Adolescent subdural empyema in setting of COVID-19 infection: illustrative case

BACKGROUND

Coronavirus disease 2019 (COVID-19) is an ongoing viral pandemic that has affected modern medical practice and can complicate known pathology. The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes symptoms that may mimic a viral pneumonia, with potential for serious sequelae, including acute respiratory distress syndrome, coagulopathy, multiorgan dysfunction, systemic vascular abnormalities, and secondary infection.

OBSERVATIONS

The authors describe a case of a 15-year-old boy who presented with a right subdural empyema and sinusitis while having active COVID-19 infection. The patient initially presented with left-sided weakness, frontal sinusitis, and subdural empyema. Emergent surgery was performed for evacuation of empyema and sinus debridement. Samples of purulent material within the subdural space were tested for SARS-CoV-2 by reverse transcriptase polymerase chain reaction. The patient had a successful recovery and regained the use of his right side after combined treatment. To our knowledge, this is the first reported case of a bacterial subdural empyema associated with frontal sinusitis in a coinfected patient with COVID-19 without evidence of COVID-19 intracranial infection.

LESSONS

A subdural empyema, which is a surgical emergency, was likely a superinfection caused by COVID-19. This, along with the coagulopathy caused by the virus, introduced unique challenges to the treatment of a known pathology.

Air Pollution Particulate Matter Exposure and Chronic Cerebral Hypoperfusion and Measures of White Matter Injury in a Murine Model

BACKGROUND

Exposure to ambient air pollution particulate matter (PM) is associated with increased risk of dementia and accelerated cognitive loss. Vascular contributions to cognitive impairment are well recognized. Chronic cerebral hypoperfusion (CCH) promotes neuroinflammation and blood-brain barrier weakening, which may augment neurotoxic effects of PM.

OBJECTIVES

This study examined interactions of nanoscale particulate matter (nPM; fine particulate matter with aerodynamic diameter ≤ 200  nm ) and CCH secondary to bilateral carotid artery stenosis (BCAS) in a murine model to produce white matter injury. Based on other air pollution interactions, we predicted synergies of nPM with BCAS.

METHODS

nPM was collected using a particle sampler near a Los Angeles, California, freeway. Mice were exposed to 10 wk of reaerosolized nPM or filtered air (FA) for 150 h. CCH was induced by BCAS surgery. Mice (C57BL/6J males) were randomized to four exposure paradigms: a) FA, b) nPM, c) FA   +   BCAS , and d) nPM   +   BCAS . Behavioral outcomes, white matter injury, glial cell activation, inflammation, and oxidative stress were assessed.

RESULTS

The joint nPM   +   BCAS group exhibited synergistic effects on white matter injury (2.3× the additive nPM and FA   +   BCAS scores) with greater loss of corpus callosum volume on T2 magnetic resonance imaging (MRI) (30% smaller than FA group). Histochemical analyses suggested potential microglial-specific inflammatory responses with synergistic effects on corpus callosum C5 immunofluorescent density and whole brain nitrate concentrations (2.1× and 3.9× the additive nPM and FA   +   BCAS effects, respectively) in the joint exposure group. Transcriptomic responses (RNA-Seq) showed greater impact of nPM   +   BCAS than individual additive effects, consistent with changes in proinflammatory pathways. Although nPM exposure alone did not alter working memory, the nPM   +   BCAS cohort demonstrated impaired working memory when compared to the FA   +   BCAS group.

DISCUSSION

Our data suggest that nPM and CCH contribute to white matter injury in a synergistic manner in a mouse model. Adverse neurological effects may be aggravated in a susceptible population exposed to air pollution. https://doi.org/10.1289/EHP8792.

Encephaloduroarteriosynangiosis Averts Stroke in Atherosclerotic Patients With Border-Zone Infarct: Post Hoc Analysis From a Performance Criterion Phase II Trial

BACKGROUND

Intracranial atherosclerotic disease (ICAD) is one of the leading causes of stroke worldwide. Patients with ICAD who initially present with ischemia in border-zone areas and undergo intensive medical management (IMM) have the highest recurrence rates (37% at 1 yr) because of association with hemodynamic failure and poor collaterals.

