Strokes in Patients With Injection Drug Use and Tricuspid Valve Endocarditis - A Case Series.

Research Design: In this study, we describe patients from a tertiary care safety-net hospital endocarditis registry with tricuspid valve infective endocarditis (TVIE), and concomitant acute or subacute ischemic stroke predominantly associated with injection drug use (IDU). We retrospectively obtained data pertinent to neurologic examinations, history of injection drug use (IDU), blood cultures, transthoracic/transesophageal echocardiography (TTE/TEE), neuroimaging, and Modified Rankin Scale (mRS) scores at discharge. Only those patients with bacteremia, tricuspid valve vegetations, and neuroimaging consistent with acute to subacute ischemic infarction and microhemorrhages in two cases were included in this series. Results: Of 188 patients in the registry, 66 patients had TVIE and 10 of these were complicated by ischemic stroke. Neurologic symptoms were largely non-specific, eight patients had altered mental status and only 3 had focal deficits. Nine cases were associated with IDU. Two patients had evidence of a patent foramen ovale on echocardiography. Blood cultures grew S. aureus species in 9 of the patients, all associated with IDU. Three patients died during hospitalization. The mRS score at discharge for survivors ranged 0-4. Conclusions: Patients with strokes from TVIE had heterogeneous presentations and putative mechanisms. We noted that robust neuroimaging is lacking for patients with TVIE from IDU and that such patients may benefit from neuroimaging as a screen for strokes to assist peri-operative management. Further inquiry is needed to elucidate stroke mechanisms in these patients.

Acute occlusion of the fetal posterior cerebral artery: diagnosis and management paradigms.

BACKGROUND AND PURPOSE: The diagnosis and management of acute fetal posterior cerebral artery occlusion are challenging. While endovascular treatment is established for anterior circulation large vessel occlusion stroke, little is known about the course of acute fetal posterior cerebral artery occlusions. We report the clinical course, radiological findings and management considerations of acute fetal posterior cerebral artery occlusion stroke. METHODS: We performed a retrospective review of consecutive patients presenting with acute large vessel occlusion who underwent cerebral angiogram and/or mechanical thrombectomy between January 2015 and January 2021. Patients diagnosed with fetal posterior cerebral artery occlusion were included. Demographic data, clinical presentation, imaging findings and management strategies were reviewed. RESULTS: Between January 2015 and January 2021, three patients with fetal posterior cerebral artery occlusion were identified from 400 patients who underwent angiogram and/or mechanical thrombectomy for acute stroke (0.75%). The first patient presented with concomitant fetal posterior cerebral artery and middle cerebral artery occlusions. Thrombectomy was performed with recanalisation of the fetal posterior cerebral artery but the patient died from malignant oedema. The second patient presented with isolated fetal posterior cerebral artery occlusion. No endovascular intervention was performed and the patient was disabled from malignant posterior cerebral artery infarct. The third patient presented with carotid occlusion and was found to have fetal posterior cerebral artery occlusion after internal carotid artery recanalisation. No further intervention was performed. The patient was left with residual contralateral homonymous hemianopia and mild left sided weakness. CONCLUSION: Fetal posterior cerebral artery occlusion is a rare, but potentially disabling, cause of ischaemic stroke. Endovascular treatment is feasible. Further investigation is needed to compare the efficacy of medical versus endovascular management strategies.

Endovascular Treatment of Infective Endocarditis-Related Acute Large Vessel Occlusion Stroke.

