Vasospasm after subarachnoid hemorrhage: interest in diffusion-weighted MR imaging

The Impact of Fluid Balance on Acute Kidney Injury in Nontraumatic Subarachnoid Hemorrhage

Background: Nontraumatic subarachnoid hemorrhage (SAH) can lead to poor neurologic outcomes, particularly when delayed cerebral ischemia (DCI) occurs. Maintenance of euvolemia following SAH is thought to reduce the risk of DCI. However, attempts at maintaining euvolemia often err on the side of hypervolemia. In this study, we assessed the relationship between fluid balance and acute kidney injury (AKI) in SAH patients, assessing hypervolemia versus euvolemia and their impact on AKI. Methods: In a quaternary care center, neuroscience intensive care unit we conducted a retrospective longitudinal analysis in adult patients who suffered a nontraumatic SAH. Results: Out of 139 patients, 15 (10.8%) patients developed an AKI while hospitalized, with 7 stage I, 3 stage II, and 5 stage III injuries. Acute kidney injury patients had higher peak sodium (150.1 mEq/L vs 142.7 mEq/L, 95% confidence interval [CI]: [2.7-12.1 mEq/L]), higher discharge chloride (109.1 mEq/L vs 104.9 mEq/L, 95% CI: [0.7-7.6 mEq/L]), and lower hemoglobin at discharge (9.3 g/dL vs 11.3 g/dL, 95% CI: [1.0-2.9 g/dL]). At 7 days, AKI patients had a fluid balance that was 1.82 L higher (P = .04), and 3.38 L higher at 14 days (P = .02), in comparison to day 3. Acute kidney injury was associated with significant mortality increases. This increase in mortality was found at 30 days from admission with a 9.52-fold increase, and at 60 days with a 6.25-fold increase. As a secondary outcome, vasospasm (19 patients, 13.7%) showed no association with AKI. Conclusions: Acute kidney injury following SAH is correlated with clinically significant hypervolemia, elevated sodium, elevated chloride, decreased urine output, and decreased hemoglobin at discharge-risk factors for all SAH patients. This study further elucidates the harm of hypervolemia and gives greater practical evidence to physicians attempting to balance the dangers of vasospasm and AKI.

Advances in biomarkers for vasospasm - Towards a future blood-based diagnostic test

Objective

Cerebral vasospasm and the resultant delayed cerebral infarction is a significant source of mortality following aneurysmal SAH. Vasospasm is currently detected using invasive or expensive imaging at regular intervals in patients following SAH, thus posing a risk of complications following the procedure and financial burden on these patients. Currently, there is no blood-based test to detect vasospasm.

Methods

PubMed, Web of Science, and Embase databases were systematically searched to retrieve studies related to cerebral vasospasm, aneurysm rupture, and biomarkers. The study search dated from 1997 to 2022. Data from eligible studies was extracted and then summarized.

Results

Out of the 632 citations screened, only 217 abstracts were selected for further review. Out of those, only 59 full text articles met eligibility and another 13 were excluded.

Conclusions

We summarize the current literature on the mechanism of cerebral vasospasm and delayed cerebral ischemia, specifically studies relating to inflammation, and provide a rationale and commentary on a hypothetical future bloodbased test to detect vasospasm. Efforts should be focused on clinical-translational approaches to create such a test to improve treatment timing and prediction of vasospasm to reduce the incidence of delayed cerebral infarction.

Early Brain Injury After Subarachnoid Hemorrhage: Incidence and Mechanisms

Aneurysmal subarachnoid hemorrhage is a devastating condition causing significant morbidity and mortality. While outcomes from subarachnoid hemorrhage have improved in recent years, there continues to be significant interest in identifying therapeutic targets for this disease. In particular, there has been a shift in emphasis toward secondary brain injury that develops in the first 72 hours after subarachnoid hemorrhage. This time period of interest is referred to as the early brain injury period and comprises processes including microcirculatory dysfunction, blood-brain-barrier breakdown, neuroinflammation, cerebral edema, oxidative cascades, and neuronal death. Advances in our understanding of the mechanisms defining the early brain injury period have been accompanied by improved imaging and nonimaging biomarkers for identifying early brain injury, leading to the recognition of an elevated clinical incidence of early brain injury compared with prior estimates. With the frequency, impact, and mechanisms of early brain injury better defined, there is a need to review the literature in this area to guide preclinical and clinical study.

Arterial Spin Labeling technique and clinical applications of the intracranial compartment in stroke and stroke mimics - A case-based review

Magnetic resonance imaging perfusion (MRP) techniques can improve the selection of acute ischemic stroke patients for treatment by estimating the salvageable area of decreased perfusion, that is, penumbra. Arterial spin labeling (ASL) is a noncontrast MRP technique that is used to assess cerebral blood flow without the use of intravenous gadolinium contrast. Thus, ASL is of particular interest in stroke imaging. This article will review clinical applications of ASL in stroke such as assessment of the core infarct and penumbra, localization of the vascular occlusion, and collateral status. Given the nonspecific symptoms that patients can present with, differentiating between stroke and a stroke mimic is a diagnostic dilemma. ASL not only helps in differentiating stroke from stroke mimic but also can be used to specify the exact mimic when used in conjunction with the symptomatology and structural imaging. In addition to a case-based overview of clinical applications of the ASL in stroke and stroke mimics in this article, the more commonly used ASL labeling techniques as well as emerging ASL techniques, future developments, and limitations will be reviewed.

Role of hydrogen sulfide in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a common acute and severe disease worldwide, which imposes a heavy burden on families and society. However, the current therapeutic strategies for SAH are unsatisfactory. Hydrogen sulfide (H2 S), as the third gas signaling molecule after carbon monoxide and nitric oxide, has been widely studied recently. There is growing evidence that H2 S has a promising future in the treatment of central nervous system diseases. In this review, we focus on the effects of H2 S in experimental SAH and elucidate the underlying mechanisms. We demonstrate that H2 S has neuroprotective effects and significantly reduces secondary damage caused by SAH via antioxidant, antiinflammatory, and antiapoptosis mechanisms, and by alleviating cerebral edema and vasospasm. Based on these findings, we believe that H2 S has great potential in the treatment of SAH and warrants further study to promote its early clinical application.

