1. Hoeritzauer I, Carson A, Statham P, et al. Scan-negative cauda equina syndrome. Neurology 2021;96:e433–47. Available from: http://www.neurology.org/lookup/doi/10.1212/WNL.0000000000011154

Cauda equina syndrome (CES) is a surgical emergency caused by compression of the cauda equina nerve roots. It is suspected when patients present with bladder, bowel, or sexual dysfunction or saddle numbness with or without new back or leg pain. An MRI scan is required to demonstrate cauda equina compression and it is recommended that this occurs within 1–4 hours of presentation to hospital, creating significant pressure on emergency care, neurosurgical, orthopedic, and radiology staff to provide a responsive 24-hour service. However, a mean of 81% of patients referred to neurosurgery with CES have normal or nonexplanatory imaging—“scan-negative”—despite having similar rates of pain and bladder and neurologic dysfunction.

The authors report a prospective study of consecutive patients presenting with the clinical features of CES to a regional neurosurgery center comprising semi-structured interview and questionnaires investigating presenting symptoms, neurologic examination, psychiatric and functional disorder comorbidity, bladder/bowel/sexual function, distress, and disability.

Clinical CES was determined by the definition of 1 or more of acute bladder/bowel/sexual dysfunction or saddle numbness ± leg or back pain. Radiologic findings were divided into (1) scan-positive CES, defined as compression of the cauda equina nerve roots with >75% central canal occlusion or no CSF around the cauda equina nerve roots on axial view7; (2) a mixed category not meeting radiologic criteria for cauda equina compression but with some radiologic evidence of nerve root compression or displacement; (3) scan-negative CES, with no nerve root compression or other radiologic reason for any of their clinical CES symptoms; and (4) neurologic or other diagnoses.

198 patients presented consecutively over 28 months. A total of 47 were diagnosed with scan positive CES (43% female, average age 48 years; discogenic n = 42; fracture n= 2; stenosis, spondylolisthesis, tumor each n = 1). A total of 76 mixed category patients had nerve root compression/displacement without CES compression and 61 patients had scan negative CES. An alternative neurologic cause of CES emerged in 14/198 patients during admission and 4/151 patients with mean duration 25 months follow-up. Patients with scan negative CES had more positive clinical signs of a functional neurologic disorder, were more likely to describe their current back pain as worst ever and were more likely to have symptoms of a panic attack at onset. Patients with scan positive CES were more likely to have reduced/absent bilateral ankle jerks.

Bottom line: Urgent neuroimaging is required in all CES presentations. Although they have demonstrated some clinical features that may help differentiate scan-negative from scan-positive CES at presentation, an urgent MRI scan continues to be essential, as none of them allows clinical separation with sufficient confidence.

3 figures, 4 tables, no imaging. Lots of discussion of functional behavior.

2. Murphy ES, Parsai S, Kano H, et al. Outcomes of stereotactic radiosurgery for pilocytic astrocytoma: an international multiinstitutional study. J Neurosurg 2019;134:162–70

Pilocytic astrocytomas (PAs) are rare tumors, with an incidence of 0.89 cases per 100,000 children and adolescents between the ages of 0 and 19 years. PAs are most often diagnosed in the first 20 years of life and most commonly occur in the cerebellum, brainstem, and optic pathway/hypothalamic areas. They are commonly slow growing and often become large by the time of diagnosis, yet they have favorable 5-year survival rates of greater than 80%. The current standard initial therapy is maximal safe resection. The extent of resection has been correlated with progression-free survival (PFS), and complete resection can be curative. Following gross total resection, observation is standard, and the procedure results in a PFS rate greater than 90% for grade I tumors. Following incomplete resection, the PFS at 5 years is only 55% according to the Children’s Cancer Group/Pediatric Oncology Group low-grade glioma trial. Conventionally fractionated radiotherapy or stereotactic radiosurgery (SRS) can be used in cases of incomplete resection, recurrent disease, or definitive management for unresectable tumors.

