Utility of MRI in surgical planning for parasagittal meningiomas

Acta Neurochirurgica (2023) 165:1717–1725

Surgical resection is the standard treatment for parasagittal meningioma (PSM), but complete resection may be challenging due to superior sagittal sinus (SSS) involvement. The SSS may be partially or completely obstructed, and collateral veins are commonly present. Thus, knowing the status of the SSS in PSM cases prior to treatment is essential to a successful outcome. MRI is utilized prior to surgery in order to determine SSS status and to check for presence of collateral veins.

The objective of this study is to evaluate the reliability of MRI in predicting both SSS involvement and presence of collateral veins in subsequent comparison to actual intra-operative findings, and to report on complications and outcomes.

Methods 27 patients were retrospectively analyzed for this study. A blinded radiologist reviewed all pre-operative images, noting SSS status and collateral vein presence. Intraoperative findings were obtained from hospital records to similarly categorize SSS status and collateral vein presence.

Results Sensitivity of the MRI to SSS status was found to be 100% and specificity was 93%. However, sensitivity and specificity of MRI to collateral vein presence was only 40% and 78.6%, respectively. Complications were experienced by 22% of patients, the majority neurologic in nature.

Conclusion MRI accurately predicted SSS occlusion status, but was less consistent in identification of collateral veins. These findings suggest MRI should be used with caution prior to PSM resection surgery particularly with regards to the presence of collateral veins which may complicate resection.

Pineal cyst: results of long-term MRI surveillance and analysis of growth and shrinkage rates

J Neurosurg 138:113–119, 2023

OBJECTIVE Pineal cyst (PC) is a relatively common true cyst in the pineal gland. Its long-term natural course remains ill defined. This study aims to evaluate the long-term natural history of PC and examine MRI risk factors for cyst growth and shrinkage to help better define which patients might benefit from surgical intervention.

METHODS The records and MRI of 409 consecutive patients with PC were retrospectively examined (nonsurgical cohort). Cyst growth and shrinkage were defined as a ≥ 2-mm increase and decrease in cyst diameter in any direction, respectively. In addition to size, MRI signal intensity ratios were analyzed.

RESULTS The median radiological follow-up period was 10.7 years (interquartile range [IQR] 6.4–14.3 years). The median change in maximal diameter was −0.6 mm (IQR −1.5 to 1.3 mm). During the observation period, cyst growth was confirmed in 21 patients (5.1%). Multivariate logistic regression analysis revealed that only age (odds ratio [OR] 0.96, 95% confidence interval [CI] 0.93–0.99, p < 0.01) was significantly associated with cyst growth. No patient required resection during the observation period. Cyst shrinkage was confirmed in 57 patients (13.9%). Multivariate analysis revealed that maximal diameter (OR 1.22, 95% CI 1.12–1.35, p < 0.01) and cyst CSF T2 signal intensity ratio (OR 9.06, 95% CI 1.38–6.62 × 101, p = 0.02) were significantly associated with cyst shrinkage.

CONCLUSIONS Only 5% of PCs, mainly in patients younger than 50 years of age, have the potential to grow, while cyst shrinkage is more likely to occur across all age groups. Younger age is associated with cyst growth, while larger diameter and higher signal intensity on T2-weighted imaging are associated with shrinkage. Surgery is rarely needed for PCs, despite the possibility of a certain degree of growth.

Prevalence of incidental intracranial findings on magnetic resonance imaging: a systematic review and meta‑analysis

Acta Neurochirurgica (2022) 164:2751–2765

As the volume and fidelity of magnetic resonance imaging (MRI) of the brain increase, observation of incidental findings may also increase. We performed a systematic review and meta-analysis to determine the prevalence of various incidental findings.

Methods PubMed/MEDLINE, EMBASE and SCOPUS were searched from inception to May 24, 2021. We identified 6536 citations and included 35 reports of 34 studies, comprising 40,777 participants. A meta-analysis of proportions was performed, and age-stratified estimates for each finding were derived from age-adjusted non-linear models.

