Function-guided differences of arcuate fascicle and inferior fronto-occipital fascicle tractography as diagnostic indicators for surgical risk stratification.

BACKGROUND: Several patients with language-eloquent gliomas face language deterioration postoperatively. Persistent aphasia is frequently associated with damage to subcortical language pathways. Underlying mechanisms still need to be better understood, complicating preoperative risk assessment. This study compared qualitative and quantitative functionally relevant subcortical differences pre- and directly postoperatively in glioma patients with and without aphasia. METHODS: Language-relevant cortical sites were defined using navigated transcranial magnetic stimulation (nTMS) language mapping in 74 patients between 07/2016 and 07/2019. Post-hoc nTMS-based diffusion tensor imaging tractography was used to compare a tract's pre- and postoperative visualization, volume and fractional anisotropy (FA), and the preoperative distance between tract and lesion and postoperative overlap with the resection cavity between the following groups: no aphasia (NoA), tumor- or previous resection induced aphasia persistent pre- and postoperatively (TIA_P), and surgery-induced transient or permanent aphasia (SIA_T or SIA_P). RESULTS: Patients with NoA, TIA_P, SIA_T, and SIA_P showed distinct fasciculus arcuatus (AF) and inferior-fronto-occipital fasciculus (IFOF) properties. The AF was more frequently reconstructable, and the FA of IFOF was higher in NoA than TIA_P cases (all p ≤ 0.03). Simultaneously, SIA_T cases showed higher IFOF fractional anisotropy than TIA_P cases (p < 0.001) and the most considerable AF volume loss overall. While not statistically significant, the four SIA_P cases showed complete loss of ventral language streams postoperatively, the highest resection-cavity-AF-overlap, and the shortest AF to tumor distance. CONCLUSION: Functionally relevant qualitative and quantitative differences in AF and IFOF provide a pre- and postoperative pathophysiological and clinically relevant diagnostic indicator that supports surgical risk stratification.

Noninvasive- and invasive mapping reveals similar language network centralities - A function-based connectome analysis.

BACKGROUND: Former comparisons between direct cortical stimulation (DCS) and navigated transcranial magnetic stimulation (nTMS) only focused on cortical mapping. While both can be combined with diffusion tensor imaging, their differences in the visualization of subcortical and even network levels remain unclear. Network centrality is an essential parameter in network analysis to measure the importance of nodes identified by mapping. Those include Degree centrality, Eigenvector centrality, Closeness centrality, Betweenness centrality, and PageRank centrality. While DCS and nTMS have repeatedly been compared on the cortical level, the underlying network identified by both has not been investigated yet. METHOD: 27 patients with brain lesions necessitating preoperative nTMS and intraoperative DCS language mapping during awake craniotomy were enrolled. Function-based connectome analysis was performed based on the cortical nodes obtained through the two mapping methods, and language-related network centralities were compared. RESULTS: Compared with DCS language mapping, the positive predictive value of cortical nTMS language mapping is 74.1%, with good consistency of tractography for the arcuate fascicle and superior longitudinal fascicle. Moreover, network centralities did not differ between the two mapping methods. However, ventral stream tracts can be better traced based on nTMS mappings, demonstrating its strengths in acquiring language-related networks. In addition, it showed lower centralities than other brain areas, with decentralization as an indicator of language function loss. CONCLUSION: This study deepens the understanding of language-related functional anatomy and proves that non-invasive mapping-based network analysis is comparable to the language network identified via invasive cortical mapping.

Impact of function-guided glioma treatment on oncological outcome in the elderly.

