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Journal Scan — This Month in Other Journals, March 2019

1. Fox MD. Mapping Symptoms to Brain Networks with the Human Connectome. N Engl J Med. 2018;379(23):2237-2245. doi:10.1056/NEJMra1706158.

Single-lesion analysis has been the foundation of clinical neurology and the basis for localization of most neurologic symptoms and behaviors. The traditional neurologic approach to localization of brain function has been by the identification of focal areas of damage, (for example- stroke) that correspond to a symptom or sign, such as paralysis.

It has become apparent that lesion-based localization is sometimes flawed because similar symptoms can result from lesions in different brain locations. For example, most lesions that disrupt language are located outside the left frontal cortex, most lesions that disrupt memory are located outside the hippocampus, and lesions that disrupt social behavior are frequently outside the frontal cortex. Even when the locations of lesions overlap between patients with the same symptom, the site of overlap may not conform to conventional ideas about the function of that part of the brain. For example, brain-stem lesions that cause visual hallucinations overlap in the midbrain and medial thalamus, but these locations have no clear role in vision or visual imagery. The relationship between symptoms and lesion location is therefore not straightforward.

Lesion-based localization is also limited by the fact that many complex symptoms occur in patients without overt brain lesions. Common neurobehavioral and psychiatric conditions, such as delirium, amnesia, autism, and schizophrenia, occur in patients with no obvious brain lesions.

If a complex behavior requires integrated function of multiple connected brain regions, lesions in any of these regions can disrupt behavior and lead to similar symptoms. For example, complex problem solving requires coordinated function of frontal and parietal regions, and lesions in either location degrade performance. Similarly, damage to the connection between regions can cause complex “disconnection” syndromes, while the cortical regions required …

Accurate Patient-Specific Machine Learning Models of Glioblastoma Invasion Using Transfer Learning

Fellows’ Journal Club

The authors evaluated tumor cell density using a transfer learning method that generates individualized patient models, grounded in the wealth of population data, while also detecting and adjusting for interpatient variabilities based on each patient’s own histologic data. They collected 82 image-recorded biopsy samples, from 18 patients with primary GBM. With multivariate modeling, transfer learning improved performance (r = 0.88) compared with one-model-fits-all (r = 0.39). They conclude that transfer learning significantly improves predictive modeling performance for quantifying tumor cell density in glioblastoma.

Abstract

BACKGROUND AND PURPOSE

MR imaging–based modeling of tumor cell density can substantially improve targeted treatment of glioblastoma. Unfortunately, interpatient variability limits the predictive ability of many modeling approaches. We present a transfer learning method that generates individualized patient models, grounded in the wealth of population data, while also detecting and adjusting for interpatient variabilities based on each patient’s own histologic data.

MATERIALS AND METHODS

We recruited patients with primary glioblastoma undergoing image-guided biopsies and preoperative imaging, including contrast-enhanced MR imaging, dynamic susceptibility contrast MR imaging, and diffusion tensor imaging. We calculated relative cerebral blood volume from DSC-MR imaging and mean diffusivity and fractional anisotropy from DTI. Following image coregistration, we assessed tumor cell density for each biopsy and identified corresponding localized MR imaging measurements. We then explored a range of univariate and multivariate predictive models of tumor cell density based on MR imaging measurements in a generalized one-model-fits-all approach. We then implemented both univariate and multivariate individualized transfer learning predictive models, which harness the available population-level data but allow individual variability in their predictions. Finally, we compared Pearson correlation coefficients and mean absolute error between the individualized transfer learning and generalized one-model-fits-all models.

RESULTS

Tumor cell density significantly correlated with relative CBV (r = 0.33, P < .001), and T1-weighted postcontrast (r =

3T MRI Whole-Brain Microscopy Discrimination of Subcortical Anatomy, Part 1: Brain Stem

Editor’s Choice

The authors applied an optimized TSE T2 sequence to washed postmortem brain samples to reveal exquisite and reproducible brain stem anatomic MR imaging contrast comparable with histologic atlases. Direct TSE MR imaging sequence discrimination of brain stem anatomy can help validate other MR imaging contrasts, such as diffusion tractography, or serve as a structural template for extracting quantitative MR imaging data in future postmortem investigations.

Abstract

BACKGROUND AND PURPOSE

The brain stem is compactly organized with life-sustaining sensorimotor and autonomic structures that can be affected by numerous pathologies but can be difficult to resolve on conventional MR imaging.