Utility of automated MRI perfusion (RAPID) with or without MR angiography for detection of angiographic vasospasm after aneurysmal subarachnoid hemorrhage

Delayed cerebral ischemia (DCI) is a major etiology of poor neurologic outcomes after aneurysmal subarachnoid hemorrhage (aSAH). Although the development of DCI is certainly multifactorial, the presence of vasospasm is strongly correlated with it. Cerebral angiography remains the gold standard for evaluation of vasospasm, though it is not always practical or cost-effective. In this study, the authors assess the utility of automated MRI Perfusion imaging, with or without MR Angiography (MRA), as a confirmatory tool for suspected angiographic vasospasm. All patients admitted to a single institution with aneurysmal subarachnoid hemorrhage between January 2014 and February 2020 and who underwent MR Perfusion imaging with or without MRA for suspected vasospasm no >24 h prior to an angiogram were identified. 43 subjects were identified. 29 of these patients (67%) underwent simultaneous MRA. 25 patients (53%) received intra-arterial treatment for symptomatic vasospasm. The sensitivity, specificity, PPV, and NPV of MR Perfusion were 43%, 82%, 53%, and 75% for any angiographic vasospasm and 57%, 81%, 42%, and 89% for treated vasospasm. The sensitivity, specificity, PPV, and NPV of MR Perfusion in conjunction with MRA were 61%, 81%, 59%, and 82% for any angiographic vasospasm and 62%, 74%, 35%, and 89% for treated vasospasm. The sensitivity, specificity, PPV, and NPV of transcranial Dopplers (TCDs) in these patients were 35%, 93%, 71%, and 75% for angiographic vasospasm and 42%, 90%, 47%, and 88% for treated vasospasm. Automated MR Perfusion imaging demonstrated relatively low sensitivity and PPV for detection of angiographic and treated vasospasm in this subset of patients after aSAH.

Ruptured AComA aneurysm and asymptomatic bilateral ACA vasospasm in an infant: surgical case report

Intracranial aneurysms (IAs) are localized dilations of the cerebral vasculature, representing the leading cause for non-traumatic subarachnoid hemorrhage and an important source of morbidity and mortality. Despite it being a frequent pathology and most often diagnosed incidentally, IAs in infants are a very rare occurrence, and the ruptured variant is exceptional. A 4-month-old boy with a negative family history was brought to our department because of several episodes of incoercible vomiting and fever. Upon examination, the child was somnolent, without any noticeable deficit. Transfontanellar ultrasonography and CT angiography revealed a ruptured aneurysm of the anterior communicating artery (AComA), whereas the pre-clipping MRI showed thin, almost angiographically invisible anterior cerebral arteries (ACAs) on both sides due to vasospasm. We intervened surgically by placing an external ventricular shunt in an emergency setting, followed by clipping of the IA in a delayed manner. The child was discharged a month after admission with no deficit, despite the paradoxical aspect of the ACA. Ruptured IAs can be safely treated via microsurgery, even in infants. However, this requires a great amount of experience and surgical expertise. Furthermore, the lack of proper management would most likely result in a severe deficit in the long term. Lastly, the lack of visibility of the ACA on angiographic studies may not have neurological consequences if they occur in this age group.

Subarachnoid hemorrhage in the emergency department

BACKGROUND

Subarachnoid hemorrhage accounts for more than 30,000 cases of stroke annually in North America and encompasses a 4.4% mortality rate. Since a vast number of subarachnoid hemorrhage cases present in a younger population and can range from benign to severe, an accurate diagnosis is imperative to avoid premature morbidity and mortality. Here, we present a straightforward approach to evaluating, risk stratifying, and managing subarachnoid hemorrhages in the emergency department for the emergency medicine physician.

DISCUSSION

The diversities of symptom presentation should be considered before proceeding with diagnostic modalities for subarachnoid hemorrhage. Once a subarachnoid hemorrhage is suspected, a computed tomography of the head with the assistance of the Ottawa subarachnoid hemorrhage rule should be utilized as an initial diagnostic measure. If further investigation is needed, a CT angiography of the head or a lumbar puncture can be considered keeping risks and limitations in mind. Initiating timely treatment is essential following diagnosis to help mitigate future complications. Risk tools can be used to assess the complications for which the patient is at greatest.

CONCLUSION

Subarachnoid hemorrhages are frequently misdiagnosed; therefore, we believe it is imperative to address the diagnosis and initiation of early management in the emergency medicine department to minimize poor outcomes in the future.

Focused Ultrasound for Noninvasive, Focal Pharmacologic Neurointervention

A long-standing goal of translational neuroscience is the ability to noninvasively deliver therapeutic agents to specific brain regions with high spatiotemporal resolution. Focused ultrasound (FUS) is an emerging technology that can noninvasively deliver energy up the order of 1 kW/cm² with millimeter and millisecond resolution to any point in the human brain with Food and Drug Administration-approved hardware. Although FUS is clinically utilized primarily for focal ablation in conditions such as essential tremor, recent breakthroughs have enabled the use of FUS for drug delivery at lower intensities (i.e., tens of watts per square centimeter) without ablation of the tissue. In this review, we present strategies for image-guided FUS-mediated pharmacologic neurointerventions. First, we discuss blood–brain barrier opening to deliver therapeutic agents of a variety of sizes to the central nervous system. We then describe the use of ultrasound-sensitive nanoparticles to noninvasively deliver small molecules to millimeter-sized structures including superficial cortical regions and deep gray matter regions within the brain without the need for blood–brain barrier opening. We also consider the safety and potential complications of these techniques, with attention to temporal acuity. Finally, we close with a discussion of different methods for mapping the ultrasound field within the brain and describe future avenues of research in ultrasound-targeted drug therapies.

