Intra-arterial Air Thrombogenesis after Cerebral Air Embolism Complicating Lower Extremity Sclerotherapy

Background  

Cerebral arterial gas embolism is a potentially life-threatening event. Intraarterial air can occlude blood flow directly or cause thrombosis. Sclerotherapy is an extremely rare cause of cerebral arterial gas embolism.     

Multimodal endovascular treatment of a vertebrovertebral fistula presenting with subarachnoid hemorrhage and hydrocephalus

Vertebrovertebral fistulae are rare vascular malformations that uncommonly can rupture to present clinically as intracranial subarachnoid hemorrhage. We report a 69-year-old man presenting following spontaneous apoplectic collapse. Initial workup revealed diffuse, intracranial subarachnoid hemorrhage, intraventricular hemorrhage and hydrocephalus. However, the etiology was not apparent on CT angiography of the head. Catheter-based angiography was performed, demonstrating a single-hole, high-flow vertebrovertebral fistula, arising from the V2 segment and decompressing into both cervical and skull base venous structures. Definitive treatment consisted of endovascular fistula obliteration with a combination of coil and liquid embolic material. The patient made a full neurological recovery. High cervical and skull base fistulae are rare causes of intracranial hemorrhage; endovascular treatment is effective at disconnection of the arteriovenous shunt.     

Sex-specific differences in presentations and determinants of outcomes after endovascular thrombectomy for large vessel occlusion stroke

Journal of Neurology - Sex-specific differences in ischemic stroke outcomes are prevalent. We sought to investigate sex differences in the determinants of reperfusion and functional outcomes after...     

Analysis of Stroke Detection during the COVID-19 Pandemic Using Natural Language Processing of Radiology Reports

BACKGROUND AND PURPOSE:The coronavirus disease 2019 (COVID-19) pandemic has led to decreases in neuroimaging volume. Our aim was to quantify the change in acute or subacute ischemic strokes detected on CT or MR imaging during the pandemic using natural language processing of radiology reports.MATERIALS AND METHODS:We retrospectively analyzed 32,555 radiology reports from brain CTs and MRIs from a comprehensive stroke center, performed from March 1 to April 30 each year from 2017 to 2020, involving 20,414 unique patients. To detect acute or subacute ischemic stroke in free-text reports, we trained a random forest natural language processing classifier using 1987 randomly sampled radiology reports with manual annotation. Natural language processing classifier generalizability was evaluated using 1974 imaging reports from an external dataset.RESULTS:The natural language processing classifier achieved a 5-fold cross-validation classification accuracy of 0.97 and an F1 score of 0.74, with a slight underestimation (−5%) of actual numbers of acute or subacute ischemic strokes in cross-validation. Importantly, cross-validation performance stratified by year was similar. Applying the classifier to the complete study cohort, we found an estimated 24% decrease in patients with acute or subacute ischemic strokes reported on CT or MR imaging from March to April 2020 compared with the average from those months in 2017–2019. Among patients with stroke-related order indications, the estimated proportion who underwent neuroimaging with acute or subacute ischemic stroke detection significantly increased from 16% during 2017–2019 to 21% in 2020 (P = .01). The natural language processing classifier performed worse on external data.CONCLUSIONS:Acute or subacute ischemic stroke cases detected by neuroimaging decreased during the COVID-19 pandemic, though a higher proportion of studies ordered for stroke were positive for acute or subacute ischemic strokes. Natural language processing approaches can help automatically track acute or subacute ischemic stroke numbers for epidemiologic studies, though local classifier training is important due to radiologist reporting style differences.

There is much concern regarding the impact of the coronavirus disease 2019 (COVID-19) pandemic on the quality of stroke care, including issues with hospital capacity, clinical resource re-allocation, and the safety of patients and clinicians.^1,2 Previous reports have shown that there have been substantial decreases in stroke neuroimaging volume during the pandemic.^3,4 In addition, acute ischemic infarcts have been found on neuroimaging studies in many hospitalized patients with COVID-19, though the causal relationship is unclear.^5,6 Studies like these and other epidemiologic analyses usually rely on the creation of manually curated databases, in which identification of cases can be time-consuming and difficult to update in real-time. One way to facilitate such research is to use natural language processing (NLP), which has shown utility for automated analysis of radiology report data.⁷ NLP algorithms have been developed previously for the classification of neuroradiology reports for the presence of ischemic stroke findings and acute ischemic stroke subtypes.^8,9 Thus, NLP has the potential to facilitate COVID-19 research.In this study, we developed an NLP machine learning model that classifies radiology reports for the presence or absence of acute or subacute ischemic stroke (ASIS), as opposed to chronic stroke. We used this model to quantify the change in ASIS detected on all CT or MR imaging studies performed at a large comprehensive stroke center during the COVID-19 pandemic in the United States. We also evaluated NLP model generalizability and different training strategies using a sample of radiology reports from a second stroke center.     