Results Vascular abnormalities were observed in 423/35,706 participants (9.1/1000 scans, 95%CI 5.2–14.2), ranging from 2/1000 scans (95%CI 0–7) in 1-year-olds to 16/1000 scans (95%CI 1–43) in 80-year-olds. Of these, 204/34,306 were aneurysms (3.1/1000 scans, 95%CI 1–6.3), which ranged from 0/1000 scans (95%CI 0–5) at 1 year of age to 6/1000 scans (95%CI 3–9) at 60 years. Neoplastic abnormalities were observed in 456/39,040 participants (11.9/1000 scans, 95%CI 7.5–17.2), ranging from 0.2/1000 scans (95%CI 0–10) in 1-year-olds to 34/1000 scans (95%CI 12–66) in 80-year-olds. Meningiomas were the most common, in 246/38,076 participants (5.3/1000 scans, 95%CI 2.3–9.5), ranging from 0/1000 scans (95%CI 0–2) in 1-year-olds to 17/1000 scans (95%CI 4–37) in 80-year-olds. Chiari malformations were observed in 109/27,408 participants (3.7/1000 scans, 95%CI 1.8–6.3), pineal cysts in 1176/32,170 (9/1000 scans, 95%CI 1.8–21.4) and arachnoid cysts in 414/36,367 (8.5/1000 scans, 95%CI 5.8–11.8).

Conclusion Incidental findings are common on brain MRI and may result in substantial resource expenditure and patient anxiety but are often of little clinical significance.

The diagnostic value of contrast enhancement on MRI in diffuse and anaplastic gliomas

Acta Neurochirurgica (2022) 164:2035–2040

We evaluated differentiations in gadolinium contrast enhancement (CE) between low-grade WHO °II and high-grade WHO °III gliomas in conventional MRI, which have been repeatedly questioned.

Methods Ninety-nine patients, who underwent first resection of WHO°II and °III gliomas, were retrospectively retrieved from a prospective database. The quantitative metric volume of Gd-CE in T1-weighted pre-operative MRI was measured using volumetric segmentation.

Results The OR to detect CE in anaplastic gliomas was seven times higher than that in diffuse gliomas (CI95% 2.817.2, p<0.0001). No CE was seen in 50% (8/16) of focal anaplastic and in 28% (10/36) of entirely anaplastic gliomas. CE was present in 21% (10/47) of diffuse gliomas. Anaplasia correlated with a larger CE volume (r=0.49, p<0.0001) and provided additional 4 cm 3 of CE volume compared to entirely diffuse tumors. The OR to have CE was 3.6 times for IDH1 wild-type tumors (CI95% 1.3–10.2, p=0.05) and 4.8 for tumors with ATRX expression (CI95% 1.3–17.2, p=0.05). In all sub-groups, at least a quarter of cases showed no CE at all and there were cases with present CE.

Conclusion CE is associated with higher odds of unfavorable prognostic features like anaplasia, wild-type IDH1 and retained ATRX. There was no CE in one-fourth of anaplastic gliomas and half of gliomas with focal anaplasia.

The meningioma surface factor: a novel approach to quantify shape irregularity on preoperative imaging and its correlation with WHO grade

J Neurosurg 136:1535–1541, 2022

Atypical and anaplastic meningiomas account for 20% of all meningiomas. An irregular tumor shape on preoperative MRI has been associated with WHO grade II–III histology. However, this subjective allocation does not allow quantification or comparison. An objective parameter of irregularity could substantially influence resection strategy toward a more aggressive approach. Therefore, the aim of this study was to objectively quantify the level of irregularity on preoperative MRI and predict histology based on WHO grade using this novel approach.

METHODS A retrospective study on meningiomas resected between January 2010 and December 2018 was conducted at two neurosurgical centers. This novel approach relies on the theory that a regularly shaped tumor has a smaller surface area than an irregularly shaped tumor with the same volume. A factor was generated using the surface area of a corresponding sphere as a reference, because for a given volume a sphere represents the shape with the smallest surface area possible. Consequently, the surface factor (SF) was calculated by dividing the surface area of a sphere with the same volume as the tumor with the surface area of the tumor. The resulting value of the SF ranges from > 0 to 1. Finally, the SF of each meningioma was then correlated with the corresponding histopathological grading.

RESULTS A total of 126 patients were included in this study; 60.3% had a WHO grade I, 34.9% a WHO grade II, and 4.8% a WHO grade III meningioma. Calculation of the SF demonstrated a significant difference in SFs between WHO grade I (SF 0.851) and WHO grade II–III meningiomas (SF 0.788) (p < 0.001). Multivariate analysis identified SF as an independent prognostic factor for WHO grade (OR 0.000009, 95% CI 0.000–0.159; p = 0.020).