Introduction: Many patients with high-grade gliomas (HGG) are of older age. Research question: We hypothesize that pre- and intraoperative mapping and monitoring preserve functional status in elderly patients while gross total resection (GTR) is the aim, resulting in overall survival (OS) rates comparable to the general population with HGG. Material and methods: We subdivided a prospective cohort of 168 patients above 65 years with eloquent high-grade gliomas into four groups ([years/cases] 1: 65-69/58; 2: 70-74/47; 3: 75-79/43; 4: >79/20). All patients underwent preoperative noninvasive mapping, which was also used for decision-making, intraoperative neuromonitoring in 138 cases, direct cortical and/or subcortical motor mapping in 66 and 50 cases, and awake language mapping in 11 cases. Results: GTR and subtotal resection (STR) could be achieved in 65% and 28%, respectively. Stereotactic biopsy was performed in 8% of cases. Postoperatively, we found transient and permanent functional deficits in 13% and 11% of cases. Postoperative Karnofsky Performance Scale (KPS) did not differ between subgroups. Patients with long-term follow-up (51%) had a progression-free survival of 5.5 (1-47) months and an overall survival of 10.5 (0-86) months. Discussion and conclusion: The interdisciplinary glioma treatment in the elderly is less age-dependent but must be adjusted to the functional status. Function-guided surgical resections could be performed as usual, with maximal tumor resection being the primary goal. However, less network capacity in the elderly to compensate for deficits might cause higher rates of permanent deficits in this group of patients with more fast-growing malignant gliomas.

Motor mapping of the hand muscles using peripheral innervation-based navigated transcranial magnetic stimulation to identify functional reorganization of primary motor regions in malignant tumors.

Tumor-related motor reorganization remains unclear. Navigated transcranial magnetic stimulation (nTMS) can investigate plasticity non-invasively. nTMS-induced motor-evoked potentials (MEPs) of different muscles are commonly used to measure the center of gravity (CoG), the location with the highest density of corticospinal neurons in the precentral gyrus. We hypothesized that a peripheral innervation-based MEP analysis could outline the tumor-induced motor reorganization with a higher clinical and oncological relevance. Then, 21 patients harboring tumors inside the left corticospinal tract (CST) or precentral gyrus were enrolled in group one (G1), and 24 patients with tumors outside the left CST or precentral gyrus were enrolled in Group 2 (G2). Median- and ulnar-nerve-based MEP analysis combined with diffusion tensor imaging fiber tracking was used to explore motor function distribution. There was no significant difference in CoGs or size of motor regions and underlying tracts between G1 and G2. However, G1 involved a sparser distribution of motor regions and more motor-positive sites in the supramarginal gyrus-tumors inside motor areas induced motor reorganization. We propose an "anchor-and-ship theory" hypothesis for this process of motor reorganization: motor CoGs are stably located in the cortical projection area of the CST, like a seated anchor, as the core area for motor output. Primary motor regions can relocate to nearby gyri via synaptic plasticity and association fibers, like a ship moving around its anchor. This principle can anticipate functional reorganization and be used as a neuro-oncological tool for local therapy, such as radiotherapy or surgery.

Cortical stimulation depth of nTMS investigated in a cohort of convexity meningiomas above the primary motor cortex.

BACKGROUND: In clinical routine, navigated transcranial magnetic stimulation (nTMS) is usually applied down to 25 mm. Yet, besides clinical experience and mathematical models, the penetration depth remains unclear. This study aims to investigate the maximum cortical stimulation depth of nTMS in patients with meningioma above the primary motor cortex, causing a displacement of the primary motor cortex away from the skull. NEW METHOD: nTMS stimulation data was reviewed regarding the maximum depth of stimulations eliciting motor-evoked potentials (MEPs). Additionally, electric field values and stimulation intensity were analyzed. RESULTS: Out of a consecutive cohort of 17 meningioma cases, 3 cases of meningioma located in motor-eloquent regions of the upper extremity and 3 cases of the lower extremity were analyzed after fulfilling all inclusion criteria. Regarding the upper extremity motor representations, the MEP could be elicited at a stimulation depth of up to 44 mm, with an electric field of 69 V/m. These results were found in 1 case with the maximum potential distance to the cortex being higher than the maximum stimulation depth eliciting MEPs. For the lower extremities, a maximum depth of 40 mm was recorded (electric field 64 V/m). COMPARISON WITH EXISTING METHODS: None available CONCLUSIONS: The effect of nTMS is not limited to superficial cortical stimulation alone. Depending on electric-field intensity and focality, nTMS stimulation can be applied at a depth of 44 mm. In all cases, electric field strength was comparable and no superficial cortex with comparable electric field strength was observed to elicit MEPs.

