Cortical oxygen extraction fraction using quantitative BOLD MRI and cerebral blood flow during vasodilation.

Introduction: We aimed to demonstrate non-invasive measurements of regional oxygen extraction fraction (OEF) from quantitative BOLD MRI modeling at baseline and after pharmacological vasodilation. We hypothesized that OEF decreases in response to vasodilation with acetazolamide (ACZ) in healthy conditions, reflecting compensation in regions with increased cerebral blood flow (CBF), while cerebral metabolic rate of oxygen (CMRO2) remained unchanged. We also aimed to assess the relationship between OEF and perfusion in the default mode network (DMN) regions that have shown associations with vascular risk factors and cerebrovascular reactivity in different neurological conditions. Material and methods: Eight healthy subjects (47 ± 13 years, 6 female) were scanned on a 3 T scanner with a 32-channel head coil before and after administration of 15 mg/kg ACZ as a pharmacological vasodilator. The MR imaging acquisition protocols included: 1) A Gradient Echo Slice Excitation Profile Imaging Asymmetric Spin Echo scan to quantify OEF, deoxygenated blood volume, and reversible transverse relaxation rate (R2 ') and 2) a multi-post labeling delay arterial spin labeling scan to measure CBF. To assess changes in each parameter due to vasodilation, two-way t-tests were performed for all pairs (baseline versus vasodilation) in the DMN brain regions with Bonferroni correction for multiple comparisons. The relationships between CBF versus OEF and CBF versus R2' were analyzed and compared across DMN regions using linear, mixed-effect models. Results: During vasodilation, CBF significantly increased in the medial frontal cortex (P=0.004), posterior cingulate gyrus (pCG) (P=0.004), precuneus cortex (PCun) (P=0.004), and occipital pole (P=0.001). Concurrently, a significant decrease in OEF was observed only in the pCG (8.8%, P=0.003) and PCun (8.7%,P=0.001). CMRO2 showed a trend of increased values after vasodilation, but these differences were not significant after correction for multiple comparisons. Although R2' showed a slightly decreasing trend, no statistically significant changes were found in any regions in response to ACZ. The CBF response to ACZ exhibited a stronger negative correlation with OEF (ß=-0.104±0.027; t=-3.852,P<0.001), than with R2' (ß=-0.016±0.006; t=-2.692,P=0.008). Conclusion: Quantitative BOLD modeling can reliably measure OEF across multiple physiological conditions and captures vascular changes with higher sensitivity than R2' values. The inverse correlation between OEF and CBF across regions in DMN, suggests that these two measurements, in response to ACZ vasodilation, are reliable indicators of tissue health in this healthy cohort.

Gene expression changes implicate specific peripheral immune responses to Deep and Lobar Intracerebral Hemorrhages in humans.

The peripheral immune system response to Intracerebral Hemorrhage (ICH) may differ with ICH in different brain locations. Thus, we investigated peripheral blood mRNA expression of Deep ICH, Lobar ICH, and vascular risk factor-matched control subjects (n = 59). Deep ICH subjects usually had hypertension. Some Lobar ICH subjects had cerebral amyloid angiopathy (CAA). Genes and gene networks in Deep ICH and Lobar ICH were compared to controls. We found 774 differentially expressed genes (DEGs) and 2 co-expressed gene modules associated with Deep ICH, and 441 DEGs and 5 modules associated with Lobar ICH. Pathway enrichment showed some common immune/inflammatory responses between locations including Autophagy, T Cell Receptor, Inflammasome, and Neuroinflammation Signaling. Th2, Interferon, GP6, and BEX2 Signaling were unique to Deep ICH. Necroptosis Signaling, Protein Ubiquitination, Amyloid Processing, and various RNA Processing terms were unique to Lobar ICH. Finding amyloid processing pathways in blood of Lobar ICH patients suggests peripheral immune cells may participate in processes leading to perivascular/vascular amyloid in CAA vessels and/or are involved in its removal. This study identifies distinct peripheral blood transcriptome architectures in Deep and Lobar ICH, emphasizes the need for considering location in ICH studies/clinical trials, and presents potential location-specific treatment targets.