CONCLUSIONS The SF is a proposed mathematical model for a quantitative and objective measurement of meningioma shape, instead of the present subjective assessment. This study revealed significant differences between the SFs of WHO grade I and WHO grade II–III meningiomas and demonstrated that SF is an independent prognostic factor for WHO grade.

Recovery of Supraspinal Microstructural Integrity and Connectivity in Patients Undergoing Surgery for Degenerative Cervical Myelopathy

Neurosurgery 90:447–456, 2022

It remains unknown if the progressive loss of axonal conduction along sensorimotor tracts can be recovered after surgery in patients with degenerative cervical myelopathy (DCM) and if subsequent adaptive microstructural changes are associated with the neurological improvement.

OBJECTIVE: To investigate the upstream recovery of microstructural integrity and reorganization of microstructural connectivity that occurs in patients with DCM after surgical decompression.

METHODS: Preoperative and postoperative cerebral diffusion tensor imaging and diffusion spectrum imaging data were collected for 22 patients with DCM (age = 56.9 ± 9.1 years). Paired t-tests were used to identify significant microstructural changes within cohorts, and correlation analysis was used to identify whether those changes are associated with neurological improvement.

RESULTS: Before surgery, higher structural connectivity (SC) was observed in the prefrontal/ frontal lobes, anterior cingulate, the internal and external capsules, and the anterior, posterior, and superior regions of the corona radiata fibers. Following surgery, an increased modified Japanese Orthopaedic Association score was associated with increased SC from the primary sensorimotor regions to the posterior cingulate and precuneus; increased SC between the cerebellum and the bilateral lingual gyri; and decreased SC from areas of the limbic system to the basal ganglia and the frontal lobe. In addition, increased fractional anisotropy and normalized quantitative anisotropy values along white matter fibers responsible for conveying sensory information and motor coordination and planning were associated with neurological improvement of patients with DCM after surgery.

CONCLUSION: Recovery of microstructural integrity along the corticospinal tract and other sensorimotor pathways, together with supraspinal reorganization of microstructural connectivity within sensory and motor-related regions, was associated with neurological improvement after surgical decompression.

Prevalence of incidental meningiomas and gliomas on MRI: a meta‐analysis and meta‐regression analysis

Acta Neurochirurgica (2021) 163:3401–3415

The chance of incidentally detecting brain tumors is increasing as the utilization of magnetic resonance imaging (MRI) becomes more prevalent. In this background, knowledge is accumulating in relation to the prediction of their clinical sequence. However, their prevalence—especially the prevalence of glioma—has not been adequately investigated according to age, sex, and region.

Method We systematically reviewed the articles according to the PRISMA statement and calculated the prevalence of meningiomas and diffuse gliomas in adults using a generalized linear mixed model. Specifically, the differences related to age, sex, and region were investigated.

Results The pooled prevalence of incidental meningiomas in MRI studies was 0.52% (95% confidence interval (CI) [0.34– 0.78]) in 37,697 individuals from 36 studies. A meta-regression analysis showed that the prevalence was significantly higher in elderly individuals, women, and individuals outside Asia; this remained statistically significant in the multivariate meta-regression analysis. The prevalence reached to 3% at 90 years of age. In contrast, the prevalence of gliomas in 30,918 individuals from 18 studies was 0.064% (95%CI [0.040 – 0.104]). The meta-regression analysis did not show a significant relationship between the prevalence and age, male sex, or region. The prevalence of histologically confirmed glioma was 0.026% (95%CI [0.013–0.052]).

Conclusions Most of meningiomas, especially those in elderlies, remained asymptomatic, and their prevalence increased with age. However, the prevalence of incidental gliomas was much lower and did not increase with age. The number of gliomas that developed and the number that reached a symptomatic stage appeared to be balanced.

MRI-guided stereotactic laser corpus callosotomy for epilepsy

J Neurosurg 135:770–782, 2021

Several small series have described stereotactic MRI-guided laser interstitial thermal therapy for partial callosotomy of astatic and generalized tonic-clonic (GTC) seizures, especially in association with Lennox-Gastaut syndrome. Larger case series and comparison of distinct stereotactic methods for stereotactic laser corpus callosotomy (SLCC), however, are currently lacking. The objective of this study was to report seizure outcomes in a series of adult patients with epilepsy following anterior, posterior, and complete SLCC procedures and to compare the results achieved with a frameless stereotactic surgical robot versus direct MRI guidance frames.

