Wireless modification of the intraoperative examination monitor for awake surgery

Theory and evidence-base for a digital platform for the delivery of language tests during awake craniotomy and collaborative brain mapping

Objectives

Build the theoretical and evidence-base for a digital platform (map-OR) which delivers intraoperative language tests during awake craniotomy and facilitates collaborative sharing of brain mapping data.

Design

Mixed methodology study including two scoping reviews, international survey, synthesis of development guiding principles and a risk assessment using failure modes and effects analysis.

Setting

The two scoping reviews examined the literature published in the English language. International survey was completed by members of awake craniotomy teams from 14 countries.

Main outcome measures

Scoping review 1: number of technologies described for language mapping during awake craniotomy. Scoping review 2: barriers and facilitators to adopting novel technology in surgery. International survey: degree of language mapping technology penetration into clinical practice.

Results

A total of 12 research articles describing 6 technologies were included. The technologies required a range of hardware components including portable devices, virtual reality headsets and large integrated multiscreen stacks. The facilitators and barriers of technology adoption in surgery were extracted from 11 studies and mapped onto the 4 Unified Theory of Acceptance and Use of Technology constructs. A total of 37 awake craniotomy teams from 14 countries completed the survey. Of the responses, 20 (54.1%) delivered their language tests digitally, 10 (27.0%) delivered tests using cards and 7 (18.9%) used a combination of both. The most commonly used devices were tablet computers (67.7%; n=21) and the most common software used was Microsoft PowerPoint (60.6%; n=20). Four key risks for the proposed digital platform were identified, the highest risk being a software and internet connectivity failure during surgery.

Conclusions

This work represents a rigorous and structured approach to the development of a digital platform for standardized intraoperative language testing during awake craniotomy and for collaborative sharing of brain mapping data.

Trial registration number

Scoping review protocol registrations in OSF registries (scoping review 1: osf.io/su9xm; scoping review 2: osf.io/x4wsc).

Localization and symptoms associated with removal of negative motor area during awake surgery

BACKGROUND

In awake surgery, cortical mapping may identify the negative motor area (NMA). However, since speech arrest occurs regardless of whether the NMA or the frontal language area (FLA) is stimulated, the presence of speech arrest alone does not distinguish the NMA from the FLA. Furthermore, the exact location and function of the NMA is not well understood. The purpose of this study was to more accurately locate the NMA in a group of cases in which the NMA and FLA could be identified in different brain gyri, and to describe symptoms in cases in which the NMA was removed.

METHODS

There were 18 cases of awake surgery at our institution between 2000 and 2013 in which cortical stimulation allowed identification of FLA and NMA in separate brain gyri. In these cases, the pre- and post-removal mapping results were projected onto a 3D model postoperatively. We investigated the symptoms and social rehabilitation in a case in which the tumour invaded the same brain gyrus as the NMA and the NMA had to be resected in combination with the tumour.

RESULTS

In cases where the NMA and FLA could be identified in different brain gyri, NMA was localized inferior to the precentral gyrus in all cases. In four cases where NMA was removed with the tumour, apraxia of speech was observed during the surgery; the same symptoms persisted after it, but it improved within a few months, and the patients were able to return to work.

CONCLUSION

In cases where NMA and FLA could be identified separately by awake mapping, the NMA was commonly localized inferior to the precentral gyrus. When NMAs were resected in combination with tumour invasion, they did not lead to serious, long-term complications.

Combining Pre-operative Diffusion Tensor Images and Intraoperative Magnetic Resonance Images in the Navigation Is Useful for Detecting White Matter Tracts During Glioma Surgery

Purpose

We developed a navigation system that superimposes the fractional anisotropy (FA) color map of pre-operative diffusion tensor imaging (DTI) and intraoperative magnetic resonance imaging (MRI). The current study aimed to investigate the usefulness of this system for neurophysiological monitoring and examination under awake craniotomy during tumor removal.

Method

A total of 10 glioma patients (4 patients with right-side tumors; 5 men and 5 women; average age, 34 years) were evaluated. Among them, the tumor was localized to the frontal lobe, insular cortex, and parietal lobe in 8, 1, and 1 patient, respectively. There were 3 patients who underwent surgery on general anesthesia, while 7 patients underwent awake craniotomy. The index of DTI anisotropy taken pre-operatively (magnetic field: 3 tesla, 6 motion probing gradient directions) was analyzed as a color map (FA color map) and concurrently co-registered in the intraoperative MRI within the navigation. In addition to localization of the bipolar coagulator and the cortical stimulator for brain mapping on intraoperative MRI, the pre-operative FA color map was also concurrently integrated and displayed on the navigation monitor. This white matter nerve functional information was confirmed directly by using neurological examination and referring to the electrophysiological monitoring.