Mechanical Thrombectomy for Sequential Bilateral Middle Cerebral Artery Occlusions in a Patient With Recurrent Cryptogenic Strokes: A Case Report.

Recurrent sequential mechanical thrombectomy for cryptogenic large vessel occlusion (LVO) can lead to excellent clinical outcome. A 68-year-old right-handed male presented with an acute proximal right middle cerebral artery (MCA) ischemic syndrome and underwent successful revascularization by mechanical thrombectomy with normal functional recovery. He was treated with dual antiplatelet therapy for 2 months following discharge, however later discontinued clopidogrel due to side effects. He then developed a recurrent, contralateral MCA occlusion 16 months later and once again received emergent endovascular reperfusion therapy with excellent neurological outcome. He has remained on off-label empiric oral anticoagulation since and has not had recurrent stroke nor evidence of cerebral ischemia. Favorable clinical outcomes can be achieved in patients despite recurrent LVO who underwent emergent mechanical thrombectomy. Optimal antithrombotic secondary stroke prevention strategies following embolic stroke of unknown source remains uncertain as recent evidence does not support rivaroxaban or dabigatran over aspirin. The benefit of apixaban over aspirin for the prevention of recurrent cerebral ischemia is under current investigation.

Neuroimaging patterns of ischemic stroke after percutaneous coronary intervention.

OBJECTIVES: We sought to determine neuroimaging patterns, ischemic mechanisms, and functional outcomes of ischemic stroke related to percutaneous coronary intervention (PCI) over a 16-year period. BACKGROUND: Stroke is a feared complication of PCI, associated with poor patient outcomes. The majority of strokes that occur after PCI are ischemic rather than hemorrhagic. However, mechanisms of cerebral ischemia in this setting are incompletely understood. METHODS: We performed a retrospective single-center cohort study of patients with radiologically confirmed ischemic stroke occurring after PCI (PCI-stroke), between January 1, 1994 and December 31, 2009. Using brain imaging, infarctions were subclassified by radiological pattern and arterial territory as embolic, small subcortical, or hemodynamic. Modified Rankin Scale scores were used to assess functional outcome at 3 and 6 months. RESULTS: Radiologically confirmed PCI-stroke was identified in 35 patients. The majority of strokes (91%) revealed an embolic pattern, while the remaining strokes were small subcortical infarctions (9%). Watershed strokes with exclusive borderzone involvement, indicative of a hemodynamic mechanism, were not identified, despite the presence of periprocedural hypotension in 23% of patients. The middle cerebral artery (MCA) territory was affected most frequently (80%), and all patients suffering a complete MCA territorial infarction (14%) died in the hospital. Functional outcome among survivors of PCI-stroke was typically favorable in those who had single rather than multiple vascular territory involvement. CONCLUSIONS: The vast majority of radiologically confirmed ischemic strokes related to PCI are embolic. MCA territory strokes are most common and uniformly fatal when the entire MCA territory is affected. Functional outcomes in survivors of PCI-stroke are improved when only a single arterial territory is affected.

Pilot randomized trial of outpatient cardiac monitoring after cryptogenic stroke.