Prediction of clinical outcome in subacute subarachnoid hemorrhage using diffusion tensor imaging

OBJECTIVE

Clinical outcome in nontraumatic subarachnoid hemorrhage (SAH) is multifactorial and difficult to predict. Diffusion tensor imaging (DTI) findings are a prognostic marker in some diseases such as traumatic brain injury. The authors hypothesized that DTI parameters measured in the subacute phase of SAH can be associated with a poor clinical outcome.

METHODS

Diffusion tensor imaging was prospectively performed in 54 patients at 8-10 days after nontraumatic SAH. Logistic regression analysis was performed to evaluate the association of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values with a poor clinical outcome (modified Rankin Scale score ≥ 3) at 3 months.

RESULTS

At 8-10 days post-SAH, after adjusting for other variables associated with a poor outcome, an increased ADC at the frontal centrum semiovale was associated with a poor prognosis (OR estimate 1.29, 95% CI 1.04-1.60, p = 0.020). Moreover, an increase of 0.1 in the FA value at the corpus callosum at 8-10 days after SAH corresponded to 66% lower odds of having a poor outcome (p = 0.002).

CONCLUSIONS

Decreased FA and increased ADC values in specific brain regions were independently associated with a poor clinical outcome after SAH. This preliminary exploratory study supports a potential role for DTI in predicting the outcome of SAH.

Role of Diffusion-weighted Imaging in Detecting Early Ischemic Brain Injury Following Aneurysmal Subarachnoid Hemorrhage

Background:

Aneurysmal SAH is the significant cause of morbidity and mortality in stroke patients. Early brain injury and delayed cerebral ischemia are the two main responsible pathophysiologic processes. Cerebral ischemia needs to be detected early so that early aggressive therapy could be started. Although Diffusion weighted imaging (DWI) has often been utilized for the measurement of acute ischemic strokes, its role in the detection of early cerebral ischemia due to aneurysmal subarachnoid hemorrhage has not been extensively investigated. This study is being carried out to describe the role of DWI in detecting early ischemic brain injury and outcome after aneurysmal SAH.

Aim:

Efficacy of DWI in detecting ischemic injury and predicting outcome after aneurysmal SAH.

Material and Methods:

In this prospective study 44 consecutive patients who had aneurysmal SAH; admitted within 7 days of their ictus were included. Hunt and Hess grade on admission and modified Fisher grade of SAH were noted. Plain CT brain and MR DWI was done on day before surgery. Diffusion restriction on DWI was correlated with postoperative neurological deficit, postoperative CT finding and outcome of the patient at 1 month follow-up.

Results:

DWI revealed restricted diffusion in 12 patients, out of which 1 patient was having infarction in preoperative CT scan, 6 patients were having postoperative deficit in the form of disorientation, hemiparesis and aphasia, and all patients were having infarction in postoperative CT scan. When DWI findings were compared on the basis of postoperative neurological deficit, postoperative CT finding and modified Rankin outcome score at 1month follow-up, results were statistically significant.

Conclusion:

DWI shows cerebral ischemia much earlier than CT scan in cases of aneurysmal SAH. It has significant correlation with postoperative neurological status and outcome of the patient.

Intra-arterial vasodilators for vasospasm following aneurysmal subarachnoid hemorrhage: a meta-analysis

Objective

The efficacy of intra-arterial vasodilators (IADs) for the treatment of vasospasm following aneurysmal subarachnoid hemorrhage (aSAH) remains debatable. The objective of this meta-analysis was to pool estimates of angiographic and neurological response, clinical outcome, and mortality following treatment of vasospasm with IADs.

Methods

We searched PubMed, Embase, Scopus, Clinicaltrials.gov, Cochrane database, and CINAHL in December 2015 and August 2016. Studies reporting angiographic and neurological response, clinical outcome, and mortality following IAD treatment of vasospasm in 10 or more adults with aSAH were included. All established IADs were allowed. Two authors independently selected studies and abstracted the data. Mean weighted probabilities (MWP) were calculated using random effects model.

Results

Inclusion criteria were met by 55 studies (n=1571). MWP for immediate angiographic response to IAD treatment was 89% (95% CI 83% to 94%), post-IAD neurological improvement 57% (95% CI 49% to 65%), good outcome 66% (95% CI 60% to 71%), and mortality was 9% (95% CI 7% to 12%). After adjusting for publication bias, MWP for mortality was 5% (95% CI 4% to 7%). When transcranial Doppler (TCD) was used along with clinical deterioration for patient selection, rates of neurological response (64%) and good outcome (72%) were better. IADs were not superior to controls (balloon angioplasty or medical management).

Conclusion

IAD treatment leads to a robust angiographic response and fair (but lower) rates of neurological response and good clinical outcome. Mortality was lower than the average reported in the literature. Rates of neurological response and good outcome were better when TCD was used for patient selection. Carefully designed studies are needed to compare IADs against medical management and balloon angioplasty.

Follow-up of Vasospasm by Transcranial Doppler Sonography (TCD) in Subarachnoid Hemorrhage (SAH)

Introduction:

Subarachnoid hemorrhage (SAH)represents hemorrhage in the space between arachnoidea and pia mater, due to aneurysm burst, spontaneously or as a consequence of trauma. It is condition that occurs more common in women than men, and its most common complications are rebleeding and vazospasm. As a result of vasospasm, develops ischemia in the portion of brain tissue that can cause additional neurological deficit. Transcranial Doppler Sonography (TCD) is a noninvasive ultrasound diagnostic method that allows monitoring of the state of intracerebral hemodynamics.

Goal:

The goal is to follow the occurrence of vasospasm after SAH, by the TCD method.

Material and methods:

We have analyzed 47 patients with SAH, by analyzing the presence of aneurysm, hypertension and smoking, and by the TCD method monitor the state of intracerebral hemodynamics during the first four days, then in the second and third week.

