Awake Craniotomy: First-Year Experiences and Patient Perception

What helps patients to prepare for and cope during awake craniotomy? A prospective qualitative study

There is growing interest in awake craniotomies, but some clinicians are concerned that such procedures are poorly tolerated by patients. Therefore, we conducted a study to assess this phenomenon. In this prospective qualitative study, 68 patients who qualified for awake craniotomy were asked to complete the Hospital Anxiety and Depression Scale (HADS)-two days before the surgery and visual analogue scales (VAS) for pain and stress, two days before the surgery and again about two days after. In addition, after their surgery, they took part in a structured interview about what helped them prepare for and cope with the surgery. Most patients tolerated the awake surgery well, scoring low on stress and pain scales. They reported a lower level of stress during the surgery (when questioned afterwards) than before it. Intensity of stress before the surgery correlated negatively with age, positively with HADS anxiety score and positively with stress subsequently experienced during surgery. The level of stress during surgery was associated with stress experienced before the surgery, pain and HADS anxiety and depression scores. Severity of pain during the surgery was positively correlated with stress during surgery and HADS depression and anxiety scores before the surgery. There was no correlation between stress, pain, anxiety and depression and the location of the lesion. Patients have a high tolerance for awake craniotomy. Various factors have an impact on how well patients cope with the operation. Extensive preoperative preparation should be considered a key part of the procedure.

A Comparison of the Asleep-Awake Technique and Monitored Anesthesia Care During Awake Craniotomy: A 10-Year Analysis

Background Awake intracranial surgery with direct electrical stimulation (DES) is considered the gold standard for the resection of tumors affecting the eloquent areas of the brain. Awake craniotomy is a challenge for the anesthesiologist, as the patient's active cooperation is required throughout the operation. There are two frequent techniques, one is asleep-awake-asleep (AAA), and the other is called monitored anesthesia care (MAC). The AAA technique is the longer standing of the two and comprises general anesthesia followed by intraoperative awakening, which is necessary for neurological monitoring. In the present study, a comparison was made between the asleep-awake (AA) technique, a variation of the AAA anesthesia technique, and the MAC, which consists of a sedation that makes it possible to control pain and anxiety. Unlike the AA technique, the MAC does not involve the use of invasive airway devices. Objective The main objective was to contrast the two anesthetic management techniques for awake brain surgery used in our hospital. Methods A retrospective observational single-center study was performed consisting of a review of patient clinical records. The study sample comprised all patients above 18 years of age undergoing brain surgery through awake craniotomy between January 2013 and December 2022 at the Miguel Servet University Hospital (HUMS) in Zaragoza (Spain). Results Of the 79 patients included in the study, 39 were operated under AA anesthesia while the remaining 40 were operated under the MAC procedure. The main age of the participants was 52.8 years, the mean height was 169 cm, and the mean weight was 74.2 kg. No statistically significant differences were observed with respect to the patients' baseline characteristics, except for obesity which was more prevalent in the MAC group. In the MAC group, the airway was managed by means of nasal cannulas in all cases, with conversion to general anesthesia being required in only one instance. In the AA group, the laryngeal mask (LM) was used in 89.7% of the patients, and the endotracheal tube (ETT) in 10.3%. The surgical and anesthetic procedure duration was 15 and 20 minutes shorter in the MAC group, respectively. A reduction of almost 20 minutes in the anesthetic procedure and 15 minutes in the surgical one was observed. Tachycardia, desaturation, and airway complications were observed in four, five, and four patients respectively in the AA group but in none of the patients in the MAC group. The mean stay in the intensive care unit (ICU) and the mean postoperative hemoglobin levels between both groups were insignificant. Conclusions Both techniques analyzed in this study turned out to be equally safe and effective for brain tumor surgery in awake patients.

