What can qEEG measure, and what can it not answer?
A qEEG report can look exact because it uses colors, percentiles, and z-scores. First check whether the recording was clean and whether the result changes a real medical decision. Sleepiness, eye or muscle movement, poor electrode contact, medicines, caffeine, migraine, pain, anxiety, and illness can change the map. Age, device, reference, and the comparison database also matter.
Power and frequency
How much measured activity sits in named frequency bands
Absolute and relative delta, theta, alpha, and beta power, plus peak alpha frequency, depend on the state, band boundaries, reference, artifact removal, age, and software.
Relationships
How readings compare across scalp locations
Asymmetry, coherence, phase, and other connectivity measures are mathematical relationships. Scalp location is not a direct picture of one brain area's function or damage.
Database distance
How far a value sits from one reference model
A z-score places a measure in standard-deviation units relative to a named model. Database age, country, device, montage, reference, state, and batch can change that comparison.
The map cannot by itself diagnose ADHD, concussion, Long COVID, ME/CFS, depression, dementia, epilepsy, dishonesty, or a cause of brain fog. It also cannot choose neurofeedback, medicine, supplements, or a treatment package. The raw EEG, technical quality, history, examination, standard diagnostic workup, and decision the result changes come first.
Save this test
Save the report, test method, and symptoms it was compared with
File the raw EEG conclusion and full quantitative method with the highlighted measures, z-scores, recording conditions, symptoms, function, and clinician explanation. A later reader can then see the method behind each color or number.
My Fog stores the report and details you enter. It does not analyze the raw EEG or calculate z-scores. A clinician must diagnose conditions, check the map, and choose treatment or repeat testing.
How do age, sex, pregnancy, sleep, medicines, illness, device, and database change qEEG results?
qEEG values change with age, recording state, device, and test method. Some databases include sex, but there is no single brain-map cutoff for males, females, pregnancy, or any life stage.
Babies and young children
EEG changes quickly during early development. A child needs a pediatric neurophysiology service, a developmentally suitable recording, and a database that actually includes the child's age. Do not apply an adult color map or adult frequency expectations.
Children and teenagers
Children have more low-frequency delta and theta activity than adults, and alpha features change with maturation. The FDA NEBA clearance covers ages 6 through 17 for one narrow ADHD-aid use, not every qEEG map. Pediatric methods still vary enough that age alone cannot rescue a poorly matched database.
Adult women and men
Ask which reference database and sex categories were used, and apply the same technical quality checks to every result. Some measures differ by sex in research datasets, but there are no universal separate male and female diagnostic maps. Symptoms, function, sleep, medicines, migraine, mood, and the clinical question remain more important than a demographic label alone.
Pregnancy and the months after birth
There is no established generic pregnancy or postpartum qEEG diagnostic range. Record gestational week or months after birth, sleep disruption, headache, blood pressure, anemia, thyroid symptoms, medicines, and any seizure history. New severe headache, visual change, weakness, seizure, marked confusion, or very high blood pressure needs maternity or emergency assessment, not a commercial map.
Older adults
EEG features change with age, so an older person needs an age-matched group. Medicines, sleep, hearing, vision, blood-vessel disease, seizure risk, confusion, and brain disease also need review. A map alone does not explain new loss of function.
What happens during qEEG brain mapping, and what should you do before the appointment?
Ask which test you're actually getting: a standard clinical EEG with quantitative analysis, a research qEEG, a commercial brain map, or a specific cleared device. Ask which clinical question the result is meant to answer and what decision would change for each possible result.
Confirm who will review the raw EEG. Historical AAN and ACNS guidance says clinical qEEG analysis should only happen alongside the routine EEG analysis. A color map alone can't show whether an apparent finding came from eye movement, muscle, drowsiness, a loose electrode, or real brain activity.
Follow the service's written instructions. Current NHS and Australian patient guidance usually asks for clean, dry hair with no gel, wax, oil, spray, or other hair product. Hair products and tightly fixed hair pieces can make scalp contact harder.
Unless the service gives a different plan, eat and drink normally and take usual medicines. Ask specifically about caffeine, nicotine, cannabis, alcohol, sleep medicines, stimulants, antiseizure medicines, and sedating medicines. Also ask about any medicine change near the recording. Do not stop a prescription or withdraw from a substance on your own.
Do not deprive yourself of sleep unless a clinician has ordered a sleep-deprived EEG and given safety instructions. The NHS and Healthdirect advise not driving after a sleep-deprived EEG. Arrange transport if that is the protocol.