Results:

SAH was more common in women (61.7%) than men (38.3%), and in the age range from 22 to 64 years. Aneurism was demonstrated in 61.7% of patients, more common in women, with hypertension 68.1% also more common in women and smoking in 87.2% of patients, also more common in women. By TCD method are recorded milder, elevated blood flow velocities at a quarter of patients in the first measurement, during the second measurement at all and it had significantly greater value, and the third measurement also more increased in about a quarter of patients, so that there is a statistically significant difference in the first and second, second and third measurement for each vessel separately, but not between the first and third measurement.

Conclusion:

Predilection factors for SAH are aneurysms, hypertension and smoking. By using TCD method were recorded milder elevated blood flow velocity in the first days of SAH, with about a quarter of patients, significantly greater increase in blood flow velocity during the second week in all patients and also milder increase blood flow velocity in the third week of the start of SAH is a quarter of patients. TCD is the method of choice in the evaluation and management of vasospasm after SAH, which allows the prevention of delayed cerebral ischemia.

Hydrogen sulfide attenuates brain edema in early brain injury after subarachnoid hemorrhage in rats: Possible involvement of MMP-9 induced blood-brain barrier disruption and AQP4 expression

AIMS

This study investigated the effect of H2S on brain edema formation and the possible underlying mechanisms in early brain injury (EBI) of SAH using the endovascular perforation model.

METHODS

96 male rats were randomly divided into four groups: sham group, SAH+vehicle group, SAH+low-dosage NaHS group, and SAH+high-dosage NaHS group. Brain samples were used for brain water content and blood-brain barrier (BBB) leakage measurement, gelatin zymography, Western blot and immunohistochemistry.

RESULTS

H2S markedly attenuated brain edema formation and apoptotic cell death, improved neurological dysfunction in the acute stage of SAH. The possible mechanisms of H2S's effect on brain edema formation were through preventing BBB disruption and reducing APQ4 expression on astrocytes. In detail, H2S prevented BBB disruption by inhibiting MMP-9 induced tight junction proteins (TJPs) degradation. H2S down-regulated AQP4 expression on astrocytes by suppressing glial cell activation and pro-inflammatory cytokines secretion.

CONCLUSION

Taken together, this study showed that H2S attenuated brain edema formation partially by inhibiting the degradation of TJPs via reducing MMP-9 expression/activity and suppressing AQP4 expression via alleviating glia activation and pro-inflammatory cytokines secretion.

Cerebral Vasospasm: A Review

Cerebral vasospasm is a prolonged but reversible narrowing of cerebral arteries beginning days after subarachnoid hemorrhage. Progression to cerebral ischemia is tied mostly to vasospasm severity, and its pathogenesis lies in artery encasement by blood clot, although the complex interactions between hematoma and surrounding structures are not fully understood. The delayed onset of vasospasm provides a potential opportunity for its prevention. It is disappointing that recent randomized, controlled trials did not demonstrate that the endothelin antagonist clazosentan, the cholesterol-lowering agent simvastatin, and the vasodilator magnesium sulfate improve patient outcome. Minimizing ischemia by avoiding inadequate blood volume and pressure, administering the calcium antagonist nimodipine, and intervention with balloon angioplasty, when necessary, constitutes current best management. Over the past two decades, our ability to manage vasospasm has led to a significant decline in patient morbidity and mortality from vasospasm, yet it still remains an important determinant of outcome after aneurysm rupture.

Diffusion tensor imaging in hemorrhagic stroke

Diffusion tensor imaging (DTI) has evolved considerably over the last decade to now be knocking on the doors of wider clinical applications. There have been several efforts over the last decade to seek valuable and reliable application of DTI in different neurological disorders. The role of DTI in predicting outcomes in patients with brain tumors has been extensively studied and has become a fairly established clinical tool in this scenario. More recently DTI has been applied in mild traumatic brain injury to predict clinical outcomes based on DTI of the white matter tracts. The resolution of white matter fiber tractography based on DTI has improved over the years with increased magnet strength and better tractography post-processing. The role of DTI in hemorrhagic stroke has been studied preliminarily in the scientific literature. There is some evidence that DTI may be efficacious in predicting outcomes of motor function in animal models of intracranial hemorrhage. Only a handful of studies of DTI have been performed in subarachnoid hemorrhage or intraventricular hemorrhage scenarios. In this manuscript we will review the evolution of DTI, the existing evidence for its role in hemorrhagic stroke and discuss possible application of this non-invasive evaluation technique of human cerebral white matter tracts in the future.

Characterisation of DWI-MRI confirmed cerebral infarcts in patients with subarachnoid haemorrhage and their association with MMP-9 levels

OBJECTIVES

It has been suggested that metalloproteinase-9 (MMP-9) could predict the onset of cerebral vasospasm after subarachnoidal haemorrhage (SAH). The aim of this study was to analyse, in patients with SAH, the difference between patients with MRI ischaemic infarcts and patients without, and to investigate the role of metalloproteases as a prognostic factor for ischaemic infarcts.

METHODS

Sixty eight consecutive patients with SAH and diffusion-weighted magnetic resonance imaging (DWI-MRI) done 3 weeks after SAH. We define two groups, with and without DWI-MRI infarcts. Blood samples were taken at entry, 3 days and 1 week MMP-9 was determined through ELISA method.

RESULTS

Forty per cent were male, with a mean age of 54 ± 14 years. Twenty five patients, 36.8%, had DWI-MRI infarcts; in patients with MRI infarcts, SAH was more severe (Fisher = 4 52 vs 25.6%, P = 0.037), with more morbi-mortality (Rankin>3 48 vs 18.6%, P = 0.014), and more symptomatic vasospasm (28 vs 7%, P = 0.031). Levels of MMP-9 were higher than controls, but there were no significant differences between patients with and without infarcts (first determination no infarcts 39.40 ng/ml ± 35.40 vs infarcts 49.75 ng/ml ± 34.54, P > 0.005, 3 days no infarcts 72.10 ng/ml ± 70.95 vs infarcts 62.28 ± 33.84, P > 0.005, 1 week no infarcts 148.48 ng/ml ± 142.73 vs infarcts 91.5 ng/ml ± 1.20, P > 0.005).