OBJECTIVES: Embolic stroke is a frequent complication of infective endocarditis yet lacks acute treatment as intravenous thrombolysis should be avoided due to high risk of intracerebral hemorrhage. Mechanical thrombectomy for large vessel occlusion may be a promising treatment but there is limited data on safety outcomes in infective endocarditis. MATERIALS AND METHODS: In this multi-center retrospective case series, we reviewed data from patients with infective endocarditis-related large vessel occlusion who underwent mechanical thrombectomy in 9 US hospitals. RESULTS: We identified 15 patients at 9 hospitals. A minority presented with signs suggesting infection (2 patients (14%) had fever, 7 (47%) were tachycardic, 2 (13%) were hypotensive, and 8 (53%) had leukocytosis). The median National Institute of Health Stroke Score decreased from 19 (range 9-25) at presentation to 7 post-thrombectomy (range 0-22, median best score post-thrombectomy), and the median modified Rankin Scale on or after discharge for survivors was 3 (range 0-6). Approximately 57% of patients had a modified Rankin Scale between 0 and 3 on or after discharge. Hemorrhagic transformation was observed in 7/15 (47%). The mechanical thrombectomy group had 2/9 petechial hemorrhagic transformation (22%), compared to 4/6 parenchymal hematomas (67%) in the tissue plasminogen activator + mechanical thrombectomy group. CONCLUSIONS: Our findings suggest that patients with large vessel occlusion due to infective endocarditis may not present with overt signs of infection. Mechanical thrombectomy may be an effective treatment in this patient population for whom intravenous thrombolysis should be avoided.

Seizure as the presenting symptom of COVID-19: A retrospective case series.

BACKGROUND: Coronavirus Disease 2019 (COVID-19) has rapidly become a global pandemic, with over 1.8 million confirmed cases worldwide to date. Preliminary reports suggest that the disease may present in diverse ways, including with neurological symptoms, but few published reports in the literature describe seizures in patients with COVID-19. OBJECTIVE: The objective of the study was to characterize the risk factors, clinical features, and outcomes of seizures in patients with COVID-19. METHODS: This is a retrospective case series. Cases were identified through a review of admissions and consultations to the neurology and neurocritical care services between April 1, 2020 and May 15, 2020. SETTING: The study setting was in a tertiary care, safety-net hospital in Boston, MA. PARTICIPANTS: Patients presenting with seizures and COVID-19 during the study period were included in the study. RESULTS: Seven patients met inclusion criteria (5 females, 71%). Patients ranged in age from 37 to 88 years (median: 75 years). Three patients had a prior history of well-controlled epilepsy (43%), while 4 patients had new-onset seizures, including 2 patients with prior history of remote stroke. Three patients had no preceding symptoms of COVID-19 prior to presentation (57%), and in all cases, seizures were the symptom that prompted presentation to the emergency department, regardless of prior symptoms of COVID-19. CONCLUSIONS: Provoking factors for seizures in patients with COVID-19 may include metabolic factors, systemic illness, and possibly direct effects of the virus. In endemic areas with community spread of COVID-19, clinicians should be vigilant for the infection in patients who present with seizures, which may precede respiratory symptoms or prompt presentation to medical care. Early testing, isolation, and contact tracking of these patients can prevent further transmission of the virus.

Neurosurgical Infections.

Patients in the neurointensive care unit often undergo life-saving neurosurgical interventions that can be associated with serious complications. Infection is a common and sometimes fatal complication of such procedures. Infection may occur not only in the setting of major cranial and spinal surgery, but also with common minor procedures that utilize neurosurgical devices, such as placement of external ventricular drains, ventriculoperitoneal shunts, and deep brain stimulators. In this article, we review the epidemiology and microbiology of these infections, and discuss their general and procedure-specific risk factors and treatment options.

The brain-structural correlates of mathematical expertise.

Studies in several domains of expertise have established that experience-dependent plasticity brings about both functional and anatomical changes. However, little is known about how such changes come to shape the brain in the case of expertise acquired by professional mathematicians. Here, we aimed to identify cognitive and brain-structural (grey and white matter) characteristics of mathematicians as compared to non-mathematicians. Mathematicians and non-mathematician academics from the University of Oxford underwent structural and diffusion MRI scans, and were tested on a cognitive battery assessing working memory, attention, IQ, numerical and social skills. At the behavioural level, mathematical expertise was associated with better performance in domain-general and domain-specific dimensions. At the grey matter level, in a whole-brain analysis, behavioural performance correlated with grey matter density in left superior frontal gyrus - positively for mathematicians but negatively for non-mathematicians; in a region of interest analysis, we found in mathematicians higher grey matter density in the right superior parietal lobule, but lower grey matter density in the right intraparietal sulcus and in the left inferior frontal gyrus. In terms of white matter, there were no significant group differences in fractional anisotropy or mean diffusivity. These results reveal new insights into the relationship between mathematical expertise and grey matter metrics in brain regions previously implicated in numerical cognition, as well as in regions that have so far received less attention in this field. Further studies, based on longitudinal designs and cognitive training, could examine the conjecture that such cross-sectional findings arise from a bidirectional link between experience and structural brain changes that is itself subject to change across the lifespan.

