*1.5.1 Neuroanesthetic perioperative management*

Benefits of awake craniotomy are greater resection of the lesion, with improvement in survival, while the damage to the eloquent cortex, which generates postoperative neurological dysfunction, is minimized. Other advantages include shorter hospitalization times, hence a reduction in care costs, and a decrease in the incidence of postoperative complications.

The term "awake craniotomy" is misleading as the patient is not fully awake during the entire procedure. The most painful moments of surgery require different levels of sedation or anesthesia, nonetheless, patient is fully awake while mapping or during resection [33].

**Figure 5.** *Functional MRI with motor paradigm.*

## *1.5.2 Preoperative evaluation*

A very important aspect in an awake craniotomy is the adequate selection and full preparation of the patient by a multidisciplinary team in order to avoid intraoperative failures [34].

All patients should have consultations with the neurosurgeon and neuroanesthesiologist to assess whether the patient is a good candidate for this technique (**see Table 3)** and to prepare the patient for the procedure. This includes a complete evaluation of patient's comorbidities, which must be optimized before surgery, in or Patients in whom a difficult airway is anticipated may have problems during the intraoperative period that possess the neuroanesthesiologist to a very difficult airway scenario. Children are not psychologically fit to undergo this procedure although individual development of each child must be considered.

Preoperative evaluation includes getting detailed information from the patient, in turn the patient must know what to expect and know the risks inherent to anesthesia. Usually this includes verbal and written informed consent [34, 35].

Pre-operative consultations provide an invaluable opportunity for the multidisciplinary team to create a rapport with the patient and therefore encourage trust.

#### *1.5.3 Operating room preparation*

The layout of the operating room and the position of the patient must be taken into account. The ability to communicate with the patient must be maintained at all times and access to the patient during adverse events is of equal importance.

As in every surgery, the operating table should be as comfortable as possible, since the patient is going to be lying in the same position for several hours. The operating room temperature should be comfortable for the patient, and the number of people should be minimized to reduce unnecessary noise and reduce patient anxiety [36].

The position of the patient is determined by the location of the lesion. **(Figure 6)** This is usually a lateral or supine position, in the case of occipital lesions and evaluation of the visual cortex, a sitting position may be used. In either position, it's important that when patient is fully awake during mapping, he can see and communicate with the neuroanesthesiologist or neuropsychologist. Sterile drapes used should not invade the patient's face, as this may cause claustrophobia and difficulty in communicating [37].


#### **Table 3.** *Anesthetic contraindications.*

#### **Figure 6.**

*Position of the patient and the evaluator during the surgical procedure to carry out the neuropsychological and movement evaluation.*

#### *1.5.4 Anesthetic generalities*

The choice of the anesthetic agent even within a preferred anesthetic technique varies, but the general principles are common to all of them; the need to maximize patient comfort, prevention of nausea and vomiting that may increase intracranial pressure, the need for hemodynamic stability, and the use of short-acting drugs that allow acute control of the patient's level of consciousness.

Premedication is not common, but reflux prophylaxis should be considered, patients should continue their prescribed medication such as steroids, antiepileptic drugs, or antihypertensives. Prophylactic antibiotics and usually one or more antiemetics are administered in every patient before the incision. The most common options are ondansetron and dexamethasone. Dexamethasone can also be used to diminish brain edema during the operation.

Standard anesthetic monitoring is used. Depth of anesthesia monitors, for example Bispectral Index Monitoring (BIS™), are sometimes used to reduce the dose of anesthetic agents administered and thus time required for patient emergence and cortical mapping cooperation [37, 38].

Capnography under general anesthesia is considered basic monitoring, but carbon dioxide monitoring for sedated or awake patients during mapping is also a common practice. Although carbon dioxide levels may be inaccurate, it is used to confirm ventilation [39].

A large-bore intravenous access is obtained and most neuroanesthesiologist place also an arterial line, usually sedated or asleep. The use of other forms of monitoring is variable.

#### *1.5.5 Anesthetic techniques*

There is not a recognized consensus on the best anesthetic approach for awake craniotomy. This is because neuroanesthesiologists vary the technique depending on neurosurgeon's preferences, pathology, duration of the surgery and patient's factors.

There are two dominant anesthetic approaches to solving this problem: monitored anesthetic care (MAC) and asleep-awake-asleep (AAA).

The goal of the MAC approach is to decrease the sedative dose to avoid an abrupt transition from sleep to awakening, which can lead to hypoactive or hyperactive delirium upon emergence and to decrease the reliability of mapping. MAC technique for awake craniotomy involves spontaneous ventilation and low doses of sedative drugs [38].