METHODS The authors retrospectively reviewed sequential adult epilepsy surgery patients who underwent SLCC procedures at a single institution. They describe workflows, stereotactic errors, percentage disconnection, hospitalization durations, adverse events, and seizure outcomes after performing anterior, posterior, and complete SLCC procedures using a frameless stereotactic surgical robot versus direct MRI guidance platforms.

RESULTS Thirteen patients underwent 15 SLCC procedures. The median age at surgery was 29 years (range 20–49 years), the median duration of epilepsy was 21 years (range 9–48 years), and median postablation follow-up was 20 months (range 4–44 months). Ten patients underwent anterior SLCC with a median 73% (range 33%–80%) midsagittal length of callosum acutely ablated. Following anterior SLCC, 6 of 10 patients achieved meaningful (> 50%) reduction of target seizures. Four patients underwent posterior (completion) SLCC following prior anterior callosotomy, and 1 patient underwent complete SLCC as a single procedure; 3 of these 5 patients experienced meaningful reduction of target seizures. Overall, 8 of 10 patients in whom astatic seizures were targeted and treated by anterior and/or posterior SLCC experienced meaningful improvement. SLCC procedures with direct MRI guidance (n = 7) versus a frameless surgical robot (n = 8) yielded median radial accuracies of 1.1 mm (range 0.2–2.0 mm) versus 2.4 mm (range 0.6–6.1 mm; p = 0.0011). The most serious adverse event was a clinically significant intraparenchymal hemorrhage in a patient who underwent the robotic technique.

CONCLUSIONS This is the largest reported series of SLCC for epilepsy to date. SLCC provides seizure outcomes comparable to open surgery outcomes reported in the literature. Direct MRI guidance is more accurate, which has the potential to reduce the risks of SLCC. Methodological advancements and larger studies are needed.

Predicting Spinal Surgery Candidacy From Imaging Data Using Machine Learning

Neurosurgery 89:116–121, 2021

The referral process for consultation with a spine surgeon remains inefficient, given a substantial proportion of referrals to spine surgeons are nonoperative.

OBJECTIVE: To develop a machine-learning-based algorithm which accurately identifies patients as candidates for consultation with a spine surgeon, using only magnetic resonance imaging (MRI).

METHODS: We trained a deep U-Net machine learning model to delineate spinal canals on axial slices of 100 normal lumbar MRI scans which were previously delineated by expert radiologists and neurosurgeons. We then tested the model against lumbar MRI scans for 140 patients who had undergone lumbar spine MRI at our institution (60 of whom ultimately underwent surgery, and 80 of whom did not). The model generated automated segmentations of the lumbar spinal canals and calculated a maximum degree of spinal stenosis for each patient,which served as our biomarker for surgical pathology warranting expert consultation.

RESULTS: Themachine learning model correctly predicted surgical candidacy (ie, whether patients ultimately underwent lumbar spinal decompression) with high accuracy (area under the curve = 0.88), using only imaging data from lumbar MRI scans.

CONCLUSION: Automated interpretation of lumbar MRI scans was sufficient to correctly determine surgical candidacy in nearly 90% of cases. Given that a significant proportion of referrals placed for spine surgery evaluation fail to meet criteria for surgical intervention, our model could serve as a valuable tool for patient triage and thereby address some of the inefficiencies within the outpatient surgical referral process.

Machine Learning for the Prediction of Molecular Markers in Glioma on Magnetic Resonance Imaging: A Systematic Review and Meta-Analysis

Neurosurgery 89:31–44, 2021

Molecular characterization of glioma has implications for prognosis, treatment planning, and prediction of treatment response. Current histopathology is limited by intratumoral heterogeneity and variability in detection methods. Advances in computational techniques have led to interest in mining quantitative imaging features to noninvasively detect genetic mutations.

OBJECTIVE: To evaluate the diagnostic accuracy of machine learning (ML) models in molecular subtyping gliomas on preoperative magnetic resonance imaging (MRI).

METHODS: A systematic search was performed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines to identify studies up to April 1, 2020. Methodological quality of studies was assessed using the Quality Assessment for Diagnostic Accuracy Studies (QUADAS)-2. Diagnostic performance estimates were obtained using a bivariate model and heterogeneity was explored using metaregression.

