Normal variant Flashcards
What is Subclinical Rhythmic Electrographic Discharge of Adults (SREDA)?
5-7 Hz, sharp and slow waves lasting 40-80 seconds, typically in individuals 50+ years old, seen at T5/T6 + posterior regions, associated with drowsiness
SREDA is characterized by specific wave patterns and age demographics.
What are the frequency ranges for the Slow Alpha Variant and Fast Alpha Variant?
Slow Alpha Variant: half the alpha frequency; Fast Alpha Variant: double the alpha frequency
These variants may appear in only one hemisphere.
What is the frequency range for Alpha waves?
8-13 Hz
Alpha waves have an average voltage of 50 µV.
How does Alpha wave amplitude differ between hemispheres?
Non-dominant hemisphere is 50% taller
This characteristic can indicate lateralization of brain activity.
What happens to Alpha waves with eye opening and mental alerting?
Alpha attenuates
This phenomenon is known as QNDP (Quantitative Neurophysiological Data Processing).
Where are Posterior Slow Waves of Youth (PSWY) primarily located?
Occipital region
PSWY is seen in children and young adults, attenuates with eye opening, and disappears in sleep.
What is the frequency range for Beta waves?
14-30 Hz
Beta waves are associated with benzodiazepines and barbiturates.
What is the frequency range for Mu waves?
7-11 Hz
Mu waves are primarily located at C3/C4.
What is the characteristic of Rhythmic Mid-Temporal Theta of Drowsiness (RMTD)?
5-7 Hz, may have a notched peak, lasts from 1-2 seconds to 1 minute
RMTD is observed during drowsiness.
Where are 14 and 6 Hz Positive Spikes maximal?
Maximal in posterior temporal, also seen elsewhere
14 Hz spikes are more common in older children and adolescents, while 6 Hz spikes appear in early childhood and adults.
What is the voltage range for Lambda waves?
20-30 µV
Lambda waves have a bi/triphasic waveform and a positive polarity.
What are Wicket Spikes characterized by?
6-11 Hz, less than a second duration, observed in mid-temporal region
They occur during drowsiness and light sleep.
What is the frequency and characteristic of the 6 Hz Spike and Wave (phantom)?
5-7 Hz, low voltage, rhythmic 1-2 seconds
It can be diffuse or anteriorly/posteriorly predominant during drowsiness and light NREM sleep.
What defines Benign Epileptiform Transients of Sleep (BETS or SSS)?
Fast spike without slow wave, seen in ages 30-60, phase is surface negative
They are associated with drowsiness and light sleep.
What is the frequency range for Midline Theta Rhythm (Ciganek)?
5-7 Hz
Maximal at Cz or Fz and observed during wakefulness and drowsiness.
What are Benign Spike-Like Patterns (BETS)?
Includes:
* Small sharp spikes (SSS)
* Wicket spikes
* 14 - 6 Hz positive bursts
* 6 Hz spike and wave
BETS are typically benign and observed in specific conditions.
Who typically exhibits Small Sharp Spikes (SSS)?
Adults aged 30 - 60 years
SSS are observed during drowsiness and non-REM sleep.
Where are Small Sharp Spikes (SSS) highest in amplitude?
Over temporal regions
* Both hemispheres
The best montage for observing SSS is referenced in EEG studies.
What are the characteristics of Small Sharp Spikes (SSS) discharges?
- Low voltage & amplitude
- Short in duration
Morphologically, SSS can be monophasic or diphasic.
In which conditions are Small Sharp Spikes (SSS) seen?
- Cerebrovascular disease
- Syncope
- Psychiatric disturbances
These conditions often present with SSS on EEG.
Who typically exhibits Wicket Spikes?
Adults older than 30 years
Wicket spikes occur during drowsiness, light sleep, or when awake.
What does Wicket Spikes look like?
Mu rhythm frequency of 6-11 Hz with clusters of surface negative waves
Wicket spikes are seen bilaterally and independently.
How can you differentiate Wicket Spikes from real seizure discharges?
