Depth, Strip and Grid Electrode Placement
for EEG Monitoring in Partial Seizures
Types of Seizures
Seizures can be placed in two broad groups of
partial seizures and generalized seizures.
Partial seizures begin in a small area in the
brain. Generalized seizures happen in many
places of the brain. For most patients with
seizures, treatment with drugs is the first
choice for care. Surgery is an option for some
patients, most often those with partial seizures.
Electrodes are placed on the surface of the
brain to measure seizure activity. The part of
the brain found to be causing the seizures is
labeled the “seizure focus”. If only one place is
found, that part of the brain is removed. If the test shows more than one seizure focus, surgery
may not be helpful.
Who would be helped by Electrode Placement?
Adults and children with seizures are considered for this test to measure seizure activity if they
ξ Partial Seizures--seizures with a fairly small area where seizure begins
ξ Seizures that are not controlled by any of three anti-seizure drugs
ξ Seizures which lessen the quality of life
ξ Seizures that begin at an early age
ξ Seizures that start in one area and spread to cause a generalized seizure
What are Electrodes?
Electrodes placed under the skull are attached to a monitor. They are used to pick up seizure
action in the brain. This tells us the kind of seizure and the part of the brain causing the problem.
After finding that part of the brain, your doctor and the brain surgeon can decide if it can be
There are three common types of electrodes used.
They are depth electrodes, strip electrodes and
Depth Electrodes are made of thin wires. These
can record seizures which start deep in the brain.
Strip and Grid Electrodes are those planted in a
thin sheet of plastic. These strips and grids are
placed on the surface of the brain. They pick up
signs of seizures.
How are the Electrodes Placed?
Depth, strip and grid electrodes are all placed in
or on the brain during surgery. A cut is made in
the scalp near the area where the electrode will
be placed. A small burr hole is made in the skull
to place the depth and strip electrodes. A piece
of skull is removed to place the grid electrode. The piece of skull is replaced when the grid
electrode is removed. You may have one or many electrodes placed to watch for seizure action.
Your hair will be shaved for this test. While the electrodes are in place, you will need to wear a
gauze bandage on your head to keep them firmly in place. You will stay in the hospital for many
days to monitor the seizures while the electrodes are in place.
To prepare for this, you will need a health history and physical exam. This includes a review of
your health, an exam of your body, and blood tests. The night before and the morning of surgery
you will be asked to wash your hair with an antibacterial soap. We often use Hibiclens .
After placement, you will go to the Intensive Care Unit (ICU) to watch and keep a record of the
seizures. You may be given less medicine or it may be stopped in order to cause seizures. If this
shows seizures that start in many places or on both sides of the brain, surgery may not be done.
If this shows that seizures are starting in a small area of the brain, the surgeon may be able to take
out that part of the brain.
Removal of the Electrodes
After we record enough information about the seizures, the electrodes will be removed. Strip and
depth electrodes are often removed at the bedside. Grids need to be removed in surgery.
Who to Call with Questions
Whenever you have a question or concern, please call your neurosurgeon or nurse practitioner.
You can call:
Department of Neurosurgery at (608) 263-1410
Spanish HFFY #6965
Your health care team may have given you this information as part of your care. If so, please use it and call if you
have any questions. If this information was not given to you as part of your care, please check with your doctor. This
is not medical advice. This is not to be used for diagnosis or treatment of any medical condition. Because each
person’s health needs are different, you should talk with your doctor or others on your health care team when using
this information. If you have an emergency, please call 911. Copyright 10/2015 University of Wisconsin Hospitals
and Clinics Authority. All rights reserved. Produced by the Department of Nursing. HF#5334