Neurophysiology - Stereo Electro-Encephalography

You have been given this leaflet because you are being considered for brain surgery for treatment of your epilepsy.

Stereo Electro-encephalography or SEEG is a specialised EEG (brainwave) test that is performed for some patients who are being considered for epilepsy surgery.

The SEEG test helps to pinpoint where epileptic seizures start in your brain. This will allow the team looking after you to decide regarding the option of brain surgery as a treatment for your epilepsy.

SEEG involves placing thin wires called depth electrodes into the brain, to record the electrical activity of the brain during seizures. Placing the electrodes is done under general anaesthesia (which means you will be asleep) in the operating theatre. The wires are placed through tiny holes made in the skull under robot guidance by your neurosurgeon. Following this, your head will be bandaged, and you will be admitted to a high dependency ward overnight. You will be moved to the Video Telemetry Unit the following day. The electrodes will then be connected to the EEG machine to record your brainwaves and we will video your seizures, like what occurs during video telemetry (VT).

The SEEG test will require you to stay in hospital, commonly for up to 10 days and, in rare cases, up to 21 days.

Why is SEEG performed?

The purpose of SEEG is to pinpoint the area of your brain where your seizures start from. This is the part of the brain that needs to be removed to stop your seizures. SEEG allows this area to be identified more precisely than from videotelemetry or scans. It also allows doctors to work out if an operation on this area would cause you any problems.

How is SEEG performed?

Before the test you will have seen members of your epilepsy surgery team and had the opportunity to ask questions. You will be given details of the date and time of admission in advance.

Day of admission

You should not eat or drink anything after midnight on the day of admission. You will be asked to attend the Surgical Admissions Lounge. You will be met by members of the team, including your neurosurgeon and anaesthetist. You will be taken down to the operating theatre and the anaesthetist will put you to sleep.

How are depth electrodes placed?

In the operating theatre, the neurosurgical team will use robotic guidance to drill tiny holes in the skull. Your hair may be trimmed or shaved around these areas. Electrodes are then placed very precisely into the brain. Where the electrodes are placed will depend on your previous test results. Your neurologist and neurosurgeon will have discussed the plan with you.

Most patients have between 6 and 15 electrodes inserted. Placing the electrodes takes between 3 and 5 hours.

What are depth electrodes?

They are fine wires with many contact points along their length. Each contact point can record electrical activity of the brain.

A CT scan will be performed in theatre after the electrodes are placed, to ensure that they are in the correct place, and no complications have occurred. You will have bandages applied to the head and you will be admitted to a high dependency ward overnight. The next day, if everything is satisfactory, you will be moved to the Video Telemetry (VT) Unit.

What can I expect afterwards?

When you wake up, you may feel sleepy and tired. You may also experience some headache and discomfort from the bandage.
You can receive pain relief if required.

You will be able to eat and drink once you have recovered from the general anaesthetic. You may feel some discomfort while chewing.

If you wear glasses, they may need to be modified due to the bandages on your head.

Once on the VT Unit (you will be in a single side room with an ensuite bathroom) the electrodes will then be connected to the EEG monitoring system and the recording of your brainwaves and video will begin. There are no cameras in the bathroom or toilet areas.

You will be able to eat, drink, read, watch TV, or use personal CD/DVD players, iPods, laptop, mobile phones etc. Free Wi-Fi access is available. There is also free TV.

You will be able to move around your room. However, we would like you to stay in bed as much as possible. This is to make sure you are “on camera” as much as possible, so that seizures are not missed on the video recording.

You will not be able to leave the room to smoke. Nicotine patches and an inhaler can be provided. If you wish you can be referred to the smoking cessation nurse team.

There are specially trained nurses on the ward to look after you if you should have a seizure.

A neurophysiology technician will check on the wires and equipment daily.

You may feel anxious, stressed, or upset during your stay. It is important that you talk to the clinical team looking after you if you are worried or don’t feel that you are coping well.

The team will do their best to answer questions that you might have and help you with any difficulties.

Your doctors may decide to carry out testing of your brain function such as speech, memory, movements, and sensations, by sending small electrical pulses through the electrodes whilst they ask you to perform certain tasks, for example, naming pictures. This is called functional electrical stimulation. This happens at the bed side while you are awake, and the doctors will be in the same room as you. This may cause feelings like what you experience with your seizures. This may lead on to some of your typical seizures. We will take care of you if this happens. Most are brief and stop on their own; but you may need your rescue medication to be given if necessary.

Radio Frequency Thermocoagulation (RFTC)

Following your recordings your doctor may feel that thermocoagulation could aid in locating your seizure onset zone and may benefit your seizures.

This will be performed on the ward prior to your electrodes being removed and takes around 10 minutes.

The procedure involves heating selected electrodes with specialist equipment.

You will not feel anything but may hear a 'pop' in your head.

We will continue to monitor your EEG for around 1-2 hours before you go to theatre to have the electrodes removed.

Removing the electrodes

Once enough information has been gathered from your seizures, the electrodes are removed, under either a general or local anaesthetic, in the operating theatre. You will then be kept under observation for a few hours. If there are no complications, you will be discharged home later that day.