- No slow wave component following wicket
- Trains or isolation
- Doesn’t disrupt background
These features help in distinguishing between wicket spikes and seizures.
Who are more likely to exhibit 14 - 6 Hz positive bursts?
Children & adolescents, peaking at ages 13-14 years
These bursts are observed during drowsiness and non-REM sleep.
Where are 14 - 6 Hz positive bursts typically observed?
Temporal regions, both hemispheres
The appearance resembles trains of arch-shaped waves with spiky components.
In which conditions are 14 - 6 Hz positive bursts seen?
- Comatose patients with acute hepatic failure
- Mostly with Reye’s syndrome
These bursts are indicative of certain pathological states.
Who typically exhibits 6 Hz spike and wave patterns?
Adolescents & young adults
This pattern disappears during deeper sleep.
What does the 6 Hz spike and wave pattern look like?
Low voltage, fast frequency with slow waves higher than spikes
This pattern is associated with specific characteristics like WHAM and FOLD.
What does WHAM stand for in the context of 6 Hz spike and wave?
Wake, High amp, Anterior, Male
If WHAM is slower than 5 to 6 Hz, the discharge is likely a seizure tendency.
What does FOLD stand for in the context of 6 Hz spike and wave?
Female, Occipital, Low amp, Drowsiness
This pattern is mostly benign.
What are some rhythmic patterns with an epileptiform morphology?
- Rhythmic temporal theta bursts of drowsiness
- Subclinical Rhythmic Electrographic Discharge in Adults (SREDA)
- Midline Theta Rhythm
- Breach Rhythms
These patterns can be important for diagnosis in EEG readings.
Who typically exhibits Rhythmic temporal theta bursts of drowsiness?
Adolescents & young adults
These bursts occur during relaxed wakefulness and drowsiness.
What are the characteristics of Rhythmic temporal theta bursts of drowsiness?
- 5 to 7 Hz
- Can increase in amplitude at onset
- Decrease at end
These bursts can sometimes be bilateral.
How can you differentiate Rhythmic temporal theta bursts of drowsiness from ictal discharges?
- Does not evolve in frequency or morphology
- Brief durations (few seconds)
- Lack of disruption of background
These features help in distinguishing theta bursts from seizures.
Who typically exhibits Subclinical Rhythmic Electrographic Discharge in Adults (SREDA)?
Adults over 50 years
SREDA often occurs with hyperventilation, drowsiness, or resting.
What does SREDA look like?
Rhythmic sharply contoured waveforms evolving to 5-6 Hz
This pattern starts abruptly and can end abruptly or gradually.
Who typically exhibits Midline Theta Rhythm?
Children and adults
This rhythm is observed when awake and drowsy.
What are the characteristics of Midline Theta Rhythm?
- Smooth, sinusoidal arciform
- Spikey or mu appearance
- Lasts 4-20 seconds
Recorded over midline electrodes.
Who can exhibit Breach Rhythms?
Any age with a skull defect
Breach rhythms are associated with structural abnormalities in the skull.
What are Lambda Waves?
Positive triangular waves present when viewing an image using lateral scanning
Seen in occipital regions during wakefulness, more common in children; blocked by eye closure or looking at a blank page, and sleep.
What is the frequency range of Mu Rhythm?
8-10 Hz
Negative arch shaped rhythm, prominent at C3 and C4, typically unilateral or asymmetrical.
What is Hypnagogic Hypersynchrony?
A normal variant of drowsiness in children aged 3 months to 13 years characterized by paroxysmal bursts of high-voltage sinusoidal waves
These bursts occur at 3-5 Hz and are maximally expressed in the prefrontal-central areas.
What are Wicket Spikes?
Midtemporal spikes that occur during drowsiness
Often occur in short trains or clusters, frequently 6-11 Hz.
Where do BETS/SSS occur?
In light sleep (non-REM 1 and 2 sleep)
Located frontal, temporal uni- or bilateral, more common in adults.
What characterizes the 6 Hz spike and wave pattern?
A small spike followed by a slow wave with a frequency of 4-7 Hz
Bursts last less than 1 second and can appear in awake state, sometimes activated by photic stimulation.
