What do electrodes measure

If an EEG does not produce any abnormalities, stimuli such as strobe lights, or rapid breathing may be added to help induce any abnormalities. The technician performing the EEG is trained to safely manage any situation that might occur. Hyperventilation is also commonly induced during an EEG to produce abnormalities. Some people may not be able to hyperventilate safely, such as people with a history of stroke , asthma , or sickle cell anemia.

The person responsible for interpreting your EEG will take these movements into account. They include:. Other factors that can influence your EEG reading include:. An EEG measures the electrical impulses in your brain by using several electrodes attached to your scalp.

An electrode is a conductor through which an electric current enters or leaves. The electrodes transfer information from your brain to a machine that measures and records the data. The test usually takes roughly 30 to 60 minutes to complete and involves the following steps:. In some instances, a person may undergo a hour EEG. These EEGs use video to capture seizure activity. The EEG may show abnormalities even if the seizure does not occur during the test.

However, it does not always show past abnormalities related to a seizure. You can continue with your regular routine. However, if you were given a sedative, the medication will remain in your system for a little while. This test can record brain activity over several days, which increases the chances of catching seizure activity. However, compared to inpatient video- EEG monitoring, an ambulatory EEG is not as good at determining the difference between epileptic seizures and nonepileptic seizures.

The technician removes the electrodes or cap. If you had no sedative, you should feel no side effects after the procedure, and you can return to your normal routine. If you used a sedative, it will take time for the medication to begin to wear off.

Arrange to have someone drive you home. Once home, rest and don't drive for the rest of the day. Your doctor might schedule an office appointment to discuss the results of the test.

If possible, bring along a family member or friend to the appointment to help you remember the information you're given. Explore Mayo Clinic studies of tests and procedures to help prevent, detect, treat or manage conditions. Our patients tell us that the quality of their interactions, our attention to detail and the efficiency of their visits mean health care like they've never experienced.

See the stories of satisfied Mayo Clinic patients. Janice Breien was anxious to find a better way to manage the seizures that regularly disrupted her daily life. Enter her Mayo care team -- ready to listen and provide solutions. Now, with her seizures under control, Janice has a renewed sense of optimism. Summary Read the full fact sheet. On this page. Conditions diagnosed by EEG Normal brain waves occur at a rate of up to 30 per second, but in someone with epilepsy, for example, the EEG may show bursts of abnormal discharges in the form of spikes and sharp wave patterns.

Other conditions that may be diagnosed with the aid of an EEG include: Sleep disorders such as narcolepsy Head injuries Brain infection Brain haemorrhage Alzheimer's disease Degeneration of brain tissue Metabolic conditions that affect brain tissue Hormonal conditions that affect brain tissue Certain disorders of the central nervous system Stroke Brain tumour Brain death.

Medical issues to consider An abnormal EEG doesn't automatically mean that you, for example, have epilepsy. EEG procedure Your hair must be thoroughly clean, but most importantly dry. Immediately after the EEG Once the test is complete, the electrodes are removed and you are allowed to get up. Taking care of yourself at home EEG is a safe procedure.

Long-term outlook The EEG technologist can't interpret the test results on the spot. Other diagnostic tests Other diagnostic tests depend on the condition under investigation. Where to get help Your doctor Neurologist Things to remember The electroencephalogram EEG is a medical test used to measure the electrical activity of the brain. A number of electrodes are applied to your scalp. EEG can help diagnose a number of conditions including epilepsy, sleep disorders and brain tumours.

Give feedback about this page. Was this page helpful? Yes No. View all medical tests. Related information. If the goal of the EEG is to mimic or cause the problem your child is having like seizures , he or she may be asked to look at a bright flickering light or breathe a certain way.

The health care provider performing the EEG will know your child's medical history and will be ready for any issues that could come up during the test. Most EEGs take about an hour. If your child needs to sleep during it, the test will take longer. You might be able to stay in the room with your child, or you can step outside to a waiting area. An EEG isn't uncomfortable, and patients do not feel any shocks on the scalp or elsewhere.

Still, having electrodes pasted to the scalp can be a little stressful for kids, as can lying still during the test. A neurologist a doctor trained in nervous system disorders will read and interpret the results. Though EEGs vary in complexity and duration, results usually are available in a few days. EEGs are very safe.