Human brain mapping using co-registered fUS, fMRI and ESM during awake brain surgeries: A proof-of-concept study

Accurate, depth-resolved functional imaging is key in both understanding and treatment of the human brain. A new sonography-based imaging technique named functional Ultrasound (fUS) uniquely combines high sensitivity with submillimeter-subsecond spatiotemporal resolution available in large fields-of-view. In this proof-of-concept study we show that: (A) fUS reveals the same eloquent regions as found by fMRI while concomitantly visualizing in-vivo microvascular morphology underlying these functional hemodynamics and (B) fUS-based functional maps are confirmed by Electrocortical Stimulation Mapping (ESM), the current gold-standard in awake neurosurgical practice. This unique cross-modality experiment was performed using motor, visual and language-related functional tasks in patients undergoing awake brain tumor resection. The current work serves as an important milestone towards further maturity of fUS as well as a novel avenue to increase our understanding of hemodynamics-based functional brain imaging.

P07.11.A Impact of awake craniotomy on extent-of-resection and performance in glioma: a retrospective, propensity-score matched cohort study

Background

The goal of awake craniotomy is to safely optimize the extent-of-resection in patients with glioma. Lower postoperative tumor volume is associated with better overall survival, emphasizing the importance of optimal surgical resection. Awake craniotomy causes less postoperative neurological deficits than surgery under general anesthesia, however, it is unclear whether awake craniotomy leads to lower postoperative tumor volume compared with general anesthesia in presumed lower grade glioma.

Methods

Retrospective, matched cohort study in patients with astrocytoma, IDH-mutant grade 2 and 3, oligodendroglioma, IDH-mutant, and 1p/19q-codeleted grade 2 and 3, and low-grade glioma, IDH-wildtype (now designated glioblastoma, IDH-wildtype), who underwent resection with awake craniotomy or under general anesthesia between 2003 and 2021 at Erasmus MC Brain Tumor Center. Pre- and postoperative tumor volumes were measured by semi-automatic 3D MRI-segmentation. First, we performed a multivariate logistic regression to assess which factors predicted selection for awake craniotomy. Thereafter, matching based on propensity score was attempted. Outcome variables were postoperative tumor volume, resection percentage and Karnofsky Performance Status (KPS) 3 months after surgery.

Results

We identified 181 awake craniotomy-patients and 135 general anesthesia-patients. Awake craniotomy-patients were younger, in better condition, more often male, with tumors more often in eloquent areas, in the left side of the brain and non-contrast enhancing. When performing matching without replacement, only 68 awake craniotomy-patients could be matched with 68 general anesthesia-patients, underscoring the imbalance in the dataset. Matching with replacement yielded a matched dataset of 181 awake craniotomy-patients with 60 general anesthesia-patients with adequate matching on most baseline variables, except for eloquent area (47% for awake craniotomy and 21.7% for general anesthesia, p < 0.001). In this matched dataset, median postoperative volume in awake craniotomy was 5.8 mL (IQR 0 - 92.8) vs 12.2 mL (IQR 0 - 90.1) in general anesthesia (p-value = 0.114). Resection percentages did not differ between the awake craniotomy- and general anesthesia-groups. KPS scores at 3 months after surgery did not differ between awake craniotomy and general anesthesia (p = 0.15).

Conclusion

Postoperative tumor volume was not lower in awake craniotomy-patients than in general anesthesia-patients. Neither were resection percentage and KPS scores at 3 months after surgery significantly different between the groups. Adequate matching was only obtainable using replacement, underscoring the risk of bias in unmatched datasets. These data should be interpreted with care, given the retrospective nature, potential residual confounding and potential lack of generalizability due to unmatched normal resection patients.

P11.69.B IDH1/2wildtype gliomas grade 2 and 3 with molecular glioblastoma-like profile have a distinct course of epilepsy compared toIDH1/2wildtype glioblastomas

Background

IDH1/2 wildtype (IDHwt) glioma WHO grade 2 and 3 patients with pTERT mutation and/or EGFR amplification and/or +7/−10 chromosome gain/loss have a similar overall survival time as IDHwt glioblastoma patients, and are both considered glioblastoma IDHwt according to the WHO 2021 classification. However, differences in seizure onset have been observed. This study aimed to compare the course of epilepsy in the two glioblastoma subtypes.

Material and Methods

We analyzed epilepsy data of an existing cohort including IDHwt histologically lower-grade glioma WHO grade 2 and 3 with molecular glioblastoma-like profile (IDHwt hLGG) and IDHwt glioblastoma patients. Primary outcome was the incidence proportion of epilepsy during the disease course. Major secondary outcomes included onset of epilepsy, number of seizure days and antiepileptic drug (AED) polytherapy.

