This series includes a retrospective study of 20 cases; twelve males and 8 females operated between January 2015 and June 2018. All patients had supratentorial lesions related to language or motor cortex. The ethical approval of this study was obtained from the research ethics committee. Consent of publication was obtained from patients whose photos or radiology images are found in the paper.
Absolute contraindications to awake surgery in our institute include patients with infratentorial lesions, uncooperative patients (children and psychiatric patients), and morbid obese patients with expected obstructive sleep apnea. Relative contraindications included chronic cough, nausea, patients with anticipated difficult airway, patients with uncontrolled seizures, patients with severe dysphasia (more than 25% naming errors), and those with motor weakness who cannot move their limbs against gravity especially if they did not improve after dehydrating measures.
Preoperative preparation
All patients were subjected to detailed neurological examination, airway assessment, and routine lab investigations.
Brain CT (Aquilion One 320 slice, Toshiba America Medical System, Tustin, USA), MRI with contrast, and MRI tractography (Vantage Titan 1.5 T, Toshiba America Medical Systems, Tustin, USA) were done in all cases to clearly demarcate the lesion and its relation to eloquent brain. Functional MRI with BOLD technique was done in some cases to better localize eloquent cortex.
Patients’ data and images were carefully studied and discussed between the surgeon, anesthesiologist, and neurologist. The specific requirements in each case were fulfilled individually. All the OR team including the nurses and technicians were prepared to work in a very quiet environment.
Once the decision to operate under scalp block was made, informed consent was taken in all operations declaring the procedures advantages, difficulties, and alternatives. Some patients were shown operative videos to be psychologically prepared to their mission. Baseline sensorimotor and language assessment including naming, reading, spelling, and calculation was performed 24–48 h before surgery and the test was modified to exclude difficult tasks for the patient to be avoided during intraoperative monitoring.
Preoperative medications in the form of steroids (dexamethasone 8 mg), benzodiazepine (bromazepam 3 mg), and antiepileptic (phenytoin 500 mg) were given to the patient the night before operation. Antibiotics (ceftriaxone 1 g) and antiemetic (ondansetron 8 mg) were given 1 h before skin incision.
Operative technique
All cases were operated under scalp block using local anesthetic throughout the whole procedure. In our center, ultrashort acting opioids such as remifentanil and dexmedetomidine were not available at the time of study. Alternative short acting opioids such as propofol (75–250 μg/kg/min) and fentanyl (.5-1 μg/kg/h) were given by the anesthesiologist when highly mandatory as they should to be stopped 20 min before testing.
The tumor location was calculated from patient images and marked on the scalp and the related functional brain areas were also marked and their relation to the tumor was studied carefully. The site of the planned skin incision was marked (Fig. 1).
A local anesthetic mixture of 30 ml of 0.25% bupivacaine and 0.5% lidocaine with 20 ml saline adrenaline (1:200,000) and 23-G needle were used for scalp block. The supraorbital notch was firstly injected (supraorbital nerve block) then the needle was redirected medially to block the supratrochlear nerve. The zygomaticotemporal nerve was blocked 1 cm lateral to the outer canthus and 1 cm above the zygomatic arch; then, the auriculotemporal nerve was blocked just above the auricle and beside the parietal branch of superficial temporal artery, we do not inject at the level of the tragus to avoid facial anesthesia. The greater auricular nerve was blocked posterior to the ear at the level of the tragus. Lastly, the greater and lesser occipital nerves were blocked along the superior nuchal line anterior and posterior to the occipital artery. The same steps were repeated on the contralateral side. We also injected local anesthesia at the site of planned skin incision (Fig. 1).
The three-pin head frame (Mayfield 2000, Integra™, Cincinnati, USA) was prepared and sites of head ring pins were marked and infiltrated with local anesthesia. Patient positioning was fashioned according to the tumor location. In all cases, the patient should have comfortable position with head elevated 20° above the heart level. Surgical draping was fashioned to allow continuous direct access between the anesthesiologist and the patient (Fig. 1). The contralateral extremity should be exposed for motor evaluation and the patient should have easy visual axis to a computer screen projecting images for speech monitoring (Fig. 2).
The patient was kept warmed and covered by a blanket to avoid shivering and O2 delivered via nasal cannula or face mask. Patient monitoring by neuroanesthesia was made by noninvasive blood pressure recording, cardiac monitors, pulse oximetry, end expiratory CO2 concentration, temperature, and urine output.
Skin incision and craniotomy were made in the ordinary manner. The dura was infiltrated with local anesthesia with an insulin syringe at the site of durotomy. Before durotomy, the patient was asked to take multiple deep breaths (hyperventilation) to decrease the intracranial pressure and at the same time to check if the patient is cooperative. Extra dose of manitol was given if needed.
In our center, we had neither intraoperative neurophysiological monitoring nor trained neurophysiologist; we could not perform motor evoked potential, electromyography, or electrocorticography. So we depended on direct electrical stimulation using bipolar stimulator (ISIS, Inomed, Emmendingen, Germany) delivering biphasic waves in 4 s trains at 60 HZ at low current < 5 mA .We started stimulation at 1.5 mA and increase at 0.5 m increments each time and watched for contralateral limb movement, speech arrest during counting from 1 to 30, anomia or alexia of projected images and words, respectively. We did not stimulate above 5 mA to avoid seizures. If mapping was positive for eloquent cortex, we would mark this area with a piece of colored gloves or cottonoid and keep surgery at least 1 cm away from it (Fig. 2). If no response was encountered till 5 mA, we would consider mapping negative. We use the same stimulation technique for suspected subcortical eloquent areas.
Microscopic surgery under highest possible magnification (Leica 525 OH4, Leica Microsystems, Wetzlar, Germany) was used to help clear demarcation of tumor tissue and its differentiation from normal brain tissue. The site of cortical incision was determined after neuroimages revision. Natural transsulcual corridors were followed when feasible to minimize cortical trauma.
The patient must be fully conscious, alert, and continuously examined by the neurologist till the tumor resection is finished and hemostasis completed. Language was assessed by asking the patient to count from 1 to 30 or speak letters of alphabets and waiting for points of speech arrest. Also by naming objects, or reading and waiting for points of anomia or alexia. Motor power was assessed by asking the patient to perform simple movements. It can also be continuously monitored by asking the patient to manipulate a rosary in his hand and watching for movement cessation or falling of the rosary from the patient hand (Fig. 2).
If any early neurological affection was noticed, manipulation was stopped, an extradose of steroid was given, and irrigation with warm saline was done waiting till neurological deficit disappears. The suspected area is examined by direct electrical stimulation using the same technique mentioned before, and then we could continue the procedure. If intraoperative seizures occurred, we stop brain manipulation and irrigate with cold ringer till fits stop.
After tumor resection, careful hemostasis was done and the patient was examined again to exclude any neurological deficit. Wound was closed and the Mayfield was removed and the patient was examined one more time before leaving the OR.
Follow-up CT brain with contrast was routinely asked the next day and the patient could go home 48 h after surgery. Follow-up MRI brain with contrast was performed within 3 months later (Figs. 3, 4, 5, and 6).