Headache in Pregnancy, the Puerperium, and menopause.

Headache is a neurologic disorder that displays gender dichotomy. It is well established that there is a strong link between migraine headache and sex hormones, specifically estrogen, which influences the severity of migraines during the menstrual cycle, pregnancy, and menopause. Furthermore, the epidemiology of headaches during pregnancy and the postpartum period is very distinct from that in males or nonpregnant females, in part due to the hemodynamic and hematologic changes that occur during pregnancy. These changes put women at higher risk for cerebral venous thrombosis, hemorrhagic stroke, and hypertensive disorders of pregnancy like preeclampsia, eclampsia, posterior reversible encephalopathy syndrome, and reversible cerebral vasoconstriction syndrome. Headache in pregnancy and the puerperium can be a cause of heightened anxiety in most women, who are concerned not only about the effect of the headache itself on the pregnancy but also about the effect of the treatment options on the pregnancy and the fetus. In this review, we discuss the latest literature on type and distribution of headaches during pregnancy and the postpartum period, and provide a digestible overview of the safety profile of commonly used abortive and prophylactic medications. We also discuss important considerations when treating migraine during menopause.

Barriers to Neurosurgical Training in Sub-Saharan Africa: The Need for a Phased Approach to Global Surgery Efforts to Improve Neurosurgical Care.

BACKGROUND: Neurosurgery in low-income countries is faced with multiple challenges. Although the most common challenges include infrastructure and physical resource deficits, an underemphasized barrier relates to the methods and components of surgical training. The role of important aspects, including didactic surgical training, surgical decision-making, workshops, conferences, and assessment methods, has not been duly studied. Knowledge of these issues is a crucial step to move closer to strengthening surgical capacity in low-income countries. METHODS: We designed an online survey to assess self-perceived and objectively measured barriers to neurosurgical training in various Sub-Saharan African countries. Key outcomes included perception toward adequacy of neurosurgery training and barriers to neurosurgical training at each individual site. RESULTS: Only 37% of responders felt that their training program adequately prepared them for handling incoming neurosurgical cases. Top perceived limitations of neurosurgery training included lack of physical resources (25% of all responses), lack of practical workshops (22%), lack of program structure (18%), and lack of topic-specific lectures (10%). CONCLUSIONS: Our results show that most responders believe their training program is inadequate and are interested in improving it through international collaborations. This implies that activities directed at strengthening surgical capacity must address this important necessity. One important strategy is the use of online educational tools. In consideration of the observed limitations in care, resources, and training, we recommend a phased approach to neurosurgical growth in low-income settings.

Assessing Barriers to Neurosurgical Care in Sub-Saharan Africa: The Role of Resources and Infrastructure.