Evaluating a cutting-edge augmented reality-supported navigation system for spinal instrumentation.

OBJECTIVE: Dorsal instrumentation using pedicle screws is a standard treatment for multiple spinal pathologies, such as trauma, infection, or degenerative indications. Intraoperative three-dimensional (3D) imaging and navigated pedicle screw placement are used at multiple centers. For the present study, we evaluated a new navigation system enabling augmented reality (AR)-supported pedicle screw placement while integrating navigation cameras into the reference array and drill guide. The present study aimed to evaluate its clinical application regarding safety, efficacy, and accuracy. METHODS: A total of 20 patients were operated on between 06/2021 and 01/2022 using the new technique for intraoperative navigation. Intraoperative data with a focus on accuracy and patient safety, including patient outcome, were analyzed. The accuracy of pedicle screw placement was evaluated by intraoperative CT imaging. RESULTS: A median of 8 (4-18) pedicle screws were placed in each case. Percutaneous instrumentation was performed in 14 patients (70%). The duration of pedicle screw placement (duration scan-scan) was 56 ± 26 (30-107) min. Intraoperative screw revision was necessary for 3 of 180 pedicle screws (1.7%). Intraoperatively, no major complications occurred-one case of delay due to software issues and one case of difficult screw placement were reported. CONCLUSION: The current study's results could confirm the use of the present AR-supported system for navigated pedicle screw placement for dorsal instrumentation in clinical routine. It provides a reliable and safe tool for 3D imaging-based pedicle screw placement, only requires a minimal intraoperative setup, and provides new opportunities by integrating AR.

CompreTAP: Feasibility and reliability of a new language comprehension mapping task via preoperative navigated transcranial magnetic stimulation.

OBJECTIVE: Stimulation-based language mapping approaches that are used pre- and intraoperatively employ predominantly overt language tasks requiring sufficient language production abilities. Yet, these production-based setups are often not feasible in brain tumor patients with severe expressive aphasia. This pilot study evaluated the feasibility and reliability of a newly developed language comprehension task with preoperative navigated transcranial magnetic stimulation (nTMS). METHODS: Fifteen healthy subjects and six brain tumor patients with severe expressive aphasia unable to perform classic overt naming tasks underwent preoperative nTMS language mapping based on an auditory single-word Comprehension TAsk for Perioperative mapping (CompreTAP). Comprehension was probed by button-press responses to auditory stimuli, hence not requiring overt language responses. Positive comprehension areas were identified when stimulation elicited an incorrect or delayed button press. Error categories, case-wise cortical error rate distribution and inter-rater reliability between two experienced specialists were examined. RESULTS: Overall, the new setup showed to be feasible. Comprehension-disruptions induced by nTMS manifested in no responses, delayed or hesitant responses, searching behavior or selection of wrong target items across all patients and controls and could be performed even in patients with severe expressive aphasia. The analysis agreement between both specialists was substantial for classifying comprehension-positive and -negative sites. Extensive left-hemispheric individual cortical comprehension sites were identified for all patients. Apart from one case presenting with transient worsening of aphasic symptoms, pre-existing language deficits did not aggravate if results were used for subsequent surgical planning. CONCLUSION: Employing this new comprehension-based nTMS setup allowed to identify language relevant cortical sites in all healthy subjects and severely aphasic patients who were thus far precluded from classic production-based mapping. This pilot study, moreover, provides first indications that the CompreTAP mapping results may support the preservation of residual language function if used for subsequent surgical planning.

Improving specificity of stimulation-based language mapping in stuttering glioma patients: A mixed methods serial case study.