CONCLUSION

Thirty eight percent in a well-studied series of patients with SAH have DWI-MRI infarcts; the infarcts were associated to SAH severity, SAH outcome and symptomatic vasospasm. Metalloproteinase-9 was higher in SAH patients than in controls, but it could not discriminate the infarct patients.

Bilateral substantia nigra and pyramidal tract changes following experimental intracerebral hemorrhage: an MR diffusion tensor imaging study

The amelioration of secondary neurological damage is among the most important therapeutic goals for patients with intracerebral hemorrhage (ICH). Secondary injury of the ipsilateral substantia nigra (SN) and pyramidal tract (PY) is common after cerebral stroke. Such injury has been characterized previously by anatomical or diffusion MRI, but not in a comprehensive manner, and the knowledge regarding the contralateral changes is relatively poor. This study examined longitudinally both contralateral and ipsilateral SN and PY changes following experimental ICH with diffusion tensor imaging (DTI) and histology. ICH was induced in 14 Sprague-Dawley rats by the infusion of collagenase into the right striatum. Four-shot, spin-echo, echo-planar DTI was performed at 7 T with a b value of 1000 s/mm(2) and 30 diffusion gradient directions at 3.5 h and days 1, 3, 7, 14, 42 and 120 after ICH. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ// ) and radial diffusivity (λ┴ ) were measured in SN and PY accordingly. Two to three rats were sacrificed at days 3, 7, 42 and 120 for histology. The contralateral SN showed an increase in λ// with perivascular enlargement during the first 3 days after ICH. The ipsilateral SN showed increases in FA, λ// , λ┴ and MD at day 1, dramatic decreases at day 3 with neuronal degeneration and neuropil vacuolation, and subsequent gradual normalization. The contralateral PY showed diffusivity decreases at day 1. The ipsilateral PY showed early decreases and then late increases in MD and λ┴, and continuously decreasing FA and λ// with progressive axonal loss and demyelination. In summary, DTI revealed early bilateral changes in SN and PY following ICH. The evolution of the ipsilateral parameters correlated with the histological findings. In the ipsilateral PY, λ// and λ┴ changes indicated evolving and complex pathological processes underlying the monotonic FA decrease. These results support the use of quantitative multiparametric DTI for the evaluation of SN and PY injuries in clinical and preclinical investigations of ICH.

Advanced imaging modalities in the detection of cerebral vasospasm

The pathophysiology of cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH) is complex and is not entirely understood. Mechanistic insights have been gained through advances in the capabilities of diagnostic imaging. Core techniques have focused on the assessment of vessel caliber, tissue metabolism, and/or regional perfusion parameters. Advances in imaging have provided clinicians with a multifaceted approach to assist in the detection of cerebral vasospasm and the diagnosis of delayed ischemic neurologic deficits (DIND). However, a single test or algorithm with broad efficacy remains elusive. This paper examines both anatomical and physiological imaging modalities applicable to post-SAH vasospasm and offers a historical background. We consider cerebral blood flow velocities measured by Transcranial Doppler Ultrasonography (TCD). Structural imaging techniques, including catheter-based Digital Subtraction Angiography (DSA), CT Angiography (CTA), and MR Angiography (MRA), are reviewed. We examine physiologic assessment by PET, HMPAO SPECT, ¹³³Xe Clearance, Xenon-Enhanced CT (Xe/CT), Perfusion CT (PCT), and Diffusion-Weighted/MR Perfusion Imaging. Comparative advantages and limitations are discussed.

The many faces of posterior reversible encephalopathy syndrome

The classic imaging findings of posterior reversible encephalopathy syndrome (PRES) are of bilateral parietal and occipital subcortical vasogenic oedema, and are well established in the literature. As experience with PRES grows, varied and atypical presentations are being increasingly described. This pictorial review illustrates the variable presentations of PRES, including cases with atypical imaging findings. We illustrate cases of PRES with varying distributions of vasogenic oedema as well as cases with atypical imaging findings, such as variations of haemorrhage and restricted diffusion. Atypical imaging findings should not dissuade the diagnosis of PRES in the appropriate clinical situation, and knowledge of the varied appearance and atypical findings of PRES allows the radiologist to make this diagnosis.

Detection of symptomatic vasospasm after subarachnoid haemorrhage: initial findings from single time-point and serial measurements with arterial spin labelling

OBJECTIVES

To detect symptomatic hemispheres during the postoperative course of subarachnoid haemorrhage (SAH) using arterial spin labelling (ASL).

METHODS

Eighteen patients with aneurysmal SAH were included; four exhibited symptomatic vasospasm postoperatively. All patients underwent ASL on days 9-10 (single time-point ASL). Nine patients underwent serial measurements of ASL (serial ASL) on days 1-2, 9-10 and 13-21, and seven patients also underwent imaging on days 4-7. CBF in the posterior part of the MCA territory was measured, and the ipsilateral/contralateral ratio of CBF was calculated. Differences between symptomatic hemispheres and others underwent ROC analysis.

RESULTS

Single time-point ASL revealed that CBF(day9-10) and CBF(i/c_day9-10) were significantly lower in symptomatic hemispheres than in asymptomatic hemispheres (P < 0.001). Serial ASL was significantly decreased on CBF(day4-7) compared with CBF(day1-2) and on CBF(day9-10) compared with CBF(day4-7), and significantly increased on CBF(day13-21) compared with CBF(day9-10). ROC analysis of single time-point ASL revealed that AUC for CBF(day9-10) was 0.95, significantly higher than CBF(i/c_day9-10) (P < 0.001). ROC analysis of serial ASL showed that AUC for CBF(day9-10) was 0.93 and significantly higher than CBF(day9-10/day1-2) and CBF(i/c_day9-10) (P < 0.001).

CONCLUSIONS

Single time-point ASL revealed significant CBF reduction in symptomatic hemispheres compared with asymptomatic hemispheres. Serial ASL showed time-dependent CBF changes after SAH.