A total of 141 patients were analyzed in the study. The median patient age was 14 years (range 2–84 years) at the time of GKRS. The median follow-up was 67.3 months. Thirty-nine percent of patients underwent SRS as the initial therapy, whereas 61% underwent SRS as salvage treatment. The median tumor volume was 3.45 cm3. The tumor location was the brainstem in 30% of cases, with a non-brainstem location in the remainder. Five- and 10-year overall survival rates at the last follow-up were 95.7% and 92.5%, respectively. Five- and 10-year progression-free survival (PFS) rates were 74.0% and 69.7%, respectively. On univariate analysis, an age < 18 years, tumor volumes < 4.5 cm3, and no prior radiotherapy or chemotherapy were identified as positive prognostic factors for improved PFS. On multivariate analysis, only prior radiotherapy was significant for worse PFS.

4 figures, 4 tables with a bunch of Kaplan-Meier curves

3. Kan P, Maragkos GA, Srivatsan A, et al. Middle meningeal artery embolization for chronic subdural hematoma: a multi-center experience of 154 consecutive embolizations. Neurosurgery 2020;88:268–77. Available from: https://academic.oup.com/neurosurgery/advance-article/doi/10.1093/neuros/nyaa379/5918981

Patients with multiple recurrences after subdural evacuation procedures are particularly challenging and are commonly elderly, coagulopathic, or on anticoagulation with multiple comorbidities. Repeated recurrence is potentially due to the failure of surgical evacuation alone to address the underlying pathophysiologic mechanism of cSDH formation, which involves the formation of fragile capillaries along the subdural membrane encapsulating the collection. Endovascular embolization of the middle meningeal artery (MMA) has been proposed as a minimally invasive method to permanently address the vascular supply of cSDH. Preliminary studies have evaluated the safety and efficacy of MMA embolization as a standalone procedure and in combination with surgical evacuation, with encouraging results. The authors present a large MMA embolization series, involving 15 major neurosurgical centers from across the United States to delineate the current practices of MMA embolization as well as its safety and efficacy in permanently treating cSDH.

A total of 138 patients were included. A total of 15 patients underwent bilateral interventions for 154 total embolizations (66.7% primary treatment). At presentation, 30.4% and 23.9% of patients were on antiplatelet and anticoagulation therapy, respectively. Median admission cSDH thickness was 14 mm. A total of 46.1% of embolizations were performed under general anesthesia, and 97.4% of procedures were successfully completed. A total of 70.2% of embolizations used particles, and 25.3% used liquid embolics with no significant outcome difference between embolization materials. On last follow-up, median cSDH thickness was 4 mm (71% median thickness reduction). A total of 70.8% of patients had >50% improvement on imaging (31.9% improved clinically), and 9 patients (6.5%) required further cSDH treatment. There were 16 complications with 9 (6.5%) because of continued hematoma expansion. Mortality rate was 4.4%.

They conclude that MMA embolization may provide a safe and efficacious minimally invasive alternative to conventional surgical techniques.

4 figures and 8 tables, including CT and angio

4. Sheth KN, Mazurek MH, Yuen MM, et al. Assessment of brain injury using portable, low-field magnetic resonance imaging at the bedside of critically ill patients. JAMA Neurol 2021;78:41–47

The authors developed and deployed a novel bedside neuroimaging solution, for which this is their first clinical report. They investigated patients with neurological injury or alteration using a low-field (0.064-T) portable MRI device at the bedside in neuroscience intensive care units (ICUs) and COVID-19 ICUs. This point-of-care (POC) MRI used no cryogens and plugged into a single, 110-V, 15-A standard power outlet. The device dimensions rendered it maneuverable within the confines of an ICU patient room. A self-contained motor and driving capability facilitated the deployment of a single device across the institution. The 5-Gauss (0.0005-T) safety perimeter had a radius of 79 cm from the center of the magnet.

