EEG stands for electroencephalogram. It is a medical test that measures brain waves. Electrodes are placed on the scalp and the small amounts of electricity emitted by the brain is recorded.
EEGs are extremely useful tests for a neurologists. We use them mostly for patients that have seizures. However, we use them for many other reasons, too.
Sometimes, patients can have altered levels of consciousness due to other medical conditions. We call this “encephalopathy.” Encephalopathy literally means that there is a problem with the brain. It is a very non-specific term but we use it to describe patients that suffer from confusion, altered attention, and/or drowsiness. EEGs can show that the brain waves are slower than normal. It can also detect whether or not the encephalopathy is due to complex-partial seizures (see What is a seizure?).
We can also use EEGs for patients that suffer from intermittent dizziness. Sometimes, episodic dizziness can be due to very brief, temporal lobe seizures without any other manifestations. This is not very common because most cases of dizziness are NOT due to temporal lobe seizures. However, we will often use an EEG to help us rule our temporal lobe seizures in dizzy patients.
EEGs are mostly used in the prognosis and diagnosis of seizures and epilepsy. They are very important because they help us understand why a patient is having seizures. When we understand what type of epilepsy a patient is suffering from, we can more carefully target treatments. We are typically not trying to capture a seizure on EEG (with a few exceptions). The likelihood of a patient having a seizure while hooked up to EEG is very slim. We are typically looking for certain characteristic waveforms, or signatures, that are emitted from the brain. These tell us why a patient has seizures and from what type of epilepsy they suffer.
We have several different types of EEGs. There are routine EEGs, sleep-deprived EEGs, prolonged EEGs, overnight EEGs, video EEGs, ambulatory EEGs, and several others.
Routine EEGs last about 20-30 minutes. They are almost always the first step in the diagnostic workup for epilepsy and seizures.
A sleep-deprived EEG is usually the next step. It is very helpful because sleep deprivation is very activating for the signature waveforms that give us the information necessary to make a diagnosis.
Prolonged EEGs, overnight EEGs, video EEGs, and ambulatory EEGs are utilized when an extended amount of EEG data is warranted. Sometimes, we are attempting to capture a seizure while hooked up to EEG. But, usually, we just need a prolonged amount of EEG data in order to make a proper diagnosis.
In my clinic, we are capable of performing all the different types of EEG listed above. I personally read and interpret every single EEG performed on my patients. I spend hours every day examining EEG data in order to ensure that my patients receive proper diagnosis and treatment. If you have any further questions about EEGs, please contact my office.