Awake craniotomy is a procedure in which a surgeon temporarily removes a piece of skull to access the brain while the patient remains awake.1 The advantage of an awake craniotomy is that it allows the physician to ensure that the patient’s critical functions, such as language and movement, remain intact, despite manipulation of the brain.1 For example, the surgeon may want to evaluate a patient’s motor functions throughout surgery in order to prevent causing permanent disability.2 Awake craniotomies are frequently used for extraction of brain tumors such as gliomas, which occur in the frontal and temporal lobes near areas that control speech and motor function.1 While brain tissue is not sensitive to pain, anesthesia providers are responsible for sedation before surgery; waking up the patient during the operation; and numbing the muscles, skin and bone surrounding the surgical area.1 Anesthesiology practitioners must be familiar with the anesthetic techniques available for awake craniotomy and the efficacy of these techniques.
Anesthesia provision for awake craniotomy is a complex endeavor. For one, such a procedure is associated with significant anxiety, and some patients may be reluctant to undergo surgery while awake.3 Thus, the anesthesiologist, surgeon and other health care professionals should establish a good relationship with the patient before surgery in order to optimize patient comfort.3 The anesthesia provider may also choose to premedicate patients who have conditions such as epilepsy or are of young age.3 However, the clinician must avoid providing medications that could impair neurocognitive function or delay the intraoperative wake-up period.3 During the procedure, the patient will require distinct anesthetic management in the pre-awake and awake stages.3 A study by Eseonu et al. found that monitored anesthesia care (MAC), using an unprotected airway, and the asleep-awake-asleep (AAA) technique, using a partially or totally protected airway, were both safe and effective.4 The literature show a variety of options for patient positioning,3 airway management5 and anesthetic or analgesic agents6 throughout the awake and asleep phases. According to a recent review by Sewell and Smith, there is no evidence that one anesthetic approach is better than the others, and failure of awake craniotomy is not associated with anesthetic technique.6 Anesthesia providers may use different strategies within and among patients depending on institution policy and patient-related factors.
Despite the widespread use of awake craniotomy, the evidence is mixed on its advantages over brain surgery under general anesthesia.3 For example, a study by Gravesteijn et al. on insular glioma surgery found no differences between awake craniotomy and craniotomy under general anesthesia in extent of resection, neurological outcomes or patient survival.7 Given that awake craniotomy was more challenging for patients and their caregivers after surgery, the authors suggest that awake craniotomy may not be the better solution.7 A different study by Eseonu et al. found that awake craniotomy had advantages over general anesthesia for perirolandic glioma resection, with more frequent total resections, better postoperative function and shorter hospitalizations.8 A trial by Sacko et al. showed that awake craniotomy was associated with sooner discharge than craniotomy under general anesthesia, as well as maximal removal of lesions and low neurological complication rates.9 Furthermore, Ohtaki et al. found that depth of anesthesia was related to motor response during awake craniotomy, with awake patients producing the most reliable measurements and allowing for best interpretation of motor function.2 Though awake craniotomy may have several advantages over surgery under general anesthesia, it may not be useful for all types of tumor resections.
Anesthesiologists are faced with decisions regarding anesthetic drugs, patient positioning and sleep-wake techniques during awake craniotomy. Additionally, anesthesia providers must consider the possibility of using general anesthesia for craniotomies in specific situations. More studies are needed to establish evidence-based practices in anesthesia for awake craniotomy. Once more data are available, future policy should standardize awake craniotomy anesthetic techniques across institutions.
References
1) Raeke M. Awake craniotomy for brain tumors: 8 questions. Cancerwise April 24, 2018; https://www.mdanderson.org/publications/cancerwise/awake-craniotomy-for-brain-tumors–8-questions.h00-159223356.html.
2) Ohtaki S, Akiyama Y, Kanno A, et al. The influence of depth of anesthesia on motor evoked potential response during awake craniotomy. Journal of Neurosurgery JNS. 2017;126(1):260–265.
3) Meng L, McDonagh DL, Berger MS, Gelb AW. Anesthesia for awake craniotomy: A how-to guide for the occasional practitioner. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2017;64(5):517–529.
4) Eseonu CI, ReFaey K, Garcia O, John A, Quiñones-Hinojosa A, Tripathi P. Awake Craniotomy Anesthesia: A Comparison of the Monitored Anesthesia Care and Asleep-Awake-Asleep Techniques. World Neurosurgery. 2017;104:679–686.
5) Sivasankar C, Schlichter RA, Baranov D, Kofke WA. Awake Craniotomy: A New Airway Approach. Anesthesia & Analgesia. 2016;122(2):509–511.
6) Sewell D, Smith M. Awake craniotomy: Anesthetic considerations based on outcome evidence. Current Opinion in Anesthesiology. 2019;32(5):546–552.
7) Gravesteijn BY, Keizer ME, Vincent AJPE, Schouten JW, Stolker RJ, Klimek M. Awake craniotomy versus craniotomy under general anesthesia for the surgical treatment of insular glioma: choices and outcomes. Neurological Research. 2018;40(2):87–96.
8) Eseonu CI, Rincon-Torroella J, ReFaey K, et al. Awake Craniotomy vs Craniotomy Under General Anesthesia for Perirolandic Gliomas: Evaluating Perioperative Complications and Extent of Resection. Neurosurgery. 2017;81(3):481–489.
9) Sacko O, Lauwers-Cances V, Brauge D, Sesay M, Brenner A, Roux F-E. Awake Craniotomy vs Surgery Under General Anesthesia for Resection of Supratentorial Lesions4. Neurosurgery. 2011;68(5):1192–1199.