Objective: Stimulation-based language mapping relies on identifying stimulation-induced language disruptions, which preexisting speech disorders affecting the laryngeal and orofacial speech system can confound. This study ascertained the effects of preexisting stuttering on pre- and intraoperative language mapping to improve the reliability and specificity of established language mapping protocols in the context of speech fluency disorders. Method: Differentiation-ability of a speech therapist and two experienced nrTMS examiners between stuttering symptoms and stimulation-induced language errors during preoperative mappings were retrospectively compared (05/2018-01/2021). Subsequently, the impact of stuttering on intraoperative mappings was evaluated in all prospective patients (01/2021-12/2022). Results: In the first part, 4.85 % of 103 glioma patients stuttered. While both examiners had a significant agreement for misclassifying pauses in speech flow and prolongations (Κ ≥ 0.50, p ≤ 0.02, respectively), less experience resulted in more misclassified stuttering symptoms. In one awake surgery case within the second part, stuttering decreased the reliability of intraoperative language mapping.Comparison with Existing Method(s): By thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions, the reliability and proportion of stuttering symptoms falsely attributed to stimulation-induced language network disruptions can be improved. This may increase the consistency and specificity of language mapping results in stuttering glioma patients. Conclusions: Preexisting stuttering negatively impacted language mapping specificity. Thus, surgical planning and the functional outcome may benefit substantially from thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions by trained specialists.

The impact of intraoperative MRI on cranial surgical site infections-a single-center analysis.

PURPOSE: The use of intraoperative MRI (ioMRI) contributes to an improved extent of resection. Hybrid operating room MRI suites have been established, with the patient being transferred to the MRI scanner. In the present descriptive analysis, we compared the rate of surgical site infections (SSI) after intracranial tumor surgery with and without the use of ioMRI. METHODS: In this retrospective study, we included 446 patients with open craniotomy performed for brain tumor surgery. One hundred fourteen patients were operated on with the use of ioMRI between June 1, 2018, and June 30, 2019 (group 1). During the same period, 126 patients were operated on without ioMRI (group 2). As an additional control group, we analyzed 206 patients operated on from February 1, 2017, to February 28, 2018 when ioMRI had not yet been implemented (group 3). RESULTS: The rate of SSI in group 1 (11.4%), group 2 (9.5%), and group 3 (6.8%) did not differ significantly (p = 0.352). Additional resection after ioMRI did not result in a significantly elevated number of SSI. No significant influence of re-resection, prior radio-/chemotherapy, blood loss or duration of surgery was found on the incidence of SSI. CONCLUSION: Despite the transfer to a non-sterile MRI scanner, leading to a prolonged operation time, SSI rates with and without the use of ioMRI did not differ significantly. Hence, advantages of ioMRI outweigh potential disadvantages as confirmed by this real-life single-center study.

Improving tractography in brainstem cavernoma patients by distortion correction.

Introduction: The resection of brainstem cerebral cavernous malformations (CCM) harbors the risk of damaging the corticospinal tract (CST) and other major tracts. Hence, visualization of eloquent fiber tracts supports pre- and intraoperative planning. However, diffusion tensor imaging fiber tracking at brainstem level suffers from distortion due to field inhomogeneities and eddy currents by steep diffusion gradients. Research question: This study aims to analyze the effect of distortion correction for CST tractography in brainstem CCM patients. Material and methods: 25 patients who underwent resection of brainstem CCM were enrolled, 24 suffered from hemorrhage. We performed an anatomically based tractography of the CST with a mean minimal fractional anisotropy of 0.22 ± 0.04 before and after cranial distortion correction (CDC). Accuracy was measured by anatomical plausibility and aberrant fibers. Results: CDC led to a more precise CST tractography, further approximating its assumed anatomical localization in all cases. CDC resulted in a significantly more ventral location of the CST of 1.5 ± 0.6 mm (6.1 ± 2.7 mm before CDC vs. 4.6 ± 2.1 mm after CDC; p < .0001) as measured by the distance to the basilar artery and of 1.7 ± 0.6 mm (8.9 ± 2.7 mm vs. 7.2 ± 2.1 mm; p < .0001) in relation to the clivus. Aberrant fibers were reduced by CDC in 44% of cases. We found a mean difference in CST volume of 0.6 ± 0.8 ccm. We could not detect motor deficits after resection of irregular fibers. Discussion and conclusion: CDC effectively corrects tractography for distortion at brainstem level, especially in patients suffering from brainstem CCM, further approximating its actual anatomical localization.

