EEG Terms/ Seizure Classification Flashcards
Epileptic seizures fall broadly into 3 main types
1.) Focal
2.) Generalized
3.) Uknown
How to classify/ describe focal onset seizures?
Aware or Impaired Awareness
&
Motor onset
Non motor onset (sensory, cognitive, emotional, autonomic, behavioral arrest)
automatic behaviors
automatisms
extension or flexion postures
tonic
flushing/ sweating/ piloerection
autonomic
jerking arrhythmically
myoclonus
jerking rhythmically
clonus
loss of tone/ limp
atonic
thrashing/ pedaling
hyperkinetic
trunk flexion
spasm
Elements of Consciousness
AWARENESS of ongoing activities
MEMORY of time during the event
RESPONSIVENESS to verbal or nonverbal stimuli
SENSE OF SELF as being distinct from others
Definition of Epilepsy
- At least two unprovoked seizures occurring >24 hr apart
- One unprovoked seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years
- Diagnosis of an epilepsy syndrome
Epilepsy is considered to be resolved when…
individuals who had an age-dependent epilepsy syndrome are now past the applicable age
Or for those who have remained seizure-free for the last 10 years, with no seizure medicines for the last 5 years
How to classify epilepsy type per the ILEA (International League Against Epilepsy).
classification at three levels
1.) the seizure type
2.) epilepsy type
3.) epilepsy syndrome.
Imaging, EEG and other investigations contribute to optimized classification at all three levels.
Recommended settings for ECOG (Electrocorticography) Mapping
Bandpass 1-70Hz
Sampling Rate >1000kOhms
Sensitivity 70-100uV
Name the two different forms of the normal variant:
6 Hz spike and wave discharge
WHAM (Wake High-Amplitude Male), which is frontally dominant
FOLD (Female Occipital Low-amplitude Drowsiness)
What does the normal variant SREDA acronym mean?
Subclinical Rhythmic EEG Discharge of Adults (SREDA)
characterized as symmetrical, diffuse, rhythmic monomorphic theta waves with sharp contours, maximally on the parietal and posterior temporal regions.
What does the normal variant RMTD acronym mean?
Rhythmic Mid-temporal Theta of Drowsiness (RMTDs)
Other than RMTD, what other normal variants come from the temporal region?
Wickets, 14 and 6 Hz Positive Spikes, BETS or BSSS (benign epileptiform transient of sleep) or (Benign sporadic sleep spikes),
What is Ciganek’s Rhythm?
a nonspecific benign theta rhythm of drowsiness occurring at the midline
What is Bancaud phenomenon?
Uncommon unilateral failure of the alpha to attenuate with eye opening. It may occur in lesions of the temporal or parietal lobes.
The temporal factor refers to the ________ and the spatial factor refers to the __________.
timing and location
Most common form of focal epilepsy
temporal lobe epilepsy
to prevent** Aliasing**
waveforms must be sampled at a rate at least half as fast or faster than their actual frequency
This is the Nyquist Frequency
EEG changes with CBF (cerebral blood flow)
loss of faster frequencies and increased slower frequencies as CBF decreases
Normal CBF (cerebral blood flow)
35-50 ml/ 100g/min
Stage I sleep is characterized by
-Slowing, increasing irregularity, and ultimate disappearance of the PDR
-Vertex waves (V-waves) are a part of 1a sleep stage, the more formed/ regular they are then you’re in Stage 2.
-Positive Occipital Sharp Transients of Sleep (POSTs) may be quite prominent, are electropositive at the occipital electrodes.
It’s important to capture Stage 1&2 Sleep on patients because…
Focal spike or sharp wave discharges often appear or are increased during stage I (drowsiness) and stage II sleep.
Stage II sleep arrives with the appearance of
-well-defined sleep spindles and V-waves, +/-K-complexes *If spindles are only fragmentary or very brief, the patient is not considered to be firmly in Stage II.
*Sleep spindles often follow the K-complexes
A K-complex can be evoked by
a sudden auditory stimulus (noise)
Another name for Sleep Stage 3
Slow Wave Sleep (SWS)
-Characterized by increasing amounts of diffuse delta activity, occupying variable amounts of the background.
-At the same time there is a progressive decline in sleep spindles
Rapid eye movement (REM) sleep (Stage IV) is characterized by
-Rapid eye movements and loss of muscle tone.
-EEG background consists of low-voltage theta activity, and eye channels demonstrate irregular vertical and horizontal eye movements.