Results

Intraoperative MRI, integrated pre-operative FA color map, and microscopic surgical view were displayed on one screen in all 10 patients, and white matter fibers including the pyramidal tract were displayed as a reference in blue. Regarding motor function, motor-evoked potential was monitored as appropriate in all cases, and removal was possible while directly confirming motor symptoms under awake craniotomy. Furthermore, the white matter fibers including the superior longitudinal fasciculus were displayed in green. Importantly, it was useful not only to localize the resection site, but to identify language-related, eye movement-related, and motor fibers at the electrical stimulation site. All motor and/or language white matter tracts were identified and visualized with the co-registration and then with an acceptable post-operative neurological outcome.

Conclusion

Co-registering an intraoperative MR images and a pre-operative FA color map is a practical and useful method to predict the localization of critical white matter nerve functions intraoperatively in glioma surgery.

Integrated datasets of normalized brain with functional localization using intra-operative electrical stimulation

PURPOSE

The purpose of this study was to transform brain mapping data into a digitized intra-operative MRI and integrated brain function dataset for predictive glioma surgery considering tumor resection volume, as well as the intra-operative and postoperative complication rates.

METHODS

Brain function data were transformed into digitized localizations on a normalized brain using a modified electric stimulus probe after brain mapping. This normalized brain image with functional information was then projected onto individual patient's brain images including predictive brain function data.

RESULTS

Log data were successfully acquired using a medical device integrated into intra-operative MR images, and digitized brain function was converted to a normalized brain data format in 13 cases. For the electrical stimulation positions in which patients showed speech arrest (SA), speech impairment (SI), motor and sensory responses during cortical mapping processes in awake craniotomy, the data were tagged, and the testing task and electric current for the stimulus were recorded. There were 13 SA, 7 SI, 8 motor and 4 sensory responses (32 responses) in total. After evaluation of transformation accuracy in 3 subjects, the first transformation from intra- to pre-operative MRI using non-rigid registration was calculated as 2.6 ± 1.5 and 2.1 ± 0.9 mm, examining neighboring sulci on the electro-stimulator position and the cortex surface near each tumor, respectively; the second transformation from pre-operative to normalized brain was 1.7 ± 0.8 and 1.4 ± 0.5 mm, respectively, representing acceptable accuracy.

CONCLUSION

This image integration and transformation method for brain normalization should facilitate practical intra-operative brain mapping. In the future, this method may be helpful for pre-operatively or intra-operatively predicting brain function.

Quantitative Evaluation of Efficacy of Intraoperative Examination Monitor for Awake Surgery

BACKGROUND

When brain tumors are located near the language area, a test to assess language function is required. During the test, it is practical to display combined information obtained from all the equipment so that the surgeon can confirm the patient's response to the tasks. We developed the intraoperative examination monitor for awake surgery (IEMAS) mainly to combine all information so that the language function test could be performed efficiently. The IEMAS has proved to be useful in clinical settings; however, no quantitative evaluation has been performed. This study aimed to demonstrate the clinical usefulness of the IEMAS through comparison of cases with and without IEMAS use in language function test simulation.

METHODS

The language function test simulator was created to eliminate any uncertain factors, such as symptoms, which vary among patients. Neurosurgeons participated in the test, and the usefulness of the IEMAS was investigated. We analyzed test duration and number of information exchanges between surgeon and examiner.

RESULTS

Total test duration with IEMAS use was significantly shorter than without IEMAS use (116.1 ± 23.1 seconds vs. 147.8 ± 48.7 seconds; P < 0.02). The number of information exchanges between surgeon and examiner was significantly lower with IEMAS use than without IEMAS use (0.2 ± 0.6 times vs. 16.1 ± 15.6 times; P < 0.02).

CONCLUSIONS

We compared cases with and without IEMAS use. Total test duration decreased with IEMAS use, and number of information exchanges was reduced, thus demonstrating the usefulness of the IEMAS.

