Brain Mapping - How Does it Work? The human brain is a complex system of 100 billion neurons and cells which store a lifetime of memories and knowledge. However, due to their complex nature brain surgery can be a risky business and surgeons must ensure they know exactly what they are doing.

In the case of epilepsy surgery, to either remove or reduce seizure enhancing focus spots, surgeons must understand how the varying areas of your brain are affected by seizures without damaging close by nerves and essential brain functions.

So whether your surgery is an option for you or your simply interested in how the procedure works, read on as Alert-it explains exactly what brain mapping is.

Epilepsy Surgery

Aiming to remove the seizure producing area of the brain, or limit the spread of seizure activity, surgery is often an option for many who have epilepsy. Generally you are only a candidate for surgery if you have tried a number of medications which have not worked or have been subjected to severe side effects. You may also require surgery if you have:

  • partial seizures which always start in one area of the brain (localised seizure focus)
  • seizures that significantly affect your quality of life
  • seizures caused by a lesion such as scar tissue, birth defect, or brain tumour
  • seizure discharge that spreads to the whole brain (Secondary generalisation)

Different regions of your brain have specific functions. Surgery aims to remove much of the seizure focus as possible in order to control seizures. In order to preserve important functions such as speech, understanding, vision, movement, and sensation an extensive pre-surgery evaluation must take place.

A Pre Surgery Evaluation

Before surgery can take place an extensive evaluation must be conducted whereby your medical history is reviewed along with seizure activity deducing their type, frequency, and duration. Once evaluation is finished and it is determined that the patient?s seizures relate directly to epilepsy, and symptoms have not improved following medication.

Identifying Your Brains Functionality

Brain mapping, or electrocorticography, is a procedure which helps identify the functions of different regions of the brain. Such tests help pinpoint the area in the brain where seizures begin, referred to as the seizure focus, allowing physicians to determine if surgery is in fact possible. Brain mapping is particularly important if the seizure focus is believed to lie close to important functional areas or if the exact location of the seizure remains unclear despite standard EEG and other tests.

Brain mapping allows surgeons to identify important structures in the brain so that the seizure focus can be identified and removed without causing damage to important nearby brain regions.

Mapping Activity

The exact locations of various brain functions differ significantly from person to person and the presence of seizures, tumours, and other brain abnormalities can obscure their usual location. It is therefore extremely important that brain mapping takes place. Using a computer generate image of how electrical activity is distributed across the brain, surgeons are able to see which areas of the brain are active during specific tasks in order to protect vital areas of the brain during surgery.


Extraoperative brain mapping, which happens outside of the operating room where the patient is always awake and conscious, is the first of two approaches to brain mapping.

This two stage process begins when a surgeon creates a small opening in the skull exposing the surface of the brain where small electrodes are then place. The scalp is closed and the patient returns to their hospital bed where they are closely monitored.

The electrodes will record the patients? seizure activity electrically, pointing out where in the brain they start, and allow mapping of the brain areas. The 2nd stage of this surgery occurs several days later when the surgeon is able to remove the abnormal brain tissue using the information which he has gathered from the electrical recordings.


The second approach to brain mapping, referred to as intraoperative, occurs during an operation. This generally takes place when the first approach, extraoperative mapping, found important functions very close to the area targeted for surgery.

Small electrical probes are used to test locations on the brains surface one after another to create a map of function. Areas mapping movement can be identified with the patient under anaesthesia, however other responses such as language, sensation and vision require the patients to be awake during surgery. Whilst awake the doctor uses special probes to stimulate different areas of the brain. At the same time the patient is asked to count, identify pictures, or perform other tasks in order for the surgeon to identify the area of the brain associated with each task.

What Are the Associated Risks?

No surgery is without its risks where general complications including bleeding, infection, blood clots, and reactions to anaesthesia are prevalent.

The main risk during brain mapping, and particularly for those with epilepsy, is that a seizure may be triggered as the areas being mapped are generally close to where the patient?s seizure ordinarily begin. Often electrical current applied in this location can set off a seizure and therefore physicians must pay close attention to the patient?s brainwaves during stimulation.

More Help and Advice

If you are currently experiencing seizures, or care for someone who is, you could benefit from a range of epilepsy support monitors. Designed to provide peace of mind and increased independence for both individuals and their carers Alert-it alarms are an excellent investment.

For more information and advice why not get in contact with our fantastic team? Just give us a call on 01530 231484 or 0845 217 9952.