Decoding Brain Activity with an EEG

What is an Electroencephalogram (EEG) test?

An electroencephalogram (EEG) is a study that records electrical activity in the brain.  It records the brain's electrical patterns using small, flat metal discs (electrodes) placed on the scalp.

Key Features of EEG:

• Detects and records electrical impulses in the brain.
• EEG shows brain activity as wave patterns on a monitor or paper.
• Non-invasive and painless procedure.

Uses of EEG:

• Diagnosing epilepsy and determining seizure types.
• Identifying sleep disorders, such as narcolepsy.
• Assessing brain function in coma patients.
• Detecting brain conditions, including tumours, strokes, or inflammation.
• Monitoring brain activity during surgery.

Electroencephalogram

Procedure Overview:

• Electrodes are attached to the scalp with adhesive or a cap.
• The doctor advises the patient to remain still and follow instructions, such as closing their eyes or breathing deeply.
• The test typically lasts 20-60 minutes but can be extended for specific conditions.

It is a safe and widely used tool for evaluating brain health.

What is the purpose of an EEG?

An electroencephalogram (EEG) evaluates the brain's electrical activity and detects abnormalities. It helps diagnose and monitor neurological and medical conditions.

Prime Purposes of an EEG:

• Detecting Seizure Disorders: Identifies abnormal brain activity associated with epilepsy and determines seizure types.
• Diagnosing Brain Disorders: Assesses conditions like tumours, strokes, infections, or brain injuries.
• Evaluating Sleep Disorders: Helps identify problems such as sleep apnoea or narcolepsy.
• Monitoring Brain Activity: Tracks brain function in coma patients or during surgery.
• Studying Brain Function: Used in research to understand brain activity and cognitive processes.

An EEG provides critical information for effective diagnosis and treatment planning.

Which kinds of EEG testing exist?

Experts classify EEG testing into several types, depending on the purpose and duration of the recording. Below are the main kinds of EEG tests:

Types of EEG Testing:

• Standard EEG:
  • Records brain activity for a short duration (20–60 minutes).
  • Conducted while the patient is awake or lightly asleep.
• Ambulatory EEG:
  • Portable EEG that monitors brain activity over an extended period, often 24–72 hours.
  • Allows patients to continue normal activities while wearing the device.
• Sleep EEG:
  • Specifically, it records brain activity during sleep.
  • Sleep EEG helps diagnose sleep-related disorders like narcolepsy or sleep apnoea.
• Sleep-Deprived EEG:
  • Performed after the patient is intentionally kept awake for 24 hours.
  • It enhances the likelihood of detecting abnormalities, particularly seizures.
• Video EEG Monitoring:
• EEG merges EEG data and video images of the patient.
• It is often used in hospitals to correlate brain activity with physical symptoms like seizures.
• Typically conducted over several days.

Video EEG Monitoring

• Invasive EEG:
  • Electrodes are surgically placed directly on or within the brain.
  • Used in cases where precise localisation of seizure activity is required (e.g., pre-surgical evaluation for epilepsy).

Each type is tailored to specific diagnostic needs, ensuring accurate insights into brain activity.

How exactly does an EEG work?

An EEG detects and records the brain's electrical activity, which is tiny electrical impulses generated by nerve cells (neurons). Doctors capture these signals amplified and displayed as wave patterns on a monitor or printout.

Steps in How an EEG Works:

• Preparation:
  • Electrodes (small metal discs) are placed on the scalp using conductive gel or an adhesive cap.
  • These electrodes act as sensors to pick up electrical signals from the brain.
• Signal Capture:
  • Neurons communicate through electrical impulses, producing activity that the electrodes detect.
  • The impulses are faint, and the EEG equipment improves them.
• Signal Processing:
  • The computer receives the amplified signals and converts them into waveforms.
  • These waveforms represent different brain activity patterns (e.g., alpha, beta, theta, and delta waves).
• Interpretation:
  • Doctors analyse brain waves for patterns or abnormalities.
  • Neurologists use these patterns to identify conditions like seizures, sleep disorders, or brain injuries.

Types of Brain Waves Monitored:

• Delta Waves: Dominant during deep sleep.
• Theta Waves: Seen in light sleep or relaxation.
• Alpha Waves: Associated with calm, awake states.
• Beta Waves: Linked to active thinking and problem-solving.
• Gamma Waves: Related to high-level cognitive functioning.

