Awake brain surgery (craniotomy)

In “awake neurosurgery” patients are woken up during the operation so that they can cooperate during surgery.

Why and when should a patient be woken up during his/her operation?

In the course of the history of neurosurgery, and particularly of brain surgery, safety has increased considerably, such by applying ever more innovative methods during surgery. In the past, a patient sometimes suffered irreparable damage after the execution of delicate brain operations, causing paralysis of one body half, as a result of which the patient could no longer speak. This was due to the limited knowledge of the important areas within the brains. This knowledge gradually increased thanks to the application of new imaging techniques.

50, 60 years ago, patients were more frequently operated while being awake because the narcosis itself was already considered dangerous then. Brain surgery was also very risky at the time. Gradually, putting the patient completely to sleep became less hazardous so that “awake surgery” became obsolete.

When today a tumour (benign or malignant) is located in important and hazardous areas – locomotory centres that execute arm, leg and facial movements, speech centres commanding the understanding and execution of language – the neurosurgeon will, in consultation with the patient, go for awake surgery.

Although functional MRI (fMRI) allows us to map the different brain areas (mapping the areas that are responsible for movements and for speech and having them lit), it still is an inaccurate physical display of the hazardous brain areas. That's why it is necessary to localise these critical areas while the patient is awake, whereby the patient must carry out certain tasks with his/her hands and fingers, arms and legs and face and also has to perform speech exercises.

What is meant by 'mapping' the brains and how does one proceed?

This is in fact making a map, as in a road book, of the brains. On this map, certain brain areas are activated/deactivated through the stimulation of the brains, also called cortical stimulation. This is done by applying a small electric rod up to the brain cortex to verify which areas are hazardous.

A human's brain can be considered as a kind of electrical battery continuously transmitting signals to the whole body; during this cortical stimulation these electrical signals are interrupted as it were by the rod, as a result of which the patient can no longer move, speak. What one actually does, can be compared with blowing fuses, thus enabling to 'map' and mark the important areas of the brains in order to avoid them during the resection of the tumour. Such stimulation does not cause pain because the brains themselves cannot feel the pain.

Why is this 'mapping' so important?

For each separate individual, the organisation of the brains and the various paths between the various areas of the brains are completely different. Besides, these areas may also have been shifted on account of the tumour, thus completely changing the anatomy. Mapping all specific and separate functions is a highly individual exercise: every area can have another location in another patient. A simple illustration: the major differences between left- and right-handed patients.

What is the procedure for such operations?

The day before the operation the patient will undergo a neuronavigation MRI. Such neuronavigation MRI makes it easier for us to repair the tumour during surgery and acts as a kind of GPS system to retrieve the tumour more easily.

On the day of the operation itself the patient will first be fully anaesthetised by the anaesthetist. He/she will be positioned on his/her side with his/her head fixed. During the narcosis, the neurosurgeon will make an incision under local anaesthesia of skin and muscles and create the skull opening. Then, the patient will be awakened - gradually and steadily – by the anaesthetist by removing the inhalation tube before also opening the cortex around the brains.

Then, the interaction between patient, neurosurgeon and speech therapist/anaesthetist starts. Gradually, the brain surface is stimulated to map the important areas. Once these areas have been mapped, the neurosurgeon can start to remove the tumour while continuously applying stimulation, also deeper in the brains, by way of control. When the tumour is fully removed or when further resection is no longer possible because of the temporary falling out of the motor system/speech during the stimulation, surgery is stopped. Subsequently, all functions are tested once more.

The awake part of the operation lasts 1 ½ to 2 hours. Before stitching up the wounds, the patient is again anaesthetised. After the operation, the patient is woken up immediately and brought to the intensive care department.

So, what are the benefits of this awake neurosurgery?

Obviously, the main benefit of such surgery is that during the operation one has direct control over the resection and over the hazardous brain areas so as to reduce the risk of permanent injuries. Also, by combining all different imaging techniques available and the mapping technique, it is now possible to operate tumours that in the past were classified as inoperable.

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