Feasibility of multimodal intraoperative neurophysiological monitoring for extramedullary spinal cord tumor surgery in elderly patients.

BACKGROUND/PURPOSE: Extramedullary spinal cord tumors (EMSCTs) are mostly benign tumors which are increasingly diagnosed and operatively treated in the elderly. While there are hints that multimodal intraoperative neurophysiological monitoring (IONM) could be influenced by age and age-related comorbidities, no study has ever systematically evaluated its feasibility and value for EMSCT surgery in elderly patients. METHODS: We retrospectively evaluated all patients with microsurgical EMSCT resection under continuous multimodal IONM with SSEPs, MEPs and electromyography between 2016 and 2020. Epidemiological, clinical, imaging and operative/IONM records as well as detailed individual outcomes were analyzed and compared for the cohort < / ≥ 65 years. RESULTS: Mean age was 45 years in cohort < 65 years (n = 109) and 76 years in cohort ≥ 65 years (n = 64), while baseline/operative characteristics did not significantly differ. Mean baseline SSEPs' latencies (left-right average) were significantly higher in the cohort ≥ 65 years for both median (20.9 ms vs. 22.1 ms; p < 0.01) and tibial nerve (42.9 ms vs. 46.1 ms; p < 0.01) without significant differences for SSEPs' amplitudes. Stimulation intensity to elicit intraoperative MEPs was significantly higher in the cohort ≥ 65 years (surrogate-marker: left-right-averaged quotient ID1-muscle/abductor-hallucis-muscle; 1.6 vs. 2.1; p < 0.001). Intraoperatively, SSEP and MEP monitoring were feasible in 99%/100% and 99%/98% for the cohort < / ≥ 65 years without significant differences in rates for significant IONM changes during surgery or postoperatively new sensorimotor deficits. Sensitivity of IONM was 29%/43%, specificity 99%/98%, positive and negative predictive values 67%/75% and 95%/93% for the cohort < / ≥ 65 years. Overall, age was no risk factor for IONM feasibility or rate of significant IONM changes. DISCUSSION: Multimodal IONM is feasible/reliable for EMSCT surgery in elderly patients. An age-related prolongation of SSEPs' latencies and demand for higher stimulation intensities for MEPs' elicitation has to be considered.

Dorsal column mapping in resection of intramedullary spinal cord tumors: a prospective comparison of two methods and neurological follow-up.

PURPOSE: In surgery for intramedullary spinal cord tumors (imSCT), distortion of the anatomy challenges the visual identification of dorsal columns (DC) for midline myelotomy. Dorsal column mapping (DCM) and spinal cord stimulation (SCS) can identify DC neurophysiologically. We compare application and feasibility of both methods. METHODS: Patients with surgically treated imSCT were prospectively included between 04/2017 and 06/2019. The anatomical midline (AM) was marked. SSEPs at the DC after stimulation of tibial/median nerve with an 8-channel DCM electrode and cortical SSEP phase reversal at C3/C4 after SCS using a bipolar concentric probe were recorded. Procedural and technical aspects were compared. Standardized neurological examinations were performed preoperatively, 1 week postoperatively and after more than 12 months. RESULTS: The DCM electrode detected the midline in 9/13 patients with handling limitations in the remaining patients. SCS was applicable in all patients with determination of the midline in 9/13. If both recordings could be acquired (6/13), concordance was 100%. If baseline SSEPs were poor, both methods were limited. SCS was less time-consuming (p = 0.001), cheaper, and easier to handle. In 92% of cases, the AM and neurophysiologic midlines were concordant. After myelotomy, 3 patients experienced > 50% reduction in amplitude of SSEPs. Despite early postoperative worsening of DC function, long-term follow-up showed significant recovery and improvement in quality of life. CONCLUSION: DCM and SCS may help confirm and correct the AM for myelotomy in imSCT, leading to a favorable long-term neurological outcome in this cohort. SCS evolved to be superior concerning applicability, cost-effectiveness, and time expenditure.

Intramedullary spinal cord cavernous malformations-association between intraoperative neurophysiological monitoring changes and neurological outcome.