Bring glasses, hearing aids, an up-to-date medicine list, earlier EEG or imaging reports, and a short description of the actual episodes or thinking problems to check. Record recent sleep, illness, fever, pain, migraine, anxiety, food, caffeine, alcohol, cannabis, nicotine, and medicine timing.
Ask about the planned recording state, such as eyes closed, eyes open, resting, drowsy, asleep, or doing a task. Ask how many minutes of clean data the report will analyze. One multinational normative project required at least 1 minute of artifact-free eyes-closed resting EEG, but that research rule is not a universal clinical minimum.
Tell the service about a first seizure, repeat spells, fainting, a head injury, or a severe new headache. Also report pregnancy, implanted or metal devices, scalp wounds, sensory needs, tremor, tics, movement problems, or trouble staying still. These facts may change the test or safety plan.
Place the scalp electrodes
The technologist measures the head, prepares the scalp, and attaches electrodes. ACNS minimum technical guidance describes all 21 electrodes and placements recommended by the IFCN for a standard clinical EEG. Research qEEG datasets often analyze 19 scalp channels, which is not the same statement.
Record named states
The recording may include eyes closed, eyes open, breathing, flashing lights, drowsiness, sleep, or a task. Keep the exact state and duration with every result, because a value from one state isn't directly comparable with another.
Remove artifact before calculating
Eye blinks, eye movement, jaw and forehead muscle, movement, heartbeat, poor contact, and electrical noise can imitate brain activity. The report should state how much data was rejected and how much clean data remained.
Read the raw EEG first
A trained clinician reviews the ordinary waveform for epileptiform discharges, slowing, asymmetry, sleep features, and artifact before treating software maps or numbers as clinically meaningful.
Calculate the named measures
Software may calculate absolute and relative delta, theta, alpha, or beta power, peak alpha frequency, asymmetry, coherence, phase, ratios, or other features. Keep the software's exact frequency boundaries and method.
Compare with the exact database
A z-score commonly subtracts the database's age-dependent mean from the person's value and divides by the database standard deviation. Save the database version, sample, age range, sex handling, device, montage, reference, and correction for testing many values.
How do you read qEEG brain maps and z-scores?
Start with recording quality and the conventional EEG interpretation. Then read the state, montage, reference, clean duration, software, database, power or connectivity measure, z-score, and multiple-comparison method. Finish with symptoms, medicines, sleep, age, the clinician's conclusion, and the decision that changed.
The recording or comparison is not usable enough
The map may be unreliable if there is too little clean data, drowsiness, eye or muscle noise, movement, or poor electrode contact. A nonstandard electrode setup, unclear reference, missing raw review, or a poor database match can also cause problems. Ask whether a repeat would help.
No clear abnormality appears under the named method
The conventional EEG is unremarkable and no clear qEEG outlier appears under the named method
This recording didn't show a clear problem. Conditions or symptoms that did not appear during the test may still need other checks.
One or more values are statistical outliers
One or more power, asymmetry, coherence, phase, ratio, or frequency values fall outside the database expectation
This is a statistical difference from the named database. Read its z-score, location, band, direction, repeatability, artifact check, raw waveform, database match, and multiple-comparison method. It isn't a diagnosis, a damaged-brain percentage, or proof that the highlighted area caused symptoms.
The raw EEG or a repeatable feature needs clinical follow-up
The raw EEG shows a clinically important finding or a repeatable quantitative change supports a defined question
A trained clinician should name the conventional EEG finding, the quantitative feature, and what it changes. Epileptiform discharges, focal or generalized slowing, or another traditional EEG abnormality may lead to a conventional neurological workup. The color map shouldn't replace that explanation.
A z-score of 2 does not mean a 2 percent chance of disease
It means that one value is two standard deviations from one database model's fitted mean. The meaning changes with direction, channel, frequency band, state, age match, device, reference, artifact, and how many values were tested. It does not show damaged-brain percentage, disease probability, or treatment need.
See research details
Electrode count, reference database, z-score method, false-positive risk, FDA-cleared scope, developmental norms, and country access all affect interpretation. Research on ADHD, concussion, and brain fog does not remove those limits.
Save the electrode count, names, montage, reference, sampling rate, filters, impedance method, recording states, and clean duration. Do not compare a reduced commercial map with a full clinical recording as though the methods were identical.
Ask whether contact quality was acceptable and balanced throughout the recording. Do not interpret a focal hot spot before the technologist and reader have excluded poor contact and electrical noise.
