Management of Brain Tumors in Eloquent Areas

Brain tumours in eloquent areas represent a great challenge for Neurosurgeons due to its surgical resection complexity. The main goal of this chapter is the comprehensive study of perioperative work-up, diagnostic and preoperative functional techniques, microsurgical skills and intraoperative monitoring for the management of brain tumours located in eloquent areas. Integral management of brain tumors in eloquent areas involves different but related disciplines. So to reach a correct diagnosis, localization, treatment and prognosis, it is necessary to follow neuroclinical, neuroanatomical, neuroradiological, neurophysiological and neuropathological protocols. A complete resection is thought to be the best initial treatment for glial – type tumors, although there is no scientific evidence that a greater extent of resection is associated with a better prognosis (Berger et al., 1994; Keles et al., 2001, 2006; Pesudo et al., 2001; Sanai & Berger, 2008; Shaw et al., 2008). The infiltrative growth pattern of the neuropil by glial tumors is the reason for surgical treatment not being curative (Claes et al., 2007) and therefore the majority of patients will suffer a relapse or local progression of the disease some time after surgery. The known molecular mechanisms that drive this pattern of cellular migration have been deeply studied (Giese et al., 1995, 1996, 2003; Hwang et al., 2008). Although until new treatments for glial tumors are developed, the cytoreduction provided by surgery will maintain its value, because it offers material for diagnosis and research, alleviates both the focal and clinical symptoms of intracranial hypertension, and contributes to a greater efficacy of oncological treatments. Following this line of reasoning, there is a large number of modern series supporting the idea of resecting the largest possible volume of tumor (Giese et al., 2003; McGirt et al., 2008, 2009; Sanai & Berger 2008). The price to pay for radical resection may be an increase in morbidity, fact that takes a special challenge in case of highly eloquent areas. In this sense, a great number of imaging, neurophysiological, neurochemical, and even surgical techniques have recently been developed and incorporated into the management of these tumors, with the ultimate objective being to optimize the resection limits; to extend them to the maximum while minimizing the eventual associated morbidity (Price et al., 2006; Provenzale et al., 2004; Stummer et al., 1998; Tanaka et al., 2009). The final objective of this approach is to resect the lesion identified as tumoral based on the imaging techniques, as well as the neighboring brain tissue that is normal in appearance during surgery, but that is suspected of being invaded by tumor cells, or with cells already affected by the molecular disorder that would convert them into tumor cells. In this way, the