Simplifying the Technique of Awake Brain Surgery in a Condition of Less Equipped Neurosurgical Institution in Uzbekistan

Currently, awake craniotomy (AC) is one of the most often employed procedures to map and resect tumors in eloquent brain areas, avoiding the use of general anesthesia (GA) and thereby reducing anesthesia-related complications and cost of surgery. Resource limitations are one of the basic reasons for avoiding AC in low- and middle-income countries (LMICs). The aim of this study is to describe the simplified protocol of awake brain surgery that can be implemented in a limited financial setting in LMICs and to share our first experience. Twenty-five patients diagnosed with tumor of the left frontotemporal lobes, all involving Broca's and Wernicke's areas, were operated on using AC. Brain mapping was executed using mono- and bipolar direct electrical stimulation including cortical and subcortical (axonal) mapping profiles, investigating basically cortical language centers. Neither neuronavigation nor intraoperative magnetic resonance imaging (MRI) was utilized due to financial constraints. AC was performed successfully in 23 of 25 patients, achieving a near-total resection in 16 (69.5%) patients, subtotal resection in 4 patients (17.39%) patients, and partial resection in 3 (13.04%) patients. In two patients, due to psychological instability-agitation and fear during the awake phase-speech test was not technically possible, so they were reintubated by giving them GA. There was no mortality in the early or postoperative period. In spite of the absence of advanced pre- and intraoperative technologies such as intraoperative MRI and navigation systems, AC can be safely performed in LMICs. These tools along with intraoperative cortical mapping and language testing can guarantee better surgical outcomes and quality of life. However, our study confirms that omitting these tools does not make a huge difference in getting good results with AC and that AC is not absolutely impossible. AC can be performed successfully, preserving eloquent brain areas, with minimum and basic set of the armamentarium like system for cortical and subcortical intraoperative neurostimulation which provides cortical/subcortical brain mapping.

Stress, Anxiety, and Depression Associated With Awake Craniotomy: A Systematic Review

BACKGROUND

Awake craniotomy (AC) enables real-time monitoring of cortical and subcortical functions when lesions are in eloquent brain areas. AC patients are exposed to various preoperative, intraoperative, and postoperative stressors, which might affect their mental health.

OBJECTIVE

To conduct a systematic review to better understand stress, anxiety, and depression in AC patients.

METHODS

PubMed, Scopus, and Web of Science databases were searched from January 1, 2000, to April 20, 2022, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline.

RESULTS

Four hundred forty-seven records were identified that fit our inclusion and exclusion criteria for screening. Overall, 24 articles consisting of 1450 patients from 13 countries were included. Sixteen studies (66.7%) were prospective, whereas 8 articles (33.3%) were retrospective. Studies evaluated stress, anxiety, and depression during different phases of AC. Twenty-two studies (91.7%) were conducted on adults, and 2 studies were on pediatrics (8.3 %). Glioma was the most common AC treatment with 615 patients (42.4%). Awake-awake-awake and asleep-awake-asleep were the most common protocols, each used in 4 studies, respectively (16.7%). Anxiety was the most common psychological outcome evaluated in 19 studies (79.2%). The visual analog scale and self-developed questionnaire by the authors (each n = 5, 20.8%) were the most frequently tools used. Twenty-three studies (95.8%) concluded that AC does not increase stress, anxiety, and/or depression in AC patients. One study (4.2%) identified younger age associated with panic attack.

CONCLUSION

In experienced hands, AC does not cause an increase in stress, anxiety, and depression; however, the psychiatric impact of AC should not be underestimated.

Speech and Language Errors during Awake Brain Surgery and Postoperative Language Outcome in Glioma Patients: A Systematic Review

Awake craniotomy with direct electrical stimulation (DES) is the standard treatment for patients with gliomas in eloquent areas. Even though language is monitored carefully during surgery, many patients suffer from postoperative aphasia, with negative effects on their quality of life. Some perioperative factors are reported to influence postoperative language outcome. However, the influence of different intraoperative speech and language errors on language outcome is not clear. Therefore, we investigate this relation. A systematic search was performed in which 81 studies were included, reporting speech and language errors during awake craniotomy with DES and postoperative language outcomes in adult glioma patients up until 6 July 2020. The frequencies of intraoperative errors and language status were calculated. Binary logistic regressions were performed. Preoperative language deficits were a significant predictor for postoperative acute (OR = 3.42, p < 0.001) and short-term (OR = 1.95, p = 0.007) language deficits. Intraoperative anomia (OR = 2.09, p = 0.015) and intraoperative production errors (e.g., dysarthria or stuttering; OR = 2.06, p = 0.016) were significant predictors for postoperative acute language deficits. Postoperatively, the language deficits that occurred most often were production deficits and spontaneous speech deficits. To conclude, during surgery, intraoperative anomia and production errors should carry particular weight during decision-making concerning the optimal onco-functional balance for a given patient, and spontaneous speech should be monitored. Further prognostic research could facilitate intraoperative decision-making, leading to fewer or less severe postoperative language deficits and improvement of quality of life.

