How to interpret EEG
Questions
- age? if older than 12yo EEG will look like adult EEG
- on sedation?
- montage?
Looking
Analyze the first page carefully, and then you move one
Adjust: time base 15 mm/sec, sensitivity 7-10 uV/mm, and HFF (hyperfiltration) 30 Hz; avoid dec more the HFF because will not differ spike & wave
How to write an EEG report
State of patient
- awake, drowsy, or sleep stages
*look at the eyes open&close w/ later alpha-rhythm means awake&alert
Descritpion of record
a) PDR: present or not present and frequency.
*5% of normal individuals do not have
*more commonly seen during photic stimulation, in rEEG
b) background: waveform organization in 1st page
- symmetric - analyze R&L amplitude & frequency
- continuous vs intermittent - pauses or not
- anterior posterior gradient - normally the frontal areas have lower amplitude waves while the posterior areas have higher amplitude waves – PDR is usually alpha waves
c) predominant frequency
d) state change: describe sleep architecture
e) stimulations: photic stimulation (adequate photic driving response)
f) epileptiform abnormalities or any other abnormalities
g) seizures: describe whether there were seizures or not.
Some tips
-Auricular areas usually pick up EKG artifacts located in the temporal region
-Beta waves – think benzos vs barbiturates
-Myogenic Artifacts are usually very high frequencies that you cannot count within 1 s
-Sharps usually have slow waves right after, stand out from the background and should have a field (not seen in a single electrode but also in adjacent electrodes with consistent morphology and voltage gradients; sharps generally appear in multiple contiguous electrodes – like sharp in F3 might also be seen in C3 and F7 with decreasing amplitude as you move away from the focus; also check for phase reversal between two electrodes suggests the sharp is maximal at the electrode where the reversal occurs).
-Focal delta waves are usually reliable indicators of focal cerebral abnormalities or structural abnormalities in that area
-In drowsiness, usually see slow rolling eye movements (SEMs) in frontal region, more common theta and delta waves, decreased eye blinks and myogenic artifacts from movements
Example of report
Smartphrases
Normal EEG description:The patient progresses through wakefulness, drowsiness, and stage II sleep during the recording. The posterior dominant rhythm is present, and reaches 10 Hz. The background during wakefulness is comprised of moderate-amplitude, well-organized, predominant alpha and beta. There is clear state change, with normal sleep architecture including vertex waves and sleep spindles recorded. The patient underwent intermittent photic stimulation without clear photic driving response. There were no epileptiform abnormalities. No clinical or electrographic seizures were recorded.
Ceribell procedure description: This EEG was obtained using a 10 lead EEG system positioned circumferentially without any parasagittal coverage (rapid EEG). Computer selected EEG is reviewed as well as background features and all clinically significant events.