MATERIALS AND METHODS

We applied an optimized TSE T2 sequence to washed postmortem brain samples to reveal exquisite and reproducible brain stem anatomic MR imaging contrast comparable with histologic atlases. This resource-efficient approach can be performed across multiple whole-brain samples with relatively short acquisition times (2 hours per imaging plane) using clinical 3T MR imaging systems.

RESULTS

We identified most brain stem structures at 7 canonical axial levels. Multiplanar or oblique planes illustrate the 3D course and spatial relationships of major brain stem white matter pathways. Measurements of the relative position, course, and cross-sectional area of these pathways across multiple samples allow estimation of pathway location in other samples or clinical subjects. Possible structure-function asymmetries in these pathways will require further study—that is, the cross-sectional area of the left corticospinal tract in the midpons appeared 20% larger (n = 13 brains, P < .10).

CONCLUSIONS

Compared with traditional atlases, multiplanar MR imaging contrast has advantages for learning and retaining brain stem anatomy for clinicians and trainees. Direct TSE MR imaging sequence discrimination of brain stem anatomy can help validate other MR imaging contrasts, such as diffusion tractography, or serve as a structural template for extracting quantitative MR imaging data in

Neuroimaging Clinics of North America: Update on Temporal Bone Imaging with Emphasis on Clinical and Surgical Perspectives

Moonis G, Juliano AF, Mukherji S. Neuroimaging Clinics of North America: Update on Temporal Bone Imaging with Emphasis on Clinical and Surgical Perspectives; Elselvier; 2019; 202 pp; $397.00.

The February 2019 edition of the Neuroimaging Clinics discusses one of the most detailed areas of neuroradiology — temporal bone imaging. Edited by Drs. Moonis and Juliano, Update on Temporal Bone Imaging with an Emphasis on Clinical and Surgical Perspectives consists of the following 13 chapters:

  • Inflammation
  • Meniere Disease
  • Ostosclerosis
  • Tinnitus
  • Third Window
  • Arterial Abnormalities
  • Pediatric Hearing Loss
  • Syndromic Temporal Bone Abnormalities
  • Temporal Bone Trauma
  • Management of Vestibelar Schwannomas
  • Otologic Surgical Procedures
  • Advanced MR Imaging

Thirty authors have contributed to this 200 page issue. Throughout the text there is an attempt to correlate — as well as possible — important clinical and surgical aspects of the topic under consideration. For example: audiograms of a number of abnormalities, tables for clinical classification of hearing loss, diagrams of aberrant arterial connections, sound conduction diagrams in normal and abnormal situations. The imaging quality is excellent throughout the book and the chapters are formatted in a similar manner.

This edition starts with a chapter on inflammation and it is particularly well done with an abundance of illustrations, tables, and well-outlined and described entities. Because of the myriad inflammatory diseases that affect the temporal bone, close attention to this material is appropriate, considering neuroradiologists’ daily evaluation of this area.

Updates on topics less frequently encountered include Meniere Disease and Third Window Lesions; however, the other topics are also important and well designed. Again, what is nice about this volume in general are the clinical correlations. In the trauma chapter, for example, many facts are emphasized and illustrated (like otic capsule involvement or sparing), the mechanism of force to cause these, and the otologic consequences. Side by …

Neuroimaging-Based Classification Algorithm for Predicting 1p/19q-Codeletion Status in IDH-Mutant Lower Grade Gliomas

Fellows’ Journal Club

One hundred two IDH-mutant lower grade gliomas with preoperative MR imaging and known 1p/19q status from The Cancer Genome Atlas composed a training dataset. Two neuroradiologists in consensus analyzed the training dataset for various imaging features: tumor or cyst texture, margins, cortical infiltration, T2-FLAIR mismatch, tumor cyst, T2* susceptibility, hydrocephalus, midline shift, maximum dimension, primary lobe, necrosis, enhancement, edema, and gliomatosis. Statistical analysis of the training data produced a multivariate classification model for codeletion prediction based on a subset of MR imaging features and patient age. Training dataset analysis produced a 2-step classification algorithm with 86.3% codeletion prediction accuracy, based on the following: 1) the presence of the T2-FLAIR mismatch sign, which was 100% predictive of noncodeleted lower grade gliomas; and 2) a logistic regression model based on texture, patient age, T2* susceptibility, primary lobe, and hydrocephalus. Independent validation of the classification algorithm rendered codeletion prediction accuracies of 81.1% and 79.2% in 2 independent readers.