BACKGROUND: Microsurgical resection of spinal cord cavernous malformations can be assisted by intraoperative neurophysiological monitoring (IONM). While the clinical outcome after surgical resection has been discussed in several case series, the association of intraoperative IONM changes and detailed neurological outcome, however, has not been analyzed so far. METHODS: Seventeen patients with spinal cavernomas underwent surgery between 02/2004 and 06/2020. Detailed neurological and clinical outcome as well as IONM data including motor-evoked potential (MEP) and somatosensory-evoked potential (SSEP) monitoring were retrospectively analyzed. Intraoperative IONM changes were compared to outcome at 3-month and 1-year follow-up in order to identify surrogate parameters for an impending neurological deficit. RESULTS: Compared to the preoperative state, McCormick score at 1-year follow-up remained unchanged in 12 and improved in five patients, none worsened, while detailed neurological examination revealed a new or worsened sensorimotor deficit in 4 patients. The permanent 80% amplitude reduction of MEP and 50% amplitude reduction of SSEP showed the best diagnostic accuracy with a sensitivity of 100% and 67% respectively and a specificity of 73% and 93% respectively. The relative risk for a new neurological deficit at 1-year follow-up, when reversible IONM-deterioration was registered compared to irreversible IONM deterioration, was 0.56 (0.23-1.37) for MEP deterioration and 0.4 (0.18-0.89) for SSEP deterioration. CONCLUSIONS: Reversible IONM changes were associated with a better neurological outcome at follow-up compared to irreversible IONM deterioration during SCCM surgery. Our study favors the permanent 80% amplitude reduction criterion for MEP and 50% amplitude reduction criterion for SSEP for further prospective evaluation of IONM significance and the effectiveness of corrective maneuvers during SCCM surgeries.

Detection of impending perfusion deficits by intraoperative computed tomography (iCT) in aneurysm surgery of the anterior circulation.

BACKGROUND: The aim of our study was to evaluate the additional benefit of intraoperative computed tomography (iCT), intraoperative computed tomography angiography (iCTA), and intraoperative computed tomography perfusion (iCTP) in the intraoperative detection of impending ischemia to established methods (indocyanine green videoangiography (ICGVA), microDoppler, intraoperative neuromonitoring (IONM)) for initiating timely therapeutic measures. METHODS: Patients with primary aneurysms of the anterior circulation between October 2016 and December 2019 were included. Data of iCT modalities compared to other techniques (ICGVA, microDoppler, IONM) was recorded with emphasis on resulting operative conclusions leading to inspection of clip position, repositioning, or immediate initiation of conservative treatment strategies. Additional variables analyzed included patient demographics, aneurysm-specific characteristics, and clinical outcome. RESULTS: Of 194 consecutive patients, 93 patients with 100 aneurysms received iCT imaging. While IONM and ICGVA were normal, an altered vessel patency in iCTA was detected in 5 (5.4%) and a mismatch in iCTP in 7 patients (7.5%). Repositioning was considered appropriate in 2 patients (2.2%), where immediate improvement in iCTP could be documented. In a further 5 cases (5.4%), intensified conservative therapy was immediately initiated treating the reduced CBP as clip repositioning was not considered causal. In terms of clinical outcome at last FU, mRS0 was achieved in 85 (91.4%) and mRS1-2 in 7 (7.5%) and remained mRS4 in one patient with SAH (1.1%). CONCLUSIONS: Especially iCTP can reveal signs of impending ischemia in selected cases and enable the surgeon to promptly initiate therapeutic measures such as clip repositioning or intraoperative onset of maximum conservative treatment, while established tools might fail to detect those intraoperative pathologic changes.

Intraspinal epidermoid and dermoid cysts-tumor resection with multimodal intraoperative neurophysiological monitoring and long-term outcome.