OBJECTIVE

To evaluate the effect of encephaloduroarteriosynagiosis (EDAS) on stroke recurrence in patients with ICAD and border-zone stroke (BDZS) at presentation.

METHODS

A phase II clinical trial of EDAS revascularization for symptomatic ICAD failing medical management (EDAS Revascularization for Symptomatic Intracranial Atherosclerosis Steno-occlusive [ERSIAS]) was recently concluded. We analyze the outcomes of the subgroup of patients with BDZS at presentation treated with EDAS vs the previously reported Stenting versus Aggressive Medical Management for Preventing Recurrent stroke in Intracranial Stenosis (SAMMPRIS) IMM subgroup with BDZS at presentation.

RESULTS

Of 52 patients included in the ERSIAS trial, 35 presented with strokes at baseline, and 28 had a BDZ pattern, including 15 (54%) with exclusive BDZS and 13 (46%) with mixed patterns (BDZ plus other distribution). Three of the 28 (10.7%) had recurrent strokes up to a median follow-up of 24 months. The rate of recurrent stroke in ICAD patients with BDZS at presentation after EDAS was significantly lower than the rate reported in the SAMMPRIS IMM subgroup with BDZS at presentation (10.7% vs 37% P = .004, 95% CI = 0.037-0.27).

CONCLUSION

ICAD patients with BDZS at presentation have lower rates of recurrent stroke after EDAS surgery than those reported with medical management in the SAMMPRIS trial. These results support further investigation of EDAS in a randomized clinical trial.

Transvenous Pressure Monitoring Guides Endovascular Treatment of Vein of Galen Malformation: A Technical Note

INTRODUCTION

Vein of Galen malformations (VGMs) are complex congenital arteriovenous malformations that generally require serial endovascular treatment sessions to slowly correct the high-flow fistulous connections that cause increased venous pressures and ultimately lead to the classic presentations of heart failure, hydrocephalus, and intracranial hemorrhages. Despite the advances in endovascular technology and embolic materials, the resolution of embolization is often limited to the subjective view of diminished flow on angiograms.

CASE REPORT

An 8-month-old patient with a VGM developed clinical signs of heart failure and growing head circumference with ventriculomegaly. The patient was treated endovascularly with a transvenous approach for coil embolization while undergoing continuous monitoring of the post-malformation venous pressures. The arterial and venous systolic blood pressures (SBP) were collected at serial time points and used to measure estimated 95% confidence interval bounds for arteriovenous SBP gradients and determine when sufficient coil embolization and flow reduction was thought to be achieved.

CONCLUSION

The transvenous pressure monitoring demonstrated progressively increasing pressure gradients between the arterial and venous systems that correlated with the degree of flow reduction on angiographic runs. The patient underwent successful coil embolization of the VGM and had improvement of heart failure and ventricular size in follow-up at 8-month post-op. This provides a novel technique to introduce an objective measurement that can guide the embolization of a VGM.

Symptomatic Cervical Tumoral Calcinosis due to Cosmetic Body Contouring Mineral Oil Injections

Tumoral calcinosis (TC) is an uncommon disease that has been linked to familial genetic mutations but can often be due to secondary causes such as chronic renal failure and hyperparathyroidism. There are rare instances of tumoral calcinosis induced by foreign body injections, often for cosmetic purposes. Here we describe operative management of spinal cord compression due to mineral oil injection induced tumoral calcinosis. A 54-year-old transgender female presented with signs of myelopathy so severe that she had become wheelchair bound. Labs demonstrated hypercalcemia and imaging of the neuroaxis revealed significant calcification resulting in cervicothoracic and lumbar central canal stenosis. Given symptomatic cervical spinal cord compression, she was taken to the OR for urgent laminectomy and decompression. Postoperatively, she recovered well and was ambulating independently by postoperative day (POD) 9. This is the first reported case of localized mineral oil injections causing distant calcification with subsequent symptomatic cord compression requiring operative intervention.

Abstract TP134: Effects of Strict Anesthesia Management in a Trial of Surgical Revascularization for Intracranial Atherosclerosis

Introduction: Specific aspects of anesthesia management in clinical trials for cerebrovascular diseases have not been systematically addressed. As part of the EDAS Revascularization for Intracranial Atherosclerosis (ERSIAS) trial, we enforced strict management of hemodynamic parameters to prevent cerebral hypoperfusion during surgery.