RESULTS: Forty-four original articles were included. The pooled sensitivity and specificity for predicting isocitrate dehydrogenase (IDH) mutation in training datasets were 0.88 (95% CI 0.83-0.91) and 0.86 (95% CI 0.79-0.91), respectively, and 0.83 to 0.85 in validation sets. Use of data augmentation and MRI sequence type were weakly associated with heterogeneity. Both O6-methylguanine-DNA methyltransferase (MGMT) gene promoter methylation and 1p/19q codeletion could be predicted with a pooled sensitivity and specificity between 0.76 and 0.83 in training datasets.

CONCLUSION: ML application to preoperative MRI demonstrated promising results for predicting IDHmutation, MGMT methylation, and 1p/19q codeletion in glioma. Optimized ML models could lead to a noninvasive, objective tool that captures molecular information important for clinical decisionmaking. Future studies should use multicenter data, external validation and investigate clinical feasibility of ML models.

Language hemispheric dominance analyzed with magnetic resonance DTI: correlation with the Wada test

J Neurosurg 134:1703–1710, 2021

Language lateralization is a major concern in some patients with pharmacoresistant epilepsy who will face surgery; in these patients, hemispheric dominance testing is essential to avoid further complications. The Wada test is considered the gold standard examination for language localization, but is invasive and requires many human and material resources. Functional MRI and tractography with diffusion tensor imaging (DTI) have demonstrated that they could be useful for locating language in epilepsy surgery, but there is no evidence of the correlation between the Wada test and DTI MRI in language dominance.

METHODS The authors performed a retrospective review of patients who underwent a Wada test before epilepsy surgery at their institution from 2012 to 2017. The authors retrospectively analyzed fractional anisotropy (FA), number and length of fibers, and volume of the arcuate fasciculus and uncinate fasciculus, comparing dominant and nondominant hemispheres.

RESULTS Ten patients with temporal lobe epilepsy were reviewed. Statistical analysis showed that the mean FA of the arcuate fasciculus in the dominant hemisphere was higher than in the nondominant hemisphere (0.369 vs 0.329, p = 0.049). Also, the number of fibers in the arcuate fasciculus was greater in the dominant hemisphere (881.5 vs 305.4, p = 0.003). However, no differences were found in the FA of the uncinate fasciculus or number of fibers between hemispheres. The length of fibers of the uncinate fasciculus was longer in the dominant side (74.4 vs 50.1 mm, p = 0.05). Volume in both bundles was more prominent in the dominant hemisphere (12.12 vs 6.48 cm3, p = 0.004, in the arcuate fasciculus, and 8.41 vs 4.16 cm3, p = 0.018, in the uncinate fasciculus). Finally, these parameters were compared in patients in whom the seizure focus was situated in the dominant hemisphere: FA (0.37 vs 0.30, p = 0.05), number of fibers (114.4 vs 315.6, p = 0.014), and volume (12.58 vs 5.88 cm3, p = 0.035) in the arcuate fasciculus were found to be statistically significantly higher in the dominant hemispheres. Linear discriminant analysis of FA, number of fibers, and volume of the arcuate fasciculus showed a correct discrimination in 80% of patients (p = 0.024).

CONCLUSIONS The analysis of the arcuate fasciculus and other tract bundles by DTI could be a useful tool for language location testing in the preoperative study of patients with refractory epilepsy.

Four-Dimensional Magnetic Resonance Imaging Assessment of Intracranial Aneurysms

Neurosurgery DOI:10.1093/neuros/nyaa021

Treatment of unruptured intracranial aneurysms can reduce the risk of subarachnoid hemorrhage and its associated morbidity and mortality. However, current methods to predict the risk of rupture and optimize treatment strategies for intracranial aneurysms are limited. Assessment of intra-aneurysmal flow using 4-dimensional magnetic resonance imaging (4D MRI) is a novel tool that could be used to guide therapy.

A systematic search of the literature was performed to provide a state-of-the-art review on 4DMRI assessment of unruptured intracranial aneurysms.

A total of 18 studies were available for review. Eccentric flow on 4D MRI is associated with a greater aspect ratio and peak wall shear stress (WSS). WSS, vorticity, and peak velocity are greater in saccular than fusiform aneurysms. Unstable aneurysms are associated with greater WSS, peak wall stress, and flow jet angle and may exhibit wall enhancement. In comparison to computational fluid dynamics (CFD), 4D MRI has a lower spatial resolution and reports lower WSS and velocity magnitudes, but these parameters equalize when spatial resolution is matched.