BACKGROUND: Intraspinal epidermoid/dermoid cysts are very rare, benign tumors arising from pathological displacement of epidermal cells into the spinal canal. Literature data about the long-term outcome after microsurgical resection with multimodal intraoperative neurophysiological monitoring (IONM) are lacking. We analyzed one of the largest case series with special regard to intraoperative characteristics and long-term outcome after IONM-aided surgery. METHOD: All 12 patients (m:f = 1.4:1) who underwent microsurgical tumor resection with multimodal IONM for intraspinal epidermoid/dermoid tumors between 1998 and 2019 in our university hospital were included. We retrospectively investigated the patients' characteristics, imaging/surgical parameters, and postoperative long-term outcomes. RESULTS: Symptomatic tumor manifestation was seen during adulthood in 4 patients (median age 33.0 years) and during childhood in 8 patients (median age 4.3 years). Spinal dysraphism was the most often comorbidity (75%). The most frequent symptoms at diagnosis were spastic pareses (75%), ataxia (58%), and vegetative disorders (42%). Tumors were most often lumbosacral (L1-L5 42%, L5-S3 50%) and intradural-extramedullary (92%). For microsurgical resection, IONM with EMG, SSEPs, and TcMEPs of the limbs and pudendal nerve/anal sphincter was always applied and feasible; intraoperative corrective actions were initiated in three cases due to transient IONM deterioration. None of the patients showed a postoperative deterioration of the neurological status with a gross total resection rate of 92%. Pain situation, McCormick grade, and mJOA Score were improved at long-term follow-up (median 4.8 years). CONCLUSIONS: IONM-aided resection of intraspinal epidermoid/dermoid tumors is feasible both in adult and pediatric cases and enables a satisfying clinical and surgical outcome.

Prognostic value of a bilateral motor threshold criterion for facial corticobulbar MEP monitoring during cerebellopontine angle tumor resection.

In intraoperative neuromonitoring (IONM), facial nerve motor function (FaNMF) is assessed by facial muscle corticobulbar motor evoked potentials (FMcoMEP). Mostly only amplitude decrease is used as warning criterion. We related a refined criterion for FMcoMEP consisting of a bilateral final-to-baseline motor threshold ratio with standard criteria and postoperative FaNMF. 79 patients (45 females; 48 ± 16 years) undergoing IONM-guided cerebellopontine angle tumor surgery were retrospectively analyzed. An intraoperative final-to-baseline motor threshold increase ≥ 20% ipsi- versus contralaterally (bFBMT20) was correlated to postoperative FaNMF at day 1 (D1), 7 (D7) and 3 months (3 M). An ipsilateral-only final-to-baseline motor threshold increase ≥ 20 mA (iAMT20) and amplitude decrement ≥ 50% (iAR50) served as reference. Tumors included vestibular schwannomas (68%), meningiomas (19%) and others (13%). Mean tumor diameter was 2.7 ± 1.1 cm. Postoperatively, HB-increase ≥ 2 was seen in 27% (D1), 17% (D7), and 6% (3 M) of patients, respectively. FMcoMEP were obtained in 75/79 cases. Pathological bFBMT20, iAMT20 and iAR50 were seen in 17, 17, and 46 cases, respectively. Area under the ROC curve for bFBMT20 (iAMT20) was 0.894 (0.868) at D1; 0.903 (0.822) at D7 and 0.941 (0.959) at 3 M. iAR50 performed worse at all time points. Diagnostic odds ratios were highest for bfBMT20 compared to iAMT20 and iAR50 for D1 (172.5 vs. 8.7 vs. 0.45) and D7 (51.4 vs. 6.1 vs. 0.8). The refined parameter bFBMT20 provides a valuable contribution to the prognostic assessment of FaNMF. Due to its bihemispheric character, it might thus circumvent false-positive events which affect FMcoMEP bilaterally.

Indication and technical implementation of the intraoperative neurophysiological monitoring during spine surgeries-a transnational survey in the German-speaking countries.

