intro to qeeg
TRANSCRIPT
Quantitative Electroencephalography
Aharon D. Shulimson, Ph.D.Attention Disorders Clinic
Murray, Utah801-281-3188
A number of brain imaging techniques have been used to study the relationshipbetween mental illness and abnormalities in the brain. These methods includemagnetic resonance imaging (MRI), positron emission tomography (PET), singleproton emission computerized tomography (SPECT) and quantitative electro-encephalography (QEEG). As noted by Hughes and John in their 1999 review ofQEEG, “Evidence from these brain imaging methods has unequivocally establishedthat mental illness has definite correlates with brain dysfunction.”
More than 500 EEG and QEEG studies have demonstrated electrographiccorrelates of mental illnesses including ADD/ADHD, depression, Obsessive-Compulsive Disorder, Anxiety, schizophrenia, bipolar disorder and substanceabuse. Clinical correlates of traumatic brain injury, learning disabilities anddementia have also been found.
The purpose of a quantitative EEG is to compare a patient’s brain wave activity tothat of the average person of his/her age and look for clinical correlates ofADD/ADHD and other conditions. A report is generated which includesdiagnostic impressions and recommendations for neurofeedback, a form of therapythan can remediate EEG abnormalities. Implications for medication management,based on QEEG research, are also discussed. QEEG has many advantages overMRI, PET and SPECT. It is non-invasive, less expensive than the other brainimaging modalities and provides information on a much greater range of brainfunctioning. The test is performed in the provider’s office.
QEEG data is recorded from 19 locations on the scalp, using the International10-20 electrode placement system. The ears are used as references. Ten minutes ofeyes closed and ten minutes of eyes open data are digitally recorded. Data can alsobe recorded during task conditions, such as while reading or doing math. The datafiles are edited to remove artefacts (eye blinks, eye rolls, EMG, drowsiness, event-related potentials, etc.).
The Attention Disorders Clinic uses normative data bases to analyze QEEG data.These include NeuroGuide, NeuroRep, NxLink and LORETA. Statistical data, intable and topographic map formats, is reported on absolute and relative power inthe four primary brain wave bands, amplitude asymmetry, phase and coherence.Discriminant function equations that look for signs of ADHD, TBI and otherconditions are calculated by two of the databases. A typical QEEG produces over100 pages of tables and maps for each patient.
Topographic maps display EEG data in the form of colorcoded Z-scores. EEG activity that is in the range of +/- 1.0 Z-scores is considered to be within normal limits. Activity that is+/- 1.5 Z-scores or more is evaluated to determine if it isclinically significant when placed in the context of thepatient’s history and current problem(s). This map, taken fromthe NeuroGuide database, shows normal relative power thetaalong with mildly elevated activity in the right occipital area.
Brain Wave BandsThere are four primary brain wave bands, which are measured in Hertz (Hz, wavesper second). Beta (12-30 Hz), the fastest of the primary bands, is associated withexternal focus and concentration. Alpha (8-12 Hz) reflects the brain being in an“idling” or relaxed state. Theta (4-8 Hz) is associated with being highly internallyfocused at the upper end of the band (6-8 Hz) and with being drowsy and on theverge of falling asleep at the lower end (4-6). Delta (0-4 Hz), the slowest waves,are prominent during sleep. The brain produces all of these waves continuously,but the relative amount of each being produced changes depending on what activitythe person is engaged in.
Absolute PowerAbsolute power is a measure of the electrical activity occurring in each of the brainwave bands as compared to what is normal for a person’s age. A patient can have a“high power” or “low power” brain and still function normally if there are noabnormalities in relative power.
Relative PowerRelative power is a measure of the balance of activity in each of the brain wavebands compared to the others. Clinical correlates of ADD/ADHD include elevatedrelative power amplitude in the theta, alpha and beta bands. Patients with elevatedtheta activity, particularly in combination with low beta, typically respond well totreatment with stimulant medications. Excess alpha can be treated with a stimulantor SSRI. Patients with the high beta type of ADD/ADHD respond to treatmentwith Tenex or a mood stabilizer. QEEG results frequently show that a patient haselevated amplitude in more than one of the bands, suggesting the need for multiplemedications. Persons with a combination of elevated theta and beta often aresuccessfully managed with a stimulant and mood stabilizer.
Elevated relative power theta and/or alpha is often seen following traumatic braininjury. High amplitude theta is also found in fibromyalgia patients who have “fibrofog.” Excess relative power beta activity is seen in patients with chronic pain.
This example, which is from the NxLink database, indicates relativepower theta amplitude that is between 2.0 and 3.0 Z-scores aboveaverage.
Power RatiosThe ratio of power between brain wave bands can provideinformation that is helpful in making a diagnosis and treatmentrecommendations. For example, extensive research has shownthat an elevated theta/beta ratio is indicative of a type ofADHD that is likely to respond well to treatment with stimulantmedications.
Amplitude AsymmetryAmplitude asymmetry is an indication of the relative balance of electrical powerbetween parts of the brain. Frontal alpha asymmetry (left > right) is a clinicalcorrelate of depression. Frontal beta asymmetry (right > left) is a correlate ofanxiety.
CoherenceCoherence is a measure of shared electrical activity betweensites on the cortex and is considered to be an indication ofefficiency of brain functioning. Hypercoherent sites areworking too closely with each other and are devoting toomuch brain resources to performing tasks. Hypocoherentsites are not working closely enough to perform efficiently.Coherence deviations are often seen in persons with traumaticbrain injury and ADD/ADHD. This is an example of betahypercoherence in a person who suffered a mild traumaticbrain injury
PhasePhase is a measure of the speed with which electrical signals are traveling from onepart of the brain to another. Phase deviations suggest abnormalities in informationprocessing. Information that is moving too quickly or too slowly through thecortex cannot be processed effectively. An analogy can be drawn between phaseand baseball. A pitch thrown at medium speed is easy to hit. When a fastballcomes at you, you may not have enough time to react in order to connect with it. Ahigh, slow pitch can be hard to get a fix on. Phase deviations can present asattention problems.
The following pages contain samples of quantitative EEG topographic maps frompatients with ADD/ADHD and other conditions with impaired attention.
Sasha BartellEyes Closed 09/16/2005
Scottsdale Neurofeedback Institute8114 E. Cactus Rd., Suite 200
Scottsdale, AZ 85260
15
DB Relative Beta 4 (24-28 HZ)
Brodmann area 20
Inferior Temporal Gyrus
Temporal Lobe
Sasha BartellEyes Closed 09/16/2005
Scottsdale Neurofeedback Institute8114 E. Cactus Rd., Suite 200
Scottsdale, AZ 85260
16
Sasha BartellEyes Closed 09/16/2005
Scottsdale Neurofeedback Institute8114 E. Cactus Rd., Suite 200
Scottsdale, AZ 85260
17
DB Relative Beta 5 (28-32 HZ)
Brodmann area 20
Inferior Temporal Gyrus
Temporal Lobe
Sasha BartellEyes Closed 09/16/2005
Scottsdale Neurofeedback Institute8114 E. Cactus Rd., Suite 200
Scottsdale, AZ 85260
18
Trevor LiteraEyes Closed 08/29/2005
Scottsdale Neurofeedback Institute8114 E. Cactus Rd., Suite 200
Scottsdale, AZ 85260
13
DB Relative Beta 3 (20-24 HZ)
Brodmann area 24
Anterior Cingulate
Limbic Lobe