4D MRI demonstrates the intra-aneurysmal hemodynamic changes associated with flow diversion, including significantly decreased flow velocity. Thus, 4D MRI is a novel, noninvasive imaging tool used for the evaluation of hemodynamics within intracranial aneurysms. Hemodynamic indices derived from 4D MRI appear to correlate well with the simulated (CFD) values and may be used to measure the success of endovascular therapies and risk factors for aneurysm growth and rupture.

Characterizing tumor invasiveness of glioblastoma using multiparametric magnetic resonance imaging

J Neurosurg 132:1465–1472, 2020

The objective of this study was to characterize the abnormalities revealed by diffusion tensor imaging (DTI) using MR spectroscopy (MRS) and perfusion imaging, and to evaluate the prognostic value of a proposed quantitative measure of tumor invasiveness by combining contrast-enhancing (CE) and DTI abnormalities in patients with glioblastoma.

METHODS Eighty-four patients with glioblastoma were recruited preoperatively. DTI was decomposed into isotropic (p) and anisotropic (q) components. The relative cerebral blood volume (rCBV) was calculated from the dynamic susceptibility contrast imaging. Values of N-acetylaspartate, myoinositol, choline (Cho), lactate (Lac), and glutamate + glutamine (Glx) were measured from multivoxel MRS and normalized as ratios to creatine (Cr). Tumor regions of interest (ROIs) were manually segmented from the CE T1-weighted (CE-ROI) and DTI-q (q-ROI) maps. Perfusion and metabolic characteristics of these ROIs were measured and compared. The relative invasiveness coefficient (RIC) was calculated as a ratio of the characteristic radii of CE-ROI and q-ROI. The prognostic significance of RIC was tested using Kaplan-Meier and multivariate Cox regression analyses.

RESULTS The Cho/Cr, Lac/Cr, and Glx/Cr in q-ROI were significantly higher than CE-ROI (p = 0.004, p = 0.005, and p = 0.007, respectively). CE-ROI had significantly higher rCBV values than q-ROI (p < 0.001). A higher RIC was associated with worse survival in a multivariate overall survival (OS) model (hazard ratio [HR] 1.40, 95% confidence interval [CI] 1.06–1.85, p = 0.016) and progression-free survival (PFS) model (HR 1.55, 95% CI 1.16–2.07, p = 0.003). An RIC cutoff value of 0.89 significantly predicted shorter OS (median 384 vs 605 days, p = 0.002) and PFS (median 244 vs 406 days, p = 0.001).

CONCLUSIONS DTI-q abnormalities displayed higher tumor load and hypoxic signatures compared with CE abnormalities, whereas CE regions potentially represented the tumor proliferation edge. Integrating the extents of invasion visualized by DTI-q and CE images into clinical practice may lead to improved treatment efficacy.

The dentato-rubro-thalamic tract as the potential common deep brain stimulation target for tremor of various origin

Acta Neurochirurgica (2020) 162: 1053–1066

Deep brain stimulation alleviates tremor of various origins. The dentato-rubro-thalamic tract (DRT) has been suspected as a common tremor-reducing structure. Statistical evidence has not been obtained. We here report the results of an uncontrolled case series of patients with refractory tremor who underwent deep brain stimulation under tractographic assistance.

Methods A total of 36 patients were enrolled (essential tremor (17), Parkinson’s tremor (8), multiple sclerosis (7), dystonic head tremor (3), tardive dystonia (1)) and received 62 DBS electrodes (26 bilateral; 10 unilateral). Preoperatively, diffusion tensor magnetic resonance imaging sequences were acquired together with high-resolution anatomical T1Wand T2W sequences. The DRTwas individually tracked and used as a direct thalamic or subthalamic target. Intraoperative tremor reduction was graded on a 4-point scale (0 = no tremor reduction to 3 = full tremor control) and recorded together with the current amplitude, respectively. Stimulation point coordinates were recorded and compared to DRT. The relation of the current amplitude needed to reduce tremor was expressed as TiCR (tremor improvement per current ratio).

Results Stimulation points of 241 were available for analysis. A total of 68 trajectories were tested (62 dB leads, 1.1 trajectories tested per implanted lead). Tremor improvement was significantly decreasing (p < 0.01) if the distance to both the border and the center of the DRT was increasing. On the initial trajectory, 56 leads (90.3%) were finally placed. Long-term outcomes were not part of this analysis.