Patient-reported intraoperative experiences during awake craniotomy for brain tumors: a scoping review

Awake craniotomy (AC) is a neurosurgical procedure that may be used to excise tumors located in eloquent areas of the brain. The techniques and outcomes of AC have been extensively described, but data on patient-reported experiences are not as well known. To determine these, we performed a scoping review of patient-reported intraoperative experiences during awake craniotomy for brain tumor resection. A total of 21 articles describing 534 patients were included in the review. Majority of the studies were performed on adult patients and utilized questionnaires and interviews. Some used additional qualitative methodology such as grounded theory and phenomenology. Most of the evaluation was performed within the first 2 weeks post-operatively. Recollection of the procedure ranged from 0 to 100%, and most memories dealt with the cranial fixation device application, cranial drilling, and intraoperative mapping. All patients reported some degree of pain and discomfort, mainly due to the cranial fixation device and uncomfortable operative position. Most patients were satisfied with their AC experience. They felt that participating in AC gave them a sense of control over their disease and thought that trust in the treatment team and adequate pre-operative preparation were very important. Patients who underwent AC for brain tumor resection had both positive and negative experiences intraoperatively, but overall, majority had a positive perception of and high levels of satisfaction with AC. Successful AC depends not only on a well-conducted intraoperative course, but also on adequate pre-operative information and patient preparation.

Intraoperative panic attack in patients undergoing awake craniotomy: a retrospective analysis of risk factors

PURPOSE

Intraoperative anxiety is the most common psychological response of the patient during awake craniotomy. Psychological stress can trigger patient decline, resulting in failed awake craniotomy and significantly poor outcomes. This study aimed to identify the risk factors for panic attack (PA) during awake craniotomies.

METHODS

With the local ethics committee approval, we conducted a manual chart review of the medical record of patients who underwent consecutive awake craniotomies between November 1999 and October 2016 at Tokyo Women's Medical University. A total of 405 patients were identified and assigned to 2 groups based on the Diagnostic and Statistical Manual of Mental Disorders-V criteria: those that met the PA criteria (Group PA) and those that did not (Group non-PA). Patient characteristics and the incidence of the PA specifier were collected. The features of the two groups were statistically compared, and risk factors for PA occurrence were determined by regression analysis.

RESULTS

Sixteen of 405 patients met the diagnostic criteria of PA. Patients' characteristics were not statistically different between the groups. Multivariate logistic regression showed that intraoperative anxiety (p = 0.0002) and age younger than 39 years (as opposed to age >  = 39 years; p = 0.0328) were significantly associated with the occurrence of PA during awake craniotomy.

CONCLUSIONS

For patients undergoing awake craniotomy, intraoperative anxiety and age younger than 39 years were considered risk factors of PA. As PA often necessitates conversion to general anesthesia, intensive perioperative psychological support and pain management are required to achieve patient satisfaction and the surgical goal of awake craniotomy.

Awake surgery for lesions near eloquent brain under scalp block and clinical monitoring: experience of single center with limited resources

Background

Surgery of the brain tumors near eloquent areas carries the risk of either disabling neurological deficit or inadequate resection with bad prognosis in both situations. Awake surgery is the gold standard procedure for such lesions. However, it requires certain anesthetic drugs, advanced techniques, and trained teams that are not available in every neurosurgical institute. This work aims to evaluate safety, feasibility, and outcome of operating on patients with space occupying lesions near eloquent areas under scalp block being continuously examined by a neurologist through retrospective study of 20 cases with supratentorial lesions related to language or sensorimotor cortex.

Results

There were 12 males and 8 females with mean age 36.8 years. Forty percent of patients were presented by motor weakness. Tumors were related to motor cortex in 11 patients and to language areas in 9 patients. Mean operative time was 210 min. Gross or near total resection was achieved in 15cases, four cases had subtotal resection and biopsy only was done in 1 case. Two patients suffered from intraoperative seizures and conversion to general anesthesia was required in one patient.

Conclusion

Operating on tumors near eloquent brain areas under scalp block and continuous neurological examination during tumor resection proved to be effective in early detection and prevention of permanent major deficits especially in the developing countries with limited resources.

