An EEG, or electroencephalogram, is a test that measures and records the electrical activity of the brain using electrodes attached to the scalp. The electrodes pick up the electrical signals produced by the brain’s nerve cells, which are then amplified and recorded by a machine. EEGs can be used to diagnose and monitor conditions such as epilepsy and other neurological disorders such as sleep disorders, brain tumors, head injuries, prolonged coma, and degenerative brain disease.
There are several types of EEGs, including:
- Continuous electroencephalography (cEEG).
Also referred to as long-term EEG video monitoring, cEEG monitoring is often used in critical care environments to identify subclinical or subtle, non-convulsive seizures. cEEG is like a routine EEG but instead of a short sample of brain activity, cEEG is designed to measure brain activity and seizure spikes over a 24–72-hour period while simultaneously recording the patient.
- Ambulatory EEG (AEEG).
AEEG is designed to capture a longer recording of brain activity that includes prolonged periods when a patient is both awake and asleep. This type of study increases the chance of capturing intermittent abnormalities and records the brainwaves of someone who is mobile and not confined to a testing room. Initial set-up and placement take about one hour and are completed in our Neurophysiology Lab. Total recording time generally ranges between 24 and 72 hours.
- Sleep-Deprived EEG.
For A sleep-deprived EEG, the patient is asked to stay awake for an extended period of time before the test. The purpose of this is to see how the brain’s electrical activity changes with sleep deprivation, as certain types of seizures, such as nocturnal seizures, may be more likely to occur.
How do EEGs work?
An EEG test is painless and non-invasive. The patient will lie down on a bed or recline in a chair and will be asked to remove any metal objects or clothing that might interfere with the test. The technician will attach electrodes to the patient’s scalp using a gel or paste to ensure good contact. The number of electrodes used can vary, but a typical test will use between 20 and 25 electrodes.
The patient will be asked to perform various tasks to elicit different patterns of brain activity, such as opening and closing their eyes, breathing deeply, or looking at a flashing light. The electrodes will record the brain’s electrical activity, which will be displayed on a computer screen as a series of wavy lines, or brainwaves. After the test, the electrodes will be removed and the patient can go about their normal activities.
How long do EEGs take?
An EEG test typically takes between 30 minutes to an hour. However, in some cases, the test may take longer if a sleep-deprived EEG is done or if the test is being used to monitor brain activity for an extended period. In some cases, the patient may need to stay overnight in the hospital for continuous monitoring.
EEGs can help diagnose:
EEGs can help diagnose a variety of neurological conditions, including:
- Brain tumors
- Degenerative brain diseases, such as Alzheimer’s disease or Lewy body dementia
- Epilepsy, a common brain disorder characterized by repeated seizures that start in the brain. Epileptic seizures range from short staring spells to loss of consciousness with uncontrollable movements of the arms and legs.
- Headaches & dizziness
- Head injuries
- Prolonged coma, a state of brain dysfunction in which a person wakes and sleeps but shows no sign of awareness
- Sleep disorders such as insomnia, narcolepsy, and sleep apnea
Do EEGs detect past seizures?
An EEG can detect both past seizures and seizures occurring during the test; however, it’s important to note that not all seizures can be detected by EEGs, and some seizures may not leave a distinctive pattern on the EEG. This is why an EEG for a person with epilepsy may come back as normal. EEG is one of many tools that can be used to diagnose epilepsy or other seizure disorders but should always be used in conjunction with other testing methods.
Why Choose NGHS
Northeast Georgia Medical Center offers diagnostic tests for a wide range of neurological disorders, conducted with the most advanced, state-of-the-art neurodiagnostic equipment. Our Neurophysiology department features a collaborative team of board-certified neurologists and experienced technicians who specialize in administering and interpreting diagnostic tests. Excellent care isn’t far from home; schedule an appointment with an NGHS provider today.