Discussion Tremor of various origins was acutely alleviated at different points along the DRT fiber tract (above and below the MCP plane) despite different tremor diseases. DRT is potentially a common tremor-reducing structure. Individual targeting helps to reduce brain penetrating tracts. TiCR characterizes stimulation efficacy and might help to identify an optimal stimulation point.

Peritumoral Edema/Tumor Volume Ratio: A Strong Survival Predictor for Posterior Fossa Metastases

Neurosurgery, Volume 85, Issue 1, July 2019, Pages 117–125

Twenty percent of all brain metastases (BM) occur in the posterior fossa (PF). Radiotherapy sometimes associated with surgical resection remains the therapeutic option, while Karnovsky performance status and graded prognostic assessment (GPA) are the best preoperative survival prognostic factors.

OBJECTIVE: To explore the prognostic role of peritumoral brain edema in the PF, which has never been explored though its role in supratentorial BM has been debated.

METHODS: A total of 120 patients diagnosed with PF metastasis who underwent surgical resection were included retrospectively in this analysis. Clinical data were retrieved from electronic patient medical files. The tumor volumes and their associated edema were calculated via manual delineation; subsequently the edema/tumor volume ratio was determined.

RESULTS: In multivariate analysis with Cox multivariate proportional hazard model, the edema to tumor volumes ratio (hazard ratio [HR]: 1.727, 95% confidence interval [CI] 1.427- 2.083; P < .0001) was identified as a new strong independent prognosis factor on overall survival (OS) whereas edema volume alone was not (P = .469). Moreover, BM complete resection (HR: 0.447, 95% CI 0.277-0.719; P < .001), low (0-1) World Health Organization status at diagnosis (HR: 2.109, 95% CI 1.481-3.015; P < .0001), high GPA class at diagnosis (HR: 1.77, 95% CI 0.9-2.9; P < .04), and postoperative brain irradiation (HR: 2.019, 95% CI 1.213-3.361; P < .007] were all confirmed as independent predictive factors for survival.

CONCLUSION: The edema/tumor ratio appears to greatly influence OS in patients suffering from PF metastases unlike the extent of edema alone. This easily determined as well as strong prognostic factor could be used as an interesting tool in clinical practice to help the management of these patients.

MRI combined with PET-CT of different tracers to improve the accuracy of glioma diagnosis

Neurosurg Rev (2019) 42:185–195

Based on studies focusing on positron emission tomography (PET)-computed tomography (CT) combined with magnetic resonance imaging (MRI) in the diagnosis of glioma, we conducted a systematic review and meta-analysis evaluating the pros and cons and the accuracy of different examinations. PubMed and Cochrane Library were searched. The search was conducted until April 2017. Two reviewers independently conducted the literature search according to the criteria set initially. Based on the exclusion criteria, 15 articles are included in this study.

Of all studies that used MRI examination, there are five involving 18F-fluorodeoxyglucose- PET, five involving 11C-methionine-PET, five involving 18F-fluoro-ethyl-tyrosine-PET, and three involving 18Ffluorothymidine- PET. Due to the limitations such as lack of data, small sample size, and unrepresentative studies, we use a non-quantitative methodology.

MRI examination can provide the anatomy information of glioma more clearly. PET-CT examinations based on tumor metabolism using different tracers have more advantages in determining the degree of glioma malignancy and boundaries. However, information provided by PET-Craneotomía of different tracers is not the same. With respect to the novel hybrid MRI/PET examination equipment proposed in recent years, the combination of MRI and PET-CT can definitively improve the diagnostic accuracy of glioma.

Comparing the diagnostic accuracies of F-18 FDG PET and MRI for the detection of spondylodiscitis: A meta-analysis

Spine. 44(7):E414-E422, April 1, 2019

The aim of this study was to compare the diagnostic accuracies of F-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI) for the detection of spondylodiscitis through a meta-analysis.

Summary of Background Data. There is no meta-analysis study that compares the diagnostic accuracies of F-18 FDG PET and MRI for the detection of spondylodiscitis.

Methods. The MEDLINE and EMBASE databases were searched from the earliest available date of indexing to January 10, 2018 for studies comparing the diagnostic performance F-18 FDG PET with that of MRI for the detection of spondylodiscitis. We determined the sensitivities and specificities across studies, calculated the positive and negative likelihood ratios (LR+ and LR-), and constructed the summary receiver operating characteristic curves.