-Epileptiform discharges are seldom present in REM sleep.
EEG vs MRI/ fMRI
EEG has a high temporal resolution and low spatial resolution, while fMRI has high spatial resolution and low temporal resolution.
EEG measures directly the electrical activity of the brain and fMRI indirectly by measuring changes in blood flow.
Temporal resolution vs Spatial resolution
-Spatial resolution refers to the capacity a technique has to tell you exactly WHERE the brain is active.
-Temporal resolution describes a technique’s ability to tell you exactly WHEN the activity happened.
EEGs and Coma Grades
Benign for survival are
Grade 1: near normal record with preserved reactivity to external stimulation
Grade 2 : reactive — with rhythmic theta activity dominant, attenuated by external stimulation; frontal rhythmic delta activity
Grade 3 : usually reactive and “spindle coma,” where sleep patterns of stage 2 sleep usually occur in the form of rhythmic 12–14 Hz spindles, with other transients of that sleep stage, usually reactive to external stimulation.
EEGs and Coma Grades
Uncertain for survival are
Grade 2 : abnormality with mixed theta and delta activity which does not react to external stimulation
Grade 3 : abnormality with dominant delta activity, which may or may not be reactive to external stimulation; alpha pattern coma of reactive type; and the presence of epileptiform discharges on a base of Grade 3 abnormality with diffuse delta activity.
EEGs and Coma Grades
Malignant for survival are
Grade 3 : low amplitude delta activity, with brief intervals of suppression (1 sec), nonreactive to stimulation;
Grade 4 : “burst suppression pattern” with prolonged intervals of suppression and bursts of activities within the alpha, theta and delta frequency ranges;
Grade 4 with Epileptiform activity with alpha pattern coma, nonreactive with activity within the alpha frequency range either widely distributed or more prominent anteriorly; theta pattern coma with clusters of 5 Hz activity maximal anteriorly, often superimposed on low amplitude delta, Grade 4 with low output EEG typically nonreactive.
Grade 5 : when the EEG becomes isoelectric. *The effect of sedation and/or hypothermia must be excluded and principles outlined in the American EEG Guidelines must be applied
Charge is measured in
Coulombs
How is sensitivity different from gain?
Sensitivity is the ratio of input voltage to output deflection
Gain is the amount by which the incoming signal is amplified directly in the amplifier.
FFT is used for processing EEG data. What’s FFT?
Fast Fourier transform (FFT)
A spike is ____ ms.
less than 70ms
A sharp wave is ____ ms.
70-200ms
Benign Sporadic Sleep Spikes (BSSS)
BSSS occur in the broad temporal region and are characteristically difficult to localize precisely. BSSS often appear in both hemispheres either independently or bisynchronously and may have shifting asymmetries. They almost exclusively occur during drowsiness or light non-REM sleep. The appearance of stereotyped, isolated, small-amplitude spikes that do not disrupt the background and appear only in drowsiness or light sleep strongly suggests that the transient may be SSS. BSSS is one of the most common benign variants with a broad range of prevalence ranging from 1.85% up to 24% of scalp EEG recordings. BSSS is usually seen in adults and is seldom seen in children.
Wicket Spikes or Wicket Rhythms
Wicket spikes or wicket rhythms are medium to high voltage, monophasic wave bursts in the range of theta or alpha range (6-11Hz). Wicket spikes occur in the anterior or middle temporal areas with a negative polarity, which usually evolves from the background as arcuate-shaped, brief (0.5-1 second) rhythmic discharges. Wicket spikes are most commonly seen in adults older than 30 years old during light sleep or in an individual whose background activity contains sharply contoured waveforms.
6 Hz Spike and Wave Discharges (“Phantom” Spike-wave)
6 Hz spike and wave discharges consist of a 4 to 7 Hz repetitive spike and wave complex with a mitten-like morphology. It is also called “phantom” spike-wave since it has a relatively low amplitude (less than 40 mV), fast spike (less than 30 ms) followed by a 5 to 7 Hz wave of equal or greater amplitude (figure 3). 6 Hz spike and wave discharges occur in young adult bilaterally, synchronously and predominantly during relaxed wakefulness, drowsiness or light sleep, and occasionally in REM sleep
2 types of 6 Hz Spike and Wave Discharges
The classical form is FOLD (Female Occipital Low-amplitude Drowsiness), which is relatively low in amplitude and is maximal over the posterior head regions. It is not associated with seizures.