Methods: All patients enrolled in ERSIAS received intensive medical management, including antiplatelet therapy, even the day of surgery. Before every operation, a set of specific goals were discussed with the anesthesia team in a preoperative briefing, including strict regulation of SBP (lower limit = patient’s baseline when asymptomatic - upper limit = 200 mmHg), end-tidal CO 2 (ETCO 2 ) (35-45 mmHg while intubated), and fluid balance (even to positive 2L). Printed goals were posted by the anesthesia stations, anesthesia equipment alarms were set to the predetermined goals, and surgeons had continuous access to the patient’s vitals. Range-deviations lasting more than 5 minutes were recorded. Mannitol and high doses of steroids were avoided.

Results: Fifty-two patients underwent EDAS surgery, four had ischemic strokes, and only one patient had perioperative ischemia. There was a significant reduction in the standard deviation variance of intraoperative SBP compared to the SBP during clinic visits (14.9 vs.23.9 mmHg p<0.01), reflecting a tighter SBP control during surgery. SBP goal deviations occurred in five cases, resulting in one perioperative stroke. In general, strokes were more common among patients with SBP goal deviations (20% vs.4.7%). Mean ETCO 2 was 38mmHg (SD=1, Range: 35-41 mmHg). There was only one ETCO 2 goal deviation with no clinical consequences. Fluid balance ranged between -0.25 and 3.1L, with a mean 1.2L (SD=0.6L). Mean estimated blood loss was 37 mL (SD=16, Range: 10-80mL). There were five deviations from the fluid protocol not associated with clinical complications.

Conclusion: A goal-oriented pre-surgical briefing with anesthesia team and practical implementations, as discussed above, were effective in reducing hemodynamic variability in the ERSIAS trial. Rigorous SBP management is key in averting stroke during EDAS. Future trials should include standardized anesthesia protocols.

Abstract 83: Encephaloduroarteriosynangiosis Surgery Averts Stroke in Atherosclerotic Patients With Border-Zone Stroke

Introduction: Intracranial atherosclerotic disease (ICAD) is one of the most common causes of stroke around the world. Among patients with ICAD being treated with Intensive Medical Management (IMM), those who initially present with ischemia in border-zone areas have the highest recurrence rates (37% at one year) due to association with poor collaterals.

Methods: We recently concluded a phase II clinical trial of EDAS revascularization for patients with symptomatic ICAD failing medical management (ERSIAS). EDAS creates new collaterals from the donor branches of the external carotid artery. We performed an analysis of ERSIAS patients who had stroke as qualifying event and ischemia of a border-zone area on their initial MRI. We compared their outcomes to the subgroup of patients with border-zone ischemia from SAMMPRIS.

Results: Of 52 patients included in the ERSIAS trial, 35 patients presented with strokes at baseline and 28 had border-zone pattern, including 15 (54%) with exclusive border-zone ischemia and 13 (46%) with mixed patterns including the border-zone. Of these 28 patients with border zone strokes as qualifying event, three (11%) presented recurrent strokes up to one year after EDAS surgery. When compared with the matched population from the medical arm of SAMMPRIS, EDAS patients had significantly lower than expected rate of recurrence (11% vs. 37% p=0.02, OR:0.21, 95%CI= 0.05-0.84), representing an absolute risk reduction of 26%.

Conclusion: When compared with matched controls on IMM, EDAS reduced the expected rate of recurrent stroke in patients at the highest risk of recurrence. This supports the concept that EDAS might avert strokes due to hypoperfusion by generating new collaterals to ischemic cerebral territories and could supplement IMM in patients with border-zone infarctions due to ICAD.

Abstract TP132: Intensive Medical Management and Life-Style Modifications Can Be Successfully Applied in Combination With Indirect Surgical Revascularization for Symptomatic Intracranial Atherosclerotic Disease

Introduction: We present the results of using the strict model of intensive medical management (IMM) and life-style modification of SAMMPRIS in a phase 2 study of EDAS revascularization in patients with symptomatic intracranial atherosclerosis (ERSIAS).

