Resting state functional connectivity magnetic resonance imaging integrated with intraoperative neuronavigation for functional mapping after aborted awake craniotomy

Awake Craniotomy Under 3-Tesla Intraoperative Magnetic Resonance Imaging: A Retrospective Descriptive Report and Canadian Institutional Experience

BACKGROUND

The role of high-field 3-Tesla intraoperative magnetic resonance imaging (I-MRI) during awake craniotomy (AC) has not been extensively studied. We report the feasibility and safety of AC during 3-Tesla I-MRI.

METHODS

This retrospective descriptive report compared 3 groups: AC with minimal sedation and I-MRI; I-MRI-guided craniotomy under general anesthesia (GA), and; AC without I-MRI. Perioperative factors, surgical, anesthetic and radiologic complications, and postoperative morbidity and mortality were recorded.

RESULTS

Overall, 85 patients are included in this report. Five of 23 patients (22%) who underwent AC with I-MRI had anesthetic complications (nausea/vomiting and conversion to GA) compared with 3 of 40 (8%) who underwent I-MRI-guided craniotomy under GA (nausea/vomiting during extubation, and arrhythmia). Intraoperative surgical complications (seizures and speech deficits) occurred in 5 patients (22%) who underwent AC and I-MRI, excessive intraoperative bleeding occurred in 2 patients (5%) who had I-MRI-guided craniotomy under GA, and 4 of 22 (18%) patients who underwent AC without I-MRI experienced neurological complications (seizures, motor deficits, and transient loss of consciousness). Eight patients (20%) who had I-MRI with GA had postoperative complications, largely neurological. The duration of surgery and anesthesia were shortest in the group of patients receiving AC without I-MRI. Seventy-three percent of the patients in this group had residual tumor postoperatively compared with 44% and 38% in those having I-MRI with AC or GA, respectively. Patients who underwent I-MRI-guided craniotomy with GA had the highest morbidity (8%) at hospital discharge.

CONCLUSIONS

Our institutional experience suggests that AC under 3-Tesla I-MRI could be an option for glioma resection, although firm conclusions cannot be drawn given the limited and heterogenous nature of our data. Future multicenter trials comparing anesthetic and imaging modalities for glioma resection are recommended.

fMRI Resting-State Connectivity between Language and Nonlanguage Areas as Defined by Intraoperative Electrocortical Stimulation in Low-Grade Glioma Patients

BACKGROUND AND OBJECTIVES

 It remains to be determined whether noninvasive functional imaging techniques can rival the clinical potential of direct electrocortical stimulation (DES). In this study, we compared the results of resting-state functional magnetic resonance imaging (rs-fMRI) to those of DES for language mapping. Our goals were twofold: (1) to replicate a previous study that demonstrated that resting-state connectivity (RSC) was significantly larger between positive DES language sites than between negative DES language sites and (2) to compare the spatial resolution of rs-fMRI to that of DES.

METHODS

 We conducted a retrospective study of nine low-grade glioma patients. Language sites were identified by intraoperative DES. We compared RSC values between and within groups of DES-positive and DES-negative regions of interest (ROIs). Both close-negative sites (i.e., DES-negative sites <1 cm apart from and on the same gyrus as DES-positive sites) and far-negative sites (i.e., purely randomly chosen sites not in the vicinity of the tumor or of the DES-positive sites but on the same lobe) were included. Receiver operating characteristics were used to quantify comparisons.

RESULTS

 Functional connectivity between all positive language sites was on average significantly higher than between all close-negative sites and between all far-negative sites. The functional connectivity between the positive language ROIs and their respective close-negative control sites was not smaller than between all positive language sites.

CONCLUSION

 rs-fMRI likely reflects similar neural information as detected with DES, but in its current form does not reach the spatial resolution of DES.

The utilisation of resting-state fMRI as a pre-operative mapping tool in patients with brain tumours in comparison to task-based fMRI and intraoperative mapping: A systematic review

PURPOSE

Resting-state functional Magnetic Resonance Imaging (rs-fMRI) is suggested to be a viable option for pre-operative mapping for patients with brain tumours. However, it remains an open issue whether the tool is useful in the clinical setting compared to task-based fMRI (T-fMRI) and intraoperative mapping. Thus, a systematic review was conducted to investigate the usefulness of this technique.