The second form is WHAM (Wake High-Amplitude Male), which is frontally dominant, often moderate or high amplitude.
14 and 6 Hz Positive Spikes
14 and 6 positive spikes are best appreciated by using long interelectrode distances and ear referential montages. 14 and 6 Hz positive spikes consist of brief runs (less than 1 second) of positive spikes at a rate of 14 Hz or 6 to 7 Hz. The amplitude is variable but rarely exceeds 75 mV. These bursts typically consist of “negative” arciform waveforms located over the posterior temporal head regions, with alternating “positive” spiky components. This pattern occurs either bisynchronously or unilaterally (independent over the two hemispheres at different times). The 14 Hz pattern often looks like a sleep spindle with a sharp positive phase, although it’s location is quite different.
Rhythmic Mid-temporal Theta of Drowsiness (RMTDs)
They are bursts of rhythmical sharp waves at the range of theta, lasting for a few seconds, which often have a top-notched by a small 10 to 12 Hz component. They occur in mid temporal regions, either on one side or on both, either independently or simultaneously. The key features distinguishing RMTDs from abnormal electrographic discharges or other benign normal variants are there is little variability in morphology and frequency during the bursts. They often begin and end with a gradual increase and decrease of amplitude, but their overall frequency remains very stable throughout their appearance.
Subclinical Rhythmic EEG Discharge of Adults (SREDA)
Subclinical rhythmic EEG discharges of adults are the least common of benign variants with a prevalence of 0.04% to 0.07%. SREDA is characterized as symmetrical, diffuse, rhythmic monomorphic theta waves with sharp contours, maximally on the parietal and posterior temporal regions. In some cases, it is either asymmetric or unilateral. SREDA typically begins abruptly or is delayed 1 to several seconds after a single high amplitude mono- or bi-phasic sharp or slow-wave component. Once established, the pattern may consist of repetitive monophasic sharp waveforms in about 1 to 2 Hz and gradually evolve into a sustained sinusoidal 4 to 7 Hz pattern. This pattern may either end abruptly or gradually diminish and merge with the background. SREDA usually lasts about 40 to 80 seconds, but it may be shorter than 10 seconds or longer than several minutes.
Ohm’s Law
states that the electric current through a conductor between two points is directly proportional to the voltage across the two points.
Ohm’s Law equation
V=IR
V is the voltage across the conductor
I is the current flowing through the conductor
R is the resistance provided by the conductor to the flow of current.
Advantages of Ref Montage
- Amplitude can be used to localize the site of maximal involvement. *if the reference is inactive.
- Little distortion of frequency or waveforms.
- Diffuse discharges are frequently better appreciated on referential montages.
Advantages of Bipolar Montage
- Phase reversal in localization
- Usually display local abnormalities well
Psychogenic Nonepileptic Seizures (PNES), Psychogenic Nonepileptic Episodes (PNEE); otherwise known as
Pseudoseizures, psychogenic seizures, and hysterical seizures
Patients with non-epileptic seizures should…
be treated exactly the same as patients with epileptic seizures.
Non-epileptic events can be autonomic disorders, sleep behavior disorders, or psychiatric disorders that are occurring separate from or along with seizures.
Who was the first to report recording of spontaneous electrical activity from the brains of animals, though no initial written or photographic record was made?
Ricard Caton
hypopnea vs apnea
Hypopnea is when you take in shallow breaths for 10 seconds or longer and your airflow is at least 30% lower than normal.
Apnea airways are fully obstructed and breathing stops.
Who developed a one channel system for Fourier Analysis?
Fred Gibbs and Albert Grass
What is a differential amplifier?
Amplifies the difference in electrical potential between 2 inputs
Why is it important to use the same type of electrode? And same kind of metal?
*Different types of recording electrodes (e.g., between needle and metal cup surface electrodes) are likely to produce impedance mismatches, and thus noisy recordings.
*Dissimilar metals causing electrostatic artifacts
Otto Loewi
identified acetylcholine as a neurotransmitter
In laboratory tests, the term ‘specific’ means…
Its ability to designate an individual who does not have a disease as negative.
*A highly sensitive test means that there are few false negative results, and thus fewer cases of disease are missed.
What are the frequencies of Delta? Theta? Alpha? Beta? Gamma?
Delta= 3Hz or less
Theta= 4-7Hz
Alpha= 8-12Hz
Beta= 13-29Hz
Gamma= 30+Hz