Analysis of risk factors and clinical sequelae of direct electrical cortical stimulation-induced seizures and afterdischarges in patients undergoing awake mapping

OBJECTIVE

Intraoperative stimulation has emerged as a crucial adjunct in neurosurgical oncology, aiding maximal tumor resection while preserving sensorimotor and language function. Despite increasing use in clinical practice of this stimulation, there are limited data on both intraoperative seizure (IS) frequency and the presence of afterdischarges (ADs) in patients undergoing such procedures. The objective of this study was to determine risk factors for IS or ADs, and to determine the clinical consequences of these intraoperative events.

METHODS

A retrospective chart review was performed for patients undergoing awake craniotomy (both first time and repeat) at a single institution from 2013 to 2018. Hypothesized risk factors for ADs/ISs in patients were evaluated for their effect on ADs and ISs, including tumor location, tumor grade (I-IV), genetic markers (isocitrate dehydrogenase 1/2, O 6-methylguanine-DNA methyltransferase [MGMT] promoter methylation, chromosome 1p/19q codeletion), tumor volume, preoperative seizure status (yes/no), and dosage of preoperative antiepileptic drugs for each patient. Clinical outcomes assessed in patients with IS or ADs were duration of surgery, length of stay, presence of perioperative deficits, and postoperative seizures. Chi-square analysis was performed for binary categorical variables, and a Student t-test was used to assess continuous variables.

RESULTS

A total of 229 consecutive patients were included in the analysis. Thirty-five patients (15%) experienced ISs. Thirteen (37%) of these 35 patients had experienced seizures that were appreciated clinically and noted on electrocorticography simultaneously, while 8 patients (23%) experienced ISs that were electrographic alone (no obvious clinical change). MGMT promoter methylation was associated with an increased prevalence of ISs (OR 3.3, 95% CI 1.2-7.8, p = 0.02). Forty patients (18%) experienced ADs. Twenty-three percent of patients (9/40) with ISs had ADs prior to their seizure, although ISs and ADs were not statistically associated (p = 0.16). The presence of ADs appeared to be correlated with a shorter length of stay (5.1 ± 2.6 vs 6.1 ± 3.7 days, p = 0.037). Of the clinical features assessed, none were found to be predictive of ADs. Neither IS nor AD, or the presence of either IS or AD (65/229 patients), was a predictor for increased length of stay, presence of perioperative deficits, or postoperative seizures.

CONCLUSIONS

ISs and ADs, while commonly observed during intraoperative stimulation for brain mapping, do not negatively affect patient outcomes.

[Sensations of patients and their satisfaction during awake craniotomy]

Awake craniotomy (AC) has gained fantastic popularity over the past years. This approach is no longer the destiny of only highly specialized neurosurgical centers. Technical features of AC are completely developed. However, certain aspects of patients' sensations and their satisfaction are still unclear. The review is devoted to these issues. It was shown that AC is positively evaluated by the vast majority of patients. Many patients would choose this technique for redo surgery. However, there are certain important details that can adversely affect satisfaction of patients. Thus, these features should be considered in AC.

Awake Craniotomy in Low-Resource Settings: Findings from a Retrospective Cohort in the Philippines

BACKGROUND

Awake craniotomy is a technique used to maximize resection of lesions in eloquent areas of the brain and preserve function. Although its use in high-income centers is well documented for tumors and vascular lesions, reports of its use in low-middle-income countries are limited. There are no published series from the Philippines.

METHODS

We performed a retrospective review of all patients who underwent awake craniotomy at a tertiary referral center in Manila, Philippines from 2010 to 2019. Data on demographics, clinical features, diagnoses, intraoperative and postoperative complications, and outcomes were collected. Regression analyses were performed to correlate use of intraoperative adjuncts with outcome measures (extent of resection, complication rate, neurologic status after surgery and on last follow-up, and in-hospital mortality).

RESULTS

A total of 65 patients were included in the cohort, who had a male predilection (60%) and a mean age at diagnosis of 40.4 years. The most common indication was tumor excision (90%), followed by excision of arteriovenous malformations (5%) and cavernomas (3%). Of the tumors, the most common histopathologic diagnosis was low-grade glioma (48%). The intraoperative complication rate was 13.8%, with the most common complication being patient intolerance. Gross total excision rate for tumors was 78.3%. Univariate analysis showed that use of a cortical stimulator was associated with improved neurologic status on last follow-up (P = 0.0471).