Results. In the seven studies (212 patients) selected, the pooled sensitivity and specificity of F- 18 FDG PET were 0.95 (95% confidence interval [CI]: 0.87-0.98) and 0.88 (95% CI: 0.73-0.95), respectively. The LR syntheses showed an overall LR+ of 7.6 (95% CI: 3.4-17.2) and LR- of 0.05 (95% CI: 0.02-0.14). The pooled diagnostic odds ratio (DOR) was 141 (95% CI: 44-444). The pooled sensitivity and specificity of MRI were 0.85 (95% CI: 0.65-0.95) and 0.66 (95% CI: 0.48-0.80), respectively. The LR syntheses showed an overall LR+ of 2.5 (95% CI: 1.5-4.2) and LR- of 0.22 (95% CI: 0.08-0.60). The pooled DOR was 11 (95% CI: 3-42). In the metaregression analysis, no variable was identified as the source of the study heterogeneity.

Conclusions. The current meta-analysis shows that F-18 FDG PET has better diagnostic accuracy than MRI for the detection of spondylodiscitis. Further large multicenter studies would be necessary to substantiate the diagnostic accuracies of F-18 FDG PET and MRI for spondylodiscitis.

Level of Evidence: 2

The role of diffusion tensor imaging in the diagnosis, prognosis, and assessment of recovery and treatment of spinal cord injury: a systematic review

Neurosurg Focus 46 (3):E7, 2019

Diffusion tensor imaging (DTI) is an MRI tool that provides an objective, noninvasive, in vivo assessment of spinal cord injury (SCI). DTI is significantly better at visualizing microstructures than standard MRI sequences. In this imaging modality, the direction and amplitude of the diffusion of water molecules inside tissues is measured, and this diffusion can be measured using a variety of parameters. As a result, the potential clinical application of DTI has been studied in several spinal cord pathologies, including SCI. The aim of this study was to describe the current state of the potential clinical utility of DTI in patients with SCI and the challenges to its use as a tool in clinical practice.

METHODS A search in the PubMed database was conducted for articles relating to the use of DTI in SCI. The citations of relevant articles were also searched for additional articles.

RESULTS Among the most common DTI metrics are fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. Changes in these metrics reflect changes in tissue integrity. Several DTI metrics and combinations thereof have demonstrated significant correlations with clinical function both in model species and in humans. Its applications encompass the full spectrum of the clinical assessment of SCI including diagnosis, prognosis, recovery, and efficacy of treatments in both the spinal cord and potentially the brain.

CONCLUSIONS DTI and its metrics have great potential to become a powerful clinical tool in SCI. However, the current limitations of DTI preclude its use beyond research and into clinical practice. Further studies are needed to significantly improve and resolve these limitations as well as to determine reliable time-specific changes in multiple DTI metrics for this tool to be used accurately and reliably in the clinical setting.


Surgical resection of skull-base chordomas: experience in case selection for surgical approach according to anatomical compartments and review of the literature

Acta Neurochir (2017) 159:1835–1845

Chordoma is a rare bony malignancy known to have a high rate of local recurrence after surgery. The best treatment paradigm is still being evaluated. We report our experience and review the literature. We emphasize on the difference between endoscopic and open craniotomy in regard to the anatomical compartment harboring the tumor, the limitations of the approaches and the rate of surgical resection.

Method: We retrospectively collected all patients with skullbase chordomas operated on between 2004 and 2014. Detailed radiological description of the compartments being occupied by the tumor and the degree of surgical resection is discussed.

Results: Eighteen patients were operated on in our facility for skull-base chordoma. Seventeen endoscopic surgeries were done in 15 patients, and 7 craniotomies were done in 5 patients. The mean age was 48.9 years (±19.8 years). When reviewing the anatomical compartments, we found that the most common were the upper clivus (95.6%) and lower clivus (58.3%), left cavernous sinus (66.7%) and petrous apex (∼60%). Most of the patients had intradural tumor involvement (70.8%). In all craniotomy cases, there was residual tumor in multiple compartments. In the endoscopic cases, the most difficult compartments for total resection were the lower clivus, and lateral extensions to the petrous apex or cavernous sinus.

Conclusions: Our experience shows that the endoscopic approach is a good option for midline tumors without significant lateral extension. In cases with very lateral or lower extensions, additional approaches should be added trying to achieve complete resection.