Intra-arterial Air Thrombogenesis after Cerebral Air Embolism Complicating Lower Extremity Sclerotherapy

Background  Cerebral arterial gas embolism is a potentially life-threatening event. Intraarterial air can occlude blood flow directly or cause thrombosis. Sclerotherapy is an extremely rare cause of cerebral arterial gas embolism. Method  Case-report. Results  A 38-year-old female suffered acute onset of a left middle cerebral artery (LMCA) syndrome with an NIH stroke score of 11 approximately ten minutes after lower extremity sclerotherapy. CT angiogram demonstrated LMCA intraarterial air. Patient fully recovered after hyperbaric oxygen treatment with complete resolution of intraarterial air. However, thrombus replaced intraarterial air despite anticoagulation with heparin. Conclusion  We provide radiological evidence of hyperbaric oxygen therapy resolving intraarterial air but also demonstrate the thrombogenic potential of this procedural complication.     

CTA Protocols in a Telestroke Network Improve Efficiency for Both Spoke and Hub Hospitals

BACKGROUND AND PURPOSE:Telestroke networks support screening for patients with emergent large-vessel occlusions who are eligible for endovascular thrombectomy. Ideal triage processes within telestroke networks remain uncertain. We characterize the impact of implementing a routine spoke hospital CTA protocol in our integrated telestroke network on transfer and thrombectomy patterns.MATERIALS AND METHODS:A protocol-driven CTA process was introduced at 22 spoke hospitals in November 2017. We retrospectively identified prospectively collected patients who presented to a spoke hospital with National Institutes of Health Stroke Scale scores ≥6 between March 1, 2016 and March 1, 2017 (pre-CTA), and March 1, 2018 and March 1, 2019 (post-CTA). We describe the demographics, CTA utilization, spoke hospital retention rates, emergent large-vessel occlusion identification, and rates of endovascular thrombectomy.RESULTS:There were 167 patients pre-CTA and 207 post-CTA. The rate of CTA at spoke hospitals increased from 15% to 70% (P < .001). Despite increased endovascular thrombectomy screening in the extended window, the overall rates of transfer out of spoke hospitals remained similar (56% versus 54%; P = .83). There was a nonsignificant increase in transfers to our hub hospital for endovascular thrombectomy (26% versus 35%; P = .12), but patients transferred >4.5 hours from last known well increased nearly 5-fold (7% versus 34%; P < .001). The rate of endovascular thrombectomy performed on patients transferred for possible endovascular thrombectomy more than doubled (22% versus 47%; P = .011).CONCLUSIONS:Implementation of CTA at spoke hospitals in our telestroke network was feasible and improved the efficiency of stroke triage. Rates of patients retained at spoke hospitals remained stable despite higher numbers of patients screened. Emergent large-vessel occlusion confirmation at the spoke hospital lead to a more than 2-fold increase in thrombectomy rates among transferred patients at the hub.

Telestroke supports thrombolytic use and screening for patients with emergent large-vessel occlusion (ELVO) across stroke systems of care.^1-3 ELVOs represent a minority of acute stroke presentations but produce most morbidity and mortality in ischemic stroke and are therefore a critical area of focus within stroke care systems.^4-6 For patients with ELVO, the current target of acute stroke therapy is penumbral salvage, which relies on numerous factors, the most important of which is timely reperfusion.^7-9 The powerful therapeutic effect of early reperfusion (<6 hours from last known well [LKW]) through endovascular thrombectomy (EVT) for patients with ELVO is now well established.^10-12 The time window for treatment expanded with the demonstration of benefit of reperfusion in patients between 6 and 24 hours from LKW, a demographic for which previously no therapeutic intervention was available.^13-14 Selection for thrombectomy in both early and late treatment windows required identification of ELVO by noninvasive imaging in all recent trials.The expansion of treatment with EVT up to 24 hours from LKW has dramatically increased the pool of patients to screen. Current telestroke care system approaches require the emergent transfer of patients from spoke hospitals (SHs), which lack the ability to perform thrombectomy, to hub hospitals, which are thrombectomy capable. Ideal triage processes within telestroke networks remain uncertain and may vary based on geographic region. Here we describe the effects of the implementation of a routine SH CTA protocol within our integrated telestroke network on SH retention rates and hub hospital thrombectomy rates.     