METHODS

A systematic literature search of rs-fMRI methods applied as a pre-operative mapping tool was conducted using the PubMed/MEDLINE and Cochrane Library electronic databases following PRISMA guidelines.

RESULTS

Results demonstrated that 50% (six out of twelve) of the studies comparing rs-fMRI and T-fMRI showed good concordance for both language and sensorimotor networks. In comparison to intraoperative mapping, 86% (six out of seven) studies found a good agreement to rs-fMRI. Finally, 87% (twenty out of twenty-three) studies agreed that rs-fMRI is a suitable and useful pre-operative mapping tool.

CONCLUSIONS

rs-fMRI is a promising technique for pre-operative mapping in assessing the functional brain areas. However, the agreement between rs-fMRI with other techniques, including T-fMRI and intraoperative maps, is not yet optimal. Studies to ascertain and improve the sophistication in pre-processing of rs-fMRI imaging data are needed.

[Resting-state fMRI in preoperative non-invasive mapping in patients with left hemisphere glioma]

Maximum resection and preservation of neurological function are main principles in surgery of brain tumors, especially glial neoplasms with diffuse growth. Therefore, exact localizing of eloquent brain areas is an important component in surgical planning ensuring optimal resection with minimal postoperative neurological deficit. Functional MRI is used to localize eloquent brain areas adjacent to the tumor. This paper is an initial stage in analysis of resting-state fMRI in assessment of functional changes of neuronal activity caused by brain gliomas of different localization. We report two patients with glial tumors localized within the precentral gyrus of the left hemisphere and near speech area. Considering data of task-based and resting-state fMRI, as well as direct cortical stimulation, we propose a methodology for assessing the overlap of activations obtained by these methods.

Language mapping: A systematic review of protocols that evaluate linguistic functions in awake surgery

Nowadays, numerous neuropsychological tests are available for multidisciplinary teams to perform awake brain surgery but none-or very few-of them constitutes a mandatory prerequisite. No consensus has been reached about the choice of intraoperative tests, which can be relatively simple for certain primary functions, but can be much more difficult for high-level cognitive functions. This review aims to give an overview about the assessment of language during awake brain surgery in adults and focus on the analysis of the different language protocols that have been published, to compile the most used standardized tests that evaluate different linguistic cognitive processes. We performed a systematic review about awake brain surgery studies that mentioned a specific test or protocol for assessing language in adults from the last 15 years. The search yielded 3,504 articles. 120 studies reported a linguistic protocol or test. This review allowed to obtain a defined neuropsychological picture of the essential tasks that a linguistic protocol in awake surgery should compile. This review will help clinicians in selecting tasks for monitoring cognition during awake brain surgery as well as contributes to enlighten the efficacy of linguistics protocols in order to minimize language deficits in awake surgery.

Intraoperative Use of Functional MRI for Surgical Decision Making after Limited or Infeasible Electrocortical Stimulation Mapping

BACKGROUND AND PURPOSE

Functional magnetic resonance imaging (fMRI) is becoming widely recognized as a key component of preoperative neurosurgical planning, although intraoperative electrocortical stimulation (ECS) is considered the gold standard surgical brain mapping method. However, acquiring and interpreting ECS results can sometimes be challenging. This retrospective study assesses whether intraoperative availability of fMRI impacted surgical decision-making when ECS was problematic or unobtainable.

METHODS

Records were reviewed for 191 patients who underwent presurgical fMRI with fMRI loaded into the neuronavigation system. Four patients were excluded as a bur-hole biopsy was performed. Imaging was acquired at 3 Tesla and analyzed using the general linear model with significantly activated pixels determined via individually determined thresholds. fMRI maps were displayed intraoperatively via commercial neuronavigation systems.

