Introduction: dEEG represents real technical advance, with numbers always available. Nevertheless, in most centers analysis continue limited to classic visual as in the past; qEEG may shed new lights in the EEG recording.
Objective: to develop and define new tools to boost EEG recording.
Method: since 2011 we record all EEG with a program named Monitor (Neurotec). It shows simultaneously 26 conventional EEG channels together with 4 Compressed Spectral Array (CSA) channels, which are user definable. We compare left to right fronto-temporal and centro-occipital derivations, focusing in the spectra from 0.5 to 20 Hz. CSA spectra is seen as “hills an valleys” depicting each frequency in a distinct color: delta is black, theta is red, and alpha is blue and beta, violet. Recently new tools were added: a time marker a spectral edge frequency marker (90%) and an asymmetry index comparing anterior and also posterior CSA channels – the assumption was that this index would improve and allow “hills” difference measurement.
Results: Monitor permits to better observe some aspects, such as didactic: blue alpha hills during wakefulness, its block during eyes opening and its effacement during drowsiness. It also permits the observation of EEG background limit values or slowing, with spectra climbing red (theta) and going down blue (alpha). Violet hills from sleep spindles occurring discontinuously and violet hills of beta drug induced effect may also be seen. Artifacts must always be considered and time is necessarily spent learning its recognition. Clinical application may involve hemispheric asymmetries evaluation. It is important if new data are revealed, especially when accompanied by clinical and therapeutic implications.
Asymmetry index is very useful online during EEG acquisition, but some considerations are mandatory: paroxysms are better viewed in classical EEG; the presence of artifacts, either short lived (electrode pops) or presented as long runs of blinking also require visual EEG analysis. Clinically more important is evaluation of persistent or intermittent asymmetries. Comparison of different records from the same patient may benefit from numerical scales measuring the differences.
Conclusion: Since raw EEG channels are always and simultaneously available, observation of these new tools – CSA and asymmetry index – should not negatively interfere with the interpretation. The risk of magnifying or enhancing asymmetries will be compensated and ascertained under the clinical “filter” validation.