Side effects and risks

As with any procedure, SEEG has some risks. The epilepsy surgery team will have spent a long time planning the SEEG procedure to minimise any risk.

The main risk is of damage to blood vessels, causing a bleed in the brain (haemorrhage). This is fortunately rare and happens in less than 1 in 100 cases. Very rarely, it can result in serious problems such as paralysis, speech, or sight problems. Less severe complications such as infections and leak of some brain fluid may occur, which may need antibiotic treatment. If any complications occur, your hospital stay may be prolonged.

Other risks of SEEG are the risks associated with having seizures. Your doctors may reduce or stop your epilepsy medication to increase the chance of you having a seizure during SEEG.

You may fall during a seizure and hurt yourself. Nurses will be on hand to check that you are alright.

After you have been discharged, you may notice minor symptoms such as headaches and/or discomfort, pins and needles, itchiness and numbness around the scalp and wound areas for a few days. These normally settle within a few days. You can contact the epilepsy specialist nurse advice line if you are worried about any ongoing symptoms. Useful contact numbers are provided at the end of this leaflet.

What to bring with you (please prepare for 10 days stay)

• Day and night-time clothes. We suggest that you try to bring shirts, blouses and pyjama tops that button up the front. Alternatively, you may wish to wear a hospital gown during your admission
• Slippers and dressing gown
• Soap, facecloth etc. (You will be unable to shower, bathe or wash your hair during admission but you will have a private ensuite bathroom where you can wash)
• Books, magazines, puzzle books
• Personal CD/DVD players, iPod, laptop, mobile phone, chargers etc.

Is there anything else I should know?

• Please remove all nail varnish before admission
• Please arrive in good time for your appointment. If you think you will be late, please ring us as soon as possible
• Visitors can attend at any reasonable time because you will be required to remain in your room for the duration of your test. There may be a restriction on the number of visitors at any one time
• Please inform the department if you may be pregnant
• There are no facilities for childcare while you are in hospital
• Please bring your medications with you
• If you are currently taking any medications you should continue to do so, unless otherwise advised by your doctor/ consultant
• If you require an ambulance, you should contact your own GP to arrange. Please let us know if you will be coming by ambulance

Patients who wear glasses

It may be difficult to wear glasses due to your bandages. If you have an old pair, please bring them with you as it may be possible to adjust the arms to make them fit.

How long will I be in hospital?

It will depend on the number and frequency of your seizures. It is commonly up to 10 days but can be up to 14 days and in exceptional circumstances up to 21 days.

When can I return to normal day to day activity and work?

You can do any routine activity you wish if you feel up to it. You can discuss this with the medical team when you are discharged.

Privacy

We take issues regarding your privacy extremely seriously and will not show your videos to anyone who is not authorised to look at them. We treat the videos as part of your confidential medical record. We always ask for your permission before showing videos at clinical meetings, for teaching/research purposes as with medical students or for publication in medical journals.

What will happen afterwards/what are the possible benefits?

A Consultant Neurophysiologist will look through all the information gathered from the SEEG test and produce a final report.

We, as the epilepsy team, will discuss the SEEG report at the Epilepsy Surgery Multi Disciplinary Team (MDT) Meeting. If the SEEG test confirms where your seizures are coming from, we will discuss the options for brain surgery that may benefit you. We will consider the likely success rate of a brain operation in stopping your seizures. We will also discuss risks associated with brain surgery. The team will then decide if you may be offered the option of brain surgery for treatment of your epilepsy.

Your neurologist will write to you with details of this decision, along with the risks and benefits of any proposed brain operation.

The neurologist and neurosurgeon will then see you in a joint appointment to go through the information and answer any questions you might have.
 
If you are offered the option of surgery, you can then think about the risks and benefits, and discuss with others before you decide.

What happens if I decide to go ahead with SEEG?

If you decide to go ahead with SEEG, you will need to inform your consultant neurologist or neurosurgeon. You will need to sign a consent form and undergo pre-operative checks before your name is placed on the waiting list.

What happens if I decide not to have SEEG?

If you decide you do not wish to go ahead with SEEG, please inform your consultant neurologist. It is likely that not undergoing SEEG will reduce the chance of you being offered epilepsy surgery.

Where can I get more information?

You can ask to speak to any member of the team (neurologist, epilepsy nurse specialist, neurosurgeon, neuropsychologist, neurophysiologist) before you decide. Your epilepsy nurse specialist can also put you in touch with other patients who have had SEEG/epilepsy surgery.

The team will do everything possible to enable you to make an informed decision and feel reassured about the proposed treatment. Please do not hesitate to ring us if you have further concerns or questions.

Contact Details

Video Telemetry Unit – 0161 206 3141 (8.30am – 4.30pm)
Epilepsy Nurse Advice Line – 0161 206 2951 (Voicemail)
Email: epilepsynurseteam@nca.nhs.uk
Acute Neurology Ward (ANU) – 0161 206 4586/2301
Department of Clinical Neurophysiology, 1st floor, Barnes Building, Salford Royal Hospital, Stott Lane, Salford, M6 8HD.