What is EEG (Electroencephalogram)? Purpose, Procedure & Results

An EEG, or electroencephalogram, is a safe and painless test that records the electrical activity in your brain. Think of it as a way for doctors to "listen" to your brain's natural electrical conversations through small sensors placed on your scalp.

This test helps doctors understand how your brain is functioning and can detect various neurological conditions. The brain constantly produces tiny electrical signals as nerve cells communicate with each other, and an EEG captures these patterns to create a visual map of your brain's activity.

What is an EEG?

An EEG measures the electrical impulses that your brain cells naturally produce when they communicate. These electrical signals create wave patterns that doctors can read and interpret to understand your brain's health.

The test uses small metal discs called electrodes that are gently placed on different areas of your scalp. These electrodes detect the brain's electrical activity and send the information to a computer that creates a visual recording of your brain waves.

Your brain produces different types of waves depending on whether you're awake, asleep, concentrating, or relaxing. Each wave pattern tells doctors something different about how your brain is working.

Why is an EEG done?

Doctors recommend an EEG to investigate various brain-related symptoms and conditions. The test helps them see if your brain's electrical activity is normal or if there are any unusual patterns that might explain your symptoms.

The most common reason for an EEG is to diagnose epilepsy and other seizure disorders. During a seizure, brain cells fire electrical signals in an abnormal, synchronized way that creates distinctive patterns on the EEG recording.

Here are some situations where your doctor might recommend an EEG:

• Suspected seizures or epilepsy
• Unexplained periods of confusion or memory loss
• Head injuries that might affect brain function
• Sleep disorders like sleep apnea or narcolepsy
• Brain tumors or infections
• Stroke or other brain blood vessel problems
• Degenerative diseases like Alzheimer's or dementia
• Monitoring brain activity during certain surgeries
• Evaluating consciousness levels in comatose patients

Sometimes doctors also use EEGs to monitor how well seizure medications are working or to determine if it's safe to stop anti-seizure drugs.

What is the procedure for an EEG?

The EEG procedure is straightforward and typically takes 20 to 40 minutes to complete. You'll be asked to lie down or sit comfortably in a quiet room while a technologist prepares your scalp and attaches the electrodes.

First, the technologist will measure your head and mark spots where the electrodes will be placed. They'll clean these areas with a gentle abrasive gel to remove any oils or dead skin that might interfere with the electrical signals.

Next, they'll apply about 16 to 25 small electrodes to your scalp using a special paste or gel. The electrodes are connected to thin wires that lead to the EEG machine. You might feel a slight pulling sensation, but the process isn't painful.

During the actual recording, you'll need to lie still with your eyes closed for most of the test. The technologist might ask you to do simple tasks like opening and closing your eyes, breathing deeply, or looking at flashing lights.

Sometimes, if doctors suspect you have seizures, they might try to trigger one during the test by using flashing lights or asking you to breathe rapidly. This helps them see what happens in your brain during a seizure episode.

After the recording is complete, the technologist will remove the electrodes and clean the paste from your scalp. You can return to your normal activities immediately after the test.

How to prepare for your EEG?

Preparing for an EEG is simple, but following the preparation instructions carefully helps ensure the most accurate results. Your doctor's office will give you specific guidelines, but here are the general steps most people need to follow.

Wash your hair the night before or morning of your test with regular shampoo, but don't use any conditioner, hair oils, sprays, or styling products. These substances can interfere with the electrodes' ability to detect your brain's electrical signals.

Here's what you should do before your EEG:

• Get a normal night's sleep unless told otherwise
• Eat your regular meals to maintain normal blood sugar
• Take your usual medications unless specifically instructed not to
• Avoid caffeine for 8 hours before the test
• Don't smoke or use nicotine products before the test
• Remove all jewelry, especially earrings and hair accessories
• Wear comfortable, loose-fitting clothes

If your doctor wants to record brain activity during sleep, they might ask you to stay awake longer than usual the night before. This makes it easier for you to fall asleep during the test.