Abstract

BACKGROUND AND PURPOSE

Isocitrate dehydrogenase (IDH)-mutant lower grade gliomas are classified as oligodendrogliomas or diffuse astrocytomas based on 1p/19q-codeletion status. We aimed to test and validate neuroradiologists’ performances in predicting the codeletion status of IDH-mutant lower grade gliomas based on simple neuroimaging metrics.

MATERIALS AND METHODS

One hundred two IDH-mutant lower grade gliomas with preoperative MR imaging and known 1p/19q status from The Cancer Genome Atlas composed a training dataset. Two neuroradiologists in consensus analyzed the training dataset for various imaging features: tumor or cyst texture, margins, cortical infiltration, T2-FLAIR mismatch, tumor cyst, T2* susceptibility, hydrocephalus, midline shift, maximum dimension, primary lobe, necrosis, enhancement, edema, and gliomatosis. Statistical analysis of the training data produced a multivariate classification model for codeletion prediction based on a subset of MR imaging features and patient age. To validate the classification model, 2 different independent neuroradiologists

Imaging of Patients with Suspected Large-Vessel Occlusion at Primary Stroke Centers: Available Modalities and a Suggested Approach

Editor’s Choice

Endovascular thrombectomy has proven efficacy for a wide range of patients with large-vessel occlusion stroke and in selected cases up to 24 hours from onset. While primary stroke centers have increased the proportion of patients with stroke receiving thrombolytic therapy, delays can be encountered until patients with LVO are identified and transferred from the primary stroke center to a comprehensive stroke center. Therefore, any extra steps need to be carefully weighed. The use of CTA (especially multiphase) at the primary stroke center level has many advantages in expediting the transfer of appropriate patients to a comprehensive center.

Abstract

SUMMARY

The overwhelming benefit of endovascular therapy in patients with large-vessel occlusions suggests that more patients will be screened than treated. Some of those patients will be evaluated first at primary stroke centers; this type of evaluation calls for standardizing the imaging approach to minimize delays in assessing, transferring, and treating these patients. Here, we propose that CT angiography (performed at the same time as head CT) should be the minimum imaging approach for all patients with stroke with suspected large-vessel occlusion presenting to primary stroke centers. We discuss some of the implications of this approach and how to facilitate them.

Read this article: http://bit.ly/2GYJ36i

Disorder in Pixel-Level Edge Directions on T1WI Is Associated with the Degree of Radiation Necrosis in Primary and Metastatic Brain Tumors: Preliminary Findings

Fellows’ Journal Club

The authors sought to investigate whether co-occurrence of local anisotropic gradient orientations (COLLAGE) measurements from posttreatment gadolinium-contrast T1WI could distinguish varying extents of cerebral radiation necrosis and recurrent tumor classes in a lesion across primary and metastatic brain tumors. On 75 gadolinium-contrast T1WI studies obtained from patients with primary and metastatic brain tumors and nasopharyngeal carcinoma, the extent of cerebral radiation necrosis and recurrent tumor in every brain lesion was histopathologically defined by a neuropathologist as the following: 1) “pure” cerebral radiation necrosis; 2) “mixed” pathology with coexistence of cerebral radiation necrosis and recurrent tumors; 3) “predominant” (>80%) cerebral radiation necrosis; 4) predominant (>80%) recurrent tumor; and 5) pure tumor. COLLAGE features were extracted from the expert-annotated ROIs on MR imaging. COLLAGE features exhibited decreased skewness for patients with pure and predominant cerebral radiation necrosis and were statistically significantly different from those in patients with predominant recurrent tumors, which had highly skewed COLLAGE values.

Abstract

BACKGROUND AND PURPOSE

Co-occurrence of local anisotropic gradient orientations (COLLAGE) is a recently developed radiomic (computer extracted) feature that captures entropy (measures the degree of disorder) in pixel-level edge directions and was previously shown to distinguish predominant cerebral radiation necrosis from recurrent tumor on gadolinium-contrast T1WI. In this work, we sought to investigate whether COLLAGE measurements from posttreatment gadolinium-contrast T1WI could distinguish varying extents of cerebral radiation necrosis and recurrent tumor classes in a lesion across primary and metastatic brain tumors.