Methods: ERSIAS was a mid-development, single surgical arm trial that enrolled patients closely matched to those recruited in SAMMPRIS with the exception of including also individuals with occlusions of the intracranial arteries. In addition to surgery, primary and secondary risk factors were strictly managed and a life-style modification program with monthly phone calls to encourage adherence to medication, diet, physical activity, and smoking cessation was applied. Every 3 months, patients were clinically evaluated and data of adherence to medical regimen was collected.

Results: As previously reported, the rate of recurrent stroke in ERSIAS at one year was 7.7%. ERSIAS required patients to have ceased smoking for at least 6 months before enrollment. Of the 52 patients enrolled only 5 had a relapse in their smoking habit (9.6%). At the end of the study four stopped smoking, representing a failure on smoking control of only 2%. Patient’s engagement in vigorous physical activity increased from 43% at baseline to 84% at follow-up (p=0.03). Median LDL values at baseline, 6 months, and 12 months were 83.9 (IQR 65.2), 70.9 (IQR 38.8), and 77 (IQR 78.25), respectively. At an individual level 75.6% of patients had improvement in LDL control. The SBP goal (<160mmHg) was achieved in 91% of patients, and a reduction of SBP was observed in 65.9% at either 6 or 12 months. Median HbA1c values in diabetic (DM2) patients were 6.3% (QR 2.5) at baseline, 5.1% (IQR 2.5) at 6 months, and 5.9% (IQR 2.8) at 12 months, accounting for an improvement in 60% of patients at either 6 or 12 months.

Conclusion: A dedicated follow-up program optimized medical adherence and results in ERSIAS. The surgery did not affect the ability of patients to engage in exercise or adhere to medical management. The IMM model of SAMMPRIS was successfully applied in this surgical trial. Strict observance of the improvements in medical management should be integrated in future interventional studies for ICAD.

Abstract TP407: Transvenous Pressure Monitoring Guides Endovascular Treatment of Vein of Galen Malformation

Background: Vein of Galen Malformation (VGM) is a complex vascular disorder with high morbidity and mortality. Mainstay management involves staged endovascular embolizations. Determining when to stop an embolization during any single intervention is challenging. If embolization is excessive, it precipitates thrombosis on the VGM, increase in cardiac post-load, and worsening on heart failure, as well as hemorrhages. Conversely, insufficient embolization may be futile. We report the use of transvenous pressure monitoring as an adjuvant for guiding the extent of embolization.

Method: Arterial and venous accesses were obtained through the common femoral artery and vein, respectively. After diagnostic angiography, the best working projection was selected in early and late venous phases. A microcatheter was placed at the VG, and an intermediate 5 Fr. catheter was located at the persistent falcine sinus. The microcatheter was used for coil embolization, while the intermediate catheter provided support and was connected for continuous venous pressure monitoring. Continuous arterial pressure monitoring was obtained via an A-line and transduction of a glide catheter located in the carotid artery. Arterial and venous SBP were recorded.

Result: Serial angiograms during treatment showed reduction of flow within the VGM. Concomitantly, there was an increase in the A-V-gradient over time (Figure 1). The difference between the A-V SBP went from 36 mmHg at the start of the case to 51 mmHg after the final coil. The average pressure gradient went from 38.3 mmHg in the first quarter to 43.5 mmHg in the last.

Conclusion: The continuous assessment of transvenous pressure monitoring during embolization of VGM provides measurable changes that correlate with degree of flow. This quantifiable metric may be used as an adjunct to guide adequate reduction of flow during endovascular treatment of VGM.

Abstract TP411: Improving Pediatric Stroke Recognition Among Pediatric Health Care Providers

Introduction: Pediatric acute ischemic stroke (P-AIS) is an under-recognized disease by pediatric healthcare providers, resulting in delay of its diagnosis. In spite of diagnostic tools such as the FAST and BE FAST mnemonics, lack of awareness leads to increased morbidity and mortality. This study aims to elucidate whether a brief educational activity would modify the identification and perception of P-AIS.

Methods: Forty-nine pediatric healthcare providers were surveyed to assess their baseline skills in recognizing P-AIS. Providers attended a 30-minute activity outlining incidence, natural history, diagnosis, and examples of P-AIS treatment. The mnemonics “FAST” and “BE FAST” as applicable to children were futher expounded. Pre and post-surveys assessed providers’ profession, type of practice, ED service involvement, familiarity with the mnemonics, and P-AIS recognition performance for infants and children.