KEY POINTS

• MR arterial spin labelling (ASL) can non-invasively assess cerebral blood flow (CBF) • ASL revealed significant CBF reduction in symptomatic hemispheres compared with asymptomatic hemispheres • Serial ASL measurements enable observation of time-dependent CBF changes after SAH • ASL is non- invasive and suitable for serial repeated examinations.

The effect of phosphodiesterase inhibitor tadalafil on vasospasm following subarachnoid hemorrhage in an experimental rabbit model

BACKGROUND

despite the years of study on it, cerebral vasospasm following subarachnoid hemorrhage is still an important cause of mortality and morbidity. The presented study was undertaken to show whether phosphodiesterase inhibitor tadalafil can attenuate the vasospasm process following subarachnoid bleeding.

METHOD

in this study, 20 male New Zealand White rabbits weighing 2,500-3,000 g were randomly assigned to four groups. Animals in group 1 were controls. In group 2, animals were given oral tadalafil at 12, 24 and 36 h and SAH was not induced. SAH induced animals in group 3 did not receive any medication. In group 4, animals received tadalafil at 12, 24 and 36 h after SAH induction. All animals were sacrificed via exsanguination at 48 h after induction of SAH. Brains and brainstems with overlying basilar arteries were removed and stored in fixative at +4°C overnight. Basilar arteries were sectioned from four separate zones, and four sections were obtained from each rabbit. Basilar artery luminal section areas were measured by using SPOT for Windows version 4.1. Statistical comparisons were performed using Kruskal Wallis and ANOVA tests.

FINDINGS

the SAH induced group which had been treated with tadalafil had significantly greater basilar artery luminal area than the untreated group (p < 0.05). There was no significant difference between control group and non-SAH induced group in terms of luminal areas.

CONCLUSION

tadalafil has a potentially preventive effect in treatment of cerebral vasospasm following subarachnoid bleeding.

The correlation between COMT gene polymorphism and early cerebral vasospasm after subarachnoid hemorrhage

BACKGROUND

The individual difference of cerebral vasospasm (CVS) degree after subarachnoid hemorrhage (SAH) is common in clinic observation. Numerous studies have found that early CVS after SAH is associated with derangements in catecholamine (CA) metabolism. Catechol-O-methyltransferase (COMT) is a key rate-limiting enzyme in the degradation of CA. In this study, we investigate the correlation between COMT gene polymorphism of patients and early CVS after SAH.

METHODS

One hundred and sixty-seven patients with spontaneous SAH in early stage were selected in this study. COMT genotyping was performed by means of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The degree of CVS was identified by TCD. Hunt-Hess classification was used to evaluate the severity of the patients' condition. The bleeding amount was evaluated by means of Fisher classification of head CT. χ2 test (SPSS13.0 software) and logistic regression were adopted to analyze the correlation of COMT gene polymorphism and other clinical data of patients with early CVS after SAH.

RESULTS

The distribution of each allele matched Hardy-Weinberg law and research samples were heredity equilibrium population. Early CVS incidence of patients with COMT-A allele was much higher than those with COMT-G allele (P<0.01). Early CVS incidence of patients with COMT A/A genotype was obviously higher than those with COMT G/G genotype (P<0.05). Univariate logistic regression demonstrated that COMT-A allele, A/A genotype and Grade 3-5 of Hunt-Hess classification were all associated with early CVS. After adjustment of general information, further multivariate logistic regression demonstrated that COMT-A allele, A/A genotype were risk factors of early CVS after SAH.

CONCLUSION

COMT-A allele, A/A genotype were risk factors of early CVS after SAH.

The role of transcranial Doppler ultrasonography in the diagnosis and management of vasospasm after aneurysmal subarachnoid hemorrhage

Transcranial Doppler ultrasonography (TCD) is a tool employed by the neurosurgeon and neurointensivist in the management of vasospasm in the intensive care unit after aneurysmal subarachnoid hemorrhage. A review of the current indications, monitoring parameters, indices, and relevance of modern TCD technology is provided, as well as algorithms for the use of TCD ultrasonography in the management of patients with subarachnoid hemorrhage. Other current uses of TCD ultrasonography are also discussed in the setting of neurocritical care.

Perfusion CT to quantify the cerebral vasospasm following subarachnoid hemorrhage

BACKGROUND AND PURPOSE

After subarachnoid hemorrhage (SAH), vasospasm is frequent and increases the risk of stroke and poor clinical outcome. The purpose of this study was to identify the best perfusion parameters in perfusion-CT (PCT) able to predict vasospasm diagnosed by angiography after SAH.

METHODS

Seventy-six patients with SAH were investigated by PCT and cerebral angiography. Using regions of interest (ROI) on parametric maps of mean transit time (MTT), time to peak (TTP), cerebral blood volume (CBV) and cerebral blood flow (CBF), PCT data were compared to an arteriographic score in two categories (severe vasospasm: ≥ 50% and non-severe vasospasm: <50%) for each artery. Best PCT predictors of the arteriographic score were tested using multiparametric logistic regression.

RESULTS

Among the 76 patients, PCT data were reliable in 65 patients. Twenty-seven patients had a severe vasospasm. Logistic regression showed that MTT was the best predictor of the arteriographic score. Using MTT, odds ratios having a vasospasm were superior to 3.1 and the occurrence of a vasospasm was accurately predicted in 78.5 to 100%, depending on the artery considered. However, no absolute value of the MTT could be identified to predict the occurrence of vasospasm. In fact, abnormal values of MTT ranged from 123 to 221% (m=146%) of the control values.

DISCUSSION AND CONCLUSIONS

PCT may accurately identify severe vasospasm and might be used as a convenient noninvasive imaging modality to monitor patients with SAH. When detected, severe vasospasm could be confirmed and managed using angiography and endovascular treatment, appropriately.