Results

Out of 254 patients, 78% (50/64) IDHwt hLGG and 68% (129/190) IDHwt glioblastoma patients developed epilepsy during the disease course (p=0.121). Epilepsy onset before histopathological diagnosis occurred more frequently in IDHwt hLGG compared to IDHwt glioblastoma patients (90% versus 60%, p<0.001), with a significantly longer median time to diagnosis (3.5 versus 1.3 months, p<0.001). Median total seizure days was also longer for IDHwt hLGG patients (7.0 versus 3.0, p=0.005), and they received more often AED polytherapy (32% versus 17%, p=0.028).

Conclusion

Although the incidence proportion of epilepsy during the entire disease course is similar, IDHwt hLGG patients show a significantly higher incidence of epilepsy before diagnosis and a significantly longer median time between first seizure and diagnosis compared to IDHwt glioblastoma patients, indicating a distinct clinical course.

P01.12.B Analysis of semi-spontaneous speech before, during and after awake craniotomy: a case study

Background

The standard treatment for patients with eloquent gliomas is awake craniotomy (AC) with direct electrical stimulation, which results in a larger extent of resection while maintaining language function. Intraoperative language monitoring includes different standardized tasks and spontaneous speech elicitation. Despite careful monitoring, it was found that spontaneous speech deteriorated long-term after surgery. However, intraoperative spontaneous speech has not been investigated before. Detailed analyses may reveal possible predictors for language outcome. For the first time, we present a case study in which we investigate and quantify semi-spontaneous speech before, during and after AC.

Material and Methods

A left-handed 50-year old male with a glioblastoma (WHO grade 4) in the left parietal lobe underwent AC. Semi-spontaneous speech was collected (audio/video recording) using the Sabadel story retelling task at: 1 day before (T1), during (T2), 2 days (T3) and 2 months (T4) after surgery. Recordings were manually transcribed and language errors were quantified. A preliminary acoustic analysis with simple automatic peak detection was performed. Comparisons between test moments were made.

Results

Manual transcription showed 1) notable changes in the number of paraphasias (T1: 1% - T2: 1% - T3: 9% - T4: 5%), interjections (T1: 9% - T2: 9% - T3: 15% - T4: 10%), minimal utterances (T1: 4% - T2: 4% - T3: 6% - T4: 1%), false starts (T1: 3% - T2: 5% - T3: 6% - T4: 8%), self-corrections (T1: 3% - T2: 2% - T3: 4% - T4: 7%) and 2) small changes in repetitions (T1: 1% - T2: 0% - T3: 2% - T4: 3%), hesitations (T1: 1% - T2: 0% - T3: 2% - T4: 0%), incomplete sentences (T1: 1% - T2: 0% - T3: 0% - T4: 1%), grammatical errors (T1: 2% - T2: 1% - T3: 2% - T4: 2%). The total number of words (T1: 273 - T2: 283 - T3: 249 - T4: 287) and utterances (T1: 39 - T2: 41 - T3: 36 - T4: 34) varied slightly. Acoustic analysis showed a slight increase in word length during and directly after surgery but it recovered to preoperative level on the long-term (T1: .66 s - T2: .75 s - T3: .87 s - T4: .69 s).

Conclusion

The semi-spontaneous speech task in this case study was sensitive to capture changes in perioperative language status. Paraphasias, interjections, minimal utterances, hesitations and word length increased directly after surgery followed by a decrease 2 months later. This is a frequently reported pattern of transient language deficits. However, other errors (false starts, repetitions, self-corrections, incomplete sentences) increased at 2 months after surgery, indicating longer term language deficits. Future exploration of both the acoustic analysis, which shows potential for real-time feedback, and the manual transcriptions, could possibly lead to a better understanding of intra- and postoperative language performance as a prognostic factor for long-term language outcome, with possible implications for language therapy.

P01.13.A The effect of musicality on language recovery after awake glioma surgery

Background

Awake craniotomy is used to resect tumor while preserving language. However, differences between patients in post-operative speech/language outcome are observed despite careful intra-operative monitoring. Literature describes improved performance in language tasks during cognitive tests in musicians. Moreover increased white matter connectivity properties in the corpus callosum are described in musicians compared to non-musicians. We hypothesize better recovery of language in musical patients after awake glioma surgery, caused by higher connectivity properties from the corpus callosum.