MATERIALS AND METHODS

On a total of 75 gadolinium-contrast T1WI studies obtained from patients with primary and metastatic brain tumors and nasopharyngeal carcinoma, the extent of cerebral radiation necrosis and recurrent tumor in every brain lesion was histopathologically defined by an expert neuropathologist as the following: 1) “pure” cerebral radiation necrosis; 2) “mixed” pathology with coexistence of cerebral radiation necrosis and

Endovascular Treatment of Unruptured MCA Bifurcation Aneurysms Regardless of Aneurysm Morphology: Short- and Long-Term Follow-Up

Editor’s Choice

Between May 2008 and July 2017, endovascular treatment of 1184 aneurysms in 827 patients was performed in a single institution. Twenty-four percent of these aneurysms were located at the MCA, and 150 unruptured MCA bifurcation aneurysms treated with coiling, stent-assisted coiling, or endovascular flow diverter (WEB device) were identified for this retrospective data analysis. The procedure-associated good clinical outcome was 89.9%, and the mortality rate was 2.7%. Short-term follow-up good clinical outcome/mortality rates were 91.3%/0.7%. At discharge, 137 patients had an mRS of 0–2 (91.3%) and 13 had an mRS of 3–6 (8.7%). The authors conclude that regardless of the architecture of MCA bifurcation aneurysms, endovascular treatment can be performed with low morbidity/mortality rates.

 

Abstract

BACKGROUND AND PURPOSE

The optimal treatment of unruptured middle cerebral aneurysms is still under debate. Although today almost any aneurysm can be treated endovascularly, there is a lack of data comparing endovascular and microsurgical repair of MCA aneurysms. The aim of our analysis is to provide data on the efficacy, clinical outcome, complications and re-treatment rates of endovascular treatment of this subtype of aneurysms.

MATERIALS AND METHODS

Between May 2008 and July 2017, endovascular treatment of 1184 aneurysms in 827 patients was performed in our department. Twenty-four percent of these aneurysms were located at the MCA, and 150 unruptured MCA bifurcation aneurysms treated with coiling, stent-assisted-coiling, or endovascular flow diverter (WEB device) were identified for this retrospective data analysis. Ninety-six percent of all aneurysms, ruptured and unruptured, were treated by an endovascular approach, which yields a low selection bias for aneurysms suitable for endovascular treatment. Follow-up examinations were performed after 12 and 36 months and then every 1–3 years after embolization. Procedures were analyzed for periprocedural complications, outcome, and retreatment rate of the WEB (n = 38) and coiling with (n =

Journal Scan – This Month in Other Journals, February 2019

1. Gallina P, Lastrucci G, Caini S, Lorenzo N Di, Porfirio B, Scollato A. Accuracy and safety of 1-day external lumbar drainage of CSF for shunt selection in patients with idiopathic normal pressure hydrocephalus. J Neurosurg. 2018:1-7. doi:10.3171/2018.6.JNS18400.

Cerebrospinal fluid shunting is the treatment of choice for idiopathic normal pressure hydrocephalus (iNPH) with a 75%–82% rate of successful outcome and 11% risk of serious adverse events. Not all patients diagnosed with iNPH are likely to benefit from shunt, and preoperative “supplemental prognostic tests” with intracranial pressure recording or CSF infusion/subtraction are recommended. External lumbar drainage (ELD) of CSF has gained wide acceptance among neurosurgeons as the best predictor of successful shunt surgery. The hypothesis underlying ELD is that prolonged drainage of a relatively large amount of CSF, more than with the spinal tap test, mimics a shunt effect.

Three to five days of external lumbar drainage of CSF is a test for ventriculoperitoneal shunt (VPS) selection in idiopathic normal pressure hydrocephalus. The accuracy and complication rates of a shorter (1-day) ELD procedure were analyzed.

Of 93 patients who underwent 1-day ELD, 3 did not complete the procedure. Of the remaining 90 patients, 2 experienced transient nerve root irritation. Twenty-four patients had negative test outcomes and 66 had positive test outcomes. Nine negative-outcome patients had intraprocedural headache, which showed 37.5% sensitivity and 100% specificity as predictors of negative 1-day ELD outcome. Sixty-eight patients (6 with negative and 62 with positive outcomes) underwent VPS insertion, which was successful in 0 and 58 patients, respectively, at 1-month follow-up.

They conclude that one-day ELD is a reliable tool in iNPH management, with low complication risk and short trial duration. The test is very consistent in predicting who will have a positive outcome with VPS placement, given the high chance of successful outcome at …