In this cohort study of a series of 50 patients imaged with a portable, bedside MRI device, including patients with ischemic stroke, hemorrhagic stroke, subarachnoid hemorrhage, traumatic brain injury, brain tumor, and COVID-19 and altered mental status, abnormal neuroimaging findings were detected in 29 of 30 patients without COVID-19 (97%); 8 of 20 patients with COVID-19 (40%) demonstrated abnormalities. There were no adverse events or complications.

Diagnostic-grade T1W, T2W, T2 FLAIR, and DWI sequences were obtained for 37, 48, 45, and 32 patients, respectively. The mean examination time was ~35 minutes. Mean axial sequence scanning times were as follows: T1W, 4 minutes and 54 seconds; T2W, 7 minutes and 3 seconds; FLAIR, 9 minutes and 31 seconds; and DWI with b set to 0 seconds/ mm2 to calculate an ADC map, 9 minutes and 4 seconds.

In conclusion, the authors claim that their experience demonstrates that low field, portable MRI can be deployed successfully into intensive care settings. This approach may hold promise for portable assessment of neurological injury in other scenarios, including the emergency department, mobile stroke units, and resource-limited environments.

2 figures and 1 table with MR images compared to CT.  Wonder how this would stand up against portable CT?

5. Elschot EP, Backes WH, Postma AA, et al. A comprehensive view on MRI techniques for imaging blood-brain barrier integrity. Invest Radiol 2021;56:10–19. Available from: https://journals.lww.com/10.1097/RLI.0000000000000723

The evaluation of BBB integrity for research purposes is commonly performed using MRI techniques that require administration of contrast agent (CA). It is the passive diffusion of a small molecular CA through the impaired BBB that is used as the detection mechanism. Two techniques that use a gadolinium-based CA are dynamic contrast enhanced (DCE) and dynamic susceptibility contrast (DSC) MRI. Dynamic contrast-enhanced MRI tracks the CA-induced signal changes on dynamic T1-weighted images, which makes it possible to obtain BBB permeability measures. Dynamic susceptibility contrast MRI measures (T2-weighted or) T2*-weighted signal changes to evaluate brain perfusion properties. Other techniques that apply different contrast mechanisms, for example, using water exchange for assessment of BBB integrity or the use of D-glucose to quantify the role of BBB integrity in the cerebral energy metabolism, show possible value and target different features of BBB transport. Because these techniques do not make use of exogenous paramagnetic CA, of which the safety has recently become of concern, imaging modalities without CA become more and more of interest.

3 figures, 1 table

6. Ellison DW, Aldape KD, Capper D, et al. cIMPACT-NOW update 7: advancing the molecular classification of ependymal tumors. Brain Pathol 2020;30:863–66

Ependymal tumors make up a heterogeneous category of central nervous system (CNS) gliomas with variably expressed morphologic, immunophenotypic and ultrastructural ependymal features. The current WHO classification (2016) lists: subependymoma (WHO grade 1), myxopapillary ependymoma (WHO grade 1), the classic ependymoma with its three histological subtypes––papillary, clear cell and tanycytic (WHO grade 2), anaplastic ependymoma (WHO grade 3) and one genetically defined type––ependymoma, RELA fusion-positive (WHO grade 2/ 3). However, aspects of this scheme are not ideal; for example, in some clinical settings, there is a poor association between tumor grading and outcome. In addition, recent studies using either DNA methylation profiling to demonstrate molecular groups of ependymoma or genome-wide sequencing to determine the genomic landscape of the disease support the proposition that ependymomas with similar morphologic features from across the neuraxis have distinct origins and oncogenic events of clinicopathologic significance and potential therapeutic utility.

Recommendations:

1) Ependymomas should be classified by anatomic site and by molecular group or an associated genetic alteration, so that classification of the disease reflects its underlying biology.