Material and Methods

Adult patients undergoing resection for glioma with an awake resection procedure at two neurosurgical centers were prospectively included. Patients without standardized language tests at pre- and post-operative level, with a glioblastoma multiforme (WHO grade 4) or undergoing re-resection were excluded. Language was assessed with the Diagnostic Instrument for Mild Aphasia (DIMA) and corrected for age and education years from a healthy population. The patients’ musical skill was assessed through questionnaires, and divided in groups based on the Musical Expertise Criterion (MEC) which defines musicality based the duration and intensity of musical training. Volumetric measures of the corpus callosum, corrected for total brain volumes, was calculated of each included patient based on the pre-operative structural MRI.

Results

Forty-six patients, enrolled between June 2015 and September 2019, were followed-up (mean/SD; 240/174 days after craniotomy) and divided in: non-musician (41.3%, n = 19), amateur-musician (34.8%, n=16) and trained-musician (23.9%, n = 11). Overall a decrease in language was observed after craniotomy (mean/SD) of -0.361/0.771. Musical abilities correlated with less decrease in language (mean/SD) when comparing non-musicians (-0.543/0.683) to amateur (-0.272/0.910) and trained (-0.176/0.693) musicians. An increased but non-significant trend (p=0.28) between musicality and corpus callosum / brain ratio (mean/SD) was observed in non-musicians (0.763, 0.718;0.808), amateur musicians (0.792, 0.745;0.838) and trained musicians (0.835, 0.778;0.891).

Conclusion

Musicality seemed to improve language outcome after awake glioma surgery, possibly attributed due to a higher white matter connectivity in the corpus callosum. Future studies with larger sample sizes are needed to confirm our findings.

P09.03 Fully integrating functional Ultrasound (fUS) into the onco-neurosurgical operating room: Towards a new real-time, high-resolution image-guided resection tool with multimodal potential

BACKGROUND

Onco-neurosurgical practice still relies heavily on pre-operatively acquired images to guide intra-operative decision-making for safe tumor removal, a practice with inherent pitfalls such as registration inaccuracy due to brain shift, and lack of real-time (functional) feedback. Exploiting the opportunity for real-time imaging of the exposed brain can improve intra-operative decision-making, neurosurgical safety and patient outcomes. Previously, we described functional Ultrasound (fUS) as a high-resolution, depth-resolved imaging technique able to detect functional regions and vascular morphology during awake resections. Here, we present for the first time fUS as a fully integrated, MRI/CT-registered imaging modality in the OR.

MATERIAL AND METHODS

fUS relies on high-frame-rate (HFR) ultrasound, making the technique sensitive for very small motions caused by vascular dynamics (µDoppler) and allowing measurements of changes in cerebral blood volume (CBV) with micrometer-millisecond precision. This opens up the possibility to 1) detect functional response, as CBV-changes reflect changes in metabolism of activated neurons through neurovascular coupling and 2) visualize in-vivo vascular morphology of tumor and healthy tissue. During a range of anesthetized and awake onco-neurosurgical procedures we acquired images of brain and spinal cord using conventional linear ultrasound probes connected to an experimental acquisition unit. Building on Brainlab’s ‘Cranial Navigation’ and ‘Intra-Operative Ultrasound’ modules, we could co-register our intra-operative Power Doppler Images (PDIs) to patient-registered MRI/CT-data. Using the ‘IGTLink’ research interface, we could access and store real-time tracking data for informed volume reconstructions in post-processing.

RESULTS

Intra-operative fUS could be registered to MRI/CT-images in real-time, showing overlays of PDIs at imaging depths of >5 centimeters. During meningioma resections, these co-registered PDIs revealed fUS’ ability to visualize the tumor’s feeding vessels and surrounding healthy vasculature prior to durotomy, with a level of detail unprecedented by conventional MRI-sequences. Comparing post-operatively reconstructed 3D-vascular maps of pre- and post-durotomy acquisitions, further confirmed the dural dependency of the vascular network feeding the tumor. During awake resections, fUS revealed distinct functional areas as activated during motor and language tasks.

CONCLUSION

fUS is a new real-time, high-resolution and depth-resolved imaging technique, combining characteristics uniquely beneficial for a potential image-guided resection tool. The successful integration of fUS in the onco-neurosurgical OR demonstrated by our team, is an essential step towards clinical integration of fUS, as well as the technique’s validation against modalities such as MRI and CT.

A Primary Extraosseous Ewing Sarcoma in the Cerebellopontine Angle of a Child: Review of Relevant Literature and Case Report

BACKGROUND AND IMPORTANCE:

We report the occurrence of a primary intracranial extraosseous Ewing sarcoma/peripheral primitive neuroectodermal tumor (EES/pPNET) in the cerebellopontine angle in a child.

