Awake Craniotomy for Glioblastoma

Introduction

The goal of modern surgery for glioblastoma is maximal safe resection. Neurosurgeons are keenly aware of the dramatic negative effects that postoperative neurologic deficits have on survival and quality of life. In contrast, achieving a complete or near-complete resection of enhancing tumor has been associated with improved survival in patients with glioblastoma. Tumor resection using the technique of awake craniotomy may allow oncologic surgeons to enhance the extent of resection while minimizing the risks of neurologic deficit. Nevertheless, like any other surgical techniques, a thorough understanding of its indication, application, limitations, and outcomes is necessary for the surgeon undertaking its use. This chapter reviews the surgical decision making and technical points, and discusses outcomes related to awake craniotomy in patients with glioblastoma.

Indications for awake craniotomy in glioblastoma

Glioblastoma is an invasive and rapidly growing primary brain tumor that can arise de novo or by transformation from a low-grade astrocytoma. In many cases, secondary glioblastoma arising from a preexisting low-grade astrocytoma occurs in eloquent regions. Those patients with long-standing preexisting tumors may show shift of critical eloquent brain function to different anatomic locations, thereby potentially rendering a greater extent of resection possible than that predicted based on preoperative imaging and knowledge of expected functional anatomy. De-novo tumors may be confined to a noneloquent gyrus and displace adjacent eloquent cortex by respecting the sulcal margin. Resection of the affected gyrus with preservation of adjacent eloquent cortex can be achieved with cortical mapping. Glioblastomas migrate via the white matter tracts and therefore subcortical stimulation to identify the location of corticospinal tract fibers can further assist in resection of tumors extending to the corona radiate and centrum semiovale and near corticospinal and speech/language fibers. In common practice, awake craniotomy has been used for tumors in or adjacent to the paracentral lobule, insula, posterior dominant frontal lobe, dominant temporal lobe, dominant perisylvian region, and dominant angular gyrus. Other surgeons have also reported the use of awake craniotomy for dominant parietal tumors, tumors near the optic radiations, and tumors near the visual cortex.

Patient selection and preoperative evaluation

Patients with preserved or partially preserved eloquent cortex function are ideal candidates for awake craniotomy because the goal is to maintain or improve on preoperative function with tumor resection. When considering age appropriateness, it is important to factor whether the patient has the age-appropriate cognitive capacity to understand the elements of the procedure and follow directions. Elderly patients with early dementia, prior stroke, or with multiple comorbidities that have affected their cognitive performance are often excluded from participation. Furthermore, patients with prior psychiatric comorbidities, such as severe anxiety or claustrophobia, may find it difficult to tolerate the procedure. Preoperative evaluation includes a detailed neuropsychiatric history to rule out claustrophobia, posttraumatic stress disorder, delusional thoughts, hallucinations, dissociative states, and severe anxiety. Furthermore, it is important to assess medical risk factors for altered response to anesthetic agents, such as alcoholism, drug abuse, polypharmacy, benzodiazepine or narcotic dependence, respiratory illness, obesity, obstructive sleep apnea, uncontrolled seizures, and prior lack of effect of local anesthetics.

The ideal patient is motivated, mature, and able to tolerate a strange and stressful environment for an extended period of time. General rules for patient preparation include providing honest information about the steps of the procedure without overuse of medical jargon as well as straightforward discussion of risks, complications, and outcomes. Some clinicians suggest proper counseling augmented with other forms of information, such as short films. Other centers perform a test run of patient positioning and language testing the day before surgery. In our center, an additional brief overview of the procedure and what the patient will experience is provided in the preoperative area on the day of surgery because the patient may have forgotten the information from the preoperative clinic visit. The patient is reminded to report any discomfort, even minor discomfort or pain, at any point during the procedure and is reassured that the team will be responsive. Regardless of the patient education strategy used, the most important factor in patient satisfaction seems to be the time spent preoperatively with members of the clinical team establishing a trusting alliance. The importance of this factor is understandable in that patients experience a sense of powerlessness and loss of control before the procedure and this can be reduced by open communication.

Anesthetic considerations

Although the awake craniotomy is generally a well-tolerated procedure, its success depends heavily on specialized anesthetic management. It requires extensive knowledge in local anesthesia for scalp block, advanced airway management, sedation sequences, management of hemodynamics, and patient coaching.