Keep the sign, measure, electrode, frequency band, state, database, and uncertainty. Ask about the number of comparisons and the correction or validation method before focusing on the most colorful value.
Ask whether the person's age, device, reference, state, and processing match the database. A large sample does not erase batch effects or make a mismatched comparison accurate for that person.
Do not use the old percentages as a modern device-accuracy estimate. Ask the current service how it controls false discovery, validates features, and confirms that a flagged region is not artifact or a database mismatch.
Check the device name, product code, age, intended use, electrodes, and exact claim. Do not transfer one device's clearance to a 19-channel or 21-electrode map, an adult, or a diagnosis and treatment claim it was not cleared to make.
Use history, onset, impairment in more than one setting, observer information, development, sleep, learning, mood, substances, medicines, and other causes. A ratio or color map cannot supply those facts.
Do not use an abnormal or expected map to confirm or exclude concussion. Keep the injury history, examination, danger signs, symptom course, function, medicines, sleep, vestibular findings, and conventional imaging or testing decisions separate.
Treat these as group-level research findings. They do not create a Long COVID, ME/CFS, fibromyalgia, or brain-fog diagnostic signature and do not tell an individual which treatment to buy.
For a child or teenager, ask whether the task, montage, processing, age model, developmental stage, and clinical use match the evidence. Do not replace pediatric assessment with a research reliability number.
Require the report to name the child's exact method and age comparison. A pediatric-looking color map cannot be interpreted without developmental and technical context.
Keep both the numbers and the limits. This supports further diagnostic research, not using one qEEG report to diagnose depression, choose an antidepressant, or explain brain fog.
Ask for the service name, clinician credentials, device, billing code, prior authorization, total cost, and what part is clinical EEG versus optional quantitative mapping. Insurance coverage doesn't prove a diagnostic claim, and lack of coverage doesn't by itself settle the science.
Make the appointment useful without trying to change the trace
Practising the task cannot make the assessment more trustworthy. You can still improve the information available at the appointment and reduce how much the symptoms disrupt daily life while assessment continues.
Keep the recording conditions ordinary and written down
Follow the clinic's plan for sleep, meals, caffeine, nicotine, and medicines. Write the actual hours slept, last caffeine, food, illness, pain, migraine, and medicine times instead of trying to create a better or worse trace.
Clean, dry hair on arrival
Wash and dry your hair. Skip gel, wax, oil, and spray. Ask about braids, extensions, wigs, scalp sensitivity, skin problems, or a religious head covering before the visit. Clean contact can reduce delay and recording noise.
Bring two daily-life examples with the qEEG report
Write what happened, how long it lasted, what you were doing, what became impossible, and how long recovery took. Include sleep, upright posture, exertion, meals, migraine, sensory load, medicine timing, and menstrual or postpartum timing when relevant.
Ask for the raw EEG and the method page
Request the clinician's ordinary EEG interpretation plus the quantitative report, electrode montage, state, artifact-free duration, software, database, z-score method, and limits. Ask which single clinical decision changed because of the result.
Reduce the cost of the symptom now
Use written steps, reminders, fewer simultaneous demands, planned breaks, a quieter work area, and help with driving or childcare when episodes make those tasks unsafe. These practical supports don't claim that a brainwave is now normal.
Check the treatment claim before paying
If a clinic suggests neurofeedback, supplements, medicine changes, or repeat maps, ask why. Request the controlled evidence, total cost, expected benefit, possible harm, other choices, stopping rule, and an independent review.
Do not stop prescribed medicine, lose sleep on purpose, trigger symptoms, or buy treatment to chase a color or z-score. Get direct medical care for a first or repeat seizure, sudden weakness or numbness, or new trouble speaking or seeing. A severe sudden headache, marked confusion, or reduced consciousness also needs direct care.
What should you keep with a qEEG report?
