EEG - Common patterns
Wave frequency
BAT-D
- beta: 12-30 Hz
- alpha: 8-12 Hz
- teta: 4-8 Hz
- delta: < 3Hz
Seizures and epileptiform discharge
Brain rhythmic activity that evolves
- sharps can increase and dec frequency, and the dec freq will be considered slowing
- focus based on amplitude and find the begining and how it spreads
- theta sharps can suggest underlying cortical irritability
- burst and suppression
*during sedation the freq can inc and dec
Out
- returning from MRI
- look at EEG to figure out the lead that is off
- EEG alert: amplitude saturated
- what to do:
> check ECG
* if c/f brain death, check sensitivity on 2 uV/ mm; specific montage called ECS (electrocerebral silence); stimulation w/ sternal rub required; check differential not only bipolar
> check yellow-green-red first leads
> press all the leads
Age EEG
- peds are beta range
Eyeblink
> bells phenomenon
> front of the eye is positive and back is negative
> look for closing, followed by alpha rhythm
Breach rhythm
> structural
Photo driving
- look at photic stimulation, and see driving response
> abnormal if unilateral
Bed precautions
> look at video EEG recording when you see a seizure, bed precautions can imitate seizures
> also, look at the flowsheet for bed precautions when ceribell
Posterior dominant rhythm (PDR)
> look at parietal and occipital regions
Muscle artifacts
> chewing
> ventilator - biting the tube
Sweat artifact
- NaCl, very low frequency oscillations (<1 Hz)
Sedation
- beta activity, inc & dec frequency
Sleep
Divided in stage I, stage II, slow wave and REM:
1) Stage I: normal to see positive occipital sharp transients of sleep (POST) – look like isosceles
triangle - and vertex waves (specially central regions)
2)Stage II: spindles, k complexes. K-complexes can also be evoked by auditory stimuli like a
knock (remember “K” for knock”)
3) REM sleep – EEG will look like “awake” but without eye blink artifacts. Can see lateral eye
movement artifacts
*During sleep state, amplitudes are usually higher in central areas