Cortical Location of Language Function May Differ between Languages While White Matter Pathways Are Similar in Brain Lesion Patients.

The neural representation of language can be identified cortically using navigated repetitive transcranial magnetic stimulation and subcortically using the fiber tracking of diffusion tensor imaging. We investigated how cortical locations of language and language-eloquent white matter pathways differ in 40 brain lesion patients speaking various languages. Error rates related to stimulations at single sites in the frontal and parietal lobe differed significantly between Balto-Slavic and Indo-European languages. Error rates related to stimulations at single sites in the temporal lobe differed significantly between bilingual individuals. No differences were found in the white matter language pathway volumes between Balto-Slavic and Indo-European languages nor between bilingual patients. These original and exploratory data indicate that the underlying subcortical structure might be similar across languages, with initially observed differences in the cortical location of language depending on the semantic processing, but these could not be confirmed using detailed statistical analyses pointing at a similar cortical and subcortical network.

The Impact of ioMRI on Glioblastoma Resection and Clinical Outcomes in a State-of-the-Art Neuro-Oncological Setup.

Intraoperative magnetic resonance imaging (ioMRI) aims to improve gross total resection (GTR) in glioblastoma (GBM) patients. Despite some older randomized data on safety and feasibility, ioMRI's actual impact in a modern neurosurgical setting utilizing a larger armamentarium of techniques has not been sufficiently investigated to date. We therefore aimed to analyze its effects on residual tumor, patient outcome, and progression-free survival (PFS) in GBM patients in a modern high-volume center. Patients undergoing ioMRI for resection of supratentorial GBM were enrolled between March 2018 and June 2020. ioMRI was performed in all cases at the end of resection when surgeons expected complete macroscopic tumor removal. Extent of resection (EOR) was performed by volumetric analysis, with GTR defined as an EOR ≥ 95%, respectively. Progression-free survival (PFS) was analyzed through univariate and multivariate Cox proportional regression analyses. In total, we enrolled 172 patients. Mean EOR increased from 93.9% to 98.3% (p < 0.0001) due to ioMRI, equaling an increase in GTR rates from 78.5% to 93.0% (p = 0.0002). Residual tumor volume decreased from 1.3 ± 4.2 cm3 to 0.6 ± 2.5 cm3 (p = 0.0037). Logistic regression revealed recurrent GBM as a risk factor leading to subtotal resection (STR) (odds ratio (OR) = 3.047, 95% confidence interval (CI) 1.165-7.974, p = 0.023). Additional resection after ioMRI led to equally long PFS compared to patients with complete tumor removal before ioMRI (hazard ratio (HR) = 0.898, 95%-CI 0.543-1.483, p = 0.67). ioMRI considerably reduces residual tumor volume and helps to achieve comparable PFS, even in patients with unexpected residual tumor after initial resection before ioMRI.

Opportunities and Alternatives of Modern Radiation Oncology and Surgery for the Management of Resectable Brain Metastases.

Postsurgical radiotherapy (RT) has been early proven to prevent local tumor recurrence, initially performed with whole brain RT (WBRT). Subsequent to disadvantageous cognitive sequalae for the patient and the broad distribution of modern linear accelerators, focal irradiation of the tumor has omitted WBRT in most cases. In many studies, the effectiveness of local RT of the resection cavity, either as single-fraction stereotactic radiosurgery (SRS) or hypo-fractionated stereotactic RT (hFSRT), has been demonstrated to be effective and safe. However, whereas prospective high-level incidence is still lacking on which dose and fractionation scheme is the best choice for the patient, further ablative techniques have come into play. Neoadjuvant SRS (N-SRS) prior to resection combines straightforward target delineation with an accelerated post-surgical phase, allowing an earlier start of systemic treatment or rehabilitation as indicated. In addition, low-energy intraoperative RT (IORT) on the surgical bed has been introduced as another alternative to external beam RT, offering sterilization of the cavity surface with steep dose gradients towards the healthy brain. This consensus paper summarizes current local treatment strategies for resectable brain metastases regarding available data and patient-centered decision-making.