Keep these together
- Referral question, symptom or event under review, and decision the test was meant to change
- Clinical EEG, qEEG analysis, commercial brain map, or named cleared device
- Clinic, qualified reader, device, amplifier, software, database, and version
- Date, start time, eyes-open or eyes-closed state, task, drowsiness, sleep, and total recording duration
- Montage, every electrode used, reference, sampling rate, filters, contact or impedance notes, and activation procedures
- Artifact methods, rejected segments, remaining artifact-free minutes, movement, eye, muscle, heart, and electrical-noise notes
- Conventional raw EEG interpretation, including epileptiform activity, focal or generalized slowing, asymmetry, or an unremarkable study
- Absolute and relative power, exact delta, theta, alpha, and beta boundaries, and peak alpha frequency
- Asymmetry, coherence, phase, ratios, connectivity, or other derived measures actually reported
- Every highlighted value, z-score, sign, channel, band, state, unit, database comparison, and multiple-comparison method
- Age and sex model, country and device match, normative sample, exclusions, and report limits
- Sleep, food, caffeine, nicotine, alcohol, cannabis, illness, fever, pain, migraine, anxiety, and medicine timing
- Pregnancy or postpartum timing, hearing, vision, scalp, movement, language, sensory, and access context
- Clinician interpretation, competing explanations, conventional follow-up, treatment recommendation, cost, expected benefit, risks, and stopping rule
- For a repeat, the reason, interval, same or changed method, clinical event, treatment, symptoms, function, and decision it will test
Question for the visit
“Which part came from the raw clinical EEG, which part came from the quantitative comparison, how well did the method and database fit me, what could be artifact or normal variation, and what clinical decision changes because of this report?”
Sources for Quantitative EEG (qEEG) Brain Mapping
Standard 21-electrode clinical recording, 10-20 placement, impedance, montage, and technical quality
Historical raw-EEG-first rule, trained interpretation, multiple-testing warning, and limited established adjunct uses
Theta-to-beta ratio diagnostic limits, false positives, and standard clinical-assessment requirement
Narrow prescription-device use, ages 6 to 17, one-channel method, duration, thresholds, and limitations
Current preparation, clean hair, ordinary food and drink, basic procedure, result review, and sleep-deprived safety
Non-invasive recording, usual duration, hair preparation, medicine review, and sleep-deprived safety
Prolonged EEG item and explicit exclusion of quantitative topographic neurometric mapping
Historical qEEG evidence classification, raw EEG, trained interpretation, and false-abnormality warning
AAN ADHD theta-to-beta ratio advisory, false-positive range, and diagnostic boundary
ACNS guideline against qEEG diagnosis of mild traumatic brain injury
HarMNqEEG sample, countries, devices, channels, clean duration, z-score method, age, and batch effects
Seventeen-study fibromyalgia, ME/CFS, and Long COVID systematic review and mixed-results limit
1,212-person youth normative framework, multi-site and montage batch effects, and research reliability
Pediatric resting-EEG methods review, screened and included counts, and method variability
Depression diagnostic-accuracy meta-analysis, pooled estimates, bias, small samples, and heterogeneity
See each claim's sources
procedure
ACNS minimum technical guidance describes all 21 IFCN-recommended electrodes for a standard clinical EEG and gives ordinary impedance guidance of 100 Ohm to 5 kOhm, with some modern systems able to record up to 10 kOhm.limitation
The retired AAN and ACNS statement says clinical qEEG analysis should not be used without accompanying routine EEG analysis and warned about false findings from many comparisons.limitation
The 2021 ACNS guideline does not support qEEG for diagnosing mild traumatic brain injury or distinguishing it from other diagnoses and calls this use investigational.limitation
The AAN advisory, reaffirmed in 2025, says EEG theta-to-beta ratio should not replace a standard clinical ADHD evaluation or confirm diagnosis outside research.indication
FDA De Novo K112711 covers a prescription one-channel Cz theta-to-beta ratio aid for ages 6 through 17 after a clinical evaluation, not generic diagnostic brain mapping.context
HarMNqEEG began with 1,564 EEGs from 9 countries and 14 devices and used 19 channels and at least 1 minute of artifact-free eyes-closed rest in its harmonized norm work.interpretation
A qEEG z-score expresses distance from the named age-dependent database mean in database standard-deviation units, not disease probability.limitation
A 2024 systematic review included 17 fibromyalgia, ME/CFS, or Long COVID qEEG studies and found differing or mixed group patterns rather than one clinical brain-fog signature.context
A 2025 normative framework used 1,212 young people and reported research-model reliability above 0.9 while addressing site and montage batch effects.limitation
A 2026 pediatric review screened more than 650 papers, extracted 56, and found substantial variation in acquisition, preprocessing, frequency bands, and multiple-comparison handling.interpretation
A 2026 depression meta-analysis pooled 18 studies and 58 results but retained case-control bias, small samples, and unexplained heterogeneity despite high pooled accuracy estimates.preparation
Current NHS and Australian EEG guidance advises clean dry hair without products, ordinary food unless told otherwise, medicine review, and no driving after a sleep-deprived EEG.context
Australian MBS item 11005 for prolonged 3-to-24-hour EEG excludes quantitative topographic mapping using neurometrics or similar devices.