pdf
EEG Atlas, Erik Louis, MD & Lauren Frey MD
Neonatal Background Evolution
Neonatal Graphoelements
Test Time