Spinal Navigation for Lateral Instrumentation of the Thoracolumbar Spine.

BACKGROUND AND OBJECTIVES: Three-dimensional imaging-based navigation in spine surgery is mostly applied for pedicle screw placement. However, its potential reaches beyond. In this study, we analyzed the incorporation of spinal navigation for lateral instrumentation of the thoracolumbar spine in clinical routine at a high-volume spine center. METHODS: Patients scheduled for lateral instrumentation were prospectively enrolled. A reference array was attached to the pelvis, and a computed tomography scan was acquired intraoperatively. A control computed tomography scan was routinely performed after final cage placement, replacing conventional 2-dimensional X-ray imaging. RESULTS: 145 cases were enrolled from April to October 2021 with a median of 1 (1-4) level being instrumented. Indications for surgery were trauma (35.9%), spinal infection (31.7%), primary and secondary tumors of the spine (17.2%), and degenerative spine disease (15.2%). The duration of surgery after the first scan was 98 ± 41 (20-342) minutes. In total, 190 cages were implanted (94 expandable cages for vertebral body replacement (49.5%) and 96 cages for interbody fusion [50.5%]). Navigation was successfully performed in 139 cases (95.9%). The intraoperative mental load was rated on a scale from 0 to 150 (maximal effort) by the surgeons, showing a moderate effort (median 30 [10-120]). CONCLUSION: Three-dimensional imaging-based spinal navigation can easily be incorporated in clinical routine and serves as a reliable tool to achieve precise implant placement in lateral instrumentation of the spine. It helps to minimize radiation exposure to the surgical staff.

Interhemispheric connections in the maintenance of language performance and prognosis prediction: fully connected layer-based deep learning model analysis.

OBJECTIVE: Language-related networks have been recognized in functional maintenance, which has also been considered the mechanism of plasticity and reorganization in patients with cerebral malignant tumors. However, the role of interhemispheric connections (ICs) in language restoration remains unclear at the network level. Navigated transcranial magnetic stimulation (nTMS) and diffusion tensor imaging fiber tracking data were used to identify language-eloquent regions and their corresponding subcortical structures, respectively. METHODS: Preoperative image-based IC networks and nTMS mapping data from 30 patients without preoperative and postoperative aphasia as the nonaphasia group, 30 patients with preoperative and postoperative aphasia as the glioma-induced aphasia (GIA) group, and 30 patients without preoperative aphasia but who developed aphasia after the operation as the surgery-related aphasia group were investigated using fully connected layer-based deep learning (FC-DL) analysis to weight ICs. RESULTS: GIA patients had more weighted ICs than the patients in the other groups. Weighted ICs between the left precuneus and right paracentral lobule, and between the left and right cuneus, were significantly different among these three groups. The FC-DL approach for modeling functional and structural connectivity was also tested for its potential to predict postoperative language levels, and both the achieved sensitivity and specificity were greater than 70%. Weighted IC was reorganized more in GIA patients to compensate for language loss. CONCLUSIONS: The authors' method offers a new perspective to investigate brain structural organization and predict functional prognosis.

Predictive value of IOM in clipping of unruptured intracranial aneurysms - A prospective study from the surgeon's point of view.