The AAA technique involves induction of general anesthesia and control of the airway with a supraglottic device such as laryngeal mask airway (LMA) or intubation. When neurocognitive testing and intraoperative mapping need to be started, anesthetic drugs are reduced or stopped, and the device is removed from the airway. Once resection of the lesion is complete, return to general anesthesia and reintroduction of the airway device is done. Advantages of this technique include the ability to control ventilation and thus control carbon dioxide concentrations and prevent airway obstruction and hypoventilation. It also facilitates a greater anesthetic depth during the most painful moments of surgery. Anesthetic drugs used for this technique are varied, but propofol and remifentanil TCI are the most common, followed by the use of a volatile anesthetic and remifentanil infusion. The use of dexmedetomidine has also been reported with this technique, and it's generally used during the awake stage of surgery and closure [39].

#### *1.5.6 Scalp block*

The cornerstone of awake craniotomy analgesia is regional scalp block along with infiltration of the incision line. A scalp block also provides hemodynamic stability and decreases the stress response to painful stimuli [40].

The scalp block technique includes infiltration of local anesthetic into seven nerves on each side. This is an anatomical block and not just a ring block. A ring block will require large volumes of local anesthetic, increase the risk of toxicity, and will not provide deep anesthesia to the temporal fascia.

Most neuroanesthesiologist place a bilateral scalp block before pinning of the head with Mayfield skull clamp. Occasionally, a scalp blocker is not applied and relies on local anesthetic infiltration by the surgeon.

The total dose of local anesthetic with and without epinephrine must be calculated individually for each patient. Studies have shown that the rise in plasma concentration of levobupivacaine and ropivacaine is faster compared to other local anesthetics and similar in all patients. Despite the quick rise in plasma levels, there were no signs of cardiovascular or central nervous system toxicity. The use of bupivacaine, levobupivacaine, and ropivacaine in varying concentrations with and without epinephrine has been described for use in a blockage of the scalp. The addition of epinephrine, usually 1: 200,000, increases the total amount of local anesthetic that can be used, decreases localized bleeding, and maximizes duration. However, systemic absorption may cause tachycardia and hypertension, and intraarterial injection into the superficial temporal artery is possible when the auriculotemporal nerve is blocked [37].

#### *1.5.7 Adverse events*

Awake craniotomy is generally a well-tolerated procedure with a low conversion rate to general anesthesia and a low complication rate. One of the most common complications is intolerance of the patient to the procedure, often due to urinary catheter or prolonged positioning and intraoperative seizures.

Seizures, focal or generalized, are more likely to occur during cortical mapping. The frequency of seizures during awake craniotomy ranges widely from 2.9–54%. These are treated by irrigating the brain tissue with ice-cold saline, they usually stop with this treatment, but sometimes benzodiazepines, antiepileptic drugs or re-sedation with airway control are required [41].

#### *Management of Brain Tumors in Eloquent Areas with Awake Patient DOI: http://dx.doi.org/10.5772/intechopen.95584*

The efficacy of prevention of intraoperative seizures with anticonvulsants remains doubtful. The latest systematic review on this topic revealed no benefit of prophylaxis. However, it should be noted that most of seizure prevention trials are based on the use of phenytoin or valproate. On the other hand, there are new data that support the superiority of levetiracetam in the prophylaxis of seizures. However, there are insufficient data to recommend its routine use in awake craniotomy.

An emergency plan for airway control must be in place at all times and this can be challenging as the patient's head is fixed on the clamp and often away from the ventilator. Options include insertion of an LMA which may be easier than endotracheal intubation.

#### *1.5.8 Closure and postoperative*

Once resection is complete, patient may be re-sedated or re-anesthetized with reattachment of the airway device, even if in the lateral position. Dura, bone flap, and scalp are then closed, pins are removed, and patient is awakened.

If remifentanil has been used, it can be given at low infusion rates to aid for a "soft" awakening and prevent coughing.

It is imperative that close neurological monitoring continues as postoperative hematomas may develop, especially in the first 6 h after operating. This may require an urgent evacuation of the clot.

After scalp block has worn off, systemic pain relief is used. The use of postoperative pain relief can be decreased in patients who have received a scalp block. Regular paracetamol and opioids are used.

#### **1.6 Neuropsychological management**

Some generalities of intraoperative neuropsychological evaluation will be mentioned in the light of new neurocognitive technological and theoretical tools that allow us to carry out current forms of evaluation, always outlined based on the objectives of the surgical plan of the transdisciplinary group of the treating physician, as well as the type of tumor, location and extension.

