1. Erbele ID, Miller LS, Mankekar G, et al. Cochlear enhancement may precede cochlear obliteration after vestibular schwannoma excision. Otol Neurotol 2020;41:202–07
Cochlear obliteration, which occurs as a response to some insults, can impair the ability to place a cochlear implant. This can occur as a consequence of labyrinthectomy, labyrinth sparing removal of internal auditory canal masses, trauma, autoimmune sensorineural hearing loss, and meningitis. Obliteration can be seen on T2 weighed sequences as fluid is replaced within the cochlea. Gadolinium contrast enhancement of the cochlea also appears to occur with cochlear insults. The purpose of this study is to evaluate whether cochlear obliteration and enhancement are correlated, and to determine if enhancement precedes obliteration. 42 patients were evaluated, and 24 received the translabyrinthine approach and 18 received a labyrinth sparing surgery. Twenty-nine had evidence of cochlear enhancement on T1 with gadolinium contrast, and 27 had evidence of cochlear obliteration on T2 images. The odds ratio of patients with cochlear enhancement having obliteration was 30.0:1. Intense cochlear enhancement appeared a median of 163 days after surgery, and complete or near complete obliteration appeared a median of 480 days after surgery. They conclude that enhancement and obliteration are associated. They note that cochlear obliteration progresses over time and that cochlear enhancement is transitory.
Neither cochlear obliteration nor enhancement were associated with loss of hearing in the labyrinth sparing group, though an association between hearing loss and cochlear enhancement was found previously in patients deafened by meningitis. The fact that cochlear obliteration and enhancement were not associated with loss of hearing here may be due to either the fact that there was a small sample size of hearing preservation surgeries in this study or that cochleae respond differently to meningitis than vestibular schwannoma excision.
2 figures, 3 tables
2. Nishi H, Oishi N, Ishii A, et al. Deep learning–derived high-level neuroimaging features predict clinical outcomes for large vessel occlusion. Stroke 2020;51:1484–92
The most widely used neuroimaging biomarker with intracranial large vessel occlusion is the Alberta Stroke Program Early CT Score (ASPECTS), which assesses ischemic changes at 10 specific sites within the territory of the middle cerebral artery. Initially, the scoring was applied to computed tomography (CT) images and later to DWI. It has been reported that ASPECTS scores correlate with clinical outcome, and ASPECTS is widely used in clinical practice for decision-making.
However, some studies have shown that the prediction of outcomes can be improved by applying more complex topological modeling of the ischemic core. Indeed, it is possible that morphological factors, such as the shape of the ischemic core, its homogeneity, and signal strength, might contribute to more precise predictions of clinical outcomes. However, creating a prediction model based on topological and morphological imaging features would require complex modeling based on high-dimensional input data, which is relatively difficult to achieve with the traditional statistical approach.
The authors applied deep learning to derive high-level imaging features from pretreatment DWI data and evaluated the ability of these features in predicting clinical outcomes for patients with large vessel occlusion.
The derivation cohort included 250 patients, and the validation cohort included 74 patients. The convolutional neural network model showed the highest area under the receiver operating characteristic curve: 0.81 compared with 0.63 and 0.64 for the ASPECTS Score and ischemic core volume models, respectively. In the external validation, the area under the curve for the convolutional neural network model was significantly superior to those for the other 2 models. Compared with the standard neuroimaging biomarkers, the deep learning model derived a greater amount of prognostic information from pretreatment neuroimaging data.
They conclude that the study has demonstrated the possibility of applying a deep learning-based approach to automatically extract imaging features for the patients with large vessel occlusion and to use this information as a clinically useful prognostic biomarker.
4 figures, 2 tables
3. Cellucci T, Van Mater H, Graus F, et al. Clinical approach to the diagnosis of autoimmune encephalitis in the pediatric patient. Neurol Neuroimmunol Neuroinflamm 2020;7:e663
This is essentially a whitepaper from the subcommittee of the Autoimmune Encephalitis International Working Group which collaborated through conference calls and email correspondence to consider the pediatric-specific approach to autoimmune encephalitis, and refined existing consensus criteria.
A number of different antibodies have been described in children with autoimmune encephalitis. Currently, the most common autoantibodies in children target the N-methyl-D-aspartate receptor (NMDAR), myelin oligodendrocyte glycoprotein (MOG), and glutamic acid decarboxylase 65 (GAD65).
Diagnosing autoimmune encephalitis is challenging because of overlap in clinical presentations between the types of AE, other inflammatory brain diseases, infections, metabolic diseases, and psychiatric disorders. It is especially difficult in children because of the complexity of normal behavioral changes during childhood and the limited capacity of younger children to describe their symptoms.