2) Supratentorial ependymomas should be classified according to the genes, C11orf95 and YAP1, that contribute to most pathogenic gene fusions in each of the two major molecular groups.

3) PF ependymomas should be classified according to the two most prevalent molecular groups, PFA and PFB.

4) Spinal cord ependymomas with MYCN amplification should be recognized as a distinctive type of ependymoma with a poor outcome.

5) The rare subependymoma should continue to be identified by morphologic criteria; no clear clinical utility is yet attached to the identification of a subependymoma molecular group at each anatomic site.

6) Spinal cord myxopapillary ependymomas should continue to be identified by morphologic criteria but designated WHO grade 2, because clinical trial datasets do not support a WHO grade 1 clinical behavior.

7) Morphologic subtypes of the classic ependymoma (papillary, clear cell, tanycytic) should be recognized as distinctive patterns in the histopathological description of ependymomas; but, affording no specific clinical utility, they should no longer be included in the classification of the disease.

1 table

7. Mac Grory B, Emmer BJ, Roosendaal SD, et al. Carotid web: an occult mechanism of embolic stroke. J Neurol Neurosurg Psychiatry 2020;91:1283–89. Available from: https://jnnp.bmj.com/lookup/doi/10.1136/jnnp-2020-323938

Cryptogenic ischemic stroke is among the most challenging conditions facing the stroke physician, representing approximately 25% of all ischemic strokes. On their first iteration, cryptogenic strokes tend to be associated with less severe deficits than other forms of stroke, presenting an invaluable opportunity to intervene and prevent the tragedy of a recurrent severe stroke. A web of the internal carotid artery (ICA) (‘carotid web’) is a putative mechanism of ischemic stroke which is readily diagnosable and treatable with available tools, however, under-recognized because of its tendency to masquerade as other pathology and lack of hemodynamic effects on the carotid circulation.

The web appears as a shelf-like projection into the lumen of the proximal cervical internal carotid artery without evidence of calcification. It is pathologically defined as intimal fibromuscular dysplasia. Altered hemodynamics distal to the web cause flow stagnation and remote embolization of fibrin-based clots. It is best demonstrated and diagnosed on CT angiography (CTA) of the neck because of its ability to resolve calcium and create multiplanar reconstructions. Although they can be readily visualized on CTA, carotid webs may be missed or misinterpreted because they do not typically cause hemodynamically significant stenosis and can mimic arterial dissection, non-calcified atherosclerotic plaque and intraluminal thrombus. Options for management include antiplatelet therapy, carotid endarterectomy and carotid artery stenting. Modern management strategies for cryptogenic stroke include long-term cardiac monitoring, further investigation for structural cardiac disease and a diagnostic workup for arterial hypercoagulability.

Which is the optimal intervention strategy—anticoagulation, CEA or CAS? Anticoagulation is mechanistically more attractive than antiplatelet therapy as the recirculation zone adjacent to the carotid web causes stagnation of blood analogous to the left atrial appendage in atrial fibrillation. This would best be addressed by means of a randomized control multi-arm trial comparing anticoagulation, CEA and CAS for secondary prevention of stroke associated with carotid web. The optimum management strategy in the case of an incidentally detected carotid web is currently not known.

4 figures, 2 tables

8. Strowd RE, Plotkin SR. Familial nervous system tumor syndromes. Continuum (Minneap Minn) 2020;26:1523–52. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33273171

In this article, five of the most common familial nervous system tumor syndromes are reviewed, including neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), schwannomatosis, tuberous sclerosis complex, and von Hippel-Lindau disease. Although other inherited tumor syndromes may be encountered in clinical practice, these five represent the more common, clinically relevant syndromes and provide important examples of the key principles that assist the clinician in evaluating and treating patients with familial nervous system tumor syndromes.

8 figures, 7 tables

The American Society of Neuroradiology is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. Visit the ASNR Education Connection website to claim CME credit for this podcast.



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