BACKGROUND: Intraoperative neurophysiological monitoring is widely used in spine surgery (sIONM). But guidelines are lacking and its use is mainly driven by individual surgeons' preferences and medicolegal advisements. To gain an overview over the current status of sIONM implementation, we conducted a transnational survey in the German-speaking countries. METHODS: We developed a Web interface-based survey assessing prevalence, indication, technical implementation, and general satisfaction regarding sIONM in German, Austrian, and Swiss spine centers. The electronic survey was performed between November 2017 and April 2018, including both neurosurgical and orthopedic spine centers. RESULTS: A total of 463 German, 60 Austrian, and 52 Swiss spine centers were contacted with participation rates of 64.1% (Germany), 68.3% (Austria), and 55.8% (Switzerland). Some 75.9% participating neurosurgical spine centers and only 14.7% of the orthopedic spine centers applied sIONM. Motor- and somatosensory-evoked potentials (93.7% and 94.3%, respectively) were the most widely available modalities, followed by direct wave (D wave; 66.5%). Whereas sIONM utilization was low in spine surgeries for degenerative, traumatic, and extradural tumor diseases, it was high for scoliosis and intradural tumor surgeries. Overall, the general satisfaction within the institutional setting regarding technical skills, staff, performance, and reliability of sIONM was rated as "high" by more than three-quarters of the centers. However, shortage of skilled staff was claimed to be a negative factor by 41.1% of the centers and reimbursement was considered to be insufficient by 83.5%. CONCLUSIONS: sIONM availability was high in neurosurgical but low in orthopedic spine centers. Main modalities were motor/somatosensory-evoked potentials and main indications were scoliosis and intradural spinal tumor surgeries. A more frequent sIONM use, however, was mainly limited by the shortage of skilled staff and restricted reimbursement.

Correction to: Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary.

The article Is the new ASNM intraoperative neuromonitoring supervision "guideline" a trustworthy guideline? A commentary, written by Stanley A. Skinner, Elif Ilgaz Aydinlar, Lawrence F. Borges, Bob S. Carter, Bradford L. Currier, Vedran Deletis, Charles Dong, John Paul Dormans, Gea Drost, Isabel Fernandez­Conejero, E. Matthew Hoffman, Robert N. Holdefer, Paulo Andre Teixeira Kimaid, Antoun Koht, Karl F. Kothbauer, David B. MacDonald, John J. McAuliffe III, David E. Morledge, Susan H. Morris, Jonathan Norton, Klaus Novak, Kyung Seok Park, Joseph H. Perra, Julian Prell, David M. Rippe, Francesco Sala, Daniel M. Schwartz, Martín J. Segura, Kathleen Seidel, Christoph Seubert, Mirela V. Simon, Francisco Soto, Jeffrey A. Strommen, Andrea Szelenyi, Armando Tello, Sedat Ulkatan, Javier Urriza and Marshall Wilkinson, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 05 January 2019 without open access. With the author(s)' decision to opt for Open Choice the copyright of the article changed on 30 January 2019 to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The original article has been corrected.

Incidence of local in-brain progression after supramarginal resection of cerebral metastases.

BACKGROUND: Microsurgical circumferential stripping of intracerebral metastases is often insufficient in achieving local tumor control. Supramarginal resection may improve local tumor control. METHODS: A retrospective analysis was performed for patients who underwent supramarginal resection of a cerebral metastasis by awake surgery with intraoperative cortical and subcortical stimulation, MEPs, and SSEPs. Supramarginal resection was achieved by circumferential stripping of the metastasis and additional removal of approximately 3 mm of the surrounding tissue. Pre- and postsurgical neurological status was assessed by the NIH Stroke Scale. Permanent deficits were defined by persistence after 3-month observation time. RESULTS: Supramarginal resection of cerebral metastases in eloquent brain areas was performed in 34 patients with a mean age of 60 years (range, 33-83 years). Five out of 34 patients (14.7%) had a new transient postoperative neurological deficit, which improved within a few days due to supplementary motor area (SMA) syndrome. Five out of 34 patients (14.7%) developed a local in-brain progression and nine patients (26.4%) a distant in-brain progression. CONCLUSIONS: Supramarginal resection of cerebral metastases in eloquent locations is feasible and safe. Safety might be increased by intraoperative neuromonitoring. The better outcome in the present series may be entirely based on other predictors than extend of surgical resection and not necessarily on the surgical technique applied. However, supramarginal resection was safe and apparently did not lead to worse results than regular surgical techniques. Prospective, controlled, and randomized studies are mandatory to determine the possible benefit of supramarginal resection on local tumor control and overall outcome.

Directional diffusion of corticospinal tract supports therapy decisions in idiopathic normal-pressure hydrocephalus.