The selection of the methodology for the intraoperative neuropsychological evaluation is described in detail in accordance with the current literature on a recent vision of Functional Neurosurgery in brain tumors called hodology [19], which implies a radical change to the classical view on a rigid and exclusively cortical cerebral organization of brain functions. (**Vignette 3)** The advances that have occurred in recent decades on neurocognitive aspects in patients with brain tumors allow the more specific evaluation of some aspects of language, for example the name by visual confrontation has been a very important way of assessing an aspect of language in the operating room [9] but until recently attention has been paid to the type of stimuli that are presented and how to do it, that is, we currently know that the findings may be different if they are presented for the naming, an image or drawing in black and white compared to a color image with three-dimensional properties, in addition to the control of psycholinguistic variables of the words [13]. The same can be mentioned in other cognitive domains, for example the advance in the knowledge of the participation of subcortical structures in cognition, the participation of the right hemisphere in language at the narrative level, social cognition, brain reorganization in the recovery process, participation of the insula in cognitive aspects, to name a few [41].

#### **Vignette 3 - Brain Hodotopy**

This term refers to a current vision in functional neurosurgery in which the classic trend of localize functions in the cerebral cortex is changed by a concept called

hodological mechanism (from the Greek hodos, path or path) related to the cognitive alteration caused by affection in anatomical connectivity rather than a lesion in the cerebral cortex.

This approach conceives the Central Nervous System as a comprehensive system integrated by a plastic network made up of functional cortical epicenters connected by short and long fibers of white matter. Thus, brain functions are the result of the confluence of parallel information pathways, dynamically modulated in a widely distributed, interactive and multimodal circuit.

This view is of great relevance, especially in brain tumor neurosurgery due to the brain plasticity that is induced by the neoplasm itself. This phenomenon makes the dissociation between anatomy and functional delimitation especially valid, that is, to determine anatomically an area (for example the precentral gyrus) does not guarantee that it functionally corresponds to motor regions. This new perspective opens the possibility of contemplating the performance of surgical procedures in regions that were previously considered inoperable. Broca's area is an example of this new vision, since if it is considered inoperable, different brain mapping techniques such as cortical electrical stimulation can currently be used to functionally delimit this region through naming tasks. Broca's area is also a good example to show the brain plasticity that the hodological approach considers, since we frequently observe neoplasms in these regions with a patient without deficit (dynamic, not rigid system), and it is well known that in order to presents an alteration compatible with Broca's aphasia, the lesion must include cortical and subcortical regions (cortical epicenters and connectome), since a lesion limited only to the cerebral cortex corresponding to Brodmann's area 44 and 45 is associated with a transitory alteration less severe.

Transoperatively evaluating a cognitive domain with all the theoretical complexity that we currently have can take a long time, bringing an apparent contradiction, since on the one hand we require time to assess details of the domains, however, during surgical procedures with the patient awake, only they have several seconds and in some cases minutes. This leads to apparently unrelated cognitive areas that will be evident in the postoperative period. To exemplify this, we can take the case of the famous patient HM, one of the best known cases in the history of modern neurosciences who was operated awake during the bilateral resection of hippocampal structures in 1953. At that time, it was only considered important to explore the understanding and expression of language, without considering the exploration of other cognitive domains, resulting in the tragic history of memory loss that we all know. Without devaluing the merit of surgery in the context of the time, this story teaches us that it is essential to carry out a broader neuropsychological evaluation in terms of cognitive domains, apparently little related to the intervened brain region, so that the consideration of the activities to perform during the intraoperative is essential in order to optimize the time and tasks to be performed.

Among the most important neuropsychological criteria is that the patient wishes to cooperate and his neurological and psychological condition allows it, that is, the patient must understand why the suggestion of this surgery modality so that he openly expresses that he wants awake modality, knowing that it can be stressful to a certain extent and that your participation is essential. A second important criterion is not to present alterations that may obstruct the intraoperative neuropsychological evaluation. In this sense, the patient could find conditions that allow him to have a functional daily life, however, it may be that for the surgical procedure it is not suitable, for example a tumor in prefrontal regions that could affect uninhibited behavior. This could be dangerous because the integrity of the patient could be compromised by refusing to participate during surgery. Another example could be the difficulty in understanding long sentences or marked slowness when carrying out the instructions. These examples show that, even though the patient understands

#### *Management of Brain Tumors in Eloquent Areas with Awake Patient DOI: http://dx.doi.org/10.5772/intechopen.95584*

the importance of the procedure and shows the willingness to cooperate, it should be considered, since in the last example it could be determined that it would be enough to be able to carry out the monitoring of gross motor aspects, so it could be done.

An important aspect is to know, through anxiety, depression and impulsivity scales, the degree that the patient can manifest in the face of stress, since the procedure can facilitate the appearance of behaviors that could hardly be observed in daily life.