Cerebral Angiography for Evaluation of Patients with CT Angiogram-Negative Subarachnoid Hemorrhage: An 11-Year Experience

BACKGROUND AND PURPOSE:CT angiography is increasingly used to evaluate patients with nontraumatic subarachnoid hemorrhage given its high sensitivity for aneurysms. We investigated the yield of digital subtraction angiography among patients with SAH or intraventricular hemorrhage and a negative CTA.MATERIALS AND METHODS:An 11-year, single-center retrospective review of all consecutive patients with CTA-negative SAH was performed. Noncontrast head CT, CTA, DSA, and MR imaging studies were reviewed by 2 experienced interventional neuroradiologists and 1 neuroradiologist.RESULTS:Two hundred thirty patients (mean age, 54 years; 51% male) with CTA-negative SAH were identified. The pattern of SAH was diffuse (40%), perimesencephalic (31%), sulcal (31%), isolated IVH (6%), or identified by xanthochromia (7%). Initial DSA yield was 13%, including vasculitis/vasculopathy (7%), aneurysm (5%), arteriovenous malformation (0.5%), and dural arteriovenous fistula (0.5%). An additional 6 aneurysms/pseudoaneurysms (4%) were identified by follow-up DSA, and a single cavernous malformation (0.4%) was identified by MRI. No cause of hemorrhage was identified in any patient presenting with isolated intraventricular hemorrhage or xanthochromia. Diffuse SAH was due to aneurysm rupture (17%); perimesencephalic SAH was due to aneurysm rupture (3%) or vasculitis/vasculopathy (1.5%); and sulcal SAH was due to vasculitis/vasculopathy (32%), arteriovenous malformation (3%), or dural arteriovenous fistula (3%).CONCLUSIONS:DSA identifies vascular pathology in 13% of patients with CTA-negative SAH. Aneurysms or pseudoaneurysms are identified in an additional 4% of patients by repeat DSA following an initially negative DSA. All patients with CT-negative SAH should be considered for DSA. The pattern of SAH may suggest the cause of hemorrhage, and aneurysms should specifically be sought with diffuse or perimesencephalic SAH.

Nontraumatic subarachnoid hemorrhage occurs in 30,000 patients per year in the United States, which accounts for 5% of strokes.¹ Patient mortality approximates 45% within a month after SAH,¹ and the identification of a treatable cause of SAH is imperative.Cerebral aneurysm rupture accounts for most SAHs,² but a cause of hemorrhage is not identified in 15%–20% of patients.^2–4 Prior studies have demonstrated that the pattern of SAH on a noncontrast head CT may predict the probability of identifying a causative vascular lesion, though CT angiography or digital subtraction angiography is needed to identify these lesions.^5–9The evaluation of SAH varies, and no consensus exists as to the best algorithm. Increasingly, CTA is performed in the evaluation of SAH, given its noninvasive nature and wide availability. CTA has a reported a sensitivity of 97%–100% for the detection of intracranial aneurysms.^10–13 However, it fails to identify a cause for SAH in 5%–30% of patients.^14,15 DSA remains the criterion standard in the diagnosis of vascular lesions resulting in SAH with a reported sensitivity of 99%.^16,17 Given the superior sensitivity of DSA and the importance of identifying a treatable cause of SAH, DSA is frequently performed in patients presenting with SAH and negative CTA findings.Prior studies demonstrated that DSA identifies a cause of SAH in 4%–14% of patients with negative CTA findings.^{3,4,14,18–20} Moreover, the diagnostic yield of repeat DSA after initially negative DSA findings is reported to be between 4% and 16%.^14,15,21 We describe our experience with initial and repeat DSA in patients with CTA negative for SAH during an 11-year period at a large neurovascular referral center.