INTRODUCTION: Gait disturbance in patients with idiopathic normal pressure hydrocephalus (iNPH) may be caused by alterations of the corticospinal tract that we aimed to measure with diffusion tensor imaging (DTI). The directional diffusion parameters axial diffusivity and fractional anisotropy (FA) reflect axon integrity, whereas mean diffusivity, radial diffusivity and magnetization transfer ratio (MTR) reflect myelin content. METHODS: Twenty-six patients with probable iNPH were grouped into drainage responders (n = 12) and drainage non-responders (n = 14) according to their improvement on gait assessment tests after a 3-day lumbar CSF drainage. We measured DTI and MTR of the corticospinal tract and, as reference, of the superior longitudinal fascicle before and after CSF withdrawal in iNPH and in ten age-matched controls. Drainage responders were re-examined after ventricoperitoneal shunting. Differences before any intervention and changes upon CSF withdrawal were evaluated. RESULTS: Axial diffusivity in corticospinal tract and superior longitudinal fascicle was higher in both patient groups compared to controls (p < 0.001). Only in the corticospinal tract of drainage responders was FA higher compared to controls, and both FA and axial diffusivity decreased after shunting. For axial diffusivity upon CSF drainage, a decrease of >0.7 % discriminated drainage responders from drainage non-responders with 82 % sensitivity, and a decrease of >1 % predicted overall improvement after shunting with 87.5 % sensitivity and 75 % specificity. The specificity to discriminate responders/non-responders was low for all DTI values (max. 69 % for FA values). CONCLUSION: High values of directional diffusion parameters in the corticospinal tract are found in iNPH patients indicating affection of its axons. Increased values and their decrease upon CSF drainage may facilitate treatment decisions in clinically uncertain cases.

Establishment of Different Intraoperative Monitoring and Mapping Techniques and Their Impact on Survival, Extent of Resection, and Clinical Outcome in Patients with High-Grade Gliomas-A Series of 631 Patients in 14 Years.

BACKGROUND: The resection of brain tumors can be critical concerning localization, but is a key point in treating gliomas. Intraoperative neuromonitoring (IONM), awake craniotomy, and mapping procedures have been incorporated over the years. Using these intraoperative techniques, the resection of eloquent-area tumors without increasing postoperative morbidity became possible. This study aims to analyze short-term and particularly long-term outcomes in patients diagnosed with high-grade glioma, who underwent surgical resection under various technical intraoperative settings over 14 years. METHODS: A total of 1010 patients with high-grade glioma that underwent resection between 2004 and 2018 under different monitoring or mapping procedures were screened; 631 were considered eligible for further analyses. We analyzed the type of surgery (resection vs. biopsy) and type of IONM or mapping procedures that were performed. Furthermore, the impact on short-term (The National Institute of Health Stroke Scale, NIHSS; Karnofsky Performance Scale, KPS) and long-term (progression-free survival, PFS; overall survival, OS) outcomes was analyzed. Additionally, the localization, extent of resection (EOR), residual tumor volume (RTV), IDH status, and adjuvant therapy were approached. RESULTS: In 481 patients, surgery, and in 150, biopsies were performed. The number of biopsies decreased significantly with the incorporation of awake surgeries with bipolar stimulation, IONM, and/or monopolar mapping (p < 0.001). PFS and OS were not significantly influenced by any intraoperative technical setting. EOR and RTV achieved under different operative techniques showed no statistical significance (p = 0.404 EOR, p = 0.186 RTV). CONCLUSION: Based on the present analysis using data from 14 years and more than 600 patients, we observed that through the implementation of various monitoring and mapping techniques, a significant decrease in biopsies and an increase in the resection of eloquent tumors was achieved. With that, the operability of eloquent tumors without a negative influence on neurological outcomes is suggested by our data. However, a statistical effect of monitoring and mapping procedures on long-term outcomes such as PFS and OS could not be shown.

Custom-tailored minimally invasive partial C2-corpectomy for ventrally located intramedullary cavernous malformation.

