**1. Introduction**

This chapter aims to provide an overview of the transdisciplinary work of the Neurosurgeon, Neuroanesthesiologist and Neuropsychologist before, during and after the resection of a neoplasm in eloquent areas with the patient conscious under the 3A anesthesia modality (asleep, awake, asleep). The diagnostic approach and the logistics to carry out this procedure and achieve better results will be shown.

At present there is growing evidence regarding the benefits of surgery in awake patients, with application in the treatment of epilepsy, abnormal movements and neurooncological surgery [1]. The benefits of awake craniotomy are increased lesion removal, with improved survival benefit, whilst minimizing damage to eloquent cortex and resulting postoperative neurological dysfunction. Other advantages include a shorter hospitalization time, hence reduced cost of care, and a decreased incidence of postoperative complications [2, 3]. This approach has allowed to achieve a higher degree of resection with less morbidity and a higher quality of life [2, 3].

#### **1.1 History of brain surgery with awake patient**

Throughout the history of neurosurgery it is known from archeological findings that therapeutic trepanation has existed since the Neolithic period between 8,000– 500 BC, this type of treatment was performed for headaches, fractures, localized cranial deformity, mental changes, infections or seizures [4].

The earliest descriptions in the modern era of neurosurgery date back to descriptions in the treatment of epilepsy in the 17th century. However, the most identifiable antecedent dates back to the beginning of the last century with Penfield's descriptions in the 1920s of intractable epilepsy surgery in awake patients and later in 1937 with the exposure of the intraoperative electrical stimulation technique used for the treatment of epileptogenic foci close to the language area [5, 6].

It was not until 1970 that the intraoperative cortical mapping technique began to be used for the resection of neoplastic lesions by Whitaker and Ojemann, who perfected the technique and published the first series that demonstrated the usefulness of this technique, describing it as safe, simple and adequately tolerated by most patients [5–7]. Later, in the last decade of the 20th century, Berger began to treat infiltrating neoplasms in eloquent cortical areas, improving the cortical mapping technique with the posterior publication of his experience [5, 8, 9]. Finally, in recent decades, new neuroanatomical studies and the popularization of the cortical mapping technique have led to a better understanding of the cortical and subcortical anatomy, improving the technique and prognosis of patients with infiltrating CNS lesions [10, 11].

For centuries there has been an incessant search to associate specific neurological functions with specific areas of the nervous system. At the beginning of the 19th century, explanatory models of functional neuroanatomy were built. The first to develop a model was Franz Joseph Gall (1776–1832) and his disciple Spurzheim. Dr. Gall is the founder of phrenology, based on the interpretation of the different neurological functions, on the basis that the greater development of a certain function resulted in hypertrophy of a specific brain region and that this hypertrophy conditioned a variation in the external configuration of the skull. This ability of the nervous system to "hypertrophy", erroneously in the past, is now one of the main properties of the central nervous system used by modern radiology, such as the BOLD effect (increased blood supply to an area that is developing functional activity) or PET (increased glucose metabolism) [12, 13].

Walter Moxon (1836–1886) published the first cases that exposed the principle of hemispheric lateralization, associating the right hemiplegia with aphasia and, therefore, breaking the principle of hemispheric symmetry and locating language in the dominant left hemisphere. Later, Paul Broca presented the case of Monsieur Leborgne a patient suffering from septic gangrene in the lower limb. He was admitted to the Salpetriere hospital in Paris with a clinical presentation described by Broca as "expressive aphemia", that is, he did not present facial motor deficit or comprehension problems, but the patient was unable to articulate words. An autopsy study identified the lesion in the posterior part of the lower left frontal gyrus. Pierre Marie (1853–1940), reexamined the brain of M. Leborgne, despite confirming the anatomical - functional association made by Broca 50 years earlier, he also concluded that the lesion was not limited to Broca's area only, but it extended subcortically to the striatum and posterior to the angular gyrus [12–14].

Carl Wernicke in 1874 gave name and anatomical location to sensory aphasia that he located in the primary auditory cortex, in the posterior part of the superior left temporal gyrus. Decades later Theodore Meynert (1833–1892) was the first to associate auditory aphasia with the posterior part of the superior left temporal gyrus. Wernicke not only correlated the types of aphasia with different areas, but

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

also established the term conduction aphasia (inability to repeat words) for those syndromes of disconnection between the sensory and motor areas of language, associated with the lesion of the arcuate fascicle (AF) [13, 15].

Geschwind succeeded in introducing one more level into the theory of language: the fundamental idea of networking and interconnection of the central nervous system. There are some basic Broca - Wernicke nodes and their main connection, which is the arcuate fascicle, but they do not work in isolation [16].

Damasio published the implication of the associative areas of the left medial frontal gyrus and the premotor area when performing tasks of understand words when related to animals, tools, or people. Also the implication of the inferotemporal cortex in the assimilation of the semantic concept of language, regardless of the stimulus pathway through which the word, visual (reading) or auditory information arrives, the precise implication of the dominant temporal pole in the memory-language association with the name of famous faces or places. He also characterized the difference between the pure primary auditory cortex in the transverse gyrus of Heschl and the posterior temporal area in T1 proper language, establishing the high regional cortical specialization for language understanding and he introduced the participation of the right hemisphere in the assimilation of concepts [17, 18].

### **1.2 Anatomy of brain eloquent areas**

Once the historical review of the intraoperative cortical mapping has been carried out, it is important to emphasize that it is an evolving paradigm. Nowadays the vision of functions dependent on a specific anatomical cortical site has given way to a new dynamic and integrative paradigm with structural and functional connectivity and reciprocal influence, in this manner a lesion in a given site does not affect only one function, but the system as a whole [19, 20]. For this reason, pre-surgical functional studies are not superior to intraoperative mapping.

Although it is accepted that the mapping should be directed towards the area where the lesion is located, the wide anatomical and functional variability between individuals, limitations in presurgical neuroimaging, and functional modifications caused by the tumor must be considered [21, 22]. Usually, the evaluation of 8 main domains is accepted, which are adapted to the location of the lesion, activity of each patient and the evaluation of the benefit of a broad resection against the loss of functionality/neuroplasticity [20, 22]:



*From: De Benedictis A, Duffau H. Brain hodotopy: From esoteric concept to practical surgical applications. Neurosurgery 2011;68:1709–23.*

#### **Table 1.**

*Cortical and subcortical structures involved in major brain functions as detected by direct cerebral stimulation.*

The cortical mapping must be adapted in each patient, according to location of the lesion. The following paragraphs review the main tasks and effects of cortical stimulation.
