An electroencephalogram, commonly known as an EEG, is a medical test that records the electrical activity of the brain. This non-invasive procedure involves placing small sensors on the scalp to detect the electrical signals produced by brain cells. The recorded signals provide insights into how the brain functions.
Understanding Electroencephalography
Electroencephalography works by detecting the tiny electrical impulses that brain cells, called neurons, use to communicate. These impulses create patterns that can be measured and recorded. Small, flat metal discs, known as electrodes, are attached to the scalp to pick up these electrical signals. A special adhesive or cap is used to secure the electrodes.
These electrodes then transmit the detected brain wave activity to a computer, which records the information as wavy lines. The process is painless and does not involve electricity being put into the body. The recorded patterns reveal information about the brain’s overall function and can highlight any potential abnormalities.
Reasons for an EEG
An EEG is widely used for diagnosing and monitoring various neurological conditions. It helps identify the cause of symptoms like seizures or memory problems and can provide more information about an already diagnosed condition.
A primary use of an EEG is in detecting and investigating epilepsy, a condition characterized by repeated seizures. The test helps identify unusual electrical activity in the brain that may indicate seizure disorders, allowing doctors to classify the type of epilepsy and determine affected brain areas for targeted treatment plans.
EEG can also investigate sleep disorders such as insomnia, narcolepsy, and sleep apnea, by identifying irregularities in brain activity during sleep. Furthermore, it assists in assessing altered consciousness or coma by determining the level of brain activity. The test can also evaluate brain function following a head injury or stroke, complementing imaging tests like MRI or CT scans. In some cases, an EEG may be used to confirm brain death.
The EEG Procedure
Before an EEG, patients are typically advised to wash their hair to ensure a clean scalp, as this helps the electrodes adhere properly. It is also generally recommended to avoid caffeine on the day of the test, as stimulants can affect brain activity and the test results. Patients usually do not need to shave their hair for the procedure.
During the procedure, a trained specialist places between 8 and 23 electrodes on the scalp using a special gel or paste to ensure good contact. The patient will lie quietly, often with eyes open or closed, to prevent muscle contractions from interfering with the electrical readings. The technician may ask the patient to perform specific actions, such as opening and closing their eyes, taking deep breaths (hyperventilation), or observing flashing lights, as these stimuli can sometimes trigger abnormal brain activity that aids in diagnosis.
A routine EEG usually takes approximately 30 to 60 minutes to complete. After the recording is finished, the electrodes are removed, and the scalp is cleaned. Patients can typically go home soon after the test and resume their normal activities, though their hair might feel a bit sticky. The procedure is generally considered painless and safe.
Interpreting EEG Findings
EEG recordings are analyzed by neurologists, who are doctors specializing in brain disorders. The electrical impulses recorded by the EEG appear as wavy lines with peaks and valleys. These patterns allow doctors to quickly assess brain activity for any abnormalities.
The brain’s electrical activity is categorized into different wave types, each associated with different states of consciousness. For instance, alpha waves typically appear when a person is awake but relaxed with their eyes closed, while beta waves are characteristic of an alert and active mind. Theta waves are often seen during light sleep or drowsiness, and delta waves are prominent during deep sleep.
Abnormal patterns, such as spikes or slow waves, can indicate underlying neurological issues. Erratic electrical activity during a seizure creates distinct patterns on the EEG recording, which helps confirm the diagnosis of epilepsy.