Approaches to ventrally located intramedullary lesions of the upper cervical spine can be extremely challenging. We present a custom-tailored, minimally invasive anterior approach to a ventrally located, intramedullary cavernous hemangioma with partial lateral corpectomy of C2, complete resection of the lesion and subsequent reconstruction. A 20-year-old woman presented with the history of progressive numbness of the left upper and lower extremities and some episodes of severe headaches was referred to magnetic resonance imaging: Here, an intramedullary lesion with typical radiological features for a cavernous malformation at the ventral surface of the spinal cord at the C2 level was detected. The surgical procedure was performed under general anesthesia and electrophysiological monitoring (somatosensory-evoked potentials (SEP), muscle motor-evoked potentials (MEP), and D-wave recording). Complete resection of the cavernous malformation was achieved and reconstruction of the cervical spine was performed using a custom-tailored cage. Intraoperative neuromonitoring during resection, revealed a transient MEP loss, but unchanged D-wave and SEP recordings indicated unchanged neurological outcome. Early clinical follow-up of the patient revealed no new neurological deficits. At 3-month follow-up, there was some improvement of the sensory function. This custom-tailored minimally invasive anterior approach to a ventrally located intramedullary cavernous malformation with partial C2-corpectomy describes a possible and successful approach to ventrally located intramedullary lesions of the upper cervical spinal cord. Additionally, the hereby-described approach is not related to cervical instability.

Tolerance of awake surgery for glioma: a prospective European Low Grade Glioma Network multicenter study.

BACKGROUND: Gross total removal of glioma is limited by proximity to eloquent brain. Awake surgery allows for intraoperative monitoring to safely identify eloquent regions. However, data on adverse psychological effects induced in these patients is limited. OBJECTIVE: This study explored patients' perception of awake surgery for glioma, with special focus on intraoperative pain and anxiety. METHODS: This study was conducted at five neurosurgical centers within the European Low Grade Glioma Network. Patients underwent awake surgery for glioma according to the protocol of the individual center. Pain and discomfort were measured during the awake phase. Postoperatively, patients answered a questionnaire on aspects of their operation. RESULTS: One hundred five patients were enrolled. Pain levels on a 10-cm visual analogue scale were 1.3 cm at the beginning, 1.9 cm the middle, and 2.1 cm at the end of awake phase. Levels of anxiety were 2.2 cm, 2.5 cm and 2.6 cm, respectively. Women and patients younger than 60 years exhibited highest mean anxiety levels. The patient questionnaire revealed that the majority of patients feel comfortable with the procedure. Discomfort resulted from head fixation or positioning on the operating table. CONCLUSIONS: We demonstrate that awake surgery is well tolerated, as neither intraoperative nor postoperative assessment revealed major disadvantages. Concerning practical lessons learned from this study, we emphasize the importance of minimizing pain and preparing patients thoroughly to reduce anxiety and maximize cooperation. Awake surgery is an excellent treatment modality for brain tumors with very positive perception by patients.

Resection of gliomas in the cingulate gyrus: functional outcome and survival.

Functional outcome after resection of tumors arising from the gyrus cinguli (GC), part of the limbic system, is not well analyzed. The purpose of this study was to evaluate the feasibility and functional outcome of surgical treatment for a series of 65 patients with gliomas involving the GC. Preoperative data, extent of resection, functional outcome (Karnofsky performance index, KPI, and the National Institute of Health Stroke Scale, NIHSS), and survival of 65 patients with gliomas arising from the GC were analyzed on the basis of a prospectively conducted database of gliomas between 06/1999 and 07/2010. Extent of resection (complete, subtotal, or partial) was based on early postoperative MRI. Eighty-six percent of the gliomas were located in the anterior part of the GC and 14 % in the posterior part. Fifty-five percent of the patients presented with seizures and 17 % with hemiparesis (mean preoperative KPI = 86 ± 17, NIHSS = 1.4 ± 1.7). Histologically, the tumors were WHO Grade II in 25 %, Grade III in 26 %, and Grade IV in 49 %. Complete resection was achieved for 59 %, subtotal resection for 32%, and partial resection for 9 %. Postoperative transient deficits included SMA lesion (14 %) and new or worsened hemiparesis (8 %), which resolved within 30 days (NIHSS early postoperatively 1.7 ± 1.4, late postoperatively 0.8 ± 1.4, and after 6 months 0.6 ± 1.4). According to histopathological grading, median survival was 67 months (WHO°II), 87 months (WHO°III), and 16.5 months (WHO°IV), and overall survival was 34 months. Microsurgical resection of gliomas arising from the GC is feasible; gross total resection can be achieved for 90 % of gliomas arising from the GC with 5 % long-term morbidity.

