EEG (electroencephalogram) - Mayo Clinic (2024)

FAQs

How reliable are EEG tests? ›

Approximately one-half of all EEGs done for patients with seizures are interpreted as normal. Even someone who has seizures every week can have a normal EEG test. This is because the EEG only shows brain activity during the time of the test.

An EEG can find changes in brain activity that might be useful in diagnosing brain disorders, especially epilepsy or another seizure disorder. An EEG might also be helpful for diagnosing or treating: Brain tumors. Brain damage from head injury.

EEG can help diagnose a number of conditions, including epilepsy, sleep disorders and brain tumours. Another name for EEG is brain wave test.

An EEG can usually show if you are having a seizure at the time of the test, but it can't show what happens to your brain at any other time. So even though your test results might not show any unusual activity it does not rule out having epilepsy. Some types of epilepsy are very difficult to identify with an EEG.

For patients with seizures, up to 30% referred to epilepsy monitoring units are ultimately discovered to have an alternate diagnosis. A significant number of patients identified with psychogenic nonepileptic events have had at least one EEG that was misinterpreted as abnormal.

EEG poorly measures neural activity that occurs below the upper layers of the brain (the cortex). Unlike PET and MRS, cannot identify specific locations in the brain at which various neurotransmitters, drugs, etc.

Neurologists use EEG testing, mainly, to diagnose and treat epilepsy as well as sleep problems, such as narcolepsy and insomnia, a variety of brain tumors, brain injury, infections of the brain, dementia, attention deficit disorder, behavioral delays in children, and behavioral disorders that disrupt normal daily ...

Therefore, temporospatial analysis of the EEG record is a useful indicator of cortical dysfunction in dementia and correlates with the degree of cognitive impairment. Apparently, temporospatial analysis may be useful in distinguishing patients with dementia from those experiencing normal aging.

3.2.

EEG can diagnose the two most common types of dementia (i.e., AD and VaD) because both of these types are cortical, and EEG reflects hidden brain abnormalities [72, 73]. The first EEG clinical observation was illustrated by Berger in the beginning of the last century [74, 75].

The main use of an EEG is to detect and investigate epilepsy, a condition that causes repeated seizures. An EEG will help your doctor identify the type of epilepsy you have, what may be triggering your seizures and how best to treat you. Less often, an EEG may be used to investigate other problems, such as: dementia.

Will an EEG show a stroke? ›

Electroencephalography is particularly useful following stroke if the initial CT excludes hemorrhage but does not detect infarction. In conjunction with clinical details, the EEG can then be used to indicate the likelihood of cortical involvement and thus suggest the likely pathophysiologic mechanism of infarction.

Bosl and Bosquet Enlow found that EEG signals at age 7 most robustly distinguished children with an anxiety disorder from healthy controls. However, there were signals even at 3 and 5 years of age. Recordings from two or three time points (excluding infancy) gave much better results than the age 7 recordings alone.

An EEG only shows if a person has a seizure at the time of the test, not if they have had seizures before. An EEG also looks for abnormalities that may indicate they are at risk of seizures. Therefore, even if a person's EEG results do not show any unusual brain activity, it will not rule out epilepsy.

Conclusion. High EEG upper/low α power ratio was associated with cortical thinning and lower perfusion in temporoparietal areas. Moreover, both atrophy and lower perfusion rate significantly correlated with memory impairment in MCI subjects.

Everybody is different, but one study found that EEG can identify epileptiform activity in about half of people in the first 16 hours after a seizure. After more than 16 hours, it becomes harder to 'spot' the activity.

The success rate of residents for correct responses was between 17% and 50%. On the other hand, the success rate for each question varied between 0% and 91%. Overall, benign variants and focal ictal onset patterns were the most difficult to recognize.

More than 10% of normal people may have non-specific EEG abnormalities and approximately 1% may have 'epileptiform paroxysmal activity' without seizures.

How Does an EEG Compare to an MRI? MRI scans are very popular and are often used to diagnose many different medical conditions. However, they do not provide real-time physiological data as EEGs do. Thus, an MRI can only provide information about structures and tissues at one point in time.