BACKGROUND: Quantitative estimates of surgical capacity and infrastructure and perceived care limitations in low-resource countries are essential baseline measures that can provide strategies for improving access to surgical care. Information about these barriers in Africa is scarce, particularly with respect to neurosurgery. We conducted a survey to better understand the unmet surgical need and resources available for the care of neurosurgery patients in Sub-Saharan Africa. METHODS: Using SurveyMonkey, we administered a neurosurgery-specific survey to neurosurgery attending surgeons and residents in Sub-Saharan African countries. Key outcome measures included workforce, access to imaging modalities and instruments, volume and breakdown of neurosurgical cases, and perceived limitations of care. RESULTS: We obtained a 41% survey response (129/314 sent). In addition to the expected large gap in workforce between low- and high-income countries, we found a dramatic paucity of neurosurgical resources in Central Africa, whereas specific pockets in West and South Africa have better neurosurgical care. Access to neuroimaging was not a major limitation in Sub-Saharan African countries. The most commonly perceived limitations of care included infrastructure, anesthesia/nursing availability, wait times, and strength of training. CONCLUSIONS: This large survey defines important self-perceived limitations to care within neurosurgery and highlights the importance of infrastructure and allied professions in this role. A clear understanding of areas of focus will enable a more efficient and sustainable response to the limitations in surgical care in low-resource areas.

Basic and advanced numerical performances relate to mathematical expertise but are fully mediated by visuospatial skills.

Recent studies have highlighted the potential role of basic numerical processing in the acquisition of numerical and mathematical competences. However, it is debated whether high-level numerical skills and mathematics depends specifically on basic numerical representations. In this study mathematicians and nonmathematicians performed a basic number line task, which required mapping positive and negative numbers on a physical horizontal line, and has been shown to correlate with more advanced numerical abilities and mathematical achievement. We found that mathematicians were more accurate compared with nonmathematicians when mapping positive, but not negative numbers, which are considered numerical primitives and cultural artifacts, respectively. Moreover, performance on positive number mapping could predict whether one is a mathematician or not, and was mediated by more advanced mathematical skills. This finding might suggest a link between basic and advanced mathematical skills. However, when we included visuospatial skills, as measured by block design subtest, the mediation analysis revealed that the relation between the performance in the number line task and the group membership was explained by non-numerical visuospatial skills. These results demonstrate that relation between basic, even specific, numerical skills and advanced mathematical achievement can be artifactual and explained by visuospatial processing. (PsycINFO Database Record

Functional organization of excitatory synaptic strength in primary visual cortex.

The strength of synaptic connections fundamentally determines how neurons influence each other's firing. Excitatory connection amplitudes between pairs of cortical neurons vary over two orders of magnitude, comprising only very few strong connections among many weaker ones. Although this highly skewed distribution of connection strengths is observed in diverse cortical areas, its functional significance remains unknown: it is not clear how connection strength relates to neuronal response properties, nor how strong and weak inputs contribute to information processing in local microcircuits. Here we reveal that the strength of connections between layer 2/3 (L2/3) pyramidal neurons in mouse primary visual cortex (V1) obeys a simple rule--the few strong connections occur between neurons with most correlated responses, while only weak connections link neurons with uncorrelated responses. Moreover, we show that strong and reciprocal connections occur between cells with similar spatial receptive field structure. Although weak connections far outnumber strong connections, each neuron receives the majority of its local excitation from a small number of strong inputs provided by the few neurons with similar responses to visual features. By dominating recurrent excitation, these infrequent yet powerful inputs disproportionately contribute to feature preference and selectivity. Therefore, our results show that the apparently complex organization of excitatory connection strength reflects the similarity of neuronal responses, and suggest that rare, strong connections mediate stimulus-specific response amplification in cortical microcircuits.

Experience-dependent specialization of receptive field surround for selective coding of natural scenes.

At eye opening, neurons in primary visual cortex (V1) are selective for stimulus features, but circuits continue to refine in an experience-dependent manner for some weeks thereafter. How these changes contribute to the coding of visual features embedded in complex natural scenes remains unknown. Here we show that normal visual experience after eye opening is required for V1 neurons to develop a sensitivity for the statistical structure of natural stimuli extending beyond the boundaries of their receptive fields (RFs), which leads to improvements in coding efficiency for full-field natural scenes (increased selectivity and information rate). These improvements are mediated by an experience-dependent increase in the effectiveness of natural surround stimuli to hyperpolarize the membrane potential specifically during RF-stimulus epochs triggering action potentials. We suggest that neural circuits underlying surround modulation are shaped by the statistical structure of visual input, which leads to more selective coding of features in natural scenes.