Results: The forty-nine pediatric healthcare providers surveyed had the following degrees: 61% MD, 20% NP, 6% RN, 6% student, 4% PA, 2% DO. Futhermore, 78% work in private outpatient enviroments, 17% in academic outpatient institutions, 4% in private outpatient settings, and only 10% had emergency department involvement. Pre-Activity: 53% had heard of “FAST,” and 8% had heard of “BE FAST.” Correct knowledge of individual letters ranged between 12-39%, with the lowest recognition rates for “B” and “E.” At baseline, 65% of providers correctly recognized pediatric and specifically infant stroke cases. Post-Activity: 97% felt familiar with “BE FAST.”. Correct knowledge of individual letters following the educational activity improved to 100%. 95% of providers correctly recognized P-AIS, and 95% correctly identified infant stroke. Univariate logistic analysis showed that completing the training activity was the only significant factor improving the ability to identify P-AIS (OR: 10.35, CI: 2.2 to 48.2). Profession and type of practice were not significant.

Conclusion: A 30-minute focused educational activity was sufficient to improve the perception and ability to recognize P-AIS among different levels of healthcare providers. The long-term effects of these interventions should be examined.

Experimental chronic cerebral hypoperfusion results in decreased pericyte coverage and increased blood-brain barrier permeability in the corpus callosum

Murine chronic cerebral hypoperfusion (CCH) results in white matter (WM) injury and behavioral deficits. Pericytes influence blood-brain barrier (BBB) integrity and cerebral blood flow. Under hypoxic conditions, pericytes detach from perivascular locations increasing vessel permeability and neuronal injury. This study characterizes the time course of BBB dysfunction and pericyte coverage following murine experimental CCH secondary to bilateral carotid artery stenosis (BCAS). Mice underwent BCAS or sham operation. On post-procedure days 1, 3, 7 and 30, corpus callosum BBB permeability was characterized using Evans blue (EB) extravasation and IgG staining and pericyte coverage/count was calculated. The BCAS cohort demonstrated increased EB extravasation on postoperative days 1 ( p = 0.003) 3 ( p = 0.002), and 7 ( p = 0.001) when compared to sham mice. Further, EB extravasation was significantly greater ( p = 0.05) at day 3 than at day 30 in BCAS mice. BCAS mice demonstrated a nadir in pericyte coverage and count on post-operative day 3 ( p < 0.05, compared to day 7, day 30 and sham). Decreased pericyte coverage/count and increased BBB permeability are most pronounced on postoperative day 3 following murine CCH. This precedes any notable WM injury or behavioral deficits.

Nanoparticulate matter exposure results in neuroinflammatory changes in the corpus callosum

Epidemiological studies have established an association between air pollution particulate matter exposure (PM2.5) and neurocognitive decline. Experimental data suggest that microglia play an essential role in air pollution PM-induced neuroinflammation and oxidative stress. This study examined the effect of nano-sized particulate matter (nPM) on complement C5 deposition and microglial activation in the corpus callosum of mice (C57BL/6J males). nPM was collected in an urban Los Angeles region impacted by traffic emissions. Mice were exposed to 10 weeks of re-aerosolized nPM or filtered air for a cumulative 150 hours. nPM-exposed mice exhibited reactive microglia and 2-fold increased local deposition of complement C5/ C5α proteins and complement component C5a receptor 1 (CD88) in the corpus callosum. However, serum C5 levels did not differ between nPM and filtered air cohorts. These findings demonstrate white matter C5 deposition and microglial activation secondary to nPM exposure. The C5 upregulation appears to be localized to the brain.

Estradiol Protects White Matter of Male C57BL6J Mice against Experimental Chronic Cerebral Hypoperfusion

BACKGROUND AND PURPOSE

Estradiol is a sex steroid hormone known to protect the brain against damage related to transient and global cerebral ischemia. In the present study, we leverage an experimental murine model of bilateral carotid artery stenosis (BCAS) to examine the putative effects of estradiol therapy on chronic cerebral hypoperfusion. We hypothesize that long-term estradiol therapy protects against white matter injury and declarative memory deficits associated with chronic cerebral hypoperfusion.

