Using EEG and Medical History to Determine Seizure Focus

Seizures are rooted in the brain.
Seizures are rooted in the brain. CNRI/SCIENCE PHOTO LIBRARY/Getty Images

A seizure occurs when there is an abnormal discharge of electrical activity from the brain. The focus of a seizure is the area of the brain where the seizure begins, or where the abnormal electrical activity originates. Depending on the location of the electrical activity, a person will have variable symptoms.

Types of Seizures and Seizure Focus

There are a number of different types of seizures, and they are generally divided into either primary generalized seizures or partial seizures.

Primary generalized seizures originate with a surge of electrical activity throughout the brain. This reveals abnormal brain waves, or spike-and-wave discharges, widely spread throughout the brain on an EEG.

On the other hand, partial seizures refer to electrical activity in one part of the brain, like the temporal lobe. So in temporal lobe epilepsy, the temporal lobe is considered the focus of the seizure and is associated with an anterior temporal spike or sharp waves. Seizures in the temporal lobe may cause a variety of symptoms including abnormal tastes or smells, sensory or emotional disturbances, and hallucinations.

Does an EEG Help Identify the Focus of a Seizure?

Yes, an EEG can help a doctor localize a person's seizure, or find the seizure focus. That being said, the EEG is still limiting, as it cannot define the precise boundaries of the brain area. Also, EEGs can be tricky to diagnose a seizure and its focus because an EEG can be normal when a person is not undergoing a seizure.

In fact, there is only a small chance that a person will be undergoing a seizure when the EEG is being done. This is why an EEG is only used to support a diagnosis of seizure — it cannot rule it out.

What Can I Do to Help My Doctor Diagnose My Seizure Disorder?

By providing your neurologists with a thorough history of how you felt before, during, and after your seizure — assuming you can recall and were conscious — you will be giving them important clues to your precise diagnosis.

A witness or spouse's account of the seizure can also be extremely helpful. While it can be difficult to articulate how you felt during a seizure, don't fret too much about describing it perfectly —just say what comes to mind and be candid.


Epilepsy Foundation. (2013). Temporal Lobe Epilepsy. Retrieved December 31st, 2015.

Epilepsy Foundation. (2014). What is a Seizure? Retrieved December 31st, 2015.

Nadler JV & Spencer DD. What is a seizure focus? Adv Exp Med Biol. 2014;813:55-62.