Introduction: Intraoperative neuromonitoring (IOM) of motor/somatosensory evoked potentials is a well-established approach for reducing ischemic complications after aneurysm clipping. Research question: To determine the predictive validity of IOM for postoperative functional outcome and its perceived added value for intraoperative real-time feedback of functional impairment in the surgical treatment of unruptured intracranial aneurysms (UIAs). Material and methods: Prospective study of patients scheduled for elective clipping of UIAs between 02/2019-02/2021. Transcranial motor evoked potentials (tcMEP) were used in all cases, a significant decline was defined as loss of ≥50% in amplitude or 50% latency increase. Clinical data were correlated to postoperative deficits. A surgeon's questionnaire was conceived. Results: 47 patients were included, median age 57 years (range 26-76). IOM was successful in all cases. In 87.2%, IOM was stable throughout surgery, although 1 patient (2.4%) demonstrated a permanent postoperative neurological deficit. All patients with an intraoperatively reversible tcMEP-decline (12.7%) showed no surgery-related deficit, regardless of the decline duration (range 0.5-40.0 â€‹min; mean: 13.8). Temporary clipping (TC) was performed in 12 cases (25.5%), with a decline in amplitude in 4 patients. After clip-removal, all amplitudes returned to baseline. IOM provided the surgeon with a higher sense of security in 63.8%. Discussion and conclusion: IOM remains invaluable during elective microsurgical clipping, particularly during TC of MCA and AcomA-aneurysms. It alerts the surgeon of impending ischemic injury and offers a way of maximizing the time frame for TC. IOM has highly increased surgeons' subjective feeling of security during the procedure.

Radiation doses and accuracy of navigated pedicle screw placement in cervical and thoracic spine surgery: a comparison of sliding gantry CT and mobile cone-beam CT in a homogeneous cohort.

OBJECTIVE: Multiple solutions for navigation-guided pedicle screw placement are currently available. Intraoperative imaging techniques are invaluable for spinal surgery, but often there is little attention paid to patient radiation exposure. This study aimed to compare the applied radiation doses of sliding gantry CT (SGCT)- and mobile cone-beam CT (CBCT)-based pedicle screw placement for spinal instrumentation. METHODS: The authors retrospectively analyzed 183 and 54 patients who underwent SGCT- or standard CBCT-based pedicle screw placement, respectively, for spinal instrumentation at their department between June 2019 and January 2020. SGCT uses an automated radiation dose adjustment. RESULTS: Baseline characteristics, including the number of screws per patient and the number of instrumented levels, did not significantly differ between the two groups. Although the accuracy of screw placement according to Gertzbein-Robbins classification did not differ between the two groups, more screws had to be revised intraoperatively in the CBCT group (SGCT 2.7% vs CBCT 6.0%, p = 0.0036). Mean (± SD) radiation doses for the first (SGCT 484.0 ± 201.1 vs CBCT 687.4 ± 188.5 mGy*cm, p < 0.0001), second (SGCT 515.8 ± 216.3 vs CBCT 658.3 ± 220.1 mGy*cm, p < 0.0001), third (SGCT 531.3 ± 237.5 vs CBCT 641.6 ± 177.3 mGy*cm, p = 0.0140), and total (SGCT 1216.9 ± 699.3 vs CBCT 2000.3 ± 921.0 mGy*cm, p < 0.0001) scans were significantly lower for SGCT. This was also true for radiation doses per scanned level (SGCT 461.9 ± 429.3 vs CBCT 1004.1 ± 905.1 mGy*cm, p < 0.0001) and radiation doses per screw (SGCT 172.6 ± 110.1 vs CBCT 349.6 ± 273.4 mGy*cm, p < 0.0001). CONCLUSIONS: The applied radiation doses were significantly lower using SGCT for navigated pedicle screw placement in spinal instrumentation. A modern CT scanner on a sliding gantry leads to lower radiation doses, especially through automated 3D radiation dose adjustment.

The one-stop-shop approach: Navigating lumbar 360-degree instrumentation in a single position.