Always tell your doctor about all medications you're taking, including over-the-counter drugs and supplements. Some medications can affect brain wave patterns, and your doctor might adjust your doses before the test.

How to read your EEG?

Reading an EEG requires specialized training, so a neurologist or other qualified doctor will interpret your results. The test creates wave patterns that show different types of brain activity, each with its own meaning and significance.

Normal brain waves have specific patterns depending on whether you're awake, drowsy, or asleep. When you're awake and alert, your brain produces fast, low-amplitude waves called beta waves. When you're relaxed with closed eyes, slower alpha waves appear.

Your doctor looks for several key features in your EEG:

• Wave frequency (how fast the waves occur)
• Wave amplitude (how tall the waves are)
• Wave symmetry (whether both sides of the brain show similar patterns)
• Response to stimulation (how your brain reacts to flashing lights or breathing exercises)
• Abnormal spikes or sharp waves that might indicate seizure activity
• Slow waves that could suggest brain injury or disease

Abnormal EEG patterns don't always mean you have a serious condition. Sometimes factors like medications, fatigue, or even moving during the test can create unusual readings.

Your doctor will correlate your EEG results with your symptoms, medical history, and other tests to make an accurate diagnosis. They'll explain what your specific patterns mean and whether any treatment is needed.

How to fix your EEG abnormalities?

Treatment for EEG abnormalities depends entirely on what's causing the unusual brain wave patterns. The EEG itself is just a diagnostic tool - the treatment focuses on addressing the underlying condition that's creating the abnormal readings.

If your EEG shows seizure activity, your doctor will likely prescribe anti-seizure medications. These drugs help stabilize the electrical activity in your brain and prevent seizures from occurring. Finding the right medication often takes time and careful monitoring.

For other conditions that cause EEG changes, treatment varies widely:

• Sleep disorders might require sleep studies and specialized treatments
• Brain infections need antibiotic or antiviral medications
• Metabolic problems require correction of underlying imbalances
• Brain tumors might need surgery, radiation, or chemotherapy
• Stroke-related changes focus on preventing future strokes
• Degenerative diseases have specific management approaches

Sometimes lifestyle changes can help improve brain function and EEG patterns. Getting adequate sleep, managing stress, avoiding alcohol and drugs, and following a healthy diet all support optimal brain health.

Your doctor will create a treatment plan tailored specifically to your condition and symptoms. Regular follow-up EEGs might be needed to monitor how well your treatment is working.

What is the best EEG result?

A normal EEG result shows organized, symmetrical brain wave patterns that are appropriate for your age and level of consciousness. The best result is one that matches expected patterns for someone of your age during different states of awareness.

In a healthy brain, the EEG should show smooth, regular waves that change predictably when you open and close your eyes, breathe deeply, or respond to flashing lights. Both sides of your brain should produce similar patterns, indicating balanced electrical activity.

Normal EEG characteristics include:

• Alpha waves (8-12 Hz) when you're relaxed with eyes closed
• Beta waves (13-30 Hz) when you're alert and concentrating
• Theta waves (4-8 Hz) during light sleep or deep relaxation
• Delta waves (0.5-4 Hz) during deep sleep
• Symmetrical patterns on both sides of the brain
• Appropriate responses to stimulation
• No sudden spikes, sharp waves, or chaotic patterns

However, it's important to understand that a normal EEG doesn't rule out all brain problems. Some conditions only show abnormal patterns during specific events, like seizures, that might not occur during your test.

Conversely, some people have mildly abnormal EEG patterns but never experience any symptoms or problems. Your doctor will always interpret your EEG results alongside your symptoms and other clinical information.

What are the risk factors for abnormal EEG?

Several factors can increase your likelihood of having abnormal EEG patterns. Understanding these risk factors helps doctors determine who might benefit from EEG testing and what conditions to consider when interpreting results.

Age is a significant factor, as both very young children and older adults are more likely to have EEG abnormalities. In children, the brain is still developing, while in older adults, age-related changes or accumulated health problems can affect brain wave patterns.

