How do you know you have epilepsy and how can it be diagnosed?

Diagnosis is not always straightforward because seizures tend to happen randomly and are only brief. Signs and symptoms of seizures may include:

  • Temporary confusion or loss of time
  • A staring spell
  • Uncontrollable jerking movements of the body, arms and legs
  • Loss of consciousness or awareness
  • Sudden feelings of fear, anxiety or deja vu

Symptoms vary depending on the type of seizure, but mostly, people tend to have the same type of seizure, so the symptoms will be similar from episode to episode. Tiredness is common after a seizure.

Tests for epilepsy

If you have had a seizure and been to the doctor or accident and emergency, it is most likely you will have a referral for an EEG and a neurologist appointment. Sometimes you may be referred to other specialists or appointments to out-rule other medical conditions that can cause seizures.


An important part of epilepsy diagnosis is a good description of the seizure(s) and your symptoms. If possible, take someone who has seen the seizure(s) or events when visiting the doctor, so they can also be asked questions.

Many people try and capture a video of a seizure. Sometimes this is helpful, other times it is not because it is very important to capture the beginning of a seizure and this rarely happens, usually only by chance.

Try to find out if anyone in the family has ever had seizures before.

As part of diagnosis, the doctor will do routine physical and neurological examinations which may include blood tests. If epilepsy is suspected, there are some tests that may help to diagnose the condition and possibly establish a cause.

This is a brief guide to the tests that help diagnose epilepsy. Not everyone will need every test. If you are unsure why your doctor has suggested certain tests and not others, then it is best to ask.

Sometimes, all or many tests for epilepsy can return normal.

For more information about episodes that could be misdiagnosed or confused with seizures click here

Procedures to help diagnose epilepsy:

  • EEG – This is a non-invasive test used to look at the electrical activity of the brain
  • Neuroimaging – These are brain scans and include MRI, SPECT, PET and CT scans
  • Neuropsychological tests – Look at how your brain is working and how the epilepsy affects your day to day functioning

Tests for epilepsy

EEG (Electroencephalogram)

Routine EEG

An electroencephalogram (EEG) is a test done to look at the electrical activity of the brain – that is, how the brain is functioning. Brain cells communicate by producing tiny electrical impulses and seizures are a result of abnormal electrical activity, so it is logical to have an EEG.

If a person is thought to be having seizures, they will be referred to a clinic to have an electroencephalogram (EEG). It is a simple, painless test and involves no needles or injections.

An example EEG

During the test, small discs called electrodes are placed on the scalp with glue or paste. The EEG machine then records the electrical activity of the brain.

An EEG usually takes less than an hour. It is important to be relaxed because movement can affect results.

Most of the test is done with the eyes closed, and sometimes you will be asked to open them briefly. It is routine to be asked to breathe deeply (hyperventilate) for a 2-3 minutes and later have a flickering strobe light, flickering at various speeds. These forms of stimulus can provoke EEG changes in some forms of epilepsy.

It is not uncommon for people with epilepsy to have a normal EEG in-between seizures.

An EEG recorded during sleep may also give additional information. This may sometimes be needed if your first EEG returns normal.

An EEG is harmless. No electrical current from the machine passes into the person’s brain during the procedure. The technicians cannot read your thought processes or know what you are thinking.

Other types of EEG recordings

EEG video monitoring / telemetric VEEG

This is a method of recording the EEG over a few days, which uses both EEG and video recording.  This may be done in a hospital, either on a ward or in a specialised video-telemetry unit or now where suitable in your own home via the Seer Medical Video EEG-ECG ambulatory service.

This procedure aims to record the seizures (by video) and the brains electrical activity (EEG) at the same time. This combined information is one of the most valuable tools for diagnosing epilepsy. The advantage over routine EEG is the doctor is able to study exactly what happened during any episodes on the video and match this up with the EEG recording.

This monitoring may be needed for a few hours or several days, depending on the frequency of symptoms and seizures.

This monitoring is also used in the lead-up to surgery for epilepsy.

For more information on ambulatory Video EEG by Seer Medical Click Here

Sleep deprived EEG / video telemetry

Some people may be asked to have a sleep-deprived EEG or video EEG to record sleep which can increase the chance of detecting abnormal brain activity. If your routine EEG has been normal or has shown features which are not clear enough to make a definite diagnosis, the doctor may ask for a sleep EEG.

Sometimes abnormalities associated with epilepsy can become more apparent in EEG during sleep. The EEG changes a lot during sleep and sometimes these changes can trigger abnormal EEG changes seen with epilepsy.

For this procedure you will be asked to have less sleep the night before.  It is not a disaster if you do not sleep during the test, because even if you just become drowsy, there is still the chance of detecting abnormal activity.