Fill in the blank: 14 & 6Hz Positive Spikes are maximal over _______ regions.
posterior temporal and occipital
What defines POSTS?
Positive Occipital Sharp Transients of Sleep, similar to lambda waves but observed during sleep
Occur singly or in runs of 4-5 Hz, rarely seen before 5 years.
What is an Alpha Squeak?
A transient increase in alpha frequency immediately following eye closure
What are the two types of Normal Variant of Alpha?
- Slow - half of ongoing PDR
- Fast - double PDR (harmonic)
Barbiturates can also cause this; attenuates with eyes opening.
What characterizes Posterior Slow Waves of Youth?
Variation of alpha composed of delta activity intermixed with alpha frequency
Most often seen in ages 8-14, disappears in stage 1 sleep, increases with hyperventilation.
What is RMTD?
Rhythmic Mid-Temporal Theta of Drowsiness, resembling ictal discharge during complex partial seizures
5-7 Hz frequency, maximal over mid-temporals but can spread.
What is Midline Theta Rhythm?
A 5-7 Hz discharge most prominent over Cz but spreading to parasagittal leads
Seen in relaxed wakefulness and drowsiness in adults and kids.
What is SREDA?
Subclinical Rhythmic Electrographic Discharge in Adults, present in rest or drowsiness
Can look like ictal discharge but no change in consciousness.
What is Breach Rhythm?
Present over skull defects
Not considered benign variant but can be confused with ictal and interictal epileptiform activity.
What describes hypnopompic hypersynchrony?
A normal variant of arousal in children aged 3 months to 13 years characterized by paroxysmal bursts of high-voltage sinusoidal waves
Similar to hypnagogic hypersynchrony, maximally expressed in the prefrontal-central areas.
Describe rhythmic mid temporal theta of drowsiness (RMTD)
Sharply contoured trains of 4-7hz theta activity
Temporal and central location, notched look, occurs in a state of drowsiness or relaxed wakefulness
What are Positive Occipital Sharp Transients of Sleep (POSTS)?
Positive 4-5 hz theta waves in the occipital regions
Occurs in stages 1 and 2 of sleep
Describe Lamda and its occurrence
Positive 4-6 hz theta waves in the occipital regions
Occurs in the wake state with EO with visual input such as reading, scanning an image
Describe the temporal alpha rhythm and its occurrence
Alpha range activity located in the temporal regions
Occurs in wave state, seen only in some patients with skull defect
Describe Mu and its occurrence
Negative arch shaped 7-11hz, located in c3/c4
Can occur unilaterally or bilaterally, often shifting side to side, does not attenuate with EO, occurs in wake state, attenuated by having patient make fist with contralateral hand
What are benign sporadic sleep spikes also known as?
Small sharp spikes (SSS) and benign epileptiform transients of sleep (BETS)
Low voltage sharp waves that occur on one or both sides in the temporal and frontal regions, may mimic EKG artifact, seen often in referential montage, occurs in stage 1-2 sleep
Describe subclinical rhythmic electrographic discharge of adults (SRDA) and its occurrence
Periodic sharp activity most often in parietal regions that progresses into a rhythmic theta pattern usually @ 5-7 hz
Occurs in waking state of older patients
Name 3 characteristics that define and describe EEG waveforms
Amplitude, frequency, location
Describe phantom spike and wave and its occurrence
6hz spike and wave
Posterior or midparietal low voltage spike and wave or in brief bursts, occurs with drowsiness
State the frequencies of normal EEG patterns
Beta- greater than 13 hz, Alpha- 8-13hz, Theta- 3.5-7.5 hz, Delta- 3hz or less
Describe fast alpha variant and its occurrence
16-20hz posterior rhythm
Can be 2x patients’ alpha, occurs awake with EC, attenuates with EO
Describe 14 and 6 positive spikes and their occurrence
Sharply contoured trains of 14 & 6 hz spike waves in the posterior region maximal @ t5(p7) and t6 (P8)
Best seen in contra ear reference, occur in a state of drowsiness or stage 1 sleep
Describe Wicket Spikes and their occurrence
Sharply contoured waves located in the temporal regions
Seen bilaterally or independently, no slow wave following, occur in drowsiness or stage 1 sleep
Describe slow alpha variant and its occurrence
A sub harmonic of posterior dominant alpha rhythm often noticed and occurring @ 4.5-5 hz
Occurs in wake state with EC, attenuates with EO
When the patient’s PDR increases in amplitude and frequency immediately following eye closure it is known as:
Alpha Squeak
T or F: Superharmonic alpha should be temporary
TRUE
When the PDR is present in one hemisphere only, it is known as:
Bancaud Phemonena
Mu voltage is:
20 - 50 µV
The rounded portion of the Mu rhythm is:
Positive
Where is Mu seen?