RESULTS

Seventy-one cases were planned ECS; however, 18 (25.35%) of these procedures were either not attempted or aborted/limited due to: seizure (10), patient difficulty cooperating with the ECS mapping (4), scarring/limited dural opening (3), or dural bleeding (1). In all aborted/limited ECS cases, the surgeon continued surgery using fMRI to guide surgical decision-making. There was no significant difference in the incidence of postoperative deficits between cases with completed ECS and those with limited/aborted ECS.

CONCLUSIONS

Preoperative fMRI allowed for continuation of surgery in over one-fourth of patients in which planned ECS was incomplete or impossible, without a significantly different incidence of postoperative deficits compared to the patients with completed ECS. This demonstrates additional value of fMRI beyond presurgical planning, as fMRI data served as a backup method to ECS.

How much is enough-Can resting state fMRI provide a demarcation for neurosurgical resection in glioma?

This study represents a systematic review of the insights provided by resting state functional MRI (rs-fMRI) use in the glioma population. Following PRISMA guidelines, 45 studies were included in the review and were classified in glioma-related neuronal changes (n=28) and eloquent area localization (n=17). Despite the heterogeneous nature of the studies, there is considerable evidence of diffuse functional reorganization occurring in the setting of gliomas with local and interhemispheric functional connectivity alterations involving different functional networks. The studies showed evidence of decreased long distance functional connectivity and increased global local efficiency occurring in the setting of gliomas. The tumour grade seems to correlate with distinct functional connectivity changes. Overall, there is a potential clinical utility of rs-fMRI for identifying the functional brain network disruptions occurring in the setting of gliomas. Further studies utilizing standardized analytical methods are required to elucidate the mechanism through which gliomas induce global changes in brain connectivity.

Resting-state Functional Magnetic Resonance Imaging in Presurgical Functional Mapping: Sensorimotor Localization

This article compares resting-state functional magnetic resonance (fMR) imaging with task fMR imaging for presurgical functional mapping of the sensorimotor (SM) region. Before tumor resection, 38 patients were scanned using both methods. The SM area was anatomically defined using 2 different software tools. Overlap of anatomic regions of interest with task activation maps and resting-state networks was measured in the SM region. A paired t-test showed higher overlap between resting-state maps and anatomic references compared with task activation when using a maximal overlap criterion. Resting state-derived maps are more comprehensive than those derived from task fMR imaging.

Impact of Obesity on Complications and 30-Day Readmission Rates After Cranial Surgery: A Single-Institutional Study of 224 Consecutive Craniotomy/Craniectomy Procedures

BACKGROUND

The prevalence of obesity is increasing at a disparaging rate in the United States. Although previous studies have associated obesity with increased surgical complications and readmission rates, the impact of obesity on surgical outcomes after cranial surgery remains understudied. The aim of this study is to assess the effect of obesity on complication and 30-day readmission rates after cranial surgery.

METHODS

The medical records of 224 consecutive patients (nonobese, n = 164; obese, n = 60) undergoing either craniotomy or craniectomy at a major academic institution in 2011 were reviewed. Preoperative body mass index equal to or greater than 30 kg/m² was classified as obese. The primary outcome investigated in this study was the rate of intraoperative and postoperative complications and 30-day readmissions after craniectomy/craniotomy.

RESULTS

Baseline patient characteristics and comorbidities were similar between the cohorts. The mean body mass indexes for both cohorts were significantly different (nonobese, 22.8 ± 4.2 kg/m² vs. obese, 45.1 ± 15.9 kg/m²; P < 0.0001). Most patients underwent tumor excision in both cohorts (nonobese, 64.0% vs. obese, 66.7%; P = 0.75). Compared with the nonobese cohort, the obese cohort had significantly higher estimated blood loss (nonobese, 209.9 ± 201.3 mL vs. obese, 284.9 ± 250.0 mL; P = 0.04), but similar length of operation (nonobese, 187.3 ± 89.4 minutes vs. obese, 209.6 ± 100.5; P = 0.14). Length of hospital stay and rate of postoperative complications were similar between both cohorts. Obese patients had increased rate of 30-day readmission, but this was not statistically significant (nonobese, 3.1% vs. obese, 6.7%; P = 0.25).

CONCLUSIONS

Our study suggests that obesity may not have a significant impact on surgical outcomes after cranial surgery.