The test can be performed in the same way as for a routine EEG or video telemetry, depending on the unit, but the person is asked to sleep during the test. Occasionally sleep is induced by a mild sedative, but most times you will be put in a quiet, relaxing environment with a bed and lights out.

EEG ambulatory monitoring

Sometimes abnormalities, events, or seizures are not picked up on the above tests. The hospital setting is far from normal, and often you are not under the everyday stressors that can trigger events.

If the doctor would like something more, or wants to record a seizure or event, an ambulatory recording may be needed. This can be done at home.

Ambulatory recordings are done when it is necessary to do a recording over several days. A compact portable EEG recorder may be worn while the person carries out usual daytime activities, and also during sleep. The person will also be asked to keep a diary of symptoms and there is usually a button you can press to mark an episode on the device. Some systems also have a video camera you can move from room to room.

Ambulatory EEG allows EEG to be recorded over a much longer period – for several days if need be in a home setting. This increases the chances of finding abnormalities or recording an event, which may allow doctors to decide whether the events are seizures or not. The recording may also give a clear picture of any patterns and how often they are occurring.

It is a very useful and cost effective tool to help in the diagnosis of epilepsy or other events.

For more information about ambulatory EEG click here

Seer Medical offer ambulatory EEG also.

Neuroimaging – MRI, CT, SPECT and PET scans

When used for epilepsy, neuroimaging is images (pictures) taken of the brain, or a brain scan. It can be done to look at the structure or function of the brain. These scans may further help when diagnosing and treating epilepsy.

Pictures are taken of the brain that may show changes in brain tissue and how the brain is working. Changes may show for example:

  • the presence of scar tissue from an injury
  • a lesion or tumour
  • degeneration or shrinking of brain tissue
  • changes in blood flow in the brain
  • changes to how some areas are functioning

Common brain imaging tests include:

MRI Scanning

MRI or Magnetic Resonance Imaging generates clear and detailed images of the brain without the use of x-rays, instead using strong magnetic fields and radio waves. Images can be generated in either 2D or 3D.
The MRI machine makes loud thumping and banging noises. Earplugs or earmuffs should be available. Because of the strong magnetic field people with pacemakers, cerebral aneurysm clips and any other metal surgical implants will not be able to have a MRI scan. It is important to remove jewellery, hairclips, hearing aids, credit cards, coins, keys, even makeup and hair gels which could interfere with the scan. There are specific guidelines to allow an MRI to be done with VNS implanted. 
The MRI scan is not known to have any harmful effects. It is best to tell staff or your GP when booking the scan if you suffer from claustrophobia (fear of being in a confined space) and you may be allowed to take a mild relaxant before the scan.
For more information on MRI scans Click Here

Functional MRI (fMRI).

A functional MRI measures the changes in blood flow that happens when specific parts of the brain are working. Doctors may use an fMRI before surgery to identify the exact locations of critical functions, such as speech and movement, so that surgeons can avoid injuring those places while operating. Click here to see more.

SPECT Scanning

SPECT uses a computer to generate pictures of the blood flow within the brain.  Blood flow in the area of the brain causing seizures should be lower in-between seizures and higher during a seizure. This test is often used as part of the workup for surgery for epilepsy.For more information on SPECT click here 

PET Scanning

PET scanning measures metabolic activity showing how the brain is working (function) rather than how it looks (structure). It produces a 3D image of the brain.
In a person with epilepsy, the area causing seizures will have less activity because the cells are not as active in-between seizures (unless a seizure occurs when the substance is injected which will increase brain activity in this region).
This scan requires fasting because it measures glucose metabolism. With someone with epilepsy, often a VEEG is performed at the same time, so it is necessary to arrive early to set this up.PET may be done to help establish if someone is suitable for epilepsy surgery.
For more information on PET scans Click Here 

CT Scan

Computed Tomography (CT) is a procedure that uses x-rays to take pictures of the brain. It is not commonly done when trying to diagnose epilepsy. CT scans can show abnormalities in the brain that might be causing seizures, such as tumours, bleeding, and cysts.

For more information on CT scans Click Here

Other Tests

Neuropsychological tests

Although these tests don’t diagnose epilepsy, they assess a range of learning domains including thinking, memory and speech skills. This gives your doctor an overall picture of how well your brain works and if there are any areas that aren’t working well, which may be the area the seizures are being generated.

It can also help find out how the epilepsy is affecting your ability to reason, concentrate, solve problems, or remember.

Most of the tests done include answering questions or performing tasks. You may do some on a computer, using pencil and paper, or using other objects. The tests are meant to test your limits, so don’t be disheartened if they seem hard.

For more information about neuropsychological tests click here

Just diagnosed?

For further information go to:

Dr Dan McLaughlin Video: Brain Imaging

Factsheet – Diagnosing Epilepsy

EEG explained