Centrals
In what state(s) is Ciganek Rhythm seen?
Drowsiness and Wakefulness
How long does midline theta rhythm last?
< 20 seconds
A waveform that has a fast spike of 30 msec followed by a theta slow wave of equal or higher amplitude would be:
Phantom Spike & Wave
T or F: 6 Hz Spike & Wave can be seen in relaxed wakefulness, drowsiness, light sleep and N2 sleep in young adults.
FALSE
T or F: If there are discharges seen in the frontal regions of a male patient that are 6 Hz or faster - that would be a normal variant.
TRUE
14 & 6 Hz Positive Bursts are seen in adolescents in what state?
Drowsiness
Where are 14 & 6 Positive Bursts seen with the maximum amplitude?
Posterior Temporals
Benign Sporadic Small Spikes of Sleep is also known as:
Small Sharp Spikes & Benign Epileptiform Transients of Sleep
What are the characteristics of RTTD?
Rhythmic, Lasting between 5 - 15 seconds, Can be seen unilateral or bilaterally, Present in the temporal region, Seen in drowsiness
Medium to high voltage discharges with theta to alpha frequency that occurs in the mid temporal regions with negative polarity would be:
Wicket spikes
SREDA would be found in what type of patient populations?
Adults and elderly
SREDA seen in the frontal region that is seen during sleep would be:
Atypical SREDA
What is the voltage expected for POSTs?
50 - 100 µV
The background of a normal awake adult with eyes closed is typically:
10 Hz
Alpha blocking describes:
The absence of alpha during awake when the eyes are open
T or F: An alpha rhythm that is consistently slower than 8 Hz in the elderly is normal.
FALSE
The cause for the amplitude asymmetry in alpha rhythm for adults and pediatrics can be due to:
Skull thickness
Alpha asymmetry of ____ is considered abnormal.
50% or more
Alpha rhythms seen in the central regions is called:
Mu rhythm
Mu rhythm can be attenuated by:
Contralateral limb movement or thinking of moving the contralateral limb
What pattern is seen between 14 Hz - 30 Hz?
Beta rhythm
Barbiturates and benzodiazepines enhance:
beta
T or F: A 50% or greater amplitude asymmetry between the hemispheres is abnormal for beta waves.
TRUE
The first EEG sign of an acute cortical injury is:
Constant, depressed beta activity
Enhanced beta rhythm due to skull defect is:
Breach rhythm
EEG activity that is difficult to pick up using scalp electrodes is:
Gamma waves
Theta waves are defined as:
4 - 8 Hz
Delta waves are defined as:
< 4 Hz
T or F: Persistent delta activity along with theta and alpha is normal during wake.
FALSE
Posterior slow waves of youth occur maximally at what age?
9 - 14 yrs of age
Clear POSTs are seen around what age?
7 yrs old
T or F: Alpha is taller in the dominant hemisphere.
FALSE
What is the voltage expected for wicket spikes?
60 - 200 µV
What are the characteristics of wicket spikes?
6 - 11 Hz, Sharply contoured, arch shaped, Originates in the mid temporal regions, Seen in drowsiness and light sleep, No after going slow wave and no background disruption
Abrupt, repetitive monomorphic sharp discharges would be:
SREDA