CONCLUSIONS

Our experience shows that awake craniotomy is feasible in low-middle-income country settings and is safe and effective for excision of tumors, arteriovenous malformations, and cavernomas.

The Stony Brook awake craniotomy protocol: A technical note

Most current awake craniotomy techniques utilize unnecessarily complicated airway management, and cause discomfort to the patients during the awake phase of the surgery. Our manuscript is written to discuss the neurosurgical and anesthetic techniques that we have developed to optimize awake craniotomy techniques at Stony Brook University Medical Center. We used the frameless Brainlab™ skull-mounted array for stereotactic navigation. Rigid fixation of the skull was avoided. General anesthesia with established airway was used during the "asleep" phase of the surgery. Following the removal of the bone flap and the opening of the dura, the patients were woken up, and the established airway was removed. Cortical mapping was performed to establish a safe entry zone for tumor removal. While the tumors were being removed, we continued motor examination and casual conversation with the patients to ensure safety. Patients were sedated during the remaining phase of the surgery until skin closure. No patient exhibited any neurological deficits or adverse anesthesia outcomes during the postoperative period. The protocol we developed avoids rigid skull fixation and emphasizes flexible intraoperative planning, thereby maximizing patient and physician comfort while allowing for successful tumor resection.

Conscious Experience and Psychological Consequences of Awake Craniotomy

BACKGROUND

Experiencing cranial surgery under awake conditions may expose patients to considerable psychological strain.

METHODS

This study aimed to investigate the occurrence and course of psychological sequelae following awake craniotomy (AC) for brain tumors in a series of 20 patients using a broad, validated psychological assessment preoperatively, intraoperatively, postoperatively and a standardized follow-up of 3 months. In addition, the association of the preoperative psychological condition (including, but not limited to, anxiety and fear) with perioperative pain perception and interference was assessed.

RESULTS

AC did not induce any shift in the median levels of anxiety, depression, and stress symptoms already present prior to the procedure. Furthermore, anxiety and depression were all moderately to strongly associated over time (all P < 0.05). Stress symptoms also correlated positively over all times of measurement. Stress 3 days after surgery was strongly associated with stress 3 months after surgery (P < 0.001), whereas the correlation between preoperative and immediate postoperative stress showed a statistical trend (P = 0.07). Preoperative fear was not related to intraoperative pain, but to pain and its interference with daily activity on the third postoperative day (P < 0.001 and P < 0.01, respectively).

CONCLUSIONS

Postoperative psychological symptoms clearly correlated with their corresponding preoperative symptoms. Thus, mental health was not negatively affected by the AC experience in our series. Intraoperative fear and pain were not related to the preoperative psychological condition. However, preoperative fear and anxiety were positively related with pain and its interference with daily activity in the immediate postoperative period.

Who Needs Sleep? An Analysis of Patient Tolerance in Awake Craniotomy

BACKGROUND

Awake craniotomy (AC) is generally a safe and effective procedure; however, a small but not insignificant portion of cases are aborted due to patient intolerance of the awake portion of surgery. There is not yet a firm understanding of what characteristics indicate patient tolerance or failure of AC.

METHODS

We retrospectively reviewed a single-surgeon database of patients treated by AC over a 5-year period. Charts were reviewed for demographic, clinical, and operative characteristics, including anesthetic administration during the awake portion of surgery. Statistical analysis was performed to determine which factors predicted patient tolerance or failure.

RESULTS

Our study cohort comprised 120 patients with an average age of 56.0 ± 15.2 years. A majority of patients were male (55.8%). The most common surgical indication was tumor (95.8%), with gliobastoma as the most common diagnosis (43.3%). Male sex predicted surgical tolerance on univariate analysis (P = 0.015). Remifentanil administration was associated with surgical failure on univariate analysis (P = 0.068), and also predicted failure on multivariate analysis (P = 0.030). Preoperative seizure, ketamine administration, and right-sided surgery each predicted patient tolerance, but did not achieve statistical significance. Similarly, respiratory comorbidity was associated with surgical failure, but did not achieve significance.

CONCLUSIONS

AC remains an effective treatment option; the majority of patients tolerate the procedure without issue. Male patients have lower rates of surgical failure, whereas remifentanil administration may increase failure rate.