Diffusion weighted image negative transient ischaemic attack and reversible ischaemic neurological deficit. A report of 10 patients with complete recovery

Diffusion-weighted magnetic resonance imaging (DWI MRI)-negative transient ischaemic attack (TIA) in hyperacute stroke is a well-known clinical entity. However, no precise analysis of this phenomenon has been reported. We identified 10 patients with TIA or reversible ischaemic neurological deficits (RIND) with no focal hyperintensity on DWI MRI among 108 consecutive acute stroke patients who underwent DWI MRI. In these patients, we analysed the apparent diffusion coefficient (ADC) and determined the ipsilateral/contralateral ratio (IC ratio) to elucidate factors that may contribute to this phenomenon. Each patient also underwent simultaneous magnetic resonance angiography (MRA). The mean IC ratio in our study population was 0.976. Of the 10 patients, 7 had a proximal vascular stenosis on MRA. We discuss the pathophysiology underlying negative DWI MRI results in patients with TIA or RIND.

[Endovascular treatment of vasospasm following subarachnoid aneurysmal haemorrhage]

An endovascular treatment of vasospasm following a subarachnoid aneurysmal haemorrhage is to be implemented if the patient presents clinical or biological symptoms arguing for brain ischemia in conjunction with increased Doppler velocities despite well controlled systemic haemodynamic. Treatment might be either pharmacological or haemodynamic. Calcium and phosphodiesterase inhibitors can be administered. The former could also provide a neuroprotective effect as compared to the latter. In Europe, nimodipine is widely used whereas nicardipine and verapamil are the major molecules administered in North America where iv nimodipine is not FDA approved. Papaverine is less used nowadays because of its short duration of action and of the risk of aggravation of raised intracranial pressure. Balloon angioplasty has a long lasting effect but can be applied only to proximal spasm. Complications of its use are rare but life threatening. In some cases, both the pharmacological approach and the mechanical approach are used in combination.

Convenience of the computed tomography perfusion method for cerebral vasospasm detection after subarachnoid hemorrhage

BACKGROUND

Vasospasm is a frequent complication in the early clinical course after SAH. Although various methods have been used to measure cerebral perfusion including PET, SPECT, xenon CT, and TCD, these require the patients to remain still for a long period. In addition, TCD is operator dependent. The current study aimed to clarify the convenience of CTP for the assessment of cerebral vasospasm caused by SAH.

METHODS

Nineteen patients with SAH aged 44 to 85 years (mean, 64 years) were recruited with informed consent. All patients were treated with the prevailing therapy and underwent CTP on days 6 to 9, followed by DSA and 3D-CTA to detect cerebral vasospasm. In each patient, we measured the MTT, CBF, and CBV. The reliability of CTP data was verified by comparing the data from CTP and xenon CT between the controls, and the average was calculated. Six ROIs were located symmetrically in the frontal, temporal, and occipital lobes.

RESULTS

An MTT value more than 20% greater than the average indicated the progression of cerebral vasospasm, and patients with vasospasm-related infarcts exhibited an MTT more than 47% greater than the mean value (odds ratio, 50). Patients with delayed cerebral infarcts had a significantly lower mean CBF and CBV and higher MTT than patients who did not develop CI.

CONCLUSION

Significant correlations between MTT and CBF values and neurovascular findings were obtained. Computed tomography perfusion can be performed in a short time and on a regular basis, and it therefore has the potential to identify cerebral vasospasm because of SAH.

Effects of balloon angioplasty on perfusion- and diffusion-weighted magnetic resonance imaging results and outcome in patients with cerebral vasospasm

OBJECT

The aim of this study was to analyze the effects and outcome of transluminal balloon angioplasty (TBA) on brain tissue perfusion by using combined perfusion- and diffusion-weighted (PW/DW) magnetic resonance (MR) imaging in patients with cerebral vasospasm after subarachnoid hemorrhage.

METHODS

Ten consecutive patients with cerebral vasospasm treated using TBA were included in this prospective study. Hemodynamically relevant vasospasm was diagnosed using a standardized PW/DW MR imaging protocol. Digital subtraction angiography was used to confirm vasospasm, and TBA was performed to dilate vasospastic arteries. The PW/DW imaging protocol was repeated after TBA. The evaluation of the passage of contrast medium after standardized application using the bolus tracking method allowed for the calculation of the time to peak (TTP) before and after TBA. Tissue at risk was defined based on perfusion delays in individual vessel territories compared with those in reference territories. In cases with proximal focal vasospasm, TBA could dilate spastic arteries. Follow-up PW/DW MR imaging showed the disappearance of, or a decrease in, the mismatch. A TBA-induced reduction in the perfusion delay of 6.2 +/- 1 seconds (mean +/- standard error of the mean) to 1.5 +/- 0.45 seconds resulted in the complete prevention of infarction; a reduction in the delay of 6.2 +/- 2.7 to 4.1 +/- 1.9 seconds resulted in the preservation of those brain tissue parts having only small infarcts in the vessel territories. Without TBA, however, the perfusion delay remained or even increased (11.1 +/- 3.7 seconds), and the complete infarction of a territory occurred.

CONCLUSIONS

Angioplasty of vasospastic arteries leads to hemodynamic effects that can be quantified using PW/DW MR imaging. In cases of a severe PW/DW imaging mismatch successful TBA improved tissue perfusion and prevented cerebral infarction. The clinical significance of PW/DW MR imaging and the concept of tissue at risk is shown by cerebral infarction in vessels not accessible by TBA.

Clinical review: Prevention and therapy of vasospasm in subarachnoid hemorrhage

Vasospasm is one of the leading causes of morbidity and mortality following aneurysmal subarachnoid hemorrhage (SAH). Radiographic vasospasm usually develops between 5 and 15 days after the initial hemorrhage, and is associated with clinically apparent delayed ischemic neurological deficits (DID) in one-third of patients. The pathophysiology of this reversible vasculopathy is not fully understood but appears to involve structural changes and biochemical alterations at the levels of the vascular endothelium and smooth muscle cells. Blood in the subarachnoid space is believed to trigger these changes. In addition, cerebral perfusion may be concurrently impaired by hypovolemia and impaired cerebral autoregulatory function. The combined effects of these processes can lead to reduction in cerebral blood flow so severe as to cause ischemia leading to infarction. Diagnosis is made by some combination of clinical, cerebral angiographic, and transcranial doppler ultrasonographic factors. Nimodipine, a calcium channel antagonist, is so far the only available therapy with proven benefit for reducing the impact of DID. Aggressive therapy combining hemodynamic augmentation, transluminal balloon angioplasty, and intra-arterial infusion of vasodilator drugs is, to varying degrees, usually implemented. A panoply of drugs, with different mechanisms of action, has been studied in SAH related vasospasm. Currently, the most promising are magnesium sulfate, 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors, nitric oxide donors and endothelin-1 antagonists. This paper reviews established and emerging therapies for vasospasm.

