1. Deep Breathing/Hyperventilation: You will be asked to deep breathe or hyperventilate for 3 minutes with your eyes closed. Deep breathing may produce changes in brain wave activity that can help diagnosis. Sometimes during hyperventilation you may feel dizzy or your fingers and toes can tingle; this all perfectly normal and will stop once you breath normally. A child may be asked to blow to toy or windmill during this exercise.

2. Photic Stimulation: Photic stimulation tests for something called photosensitivity. Photosensitivity is where a person is sensitive to certain frequencies of flashing light and this may sometimes cause them to have seizures. You will be asked to look at a strobe light and open and close your eyes a number of times. A number of different frequencies will be tested while the scientist looks for a change on the EEG. If she sees a change the strobe will be stopped.

3. Sleep EEG: Your EEG background changes from when you are awake to when you are asleep. Often sleeping during an EEG is useful and can aid in diagnosis particularly if your seizures occur during sleep. You will be notified in advance if you have to sleep during an EEG. Often will be asked to arrive at the lab after sleep deprivation. It is important to note that lack of sleep can sometimes cause seizures in patient with epilepsy. Sometimes a mild sedative tablet is used to help you sleep. Sedation is not commonly used in EEG as sedation can cause drug induced changes in an EEG which may make it difficult to read the real waveforms beneath.

After the EEG you may still be sleepy or tired. You should not drive at this time and it is advisable to have someone to accompany you home.

Sleep EEG for Children: Sleep is very important is the diagnosis of epilepsy in children. Often you will be asked to keep your child awake 1 hour awake after normal bedtime and get up 1 hour earlier than normal. Then it is essential not to let your child sleep on the journey to the hospital. Sleep EEG’s for children can take up to 1.5 hours to perform. If you have any questions regarding Sleep EEG’s you should call the EEG department to which you have been referred for advice.

Other Important Information:

• An EEG does not hurt. You may feel a little scratch as the scientist rubs the spots where she is going to place the discs and the discs themselves may feel cold however the procedure is painless. No needles are used.

• Some children may get upset during the EEG, this is perfectly normal and they usually calm down after all the discs are applied. It is important to remember that the scientists are used to dealing with children who may get upset and do their best to ensure the procedure causes the least amount of upset for both yourself and your child.

• You cannot read someone’s mind during an EEG? The EEG is a record of the electrical activity of the brain. It is not possible to read your emotions or thoughts. It is possible to tell if you are awake or asleep, if your eyes are open or closed and if you are dreaming.

• You do not feel anything during an EEG. While we are measuring the electrical activity of the brain there is no electricity used. The EEG is not shock treatment.

• If you have a seizure during a test you will be checked to make sure you will be well enough to go home. The scientists are all trained to deal with seizure episodes.

• Continue to take your medication as prescribed unless otherwise instructed.

• Ensure to eat before an EEG and DO NOT fast.

• After the EEG is performed it needs to be interpreted by a physician, either a Neurologist or Neurophysiologist before you get a result. The scientist usually writes a report on your EEG but it is up to the physician to say what the EEG means for you and if a diagnosis can be made. You will not get a result on the day of the EEG. The full report will be sent to the doctor who referred for the EEG.

Other tests performed by Clinical Measurement Scientists, Neurophysiology:

Evoked Potentials:

Evoked Potentials are electrical signals produced naturally by your brain or nerves in response to repeated stimulation of the eyes, ears and nerves. For our brains to make sense of what we see and hear it must receive this optical and auditory information as electrical activity. This electrical activity is carried by our nerves along a specific pathway. We can test how these pathways are working using Evoked Potentials.

Visual Evoked Response (VER):

Visual Evoked response is used to test the acuity of the optic nerve. The optic nerve is the large nerve behind your eye which follows a pathway to bring visual information from your eye to the back of the brain where it is processed.

The VER tests this pathway. The scientist will apply approx 6-8 silver discs to areas on your head, held on with sticky tape (as for EEG)

You will be asked to look at the centre of a TV screen with a black and white checkerboard pattern. Each eye will be tested individually with a patch placed over the eye not being tested. If you wear glasses it is essential that you bring them with you to the study and wear them during the test. The study is performed in a dimmed or darkened room.

You will not get the results of the VER the same day as they have to be analysed by a physician. This study takes approximately 1 hour to perform.


Electroretinogram (ERG):

An Electroretinogram (ERG) looks at the electrical activity from your eye. The retina is responsible for converting optical images formed by the lens of your eye into nerve impulses which then travel along the optic nerve pathway to be processed by the brain.

An ERG involves either using small fine metal electrodes which sit in a loop between the lower eyelid and eyeball or small disc electrodes as around your eye. The study is performed in the dark and often you will be asked to sit in the dark for 20-30 minutes before the test to allow your eyes to become dark adjusted. The scientist then asks you to look at flashing lights. These flashing lights evoke a response from your eye which is measured from the electrodes or discs and processed by the computer.

You will not get the results of the VER the same day as they have to be analysed by a physician. This study takes approximately 1 hour to perform.

Brain Stem Auditory Evoked Response:

The Brain Auditory Evoked Response (BAER/BSER) is used to test the pathway from your ears to your brain. It can be used to test both auditory information (how you hear) and information from your brainstem. The scientist puts disc electrodes behind each ear and some on your head. She then puts a set of earphone over your ears. One ear is tested at a time. You will hear clicks in the ear being tested. It takes about 2-5 minutes to acquire each trial and the each ear is tested 3 times. This pathway follows a specific route and by stimulating the ear with the clicks the scientist can tell how quickly the signal gets to different locations along this route.

Nerve Conduction Studies:

A nerve conduction study is performed to test the nerves in the hands, arms and legs. It is occasionally performed in other parts of the body. Your nerves are like electrical cables carrying information to and from your brain. Sensory nerves send information from your limbs about sensation (hot, cold, texture etc) to your brain. Motor nerves carry information from your brain to the muscles in your limbs to tell them to move. A nerve conduction study may be performed if someone is experiencing tingling, numbness or paresthesia, pain or loss of power in a limb.

A nerve conduction study is performed by passing small electrical currents through the skin at the site of nerve and recording the along the natural electrical pathway along that travels along that nerve or over a muscle. It is performed by placing disc electrodes or pads on the skin. The electrical pulses will either cause a tingling sensation (sensory) or a muscle contraction (motor). For example if testing the nerve that makes your thumb move; sending an electrical impulse along that nerve will make your thumb twitch. Sometimes the tingling or twitching will be uncomfortable. The test usually takes about 30 minutes. There is no after effects to the study and you will able to return to work or school. You will not get the results of the study on the same day as they need to be analysed and looked at by a physician. The results will be sent to the physician that referred you for the nerve conduction study. You should inform the technologist if you have a pacemaker.