We are going to break down the procedure of awake brain surgery, as it is performed at the University Medical Center Groningen, into each of its phases in the next steps. As you heard before, awake surgery is not the only technique available to remove a Low Grade Glioma, and neither is the approach used at the UMCG the only existing one.
Let us see how they approach it and why, and what alternatives are. When it comes to mapping other functions such as motor functions, an awake procedure is not usually necessary: once the cortex is exposed, electrical stimulation of the motor cortex can elicit movement of the desired muscle groups without the patient being awake. Therefore, if only mapping of motor areas is needed, this can be done with a sleeping patient. Mapping of speech areas is of course not possible with a sleeping patient.
The standard procedure at the UMCG for mapping and resection of areas important for speech is the so-called asleep-awake-asleep procedure. During opening of the skull and exposure of the cerebral cortex, the patient is fully asleep thanks to careful adjustment of the right general anesthetics. This phase lasts around 1 hour. We will come back to this later this week.
The patient is then woken up once the cortex is freely accessible for the stimulation. The awake phase can start, where the surgical team maps language in cooperation with the patient. It takes between 1-3 hours. Once the areas in question are mapped, the patient is sedated with low doses of the anaesthetic drugs. The surgeon will then continue the resection based on the new information and close the skull. This again lasts around 1 hour.
The alternatives to this are an awake-awake-awake procedure (only local anaesthesia of the scalp and skull) or a sedated-awake-sedated technique (also with locally anesthesia of the scalp and skull). The benefit of these approaches is that it saves time that normally is needed to bring the patient back to full consciousness after the first asleep phase. The disadvantage lies in the fact that being awake during the first stages of the operation requires extremely complex administration of the appropriate anesthetic drugs to sedate and relax the patient sufficiently but without causing loss of consciousness.
Moreover, it increases the stress for the patient who, even though sedated, may still have a hard time coping with the stress of being conscious during a craniotomy. Depending on the patient’s characteristics, and local experience different centers use different variants of these techniques.
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