Optimizing the extent of resection in eloquently located gliomas by combining intraoperative MRI guidance with intraoperative neurophysiological monitoring.

Several methods have been introduced to improve the extent of resection in glioma surgery. Yet, radical tumor resections must not be attempted at the cost of neurological deterioration. We sought to assess whether the use of an intraoperative MRI (iMRI) in combination with multimodal neurophysiological monitoring is suitable to increase the extent of resection without endangering neurological function in patients with eloquently located gliomas. Fifty-four patients were included in this study. In 21 patients (38.9 %), iMRI led to additional tumor resection. A radiologically complete resection was achieved in 31 patients (57.4 %), while in 12 of these, iMRI had depicted residual tumor tissue before resection was continued. The mean extent of resection was 92.1 % according to volumetric analyses. Postoperatively, 13 patients (24.1 %) showed new or worsening of pre-existing sensory motor deficits. They were severe in 4 patients (7.4 %). There was no correlation between the occurrence of either any new (P = 0.77) or severe (P = 1.0) sensory motor deficit and continued resection after intraoperative image acquisition. Likewise, tumor location, histology, and tumor recurrence did not influence complication rate on uni- and multivariate analysis. We conclude that the combination of iMRI guidance with multimodal neurophysiological monitoring allows for extended resections in glioma surgery without inducing higher rates of neurological deficits, even in patients with eloquently located tumors.

Motor cortex evaluation by nTMS after surgery of central region tumors: a feasibility study.

BACKGROUND: Largely discussed during the past decade, motor cortex reorganization in brain tumor surgery has been investigated only by few studies. We therefore aimed to investigate cortical motor representation after resection of perirolandic WHO grade II and III gliomas using navigated transcranial magnetic stimulation (nTMS). METHODS: Five patients were examined before neurosurgery and after a follow-up period of 17.7 ± 6.8 months. As a control, five healthy age-matched subjects were equally studied by nTMS in two sessions spaced 12.6 (range 2-35) days apart. Resting motor thresholds (RMT), hotspots and centers of gravity (CoG) were identified for the first dorsal interosseous (FDI), abductor pollicis brevis (APB), extensor digitorum (EXT), tibialis anterior (TA) and abductor hallucis (AH) muscles. Euclidian distances, coefficients of variance and intraclass correlation coefficients (ICC) were calculated. RESULTS: Healthy subjects showed moderate to excellent reliability measurement of RMT (ICC = 0.69-0.94). Average displacement of CoGs across sessions was 0.68 ± 0.34 cm in the dominant and 0.76 ± 0.38 cm in the non-dominant hemisphere; hotspots moved 0.87 ± 0.51 cm and 0.83 ± 0.45 cm, respectively. In one patient these parameters differed significantly from the control group (p < 0.05 for both CoGs and hotspots). Overall, all patients' CoGs moved 1.12 ± 0.93 cm, and hotspots were 1.06 ± 0.7 cm apart. In both patients and healthy subjects, movement of assessed parameters was more important along the X- than the Y-axis. CONCLUSIONS: nTMS allows evaluating cortical reorganization after brain tumor surgery. It may contribute to the understanding of neurofunctional dynamics, thus influencing therapeutic strategy.

Proof of principle: supramarginal resection of cerebral metastases in eloquent brain areas.