Here are the main risk factors that can lead to abnormal EEG readings:

• Family history of epilepsy or seizure disorders
• Previous head injuries or brain trauma
• Brain infections like meningitis or encephalitis
• Stroke or other cerebrovascular diseases
• Brain tumors or masses
• Metabolic disorders affecting brain function
• Alcohol or drug abuse
• Certain medications that affect brain activity
• Sleep deprivation or severe sleep disorders
• High fever, especially in children
• Genetic conditions affecting brain development

Some temporary factors can also cause abnormal EEG patterns, including severe illness, dehydration, low blood sugar, or extreme stress. These usually resolve once the underlying problem is addressed.

Having risk factors doesn't mean you'll definitely have an abnormal EEG, but it does help your doctor understand your individual situation and interpret your results more accurately.

Is it better to have a normal or abnormal EEG?

A normal EEG is generally better because it suggests your brain's electrical activity is functioning within expected parameters. However, the interpretation of EEG results is more nuanced than simply "normal" versus "abnormal."

A normal EEG can be reassuring, especially if you've been experiencing symptoms that worried you or your doctor. It suggests that whatever symptoms you're having aren't caused by the types of brain electrical problems that EEGs can detect.

However, a normal EEG doesn't rule out all neurological conditions. Some brain problems don't show up on EEG, and some conditions only cause abnormal patterns during specific events that might not occur during your test.

An abnormal EEG isn't necessarily bad news either. The significance depends on:

• What type of abnormality is present
• How severe the changes are
• Whether the patterns correlate with your symptoms
• Your overall health and medical history
• Other test results and clinical findings

Sometimes abnormal EEG patterns help doctors identify treatable conditions, leading to effective treatments that improve your quality of life. In other cases, mild abnormalities might not require any treatment at all.

The most important thing is that your EEG results help your doctor understand your condition better and develop the most appropriate treatment plan for your specific situation.

What are the possible complications of abnormal EEG results?

The complications associated with abnormal EEG results depend on the underlying condition causing the abnormal brain wave patterns, not the EEG test itself. The test is simply revealing existing problems rather than creating them.

If your abnormal EEG indicates epilepsy or a seizure disorder, potential complications could include injury during seizures, difficulty driving or working in certain environments, and the need for long-term medication management with possible side effects.

Here are potential complications related to conditions that cause abnormal EEGs:

• Seizures that could lead to falls, injuries, or loss of consciousness
• Cognitive changes affecting memory, attention, or thinking
• Mood or behavioral changes
• Sleep disturbances or excessive daytime sleepiness
• Medication side effects from treatments
• Social or occupational limitations
• Driving restrictions in some cases
• Need for ongoing medical monitoring

For rare conditions, complications might be more serious and could include progressive neurological decline, increased risk of sudden death in certain types of epilepsy, or complications from brain tumors or infections.

However, it's important to remember that early detection through EEG testing often leads to better outcomes. Many conditions that cause abnormal EEGs are treatable, and prompt treatment can prevent or minimize complications.

Your doctor will discuss any potential complications specific to your situation and work with you to minimize risks through appropriate treatment and monitoring.

When should I see a doctor for EEG follow-up?

You should follow up with your doctor as scheduled after your EEG, typically within one to two weeks depending on your symptoms and the urgency of your situation. Your doctor will review the results and explain what they mean for your specific case.

If you had the EEG to investigate ongoing symptoms, you should continue monitoring those symptoms and report any changes to your doctor. Sometimes symptoms can help confirm what the EEG results suggest.

Contact your doctor sooner if you experience any of these concerning symptoms:

• New or worsening seizures
• Sudden changes in behavior or personality
• Severe headaches that are different from usual
• Confusion or memory problems
• Weakness or numbness in arms or legs
• Vision or speech changes
• Loss of consciousness or fainting spells
• Persistent dizziness or balance problems

If your EEG was normal but you continue having symptoms that concern you, don't hesitate to discuss this with your doctor. You might need additional tests or a different type of evaluation to find the cause of your symptoms.

For people with known conditions like epilepsy, regular EEG monitoring might be recommended to track how well treatments are working and whether any adjustments are needed.