Over half the patients will have a normal brain and spine MR at diagnosis. Inflammatory lesions (high signal on T2 and fluid-attenuated inversion recovery sequences) may develop over time, and cerebral atrophy may occur months later. MRI lesions are most likely to be present in those with antibodies to MOG or the gamma-aminobutyric acid-A receptor (GABAAR). Neuroimaging findings are not limited to the temporal lobe or cortex. A normal MRI lessens suspicion for CNS vasculitis, demyelinating diseases, infections, and malignancies. In contrast, restriction on diffusion-weighted imaging reduces the likelihood of pediatric autoimmune encephalitis and should prompt consideration of other etiologies, such as infection associated encephalopathies and vasculitis. Small retrospective adult autoimmune encephalitis studies have proposed that functional PET and SPECT studies may demonstrate brain dysfunction, but experience is limited in pediatric autoimmune encephalitis.
5 tables and 1 flow chart, including tables outlining the commonly identified pediatric AE antibodies and uncommon antibodies
4. Wendebourg MJ, Nagy S, Derfuss T, et al. Magnetic resonance imaging in immune-mediated myelopathies. J Neurol 2020;267:1233–44. Available from: http://dx.doi.org/10.1007/s00415-019-09206-2
Nice review article covering a heterogeneous group of diseases: MS, NMOSD, Anti-MOG, ADEM, SLE, sarcoid, Behcet, paraneoplastic syndromes. While for some disease entities distinctive radiographic signs have been proposed, such as, e.g. the Bagel sign in Behcet disease and the trident sign in neurosarcoidosis, for the majority of diseases, not one pathognomic sign, but rather a pattern of different morphological characteristics is postulated. Though the different entities might share some similarities on MRI despite their distinct origin; numerous unique imaging characteristics remain that help to narrow down the eligible differential diagnoses.
2 figures, 1 table. Figure 2 is useful and shows general location specificity for different types of lesions.
5. Pongpitakmetha T, Fotiadis P, Pasi M, et al. Cortical superficial siderosis progression in cerebral amyloid angiopathy. Neurology 2020;94:e1853–65. Available from: http://www.neurology.org/lookup/doi/10.1212/WNL.0000000000009321
Cerebral amyloid angiopathy (CAA) is a common small vessel disease of the brain characterized by progressive β-amyloid deposition in the small leptomeningeal and cortical arterioles. CAA is an important cause of spontaneous lobar intracerebral hemorrhage (ICH) in the elderly, and a key contributor in age related cognitive decline and dementia. CAA is associated with characteristic hemorrhagic MRI markers including multiple strictly lobar cerebral microbleeds (CMBs) and cortical superficial siderosis (cSS) on blood-sensitive sequences comprising T2*-weighted gradient recalled echo (T2* GRE) or susceptibility-weighted imaging (SWI). In patients presenting with advanced CAA, cSS is found in around 40%–60% and is included in the modified Boston criteria for CAA diagnosis. Recent studies have demonstrated a strong independent association between cortical superficial siderosis and future symptomatic lobar ICH risk in patients with CAA. In this study, the authors investigated the prevalence and predictors of cortical superficial siderosis progression on follow-up MRI within 1 year in symptomatic patients with CAA from a prospective research cohort. In a secondary analysis, they also explored the association between cortical superficial siderosis progression and risk of future symptomatic lobar ICH on clinical follow-up.
79 patients with CAA were evaluated, (mean age, 69.2 years), 56 (71%) with lobar ICH at baseline. Cortical superficial siderosis progression was detected in 23 (29%) patients: 15 (19%) patients had mild and 8 (10%) severe progression. In logistic regression, ICH presence and baseline cortical superficial siderosis were independent predictors of cortical superficial siderosis progression. In similar models, presence of disseminated (but not focal) cortical superficial siderosis at baseline was an independent predictor of cSS progression.
The results indicate that cortical superficial siderosis progression is common in symptomatic patients with CAA and can be reliably assessed on follow-up MRI scans. cSS evolution especially when severe (i.e., affecting >2 sulci) seems to be a potential MRI marker of disease severity and risk of future lobar ICH in this patient population. The findings reinforce the notion that cortical superficial siderosis is key hemorrhagic signature for CAA.
3 figures, 6 tables
6. Senova S, Fomenko A, Gondard E, et al. Anatomy and function of the fornix in the context of its potential as a therapeutic target. J Neurol Neurosurg Psychiatry 2020;91:547–59. Available from: http://jnnp.bmj.com/lookup/doi/10.1136/jnnp-2019-322375
The fornix is a white matter bundle located in the mesial aspect of the cerebral hemispheres, which connects various nodes of a limbic circuitry and is believed to play a key role in cognition and episodic memory recall. As the most prevalent cause of dementia, Alzheimer’s disease (AD) dramatically impairs the quality of life of patients and imposes a significant societal burden on the healthcare system. As an established treatment for movement disorders, deep brain stimulation (DBS) is currently being investigated in preclinical and clinical studies for treatment of memory impairment in AD by modulating fornix activity. Optimal target and stimulation parameters to potentially rescue memory deficits have yet to be determined.