BACKGROUND: Cerebral metastases are not sharply delimitatable; therefore, microsurgical circumferential stripping of intracerebral metastases is often insufficient for preventing local tumor recurrence. Supramarginal resection significantly improves local tumor control but was suggested not to be suitable for metastases in eloquent brain areas. Therefore, we retrospectively analyzed a series of patients with cerebral metastases situated in eloquent areas for newly occurring neurologic deficits after supramarginal resection performed as awake surgery. METHODS: A retrospective analysis was performed for all patients who underwent supramarginal resection for a cerebral metastasis performed as awake surgery between June 2011 and April 2012. All metastases were localized in eloquent brain areas. Pre- and postsurgical neurologic status was documented as well as data regarding the primary cancer and histopathologic data. Postoperative MRI within 72 h was scheduled routinely to verify complete resection. RESULTS: A total of 19 patients underwent awake surgery for a cerebral metastasis in eloquent brain areas. Surgery was well tolerated in all patients. Neurologic symptoms improved in five patients after surgery. In three patients, neurologic deficits existing before surgery worsened. The postoperative median National Institute of Health Stroke Scale (NIHSS) score did not differ from the preoperative value. CONCLUSIONS: Awake surgery is a feasible tool for metastases in eloquent areas, minimizing postoperative neurologic deficits and morbidity. Therefore, eloquently situated metastases may also be eligible for supramarginal resection. Further studies are needed in order to analyze the benefit of this method in achieving better tumor control.

Long latency responses in tongue muscle elicited by various stimulation sites in anesthetized humans - New insights into tongue-related brainstem reflexes.

BACKGROUND: Long Latency Responses (LLR) in tongue muscles are a scarcely described phenomenon, the physiology of which is uncertain. OBJECTIVES: The aim of this exploratory, observational study was to describe tongue-LLR elicited by direct trigeminal nerve (DTNS), dorsal column (DoColS), transcranial electric (TES) and peripheral median nerve (MNS) stimulation in a total of 93 patients undergoing neurosurgical procedures under general anesthesia. METHODS: Bilateral tongue responses were derived concurrently after each of the following stimulations: (1) DTNS applied with single monophasic or train-of-three pulses, ≤5 mA; (2) DoColS applied with a train-of-three pulses, ≤10 mA; (3) TES consisting of an anodal train-of-five stimulation, ≤250 mA; (4) MNS at wrist consisting of single or train-of-three monophasic pulses, ≤50 mA. Polyphasic tongue muscle responses exceeding the latencies of tongue compound muscle action potentials or motor evoked potentials were classified as LLR. RESULTS: Tongue-LLR were evoked from all stimulation sites, with latencies as follows: (1) DTNS: solely ipsilateral 20.2 ± 3.3 msec; (2) DoColS: ipsilateral 25.9 ± 1.6 msec, contralateral 25.1 ± 4.2 msec; (3) TES: contralateral 55.3 ± 10.2 msec, ipsilateral 54.9 ± 12.0 msec; (4) MNS: ipsilateral 37.8 ± 4.7 msec and contralateral 40.3 ± 3.5 msec. CONCLUSION: The tongue muscles are a common efferent in brainstem pathways targeted by trigeminal and cervical sensory fibers. DTNS can elicit the "trigemino-hypoglossal-reflex". For the MNS elicited tongue-LLR, we propose the term "somatosensory-evoked tongue-reflex". Although the origin of the TES related tongue-LLR remains unclear, these data will help to interpret intraoperative tongue recordings.

Electroencephalography, electrocorticography, and cortical stimulation techniques.

Electroencephalography (EEG) and electrocorticography (ECoG) are two important neurophysiologic techniques used in the operating room for monitoring and mapping electrical brain activity. In this chapter, we detail their principle, recording methodology, and address specifics of their interpretation in the intraoperative setting (e.g., effect of anesthetics), as well as their clinical applications in epilepsy and non-epilepsy surgeries. In addition, we address differences between scalp, surface, and deep cortical recordings that will help towards a more reliable interpretation of the significance of electrophysiologic parameters such as amplitude and morphology as well as in differentiation between abnormal and normal patterns of electrical brain activity. Electrical stimulation is used for intraoperative mapping of different cortical functions such as language, parietal, and motor. Stimulation paradigms used in clinical practice vary with regard to stimulation frequencies and probes being used. Parameters, such as the number of phases per pulse, pulse/phase duration, pulse frequency, organization, and polarity, define their characteristics, including their safety, propensity to trigger seizures, efficiency and reliability of stimulation, and the mapping thresholds. Specifically, in this chapter, we will address differences between monopolar and bipolar stimulation; anodal and cathodal polarity; monophasic and biphasic pulses; constant voltage, and constant current paradigms.