METHODS

Adult male C57BL/6J mice underwent either surgical BCAS or sham procedures. Two days after surgery, the mice were given oral estradiol (Sham+E, BCAS+E) or placebo (Sham+P, BCAS+P) treatments daily for 31-34 days. All mice underwent Novel Object Recognition (NOR) testing 31-34 days after the start of oral treatments. Following sacrifice, blood was collected and brains fixed, sliced, and prepared for histological examination of white matter injury and extracellular signal-regulated kinase (ERK) expression.

RESULTS

Animals receiving long-term oral estradiol therapy (BCAS-E2 and Sham-E2) had higher plasma estradiol levels than those receiving placebo treatment (BCAS-P and Sham-P). BCAS-E2 mice demonstrated less white matter injury (Klüver-Barrera staining) and performed better on the NOR task compared to BCAS-P mice. ERK expression in the brain was increased in the BCAS compared to sham cohorts. Among the BCAS mice, the BCAS-E2 cohort had a greater number of ERK + cells.

CONCLUSION

This study demonstrates a potentially protective role for oral estradiol therapy in the setting of white matter injury and declarative memory deficits secondary to murine chronic cerebral hypoperfusion.

Selective embolization of ruptured feeding artery aneurysm followed by resection of arteriovenous malformation

This is the case of a man in his 40s who suffered sudden collapse into a deep coma as a result of a ruptured arteriovenous malformation (AVM) feeding artery aneurysm within the lateral ventricle. The ruptured aneurysm was successfully treated with Onyx embolization of the feeding pedicle. The AVM and the feeding artery aneurysm were then removed via a transcallosal approach. This case highlights the utility of interrogating the AVM with microcatheterization of the feeding pedicles in order to define the exact anatomical features necessary for treatment planning. It also reviews the anatomy of the choroidal fissure. The video can be found here: https://youtu.be/UeqFzhTRU1Q .

Abstract TP438: Nanoparticulate Matter Exposure Mediates White Matter Changes in a Murine Model

Background: Clinical and epidemiologic studies suggest a relationship between long-term nano-particulate matter (nPM) exposure and white matter injury 1 . Accumulating laboratory evidence suggests that nPM exposure causes inflammation in multiple brain regions 2 .

Objective: We sought to study the effects nano-particulate matter exposure on microglia activation and complement upregulation within the corpus callosum in a murine model.

Methods: C57 black 6J mice were randomized to re-aerosolized nPM (n=18, nPM <200 nm) or filtered air (n=18) cohorts. Exposures were conducted for a total of 150 cumulative hours. Post-exposure, brains were harvested and immunohistochemical analysis performed. Reactive microglia (IBA-1), reactive astrocytes (GFAP) and C5α deposition (C5α antibody) were quantified in the medial corpus callosum.

Results: There were significant differences in IBA-1 cell count staining between the groups (filtered air- 94.7± 18.87; nPM- 158.5 ± 41.69, p<0.05). No differences in GFAP cell count staining existed between the filtered air (677.5 ± 96.09) and nPM mice (656.6 ± 120.3, p=ns). There were significant differences in C5α density staining between filtered air (8.181 ± 3.863) and nPM mice (14.77 ± 5.989, p<0.01).

Conclusion: Chronic particulate matter exposure is associated with white matter changes in a murine model. Regional increases in microglia number and C5α deposition suggest an inflammatory mechanism.

References: 1. Calderon-Garciduenas L, Mora-Tiscareno A, Ontiveros E, Gomez-Garza G, Barragan-Mejia G, Broadway J, Chapman S, Valencia-Salazar G, Jewells V, Maronpot RR, Henriquez-Roldan C, Perez-Guille B, Torres-Jardon R, Herrit L, Brooks D, Osnaya-Brizuela N, Monroy ME, Gonzalez-Maciel A, Reynoso-Robles R, Villarreal-Calderon R, Solt AC, Engle RW. Air pollution, cognitive deficits and brain abnormalities: a pilot study with children and dogs. Brain Cogn. 2008;68(2):117-27. 2. Block, M. L., & Calderón-Garcidueñas, L. (2009). Air pollution: mechanisms of neuroinflammation and CNS disease. Trends in neurosciences , 32 (9), 506-516.