BACKGROUND AND PURPOSE: Observational studies indicate that outpatient cardiac monitoring detects previously undiagnosed atrial fibrillation (AF) in 5% to 20% of patients with recent stroke. However, it remains unknown whether the yield of monitoring exceeds that of routine clinical follow-up. METHODS: In a pilot trial, we randomly assigned 40 patients with cryptogenic ischemic stroke or high-risk transient ischemic attack to wear a Cardionet mobile cardiac outpatient telemetry monitor for 21 days or to receive routine follow-up alone. After thorough investigation, we excluded patients with documented AF or other apparent stroke pathogenesis. We contacted patients and their physicians at 3 months and at 1 year to ascertain any diagnoses of AF or recurrent stroke or transient ischemic attack. RESULTS: The baseline characteristics of our cohort broadly matched those of previous observational studies of monitoring after stroke. In the monitoring group, patients wore monitors for 64% of the assigned days, and 25% of patients were not compliant at all with monitoring. No patient in either study arm received a diagnosis of AF. Cardiac monitoring revealed AF in zero patients (0%; 95% confidence interval, 0%-17%), brief episodes of atrial tachycardia in 2 patients (10%; 95% confidence interval, 1%-32%), and nonsustained ventricular tachycardia in 2 patients (10%; 95% confidence interval, 1%-32%). CONCLUSIONS: In the first reported randomized trial of cardiac monitoring after cryptogenic stroke, the rate of AF detection was lower than expected, incidental arrhythmias were frequent, and compliance with monitoring was suboptimal. Our findings highlight the challenges of prospectively identifying stroke patients at risk for harboring paroxysmal AF and ensuring adequate compliance with cardiac monitoring. Clinical Trial Registration- URL: http://clinicaltrials.gov. Unique Identifier: NCT00715533.

Prediction of potential for organ donation after cardiac death in patients in neurocritical state: a prospective observational study.

BACKGROUND: Successful donation of organs after cardiac death (DCD) requires identification of patients who will die within 60 min of withdrawal of life-sustaining treatment (WLST). We aimed to validate a straightforward model to predict the likelihood of death within 60 min of WLST in patients with irreversible brain injury. METHODS: In this multicentre, observational study, we prospectively enrolled consecutive comatose patients with irreversible brain injury undergoing WLST at six medical centres in the USA and the Netherlands. We assessed four clinical characteristics (corneal reflex, cough reflex, best motor response, and oxygenation index) as predictor variables, which were selected on the basis of previous findings. We excluded patients who had brain death or were not intubated. The primary endpoint was death within 60 min of WLST. We used univariate and multivariable logistic regression analyses to assess associations with predictor variables. Points attributed to each variable were summed to create a predictive score for cardiac death in patients in neurocritical state (the DCD-N score). We assessed performance of the score using area under the curve analysis. FINDINGS: We included 178 patients, 82 (46%) of whom died within 60 min of WLST. Absent corneal reflexes (odds ratio [OR] 2·67, 95% CI 1·19-6·01; p=0·0173; 1 point), absent cough reflex (4·16, 1·79-9·70; p=0·0009; 2 points), extensor or absent motor responses (2·99, 1·22-7·34; p=0·0168; 1 point), and an oxygenation index score of more than 3·0 (2·31, 1·10-4·88; p=0·0276; 1 point) were predictive of death within 60 min of WLST. 59 of 82 patients who died within 60 min of WLST had DCD-N scores of 3 or more (72% sensitivity), and 75 of 96 of those who did not die within this interval had scores of 0-2 (78% specificity); taking into account the prevalence of death within 60 min in this population, a score of 3 or more was translated into a 74% chance of death within 60 min (positive predictive value) and a score of 0-2 translated into a 77% chance of survival beyond 60 min (negative predictive value). INTERPRETATION: The DCD-N score can be used to predict potential candidates for DCD in patients with non-survivable brain injury. However, this score needs to be tested specifically in a cohort of potential donors participating in DCD protocols. FUNDING: None.

Aseptic meningitis in adult onset Still's disease.

Adult onset Still's disease (AOSD) is a systemic inflammatory disease characterized by high-fevers, articular involvement, maculopapular rash, hepatosplenomegaly, lymphadenopathy, and a neutrophilic leukocytosis. Though systemic complications of AOSD or its treatment are well described in the literature, CNS involvement in AOSD is exceedingly rare and can have protean manifestations. We present a patient with AOSD who developed chronic meningitis and sensorineural hearing loss on treatment, with a review of prior reported cases of aseptic meningitis, to highlight this rare complication of this uncommon illness.

