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.