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Brain Mapping (QEEG)

Tallahassee Neuro-Balance Center offers state-of-the-art assessments of brain imbalances in patients with dementia, brain injury, and cerebro-vascular disorders as well as learning and behavioral problems with the assistance of Quantitative EEG (QEEG), an advanced neuro-diagnostic technology, which measures the different frequencies of electrical activity that are generated from the brain. These frequencies called delta, theta, alpha and beta provide the clinician with information concerning the active state of various regions of the brain, effectively producing a map of the brain’s activity. 

Brain maps have been found to be abnormal in various neurological disorders ranging from ADD, ADHD and epilepsy, to Alzheimer's disease and traumatic brain injury. 

Quantitative EEG Analysis

The Quantitative EEG (QEEG or brain mapping) analysis compares the electrical activity generated from your brain with a database of normal individuals. This can help locate areas of abnormal functioning in the brain and also shed light on the nature of those abnormalities. As with all tests performed during a functional neurological assessment, the physician’s interpretation of the QEEG includes careful consideration of other signs and symptoms that a patient presents with when interpreting the QEEG. Without consideration of the presenting complaints and other examination findings the QEEG has less value. 

3D localization of abnormal brain function is now also possible with more detailed analysis of the QEEG data. This is referred to as LORETA, or Low Resolution Electromagnetic Tomographic Analysis. Additional analysis using LORETA can significantly enhance the clinical usefulness of the QEEG assessment. See below for more information about undergoing a QEEG brain mapping assessment.

Undergoing a QEEG Brain Mapping Assessment

A standard QEEG assessment takes approximately an hour to complete. A technician will measure the patient's head which allows for correct placement of the electrodes or EEG cap. These positions are standardized so that data from different laboratories or clinics can be compared more easily to one another. 

The skin at each location is then cleaned and prepared to ensure good electrode contact and therefore, good conductance of electrical signals from the brain to the electrodes. A small amount of paste or gel is applied between the electrode and the scalp to further enhance signal conductance and the contact is reinforced by the use of an adhesive tape. Patient preparation may take 15 - 30 minutes using this approach. This cap is anchored to the patient using elastic straps and connected to the EEG system via a strap that contains all of the information from the "built-in" electrodes. A small amount of gel is placed into each of the holes to enhance conductance of the EEG signals. This approach is used depending on specific patient circumstances and can be performed in a shorter amount of time.


After the patient is prepared, the EEG recording will be performed lasting between 20 and 25 minutes. The patient will be asked to remain quiet, still and as relaxed as possible for approx. 10 minutes with their eyes closed and then again with their eyes opened. Subsequent recordings may be performed during specific tasks such as auditory and visual recall/memory tasks, reading and mathematical tasks, hyperventilation or other tasks that may evoke changes in the EEG. After completion of all recordings, the electrodes (or the electrode cap) are removed and excess gel or paste is cleaned from the scalp. The data is then transferred to another computer for detailed analysis.

Visual inspection of Raw EEG Data

The first part of the analysis involves inspection of the raw EEG waveforms. Abnormal shapes, amplitudes or frequencies of brainwaves can provide significant clues to the existence of specific nervous system disorders including epilepsy. In some cases, information from this part of the analysis may be essential in diagnosing the patient's problem and determining the best course of action. It is also necessary for eliminating ‘'artifacts'’ (various forms of interference to the EEG signal) prior to the quantitative analysis.

Absolute Power 

This term refers to the amount of activity within a specific frequency band of brain waves. The activity in each frequency band is shown in the examples below in order of slowest (left)-Delta to fastest (right) Beta. Activity in each frequency band is compared to a normative database to determine the presence of suspected abnormalities. The results for each frequency band are shown with the topographic activity maps. In the example shown below, green is the color representing average activity. Red means there is a large increase in activity, yellow-moderate increase in activity when compared to the normative database, while blue means there is a large decrease.

Relative Power

This term refers to the relativeamount of activity within a specific frequency band compared to all the otherfrequency bands. Relative activity in each frequency band is compared to anormative database to determine the presence of suspected abnormalities. Theresults for each frequency band are shown with the topographic activity maps.In the example shown below, green is the color representing average activity.Red means there is a large increase in activity, yellow-moderate increase ofactivity when compared to the normative database, while blue means there is alarge decrease.

Coherence

This term refers to the similarityin EEG waves over different areas of the brain, i.e., the timing of activity inone area compared to another. Coherence in each frequency band is compared to anormative database to determine the presence of suspected abnormalities. Theresults for each frequency band are shown with the topographic connection maps.Thick lines represent larger deviations from “normal” – red refers to increasedcoherence, while blue refers to decreased coherence.

Asymmetry


This term refers to the relationship between the amounts of activity in onearea of the brain compared to another. Inter-hemispheric-means differencesbetween each side of the brain, while intra-hemispheric mean differencesbetween areas on the same side of the brain. 

Asymmetry in each frequency band is compared to a normative database todetermine the presence of suspected abnormalities. The results for each frequencyband are shown with the topographic connection maps. Thick lines representlarger deviations from “normal” – red refers to increased asymmetry, while bluerefers to decreased asymmetry.

LORETA Analysis


3-D source localization using LORETA (low resolution electromagnetictomographic analysis) produces 3 dimensional images that reflect patterns ofactivity in your brain. Each image demonstrates activity in different regionsof the brain at different frequencies. The big advantage of LORETA testing whencompared to QEEG only is the ability to find functional abnormalities in thedeeper structures of the brain-very similar to functional magnetic resonance(fMRI) of the brain but at much lower cost.