Cerebral salt wasting: pathophysiology, diagnosis, and treatment.

Cerebral salt wasting (CSW) is a syndrome of hypovolemic hyponatremia caused by natriuresis and diuresis. The mechanisms underlying CSW have not been precisely delineated, although existing evidence strongly implicates abnormal elevations in circulating natriuretic peptides. The key in diagnosis of CSW lies in distinguishing it from the more common syndrome of inappropriate secretion of antidiuretic hormone. Volume status, but not serum and urine electrolytes and osmolality, is crucial for making this distinction. Volume and sodium repletion are the goals of treatment of patients with CSW, and this can be performed using some combination of isotonic saline, hypertonic saline, and mineralocorticoids.

Predictors of apnea test failure during brain death determination.

BACKGROUND: In a recent publication (Wijdicks et al. in Neurology 71(16):1240, 2008), apnea test safety during brain death determination was evaluated at a single tertiary care center. One major conclusion was that apnea testing was safe in hemodynamically compromised patients in most circumstances and rarely aborted. Determinants of apnea test completion failure are unknown. METHODS: A-a gradients and PaO2/FiO2 ratios were calculated in the previously studied cohort. Arterial blood gas (ABG) values and systolic blood pressures (SBP) were recorded prior to apnea test initiation. Patients that completed the procedure during the declaration of brain death were compared to those whose studies were aborted. Statistical analysis was performed using Wilcoxon rank-sum and Fisher's exact tests where appropriate. Aborted apnea test risk factor assessment was by logistic regression analysis. RESULTS: 207 of the original 228 patients were evaluated. 10 of the 207 patients had aborted apnea tests because of hypoxemia and/or hypotension. 60% who failed the apnea test were male and were of younger age [median: 23 years vs. median: 47 years (P = 0.02)]. A-a gradient median values for aborted and completed apnea tests were 376 and 175 mmHg, respectively (P = 0.003). Neither the PaO2/FiO2 ratio (P = 0.14) nor SBP (P = 0.28) were associated with test completion failure. Acidemia preceding a carbon dioxide challenge was independently associated with test completion failure (P = 0.028). CONCLUSION: Acute lung injury is common in patients undergoing brain death evaluation. Patients that failed completion of apnea testing tended to be younger, had significantly greater A-a gradients, and were more acidotic.

A perfect storm in the emergency department.

BACKGROUND: Serotonin syndrome is an iatrogenic disorder that results from serotonergic overactivity. Severe myoclonus and increased restlessness are hallmarks of the disorder. METHODS: We report a case of serotonin syndrome related to poor drug elimination. RESULTS: A 74-year-old white female with moderate to severe Alzheimer's dementia was brought to the emergency department for increasingly aggressive behavior. Upon admission, her risperidone dose was increased and citalopram continued. Several days later, she developed diffuse limb and facial myoclonus, spontaneous clonus, diaphoresis, and fever. Her symptoms completely resolved after discontinuation of these medications. CONCLUSION: Serotonin syndrome should be considered in the differential when elderly patients present with severe myoclonus. If unrecognized, this syndrome can lead to more severe manifestations including rhabdomyolysis, renal failure, and coma.

Neurologic presentations of acid-base imbalance, electrolyte abnormalities, and endocrine emergencies.

Accurate identification of nervous system dysfunction is vital in the assessment of any multisystem disorder. The neurologic manifestations of acid-base disturbances, abnormal electrolyte concentrations, and acute endocrinopathies are protean and typically determined by the acuity of the underlying derangement. Detailed history and physical examination may guide appropriate laboratory testing and lead to prompt and accurate diagnosis. Neurologic manifestations of primary and secondary systemic disorders are frequently encountered in all subspecialties of medicine. This article focuses on key neurologic presentations of respiratory and metabolic acid-base derangements and potentially life-threatening endocrinopathies.