In our experience, awake surgery involves a series of stages prior to the intraoperative that the patient must undergo to guarantee a greater chance of success. That is, if it is true that success depends largely on what happens in the operating room, it is also true that a lot has to do with the preparation of the patient, the collection of neuropsychological and psychological data, and in some cases the family dynamics before the surgery, as it must be remembered that patient participation is essential, so that an inadequate preparation (eg, lack of understanding of the purpose of the procedure) could turn into limited cooperation and vulnerable to fatigue due to the small discomforts that could present.

In the same way, follow-up is important to guide the family and the patient about neuropsychological or personality changes that may occur, some of them may require neuropsychological intervention or orientation to primary caregivers.

The entire conventional neuropsychological clinical interview is conducted paying attention to traits or probable personality disorders, how to manage stress in the daily life and impulse management. It should be remembered that surgery can represent a time of stress in which the patient can behave differently from the way they do it in their daily life (explain with appropriate psychological terms that it can be psychologically unstructured), in addition to the use of medications that they could contribute for that moment. (If you are in stress, you can request to be put to sleep or decide not to cooperate, making the procedure considerably more difficult).

A conventional neuropsychological evaluation is performed. In brain tumors, large batteries are used in terms of functions, e.g. The Comprehensive Neuropsychological Exploration Program Test Barcelona completes and complementary tests.

One of the purposes is to detect qualitatively and quantitatively. All this to detect obvious or subtle alterations that the neoplasm is already causing and think about the possibility that these alterations are highlighted.

Psychological approach in which the patient's real expectations and fantasies must be detected. Anxiety and depression must be identified. Follow-up is encouraged for the next stages, gives an overview of what might happen if the tumor is malignant or non-malignant. This stage is mixed with the Psychological intervention and the intervention plan must begin here.

Other aspects that influence this stage are:

the carving explanation of the procedure, beginning, end, when waking up, when sleeping, when to sedate it, activities to perform, activities to perform, possible discomfort, procedure simulation, stereotactic frame simulation. As far as possible, visit the operating room from the outside, explanation of a video of a patient with a similar tumor.

#### *1.6.1 Family involvement*

This gives you a lot of neuropsychological material to ask questions during surgery, e.g. If so, a description of the coffee harvest can already be requested (since he is involved in the process in his place of origin). This constitutes a great deal of material to use in assessing spontaneous language.

#### **Figure 7.**

*General diagram (timeline) of the transdisciplinary treatment and location of the intraoperative neuropsychological evaluation. The steps prior to the neuropsychological assessment represented by interconnected circles represent the independence of each step, but the close relationship between them. CH: Clinical History, Pre-NP: Preoperative Neuropsychological Evaluation, PE: Psychoeducation, Inter Psicol - Psychological Intervention, Post: Postoperative neuropsychological follow-up, Rehab: Neuropsychological rehabilitation.*

Activities are designed according to the neuropsychological profile and the surgical plan. This stage can be better understood in the section on the intraoperative neuropsychological evaluation plan.

Ecological evaluation plan, what the patient requires for her daily life.

Neuropsychological rehabilitation and orientation to the family on apparently permanent and transitory alterations, including personality changes.

Follow-up at 6 months and 1 year. **Figure 7**.

## **2. Conclusions**

The most important objective of this surgical modality is the cognitive preservation and neurological function of the patient and at the same time achieving the greatest amount of tumor resection, that is, the removal of the greatest amount of brain tumor with the least amount of sequelae. This is especially valid for those patients who have a low-grade tumor with an adequate prognosis for life, recently also for those with a tumor with a higher grade of malignancy that will limit survival to several months. In both cases, the amount of pathological tissue that can be removed is of vital importance since the success of the rest of the complementary postsurgical treatments such as radio or chemotherapy depends largely on this.

The most serious intra-surgical complications include seizures, respiratory depression, air embolism, cerebral edema, and the cardiac trigeminal reflex. The total reported complication rate is about 16.5%, and in 6.4% of patients it is not possible to complete the mapping procedure.

The main causes of failure are the appearance of seizures and the loss of cooperation of the patient due to severe drowsiness, agitation, or the development of mixed dysphasia. Failed craniotomies are associated with a lower incidence of gross total resections, greater speech impairment after the procedure, and a longer hospital stay.

The application of awake craniotomy has continually evolved. The key to the success of this procedure is to pay attention to each of the components, such as careful patient selection, prior psychological preparation, building a solid relationship, ensuring the solid position of the patient, optimal regional anesthesia, the correct selection of agents and anesthetic technique, preparation and timely management of crises, and constant communication between group members.

*Management of Brain Tumors in Eloquent Areas with Awake Patient DOI: http://dx.doi.org/10.5772/intechopen.95584*