CLINICAL PRESENTATION:

A 10-year-old girl presented with symptoms and signs of an infratentorial space-occupying lesion that was confirmed by magnetic resonance imaging and followed up by subtotal surgical resection. Tumor cells displayed membranous expression of CD99, and one of the typical translocations of EES/pPNET (chromosome 22) was demonstrated by cytogenetic analysis.

CONCLUSION:

The literature regarding the histopathological, molecular, radiological, prognostic, and therapeutic features of intracranial EES/pPNET is reviewed, emphasizing the distinction of this entity from the central PNET. Although exceptionally rare, intracranial EES/pPNET should be considered in the differential diagnosis of lesions in the cerebellopontine angle.

Safety and efficacy of frameless and frame-based intracranial biopsy techniques

BACKGROUND

Frameless stereotaxy or neuronavigation has evolved into a feasible technology to acquire intracranial biopsies with good accuracy and little mortality. However, few studies have evaluated the diagnostic yield, morbidity, and mortality of this technique as compared to the established standard of frame-based stereotactic brain biopsy. We report our experience of a large number of procedures performed with one or other technique.

PATIENTS AND METHODS

We retrospectively assessed 465 consecutive biopsies done over a ten-year time span; Data from 391 biopsies (227 frame-based and 164 frameless) were available for analysis. Patient demographics, peri-operative characteristics, and histological diagnosis were reviewed and then information was analysed to identify factors associated with the biopsy not yielding a diagnosis and of it being followed by death.

RESULTS

On average, nine tissue samples were taken with either stereotaxy technique. Overall, the biopsy led to a diagnosis on 89.4% of occasions. No differences were found between the two biopsy procedures. In a multiple regression analysis, it was found that left-sided lesions were less likely to result in a non-diagnostic tissue sample (p = 0.023), and cerebellar lesions showed a high risk of negative histology (p = 0.006). Postoperative complications were seen after 12.1% of biopsies, including 15 symptomatic haemorrhages (3.8%). There was not a difference between the rates of complication after either a frame-based or a frameless biopsy. Overall, peri-operative complications (p = 0.030) and deep-seated lesions (p = 0.060) increased the risk of biopsy-related death. Symptomatic haemorrhages resulting in death (1.5% of all biopsies) were more frequently seen after biopsy of a fronto-temporally located lesion (p = 0.007) and in patients with a histologically confirmed lymphoma (p = 0.039).

CONCLUSIONS

The diagnostic yield, complication rates, and biopsy-related mortality did not differ between a frameless biopsy technique and the established frame-based technique. The site of the lesion and the occurrence of a peri-operative complication were associated with the likelihood of failure to achieve a diagnosis and with death after biopsy. We believe that using intraoperative frozen section or cytologic smear histology is essential during a stereotactic biopsy in order to increase the diagnostic yield and to limit the number of biopsy specimens that need to be taken.

Raman spectroscopic characterization of porcine brain tissue using a single fiber-optic probe

Accurate targeting of diseased and healthy tissue has significantly been improved by MRI/CT-based navigation systems. Recently, intraoperative MRI navigation systems have proven to be powerful tools for the guidance of the neurosurgical operations. However, the widespread use of such systems is held back by the costs, the time consumption during operation, and the need for MR-compatible surgical devices. Raman spectroscopy is a nondestructive optical technique that enables real-time tissue identification and classification and has proved to be a powerful diagnostic tool in a large number of studies. In the present report, we have investigated the possibility of distinguishing different brain structures by using a single fiber-optic probe to collect Raman scattered light in the high-wavenumber region of the spectrum. For the Raman measurements, 7 pig brains were sliced in the coronal plain and Raman spectra were obtained of 11-19 anatomical structures. Adjacent brain structures could be distinguished based on their Raman spectra, reflecting the differences in their biochemical composition and illustrating the potential Raman spectroscopy holds as a guidance tool during neurosurgical procedures.

Post-trauma mucocele formation in the frontal sinus; a rationale of follow-up

The aim of the investigation was the evaluation of the follow-up for mucocele formation as a complication of frontal sinus fractures. A review of the literature was performed which showed only 10 adequately documented cases of mucocele formation after trauma. In our hospital between June 2001 and July 2002 three patients were treated for mucocele as a late complication following trauma to the frontal sinus. Our patients presented themselves with a mucocele, respectively 13, 22 and 35 years after the initial trauma. From this a suggestion is done for the follow-up of post-trauma patients. Mucocele formation is a complication, which can develop years after trauma to the frontal sinus. Treatment of these forms of mucocele is multidisciplinary. The review of the literature in combination with our own data showed no peak incidence of mucocele formation after trauma. We therefore advocate following the at-risk-patients for life, and to properly inform them about the possible development and symptoms, like swelling, diplopia, etc., of a mucocele.