Clinical Application of qEEG

EEG

EEG reflects the real-time functioning of brain synapses. EEG oscillatory signals recorded at the level of the scalp are mainly due to a sum of excitatory and inhibitory postsynaptic potentials generated by bundles of pyramidal neurons in the grey matter of the brain. Pyramidal cells are spatially aligned and perpendicular to the cortical surface, generating the current that can be recorded by EEG as scalp potentials.

Routine EEG recordings in the clinical setting are generally subjected to visual assessment and analysis, which is crucial for the investigation of certain neurophysiological phenomena such as epilepsy.

The Evolution of EEG to qEEG

The evolution of quantitative EEG (qEEG) from a simple measure of electrical power at different frequencies to a dynamic, network-based assessment tool reflects a paradigm shift in neuroscience. It acknowledges that brain functions, both healthy and disordered, arise from the complex, time-varying interactions between distributed neural populations.

Modern qEEG provides a non-invasive, relatively inexpensive, and temporally precise window into these complex processes. While it has limitations (e.g., spatial resolution compared to functional MRI (fMRI), susceptibility to artifacts), its ability to capture the real-time electrical symphony of the brain, its network harmonies, and its dissonant dysfunctions makes it an increasingly valuable instrument in research, clinical diagnostics, and therapeutic interventions. The ongoing integration of qEEG with other neuroimaging modalities techniques promises to unlock its potential in further understanding and treating the complexities of the human brain.

The temporal resolution of the EEG, together with the capability and reliability of modern source imaging algorithms, has converted the EEG to a fully fledged functional neuroimaging method that is not secondary to, but instead is a perfect companion to fMRI and other neuroimaging methods. (Schomer & Lopes da Silva, 2011)

qEEG

Objective and reproducible investigation of complex EEG signals requires quantitative or automated EEG analysis. qEEG analysis provides multi-perspective information about the EEG signal such as frequency components (spectral analysis), dynamic changes (temporal analysis) and spatial estimates of cortical sources (3D source analysis). In addition, qEEG provides reliable and quantifiable (numerical) results that can be further used in association and correlation studies.

The value of qEEG as a clinical application

qEEG has been used clinically in Belgium for over 30 years, both in Neurology and Psychiatry, and can not only boast extensive clinical experience but is also based on a technical study that can achieve high sensitivity with high specificity and has good reproducibility for different qEEG analysis methods. It can also demonstrate good to very good reproducibility. Despite this scientifically supported basis, controversy still exists, mainly from neurology, around the clinical value of qEEG. However, this is based on erroneous assumptions with some positions not scientifically supported, based on missing information and selective attention.

There are concerns about standards for test-retest reliability, normal variation, quality control by eliminating artefacts, quality control by eliminating statistical spurious effects, etc. However, these are issues that concern all medical, as well as scientific, test results that are part of the daily routine of the relevant specialist and have been sufficiently scientifically highlighted and can be avoided.

Finally, the qEEG, like any other technical examination, cannot be used as a stand-alone diagnostic tool. The qEEG is a tool to provide additional insight needed to obtain objective information in combination with other diagnostic-oriented evaluations to form a clinical opinion together with a history or to arrive at a most likely clinical diagnosis.

Author: Daniel Dumalin | Date: 21/09/2020 | Last update: 29/09/2025