Subarachnoid hemorrhage in the subacute stage: elevated apparent diffusion coefficient in normal-appearing brain tissue after treatment

PURPOSE

To prospectively evaluate whether subarachnoid hemorrhage (SAH) is associated with a change in the apparent diffusion coefficient (ADC) in normal-appearing brain parenchyma.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for all patient and volunteer studies. One hundred patients (48 men, 52 women; mean age, 52 years +/- 12 [standard deviation]) with aneurysmal SAH underwent conventional and diffusion-weighted magnetic resonance (MR) imaging at a mean of 9 days +/- 3 after SAH to evaluate possible lesions caused by SAH, treatment of SAH, and vasospasm. Aneurysms were treated surgically (n = 70) or endovascularly (n = 30) before MR imaging. Diffusion-weighted MR imaging was performed at 1-year follow-up in 30 patients (10 men, 20 women; mean age, 51 years +/- 11). Thirty healthy age-matched volunteers (11 men, 19 women; mean age, 54 years +/- 16) underwent MR imaging with an identical protocol. ADC values were measured bilaterally in the gray and white matter (parietal, frontal, temporal, occipital lobes; cerebellum; caudate nucleus; lentiform nucleus; thalamus; and pons) that appeared normal on T2-weighted and diffusion-weighted MR images. Linear mixed model was used for comparison of ADC values of supratentorial gray matter and white matter; general linear regression analysis was used for comparison of ADC values of cerebellum and pons.

RESULTS

In patients with SAH, the ADC values in normal-appearing white matter, with a single exception in the frontal lobe (P = .091), were significantly higher than they were in healthy volunteers (P </= .011). The differences disappeared by 1 year, except in parietal white matter (P = .045). The ADC values of cortical gray matter did not significantly differ between patients and volunteers (P >/= .121).

CONCLUSION

SAH and its treatment may cause global mild vasogenic edema in white matter and deep gray matter that is undetectable on T2-weighted and diffusion-weighted MR images but is detectable by measuring the ADC value in the subacute stage of SAH.

[Imaging of acute stroke]

Acute stroke patients represent an important diagnostic and therapeutic challenge. Patients with brain damage in the ischemic, but not yet infarcted, phase have the greatest potential for recovery. Here we review the most commonly employed diagnostic tools that are currently used before stroke therapy. While computed tomography is pertinent to differentiate ischemic from hemorrhagic stroke, this technique cannot be used as an etiological screening too. The ischemic origin of symptoms can be confirmed with magnetic resonance imaging which also contributes to for therapeutic decision making, prognosis assessment and etiological screening.

Time Course in the Development of Cerebral Vasospasm after Experimental Subarachnoid Hemorrhage: Clinical and Neuroradiological Assessment of the Rat Double Hemorrhage Model

OBJECTIVE

The "double hemorrhage" model in the rat is frequently used to simulate delayed cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) in humans. However, an exact neurological and angiographic characterization of the CVS is not available for this model so far and is provided in the present investigation. Additionally, perfusion weighted imaging (PWI) at 3 tesla magnetic resonance (MR) tomography was implemented to assess the reduction in cerebral blood flow (CBF).

METHODS

In a prospective, randomized setting CVS was induced by injection of 0.2 ml autologous blood twice in the cisterna magna of 45 male Sprague-Dawley rats. The surviving animals were examined on Days 2, 3, 5, 7 and 9 and compared to a sham operated control group (n = 9). Rats were neurologically graded between 0 and 3, followed by MRI and selective digital subtraction angiography (DSA). The relative CBF was set in relation to the perfusion of the masseter muscle.

RESULTS

The neurological state was significantly worsened on Day 2 (Grade 3), 3 (Grade 3), and 5 (Grade 2) (medians). The relative CBF/muscle BF ratio (2.5 +/- 0.8 (SAH) versus 9.2 +/- 1.3 (sham) (mean +/- SEM) and the basilar artery (BA) diameter (0.15 +/- 0.02 mm (SAH) versus 0.32 +/- 0.01 mm (sham) were significantly decreased on Day 5. Correlation between relative CBF/muscle BF ratio and BA diameter was 0.70.

CONCLUSION

A valid and reproducible CVS simulation was proven by neurological score, DSA, and PWI on Day 5. Furthermore, our data demonstrate the practicability and validity of MR PWI for the monitoring of CVS in a rat SAH model.

Controversies in the management of aneurysmal subarachnoid hemorrhage*

BACKGROUND

The care of patients with aneurysmal subarachnoid hemorrhage has evolved significantly with the advent of new diagnostic and therapeutic modalities. Although it is believed that these advances have contributed to improved outcomes, considerable uncertainty persists regarding key areas of management.

OBJECTIVE

To review selected controversies in the management of aneurysmal subarachnoid hemorrhage, with a special emphasis on endovascular vs. surgical techniques for securing aneurysms, the diagnosis and therapy of cerebral vasospasm, neuroprotection, antithrombotic and anticonvulsant agents, cerebral salt wasting, and myocardial dysfunction, and to suggest venues for further clinical investigation.

DATA SOURCE

Search of MEDLINE and Cochrane databases and manual review of article bibliographies.

DATA SYNTHESIS AND CONCLUSIONS

Many aspects of care in patients with aneurysmal subarachnoid hemorrhage remain highly controversial and warrant further resolution with hypothesis-driven clinical or translational research. It is anticipated that the rigorous evaluation and implementation of such data will provide a basis for improvements in short- and long-term outcomes.