EEG

What Is An Electroencephalogram?

When it comes to understanding and diagnosing brain-related disorders, the electroencephalogram (EEG) is a vital diagnostic tool. This non-invasive test measures electrical activity in the brain and are widely used to diagnose or manage conditions like epilepsy, sleep disorders, and other neurological problems.

An electroencephalogram (EEG) is a diagnostic test that records electrical activity in the brain using small, flat electrodes attached to the scalp. The brain cells communicate with each other through electrical impulses, and an EEG tracks these impulses, providing valuable information about brain function.

EEGs are commonly used to diagnose epilepsy, but they are also helpful in assessing other conditions, including sleep disorders, brain tumours, and brain injuries.

A vector showing a person wearing an EEG cap — It is completely painless and non-invasive, making it a safe option for patients of all ages, including children.

What Is The Purpose of An Electroencephalogram?

The primary purpose of an EEG is to identify abnormal brain activity that may be associated with various neurological disorders. For example, during an epileptic seizure, abnormal electrical activity occurs in the brain, and an EEG can help pinpoint the origin and type of seizure activity.

In addition to diagnosing epilepsy, an EEG is often used to:

Monitor brain activity in patients with sleep disorders such as sleep apnoea or narcolepsy.
Detect brain abnormalities caused by conditions such as strokes or tumours.
Assess brain function in patients with cognitive disorders or memory problems.
Monitor brain activity in coma patients to determine their level of consciousness and brain function.

What are the types of Electroencephalograms?

Woman wearing EEG cap, sitting in a chair with eyes closed — Routine EEGs are non-invasive and able to be done efficiently in the clinic

There are several types of EEGs, each designed to meet different diagnostic needs. These include:

Routine EEG: This is the standard EEG procedure, lasting 20 to 40 minutes, during which brain activity is recorded while the patient is awake or at rest.
Ambulatory EEG: This type allows for the continuous recording of brain activity over 24 to 72 hours while the patient goes about their daily activities. It’s particularly useful in detecting seizure activity in patients whose seizures do not occur frequently.
Sleep-deprived EEG: In some cases, patients are asked to stay awake for an extended period before the EEG. Sleep deprivation increases the likelihood of capturing abnormal brain activity, especially in patients with epilepsy.
Video EEG: This combines the standard EEG with video monitoring, allowing doctors to observe and correlate physical behaviours with electrical activity in the brain, particularly during seizures.

What Are the Benefits or Risks of Electroencephalograms?

Benefits:

Non-invasive and painless: An EEG does not require any surgical procedures or injections, making it a comfortable experience for patients.
Early detection: EEGs are effective in identifying abnormal brain activity early on, allowing for timely diagnosis and treatment.
No radiation: Unlike imaging tests such as MRIs [link to MRI] or CT scans [link to CT scan], an EEG does not involve any exposure to radiation, making it a safe option for patients of all ages.

Risks:

Minor discomfort: Some patients may feel slight discomfort when the electrodes are applied or removed, but this is usually minimal.
Possible seizure triggers: In patients with epilepsy, certain types of EEGs, such as sleep-deprived EEGs, may provoke a seizure during the test. However, this is done in a controlled medical environment, and the medical team is prepared to manage it safely.

How Do Electroencephalograms Work? What Do I Need to Prepare?

An EEG works by recording the brain’s electrical activity. The brain’s neurons produce electrical signals that fluctuate in rhythmic patterns. These patterns are recorded by the electrodes attached to your scalp and are displayed as waveforms on a computer screen for the neurologist to interpret.

Illustration showing brain waves in a normal brain and a brain with a seizure — Different conditions may reveal different EEG patterns.

Preparation for an EEG:

Wash your hair: Before your EEG, ensure that your hair is clean and free of any oils, conditioners, or styling products, as these can affect the quality of the recording.
Avoid caffeine: Caffeine can influence brain activity, so it’s advisable to avoid caffeinated beverages on the day of the test.
Medication guidance: Inform your doctor about any medications you are taking, as some drugs can affect EEG results. You may be advised to stop certain medications before the test, but only under your doctor’s supervision.

What Should I Expect During and After an Electroencephalogram?

During the EEG:

You will be seated or lying down while a technician applies small, flat electrodes to your scalp using a special adhesive or cap. These electrodes are connected to the EEG machine, which will record your brain’s electrical activity.
During the procedure, you may be asked to perform specific tasks such as opening and closing your eyes, breathing deeply, or being exposed to light stimulation to observe how your brain responds.
The test usually takes 20 to 40 minutes, but longer if a more comprehensive evaluation is needed (e.g., for sleep or ambulatory EEGs).

After the EEG:

Once the test is complete, the electrodes are removed, and you can return to your normal activities. There are no after-effects, and you can resume work, driving, or any other activities immediately unless advised otherwise by your doctor.
Your neurologist will review the EEG results and discuss them with you during a follow-up appointment.

If you’re experiencing symptoms such as seizures, unexplained headaches [link to Other Headaches], or sleep disturbances, it may be time to consult a specialist. Schedule a consultation with Dr Charles Siow to explore your treatment options today.