Strategy of Surgical Resection for Glioma Based on Intraoperative Functional Mapping and Monitoring

A growing number of papers have pointed out the relationship between aggressive resection of gliomas and survival prognosis. For maximum resection, the current concept of surgical decision-making is in “information-guided surgery” using multimodal intraoperative information. With this, anatomical information from intraoperative magnetic resonance imaging (MRI) and navigation, functional information from brain mapping and monitoring, and histopathological information must all be taken into account in the new perspective for innovative minimally invasive surgical treatment of glioma. Intraoperative neurofunctional information such as neurophysiological functional monitoring takes the most important part in the process to acquire objective visual data during tumor removal and to integrate these findings as digitized data for intraoperative surgical decision-making. Moreover, the analysis of qualitative data and threshold-setting for quantitative data raise difficult issues in the interpretation and processing of each data type, such as determination of motor evoked potential (MEP) decline, underestimation in tractography, and judgments of patient response for neurofunctional mapping and monitoring during awake craniotomy. Neurofunctional diagnosis of false-positives in these situations may affect the extent of resection, while false-negatives influence intra- and postoperative complication rates. Additionally, even though the various intraoperative visualized data from multiple sources contribute significantly to the reliability of surgical decisions when the information is integrated and provided, it is not uncommon for individual pieces of information to convey opposing suggestions. Such conflicting pieces of information facilitate higher-order decision-making that is dependent on the policies of the facility and the priorities of the patient, as well as the availability of the histopathological characteristics from resected tissue.

Evaluation of Language Function under Awake Craniotomy

Awake craniotomy is the only established way to assess patients' language functions intraoperatively and to contribute to their preservation, if necessary. Recent guidelines have enabled the approach to be used widely, effectively, and safely. Non-invasive brain functional imaging techniques, including functional magnetic resonance imaging and diffusion tensor imaging, have been used preoperatively to identify brain functional regions corresponding to language, and their accuracy has increased year by year. In addition, the use of neuronavigation that incorporates this preoperative information has made it possible to identify the positional relationships between the lesion and functional regions involved in language, conduct functional brain mapping in the awake state with electrical stimulation, and intraoperatively assess nerve function in real time when resecting the lesion. This article outlines the history of awake craniotomy, the current state of pre- and intraoperative evaluation of language function, and the clinical usefulness of such functional evaluation. When evaluating patients' language functions during awake craniotomy, given the various intraoperative stresses involved, it is necessary to carefully select the tasks to be undertaken, quickly perform all examinations, and promptly evaluate the results. As language functions involve both input and output, they are strongly affected by patients' preoperative cognitive function, degree of intraoperative wakefulness and fatigue, the ability to produce verbal articulations and utterances, as well as perform synergic movement. Therefore, it is essential to appropriately assess the reproducibility of language function evaluation using awake craniotomy techniques.

Intraoperative functional mapping and monitoring during glioma surgery

Glioma surgery represents a significant advance with respect to improving resection rates using new surgical techniques, including intraoperative functional mapping, monitoring, and imaging. Functional mapping under awake craniotomy can be used to detect individual eloquent tissues of speech and/or motor functions in order to prevent unexpected deficits and promote extensive resection. In addition, monitoring the patient’s neurological findings during resection is also very useful for maximizing the removal rate and minimizing deficits by alarming that the touched area is close to eloquent regions and fibers. Assessing several types of evoked potentials, including motor evoked potentials (MEPs), sensory evoked potentials (SEPs) and visual evoked potentials (VEPs), is also helpful for performing surgical monitoring in patients under general anesthesia (GA). We herein review the utility of intraoperative mapping and monitoring the assessment of neurological findings, with a particular focus on speech and the motor function, in patients undergoing glioma surgery.

Correlation between surgical manipulations and the variation of surgeon's heart rate in brain surgery: technical note

For improvement of surgical performance and safety, we record surgeries by video cameras. However, analysis of the video records is time consuming. To help this task, we are developing methods to automatically mark up significant time points in the surgery. As a possible mean for the marking, we focused on the surgeon's heart rate. During a craniotomy of an intracranial glioma, we recorded the surgeon's electrocardiogram using a telemeter and measured the R-to-R interval (RRI). We detected the stable state of heart rate as a peak-to-peak RRI of less than 5% of the mean of RRI data from 15 consecutive heartbeats. We also quantified the frequency of brain touches by the surgeon under the surgical microscope. We examined the association between the stability of surgeon's heart rate and the brain touches using a chi-square test. As the result, the stable state of surgeon's heart rate was associated with the brain touches (p < 0.05, odds ratio 5.1). We edited a one-minute digest video of the surgery based on only the heart rate data, and it was sufficient to understand how the surgery was preceded.