EEG (Electroencephalogram)

Your son was watching TV when his eyes rolled up and his arms began to jerk. It lasted a minute, and afterwards he was confused and sleepy. After an event like this, the neurologist wants to know what the brain was doing, and an EEG is often the first test.

An EEG (electroencephalogram) records the tiny electrical signals brain cells use to communicate, through about 20 small electrodes on your scalp. Nothing is sent into your brain. The EEG only listens.

It supports a diagnosis rather than making one. It can show patterns typical of epilepsy and help identify the type, which guides the choice of medicine. But between seizures a routine EEG is normal in many people who do have epilepsy, so your neurologist reads it alongside what happened and usually an MRI.

Our neurology department offers EEG for seizure evaluation, along with long-term epilepsy care.

A neurologist reads the recording and reports, usually within a few days. Slowing in one area can point to a problem there, such as an old injury, stroke or infection. Slowing everywhere is common after a seizure and with some medicines. Epileptiform discharges (sharp spikes or waves) support a diagnosis of epilepsy, and where they appear suggests whether seizures start in one area (focal) or across the whole brain (generalised).

A normal EEG doesn't rule out epilepsy. A single routine EEG picks up these changes in only about a third to a half of people with epilepsy, and repeating it or recording sleep raises the chance. Your neurologist will combine the result with your history, and usually an MRI, before deciding on treatment.