Anxiety, memories and coping in patients undergoing intracranial tumor surgery

OBJECTIVES

The diagnosis and the surgical removal of a brain tumor can have serious impact on the quality of life of a patient. The question rises, whether having more or just less memories of the procedure is better for coping with such an event. Furthermore, for preoperative information of future patients it is important to know how patients process their emotions and memories. The primary objective of this study was to investigate the link between preoperative anxiety, the perioperative experience and the quantity and quality of postoperative memories in patients who underwent intracranial tumor surgery.

PATIENTS AND METHODS

This study was a retrospective observational study; all patients who underwent intracranial tumor surgery at the Erasmus Medical Centre Rotterdam between January 1st 2014 and December 31st 2015 were identified. In May 2016, all patients who were not registered as deceased were sent a questionnaire about their anxieties, perceptions and memories of the perioperative period.

RESULTS

In total 476 patients were included. 272 patients responded, which resulted in a response rate of 57.14%. In the general anesthesia (GA) group there was a significant negative correlation between anxiety in the perioperative period and the quantity and quality of memories. In the awake craniotomy group, there was a significant negative correlation between anxiety after the operation and the quantity of memories.

CONCLUSION

Patients in the GA group who experienced anxiety in the perioperative period had less quantity and quality of memories and less patient satisfaction. Patients in the AC group who experienced anxiety after the operation had only a lower quantity of the memory; there was no correlation with patient satisfaction.

Quality and Quantity of Memories in Patients Who Undergo Awake Brain Tumor Resection

BACKGROUND

Awake craniotomy is performed with increasing frequency for brain tumor surgery in eloquent areas; however, little is known about patients' memories of this procedure. Here we retrospectively analyzed the quality and quantity of memories in a series of patients treated following a standardized protocol.

METHODS

We treated 61 consecutive patients within 3 years, 48 of whom were alive when the study was performed. Each of these patients received a questionnaire eliciting information about their perioperative memories and perceptions. The perioperative process was broken down into steps, and for each step the patient was to judge the quantity (nothing-everything) and quality (very negative-very positive) of his or her memories.

RESULTS

Thirty-six of the 48 patients completed the questionnaire (75%). The quantity of memories was quite incomplete, even for intraoperative moments when patients were awake and cooperative. On average, the quality of memories was neutral or positive. A higher quantity of memories was associated with a higher quality of memories. The most commonly reported sources of discomfort were placement of the Mayfield clamp, followed by laying on the operating room table with movement restriction, and irritation by the urinary catheter in situ.

CONCLUSIONS

Awake craniotomy can be performed following our protocol in such a way that it is experienced as (very) comfortable. However, there are moments of discomfort, which can be managed by the team. Extensive preoperative preparation may be considered a crucial part of the procedure. Less amnesia seems to improve patient satisfaction. The results of this study can help guide protocol optimization, expectation management, and information for future patients.

Optical Neuronavigation without Rigid Head Fixation During Awake Surgery

OBJECTIVE

Optical neuronavigation without rigid pin fixation of the head may lead to inaccurate results because of the patient's movements during awake surgery. In this study, we report our results using a skull-mounted reference array for optical tracking in patients undergoing awake craniotomy for eloquent gliomas.

METHODS

Between March 2013 and December 2014, 18 consecutive patients (10 men, 8 women) with frontotemporal (n = 16) or frontoparietal (perirolandic; n = 2) lesions underwent awake craniotomy without rigid pin fixation. All patients had a skull-mounted reference array for optical tracking placed on the forehead. Accuracy of navigation was determined with pointer tip deviation measurements on superficial and bony anatomic structures. Good accuracy was defined as a tip deviation <2 mm.

RESULTS

Gross total resection (>98%) was achieved in 7 patients (38%); >90% of tumor was resected in 8 patients (44%). In 3 patients, only subtotal resection or biopsy was performed secondary to stimulation results. In all patients, good accuracy of the optical neuronavigation system could be demonstrated without intraoperative peculiarities or complications. The reference array had to be repositioned because of loosening in 1 patient. Neuronavigation could be reliably applied to support stimulation-based resection.

CONCLUSIONS

A skull-mounted reference array is a simple and safe method for optical neuronavigation tracking without rigid pin fixation of the patient's head.