Abstract W P239: Exposure to Airborne Particulate Matter from Vehicular Exhaust Results in Progression of Brain Injury Following Experimental Stroke

Inflammation is believed to play an important role in the progression of acute stroke. Air pollution is a potent environmental source of inflammation and oxidative stress. We sought to examine the impact of inhalation of airborne particulate matter (PM) derived from urban traffic on the progression of brain injury following acute stroke. Urban PM was collected with a particle sampler situated near the CA-110 Freeway in Los Angeles. Collected aerosols represented a mix of fresh PM, predominantly from vehicular traffic. These samples were then distilled to pollutant nanoparticles (<200 nm) and re-aerosolized for administration to mice through exposure chambers. Adult mice were exposed to aerosolized PM (n=12) or filtered air (n=12) for forty-five cumulative hours and then underwent middle cerebral artery ischemia (35 minutes)/ reperfusion (I/R). Infarct volumes and neurological function were compared between mice exposed to PM and filtered air on postoperative day 1. Reperfusion was assessed by percent recovery of blood flow on laser Doppler flowmetry (LDF). Following cerebral I/R, mice exposed to PM demonstrated larger infarct volumes [20.6 ±6.4% (n=8) vs. 11.3 ±6.6% (n=9); p=0.018] and less favorable neurological scores [5.8 ±2.96 (n=12) vs. 3.2 ±2.4 (n=12); p=0.019] when compared to mice exposed to filtered air. Mortality was higher for the PM cohort (8.3% vs. 0%, p=ns) Further, LDF demonstrated decreased reperfusion in the cohort of mice exposed to PM (64 ±39%, n=10) when compared to those exposed to filtered air (86 ±24%, n=10, p=ns). This data establishes a detrimental effect of particulate matter in the setting of acute stroke and suggests a potential inflammatory mechanism of action.

Abstract T P409: Experimental Chronic Cerebral Hypoperfusion Results in Decreased Pericyte Coverage and Increased Blood Brain Barrier Permeability in the Corpus Callosum

Murine chronic cerebral hypoperfusion (CCH) results in white matter (WM) injury and behavioral deficits. Underlying mechanisms remain unclear. Pericytes influence blood-brain barrier (BBB) integrity and cerebral blood flow. Under hypoxic conditions, perictyes detach from perivascular locations increasing blood vessel permeability and secondary neuronal injury.

This study aims to characterize the time course of BBB dysfunction and pericyte coverage following murine experimental CCH. White matter injury and behavioral deficits have been reported consistently on post-operative day 30 in this model.

C57BL/6J mice underwent either CCH (n=12) or sham operation (n=9). BBB permeability in the corpus callosum (CC) was characterized on post-procedure days 1, 3, 7, and 30 using Evans blue (EB) extravasation and IgG staining. Pericyte coverage (CD 13/CD31 ratio) in the paramedian region of the corpus callosum was calculated on post-procedure days 1, 3, 7, and 30.

The CCH cohort demonstrated increased EB extravasation (integrate density) on postoperative days 1,3,7 and 30 when compared to the sham cohort (CCH: 583.58 ±98.28, 1529.32 ±448.87, 366.02 ±34.51, 5.85 ±1.80; SHAM: 44.51, 230.22, 24.03, 2.55 on postoperative days 1, 3, 7, and 30 respectively.) Further EB extravasation was significantly greater (p<0.05 ) at day 3 (peak level) than at days 7 and 30 in CCH mice. Positive IgG staining was seen at post-procedure days 3, 7, and 30 in the CCH group, but not in the sham operated mice. The CCH mice demonstrated a nadir in pericyte coverage on post-operative day 3 (30.88 ±10.27%). These values were significantly lower (p<0.05) than those on postoperative days 7 (89.36 ±5.11%), and 30 (74.97 ±2.39%). The post-operative day 3 pericyte coverage ratios were also significantly decreased compared to those in the sham mice (72.09 ±3.89%; p<0.01).

Decreased pericyte coverage and increased BBB permeability are most pronounced on postoperative day 3 following murine experimental CCH. This precedes any notable WM injury or behavioral deficits (post-op. day 30). Morphologic pericyte changes are concordant with BBB breakdown. Neurotoxic macromolecule extravasation may contribute to the pathogenesis of WM lesions and resultant behavioral deficits in this model system.