The aim of this review is to consolidate the structural and functional aspects of the fornix in the context of neuromodulation for memory deficits. The authors present an anatomical and functional overview of the fibers and structures interconnected by the fornix. Recent evidence from preclinical models suggests that the fornix is subdivided into two distinct functional axes: a septohippocampal pathway and a subiculothalamic pathway. Each pathway’s target and origin structures are presented, followed by a discussion of their oscillatory dynamics and functional connectivity. Overall, neuromodulation of each pathway of the fornix is discussed in the context of evidence-based forniceal DBS strategies.
3 figures, 6 tables
7. Lucas CG, Villanueva‐Meyer JE, Whipple N, et al. Myxoid glioneuronal tumor, PDGFRA p.K385‐mutant: clinical, radiologic, and histopathologic features. Brain Pathol 2020;30:479–94. Available from: https://onlinelibrary.wiley.com/doi/abs/10.1111/bpa.12797
“Myxoid glioneuronal tumor, PDGFRA p.K385-mutant” is a recently described tumor entity of the central nervous system (CNS) that has a stereotypic location in the septum pellucidum and a characteristic dinucleotide mutation at codon 385 of the PDGFRA oncogene replacing lysine with either leucine or isoleucine (p.K385L/I) in the encoded platelet-derived growth factor receptor alpha protein. These tumors are low-grade glioneuronal neoplasms with histologic features reminiscent of either dysembryoplastic neuroepithelial tumor (DNT) or rosette-forming glioneuronal tumor (RGNT), composed of oligodendrocyte-like cells in a prominent myxoid stroma. However, they uniformly lack the well-defined mucin-patterned nodules of cortically based DNT and also lack the BRAF and FGFR1 mutations or rearrangements that genetically characterize DNT, RGNT and other low-grade neuroepithelial tumor entities. This new proposed entity likely includes the majority of cases that were previously described as “dysembryoplastic neuroepithelial tumor-like neoplasm of the septum pellucidum” and intraventricular DNT. A recent study that combined genome-wide methylation profiling and sequencing analysis on a series of 11 cases of “septal dysembryoplastic neuroepithelial tumor” found that all eight cases harboring PDGFRA p.K385L/I mutation formed a distinct methylation cluster separate from other known CNS tumor entities.
However, the septum pellucidum is not the exclusive anatomic site of involvement and should not be considered as a defining characteristic. This neoplasm likely has a distinct cell of origin located within the septum pellucidum, corpus callosum or periventricular white matter. It can present in a wide age range, including both young children and older adults. It demonstrates histologic features that are somewhat reminiscent of either DNT or RGNT, but lacks the well-defined mucin patterned nodules that characterize DNT in the cerebral cortex.
Based on the small number of patients with long-term follow-up studied to date, this tumor entity appears to follow a benign or indolent disease course that is comparable to other tumor entities assigned a grade I designation by the WHO Classification.
8 figures, 4 tables including 5 MR figures of different patients
8. McMahon NE, Bangee M, Benedetto V, et al. Etiologic workup in cases of cryptogenic stroke. Stroke 2020;51:1419–27
The authors identified clinical practice guidelines/consensus statements through searches of 4 electronic databases and hand-searching of websites/reference lists. Two reviewers independently assessed reports for eligibility. They extracted data on report characteristics and recommendations relating to etiologic workup in acute ischemic stroke and in cases of cryptogenic stroke.
The authors retrieved 16 clinical practice guidelines and 7 consensus statements addressing acute stroke management (n=12), atrial fibrillation (n=5), imaging (n=5), and secondary prevention (n=1). Five reports were of overall high quality. For all patients, guidelines recommended routine brain imaging, noninvasive vascular imaging, a 12-lead ECG, and routine blood tests/laboratory investigations. Additionally, ECG monitoring (>24 hours) was recommended for patients with suspected embolic stroke and echocardiography for patients with suspected cardiac source. Three reports recommended investigations for rarer causes of stroke. None of the reports provided guidance on the extent of investigation needed before classifying a stroke as cryptogenic.
Current CPGs on the etiologic workup of acute ischemic stroke are of variable quality but largely reach consensus about appropriate standard investigations. There is, however, little agreement and a lack of underpinning evidence for more advanced or specialized investigations for rarer causes of stroke. This lack of evidence and consensus, along with poor applicability of many of the existing guidelines, is likely to contribute to variability of access to investigations, inappropriate use of costly and specialized resources and skills, along with delays or lack of diagnosis of etiologies.
The imaging side not particularly sophisticated, with noncontrast CT in all, and MR is superior to CT for diagnostic sensitivity. Vascular imaging by CTA or MRA from arch to vertex…(or doppler ultrasound?)
3 large tables, 1 figure which is a PRISMA flow chart
And that is it for this month!
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