The EEG provides a non-invasive, real-time insight into brain activity, helping diagnose and monitor neurological conditions.

What exactly happens during a regular EEG?

During a regular EEG, the following steps occur:

• Preparation:
  • The expert explains the procedure and asks the patient to sit or lie down.
  • They clean the scalp and apply electrodes using conductive gel or an adhesive cap.
• Placement:
  • Electrodes are applied to precise places on the head to monitor brain activity.
  • The patient may opt to wear headwear with electrodes for convenience.
• Recording:
  • Psychologists advise patients to relax and remain motionless to avoid interference.
  • The expert may offer basic instructions, such as opening and shutting the eyes, deep breathing, or staring at flashing lights.
  • The equipment captures the brain's electrical impulses, which appear as wave formations on a screen.
• Monitoring:
  • The technician observes the recording and may note movements or changes in activity.
• Completion:
  • Doctors remove the electrodes or cap, and the patient can resume normal activities.
  • The process typically lasts 20–60 minutes.

Neurologists collect data, which is then analysed to identify any irregularities or confirm a diagnosis.

What occurs following a regular EEG?

After a regular EEG, the following steps occur:

• Electrode Removal:
  • The professional removes the electrodes or cap and thoroughly cleans the scalp of any residual gel.
• Immediate Activities:
  • Patients can resume normal activities unless instructed otherwise, such as avoiding driving if drs use sedation.
• Data Analysis:
  • The EEG data, recorded as waveforms, is reviewed and analysed by a neurologist.
  • The doctor examines brain wave patterns for abnormalities, like seizures or unusual activity.
• Report Preparation:
  • The neurologist prepares a detailed report based on the analysis.
  • The report may include a diagnosis, findings, or recommendations for further tests.
• Consultation:
  • During a follow-up session, the recommending clinician explains the results.
  • They may recommend treatment, lifestyle changes, or additional testing if needed.

Patients generally experience no side effects, making EEG a safe and straightforward diagnostic tool.

What are the hazards and adverse effects of getting an EEG?

An EEG is a low-risk, non-invasive, safe treatment. However, some hazards or adverse effects may occur in rare cases.

Possible Hazards:

• Skin Irritation:
  • The gel or adhesive used for electrodes may cause mild scalp irritation or an allergic reaction.
• Seizure Triggering:
  • In individuals with epilepsy, stimuli like flashing lights or hyperventilation during the test may provoke a seizure.
• Discomfort:
  • Prolonged sitting or lying still during the procedure may cause minor discomfort or stiffness.

Adverse Effects (Rare):

• Headache or Dizziness:
  • Patients may feel light-headed after hyperventilation or prolonged concentration during the test.
• Emotional Distress:
  • Being monitored or experiencing a seizure during the test might cause anxiety or emotional discomfort.

Experts treat EEGs as safe output. 

What Does an Abnormal EEG Mean?

An abnormal EEG shows that the electrical activity is not typical. It can suggest a variety of neurological conditions or disorders, but it may not necessarily imply a vital condition.

Possible Causes of Abnormal EEG:

• Epilepsy:
  • Seizure activity often shows irregular brain wave patterns, such as spikes or sharp waves.
• Sleep Disorders:
  • Abnormal patterns may indicate conditions like narcolepsy or sleep apnea.
• Brain Injury:
  • Trauma to the brain can lead to irregular brain waves, suggesting brain damage.
• Infections:
  • Conditions like encephalitis or meningitis can cause abnormal electrical activity in the brain.
• Tumours:
  • Brain tumours may disrupt normal brain function, leading to irregular EEG patterns.
• Strokes:
  • Reduced or abnormal brain wave patterns may indicate areas of the brain affected by a stroke.
• Metabolic or Toxic Conditions:
  • Imbalances in the chemical levels or exposure to toxins can disrupt brain activity.

An abnormal EEG requires further investigation by a neurologist to determine the cause and appropriate treatment.

 Conclusion:

In conclusion, an abnormal EEG indicates irregular brain activity, and doctors link it to various neurological conditions such as epilepsy, sleep disorders, brain injuries, infections, or strokes. While an abnormal result does not automatically point to a severe condition, it is a crucial diagnostic tool for further evaluation and treatment. Neurologists can interpret the EEG results with the symptoms and medical history to determine the underlying cause and the most appropriate action.