Anesthesia and Surgical Considerations in Awake Craniotomy for Eloquent Area Tumor

Introduction: Awake craniotomy is a specialized neurosurgical technique in which the patient remains conscious during surgery, enabling real-time functional mapping of the cerebral cortex. This procedure is primarily employed when a brain tumor or lesion is situated near critical areas responsible for motor, visual, or language functions. Its application minimizes the risk of postoperative neurological deficits, ensuring the preservation of vital brain functions.

Objective: The objective of this case report is to highlight the use of the awake craniotomy technique for a patient with a brain tumor located in the left parietal lobe, emphasizing the surgical and anesthetic considerations necessary for successful outcomes.

Case Report: The patient, diagnosed with a brain tumor in the left parietal lobe, presented unique surgical challenges due to the tumor's proximity to the cortical centers governing movement and speech. To mitigate the risk of neurological impairment, an awake craniotomy was performed. Bilateral scalp nerve blocks were administered for effective pain management, alongside dexmedetomidine to provide conscious sedation. The "awake-wake-wake" protocol was followed, ensuring the patient remained alert throughout critical phases of the surgery. This allowed the surgical team to conduct real-time assessments of motor and language functions, optimizing tumor resection while preserving neurological integrity.

Conclusion: This case underscores the importance of the awake craniotomy technique in neurosurgical interventions involving eloquent brain regions. The use of dexmedetomidine and precise nerve blocks provided effective sedation and analgesia, enabling active patient participation during functional mapping. The procedure highlights the value of interdisciplinary collaboration between neurosurgeons and anesthesiologists to achieve optimal patient outcomes while minimizing neurological risks.

INTRODUCTION

Awake craniotomy stands as a well established technique for the excision of brain tumors situated in close proximity to critical cerebral centers (¹). This approach facilitates maximal tumor mass reduction while preserving the integrity of pivotal functional areas, encompassing motor, speech, and visual centers (²). Various anesthetic modalities have been employed for awake craniotomy, including the "sleep-wake-sleep" technique, with or without mechanical ventilation, and the administration of local or regional scalp anesthesia to manage "wide awake" patients. The requisite level of sedation and analgesia fluctuates across different phases of the surgical procedure; however, paramount is the maintenance of the patient's wakefulness and alertness during brain function assessments (³).

Several sedative agents have been utilized in this context, notably dexmedetomidine, propofol, and remifentanil, each carrying distinct advantages and side effects (⁴,⁵). Dexmedetomidine is favored for its superior respiratory maintenance, whereas propofol is associated with a diminished occurrence of intraoperative seizures (⁶). The short duration of action of remifentanil makes it advantageous for managing pain during surgery and ensuring patient comfort in both conscious and unconscious states, although it carries a higher risk of side effects such as nausea, vomiting, and respiratory depression (⁷).

Effective patient education and preparation preoperatively, coupled with the expertise of anesthesiologists and surgical techniques aimed at averting the tension on intracranial structures sensitive to pain, constitute pivotal principles in enhancing the efficacy of pain control during surgery and ensuring postoperative patient contentment (⁸).

This case report aims to demonstrate the application of the awake craniotomy technique in managing a brain tumor situated in the left parietal lobe. It focuses on discussing the key surgical and anesthetic strategies that contribute to achieving a successful and safe outcome for the patient.

CASE REPORT

The patient was a 48-year-old man who underwent an awake craniotomy operation in Al-Zahra Hospital in Isfahan in March 2023. The patient's weight was 82 kg, height 177 cm, and body mass index 26, with initial symptoms of seizures. After examination and imaging, the initial diagnosis of glioblastoma was made in the left parietal lobe [Figure 1].

The patient's seizures were controlled with valproic acid tablets 500 mg per day. In the preoperative evaluation, since the tumor was anatomically located close to the patient's motor and speech centers, after an interdisciplinary consensus involving the anesthesia and neurosurgery team, the decision was made to conduct an awake craniotomy for intraoperative monitoring, with the goal of preserving speech functions. And the move was made. This should be done during tumor removal. Several counseling sessions were conducted two weeks before the operation by the anesthesiologist with the patient and first-class companion, and the necessary explanations and the necessity of cooperation during the operation were explained to them. Prearranged questions and exercises were conducted to evaluate the patient’s cognitive and language abilities. Also, the patient had a history of cough and allergy during the preoperative examination, and a pulmonary consultation was performed and he was treated with medication. In cardiovascular evaluation and consultation, non-obstructive surgery was reported. Sensory and motor function and preoperative tests were completely normal.

Excess oxygen of 3 to 5 L/min was measured through the nasal cannula and exhaled carbon dioxide was measured through the capnograph. Then midazolam 3 mg and fentanyl 100 μg were administered intravenously. An arterial line was placed in the left radial artery under local anesthesia with lidocaine. In order to control the intracranial pressure, 5 vials of half percent hypertonic saline and 20 mg of Lasix were prescribed 30 minutes before administration. Conscious sedation with spontaneous breathing was initiated by targeted injection of dexmedetomidine at a dose of 0.7 μg per kg of body weight for ten minutes before scalp block and fixation of the head in a Mayfield frame. Then bilateral scalp nerves were blocked with bupivacaine 0.25% in 6 areas on each side including supraorbital, supratrochlear, oricotemporal, zygomatic and temporal, small and large occipital nerves with the amount of 2 cc in each area (total dose 24 cc) by an anesthesiologist. Dexamethasone 8 mg and ondansetron 4 mg were prescribed to prevent nausea and vomiting. After ten minutes, the dose of dexmedetomidine was reduced to 0.5 μg per kg body weight per hour. The surgery started without pain and with complete relaxation of the patient. During the operation, the patient opened his eyes by calling and sometimes by skin contact and fully executed the verbal and movement commands. His level of conscious sedation varied, but he remained conscious throughout the procedure.

Vital signs and hemodynamics were completely stable during the operation, and the patient was very calm and followed motor and verbal commands and had a good understanding of the instructions. In addition to being fully sedated, the patient was so aware of time and place during the operation that he asked us to tell his wife, who was outside the operating room, that he was fine and not to worry, which was a very interesting point. The amount of bleeding was calculated to be about 200 cc, and blood sugar and arterial blood gases were checked during the operation, which were reported to be normal. After the end of the operation, which lasted for 4 and a half hours, the patient was transferred to the recovery room, and after 2 hours of hospitalization in the recovery room and ensuring full

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