An EEG (electroencephalogram) is a test that records the brain's electrical activity using electrodes attached to the scalp. It's not a nerve test, but rather a brain activity test.
Here's a breakdown:
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EEG Basics: An EEG detects and records brainwave patterns. Small, metal discs (electrodes) are placed on the scalp and connected to a machine that amplifies and records these electrical signals.
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What it Measures: The EEG measures the voltage fluctuations resulting from ionic current flows within the neurons of the brain. These fluctuations are recorded as brain waves, which can vary depending on the individual's state of consciousness (e.g., awake, asleep).
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Why it's Used: EEGs are primarily used to diagnose and monitor conditions affecting brain activity, including:
- Epilepsy and Seizure Disorders: It's a primary tool for identifying seizure activity and classifying the type of seizures.
- Sleep Disorders: EEGs can help diagnose sleep disorders like insomnia, narcolepsy, and sleep apnea through polysomnography (sleep studies).
- Brain Tumors: Although not the primary diagnostic tool, an EEG can sometimes detect abnormal brain activity associated with tumors.
- Brain Injury: EEGs can help assess the severity of brain injury and monitor recovery.
- Encephalitis and other Brain Infections: Abnormal brain activity can indicate the presence and severity of inflammation.
- Monitoring Brain Activity During Surgery: EEGs can be used during surgeries to monitor brain function and prevent damage.
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What it's NOT: An EEG does not directly test the function of individual nerves. Nerve conduction studies (NCS) and electromyography (EMG) are used for that purpose. NCS measure the speed and strength of electrical signals traveling along nerves, while EMG assesses muscle response to nerve stimulation.
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In Summary: Think of an EEG as a way to "listen" to the brain's electrical chatter. Changes in these patterns can indicate underlying neurological conditions. It assesses brain activity, not nerve function.