Objective: Treatment strategies of patients suffering from pyogenic spondylodiscitis are a controverse topic. Percutaneous dorsal instrumentation followed by surgical debridement and fusion of the infectious vertebral disc spaces is a common approach for surgical treatment. Technical advances enable spinal navigation for dorsal and lateral instrumentation. This report investigates combined navigated dorsal and lateral instrumentation in a single surgery and positioning for lumbar spondylodiscitis in a pilot series. Methods: Patients diagnosed with 1- or 2-level discitis were prospectively enrolled. To enable posterior navigated pedicle screw placement and lateral interbody fusion (LLIF) patients were positioned semi-prone in 45-degree fashion. For spinal referencing, a registration array was attached to the pelvic or spinal process. 3D scans were acquired intraoperatively for registration and implant control. Results: 27 patients suffering from 1- or 2-level spondylodiscitis with a median ASA of 3 (1-4) and a mean BMI of 27.9 ± 4.9 kg/m2 were included. Mean duration of surgery was 146 ± 49 min. Mean blood loss was 367 ± 307 ml. A median of 4 (4-8) pedicle screws were placed for dorsal percutaneous instrumentation with an intraoperative revision rate of 4.0%. LLIF was performed on 31 levels with an intraoperative cage revision rate of 9.7%. Conclusions: Navigated lumbar dorsal and lateral instrumentation in a single operation and positioning is feasible and safe. It enables rapid 360-degree instrumentation in these critically ill patients and potentially reduces overall intraoperative radiation exposure for patient and staff. Compared to purely dorsal approaches it allows for optimal discectomy and fusion while overall incisions and wound size are minimized. Compared to prone LLIF procedures, semi-prone in 45-degree positioning allows for a steep learning curve due to minor changes of familiar anatomy.

Clinical evaluation of vertebral body replacement of carbon fiber-reinforced polyetheretherketone in patients with tumor manifestation of the thoracic and lumbar spine.

PURPOSE: Radiolucent anterior and posterior implants by carbon fiber-reinforced polyetheretherketone (CFR PEEK) aim to improve treatment of primary and secondary tumors of the spine during the last years. The aim of this study was to evaluate clinical and radiological outcomes after dorsoventral instrumentation using a CFR PEEK implant in a cohort of patients representing clinical reality. METHODS: A total of 25 patients with tumor manifestation of the thoracic and lumbar spine underwent vertebral body replacement (VBR) using an expandable CFR PEEK implant between January 2021 and January 2022. Patient outcome, complications, and radiographic follow-up were analyzed. RESULTS: A consecutive series aged 65.8 ± 14.7 (27.6-91.2) years were treated at 37 vertebrae of tumor manifestation, including two cases (8.0%) of primary tumor as well as 23 cases (92.0%) of spinal metastases. Overall, 26 cages covering a median of 1 level (1-4) were implanted. Duration of surgery was 134 ± 104 (65-576) min, with a blood loss of 792 ± 785 (100-4000) ml. No intraoperative cage revision was required. Surgical complications were reported in three (12.0%) cases including hemothorax in two cases (one intraoperative, one postoperative) and atrophic wound healing disorder in one case. In two cases (8.0%), revision surgery was performed (fracture of the adjacent tumorous vertebrae, progressive construct failure regarding cage subsidence). No implant failure was observed. CONCLUSION: VBR using CFR PEEK cages represents a legitimate surgical strategy which opens a variety of improvements-especially in patients in need of postoperative radiotherapy of the spine and MRI-based follow-up examinations.

Neurosurgery for eloquent lesions in children: state-of-the-art rationale and technical implications of perioperative neurophysiology.

OBJECTIVE: In adult patients, an increasing group of neurosurgeons specialize entirely in the treatment of highly eloquent tumors, particularly gliomas. In contrast, extensive perioperative neurophysiological workup for pediatric cases has been limited essentially to epilepsy surgery. METHODS: The authors discuss radio-oncological and general oncological considerations based on the current literature and their personal experience. RESULTS: While several functional mapping modalities facilitate preoperative identification of cortically and subcortically located eloquent areas, not all are suited for children. Direct cortical intraoperative stimulation is impractical in many young patients due to the reduced excitability of the immature cortex. Behavioral requirements also limit the utility of functional MRI and magnetoencephalography in children. In contrast, MRI-derived tractography and navigated transcranial magnetic stimulation are available across ages. Herein, the authors review the oncological rationale of function-guided resection in pediatric gliomas including technical implications such as personalized perioperative neurophysiology, surgical strategies, and limitations. CONCLUSIONS: Taken together, these techniques, despite the limitations of some, facilitate the identification of eloquent areas prior to tumor surgery and radiotherapy as well as during follow-up of residual tumors.