Arterial spin labeling shows cortical collateral flow in the endovascular treatment of vasospasm after post-traumatic subarachnoid hemorrhage

Outcomes following therapeutic intervention of post-traumatic vasospasm: A systematic review and meta-analysis

BACKGROUND

Vasospasm occurrence following traumatic brain injury may impact neurologic and functional recovery of patients, yet treatment of post-traumatic vasospasm (PTV) has not been well documented. This systematic review and meta-analysis aims to assess the current evidence regarding favorable outcome as measured by Glasgow Outcome Scale (GOS) scores following treatment of PTV.

METHODS

A systematic review of PubMed, Ovid MEDLINE, and Ovid EMBASE was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included manuscripts were methodically scrutinized for quality; occurrence of PTV; rate of favorable outcome following each treatment modality; and follow-up duration. Treatments evaluated were calcium channel blockers (CCBs), endovascular intervention, and dopamine-induced hypertension. Outcomes were compared via the random-effects analysis.

RESULTS

Fourteen studies with 1885 PTV patients were quantitatively analyzed: 982 patients who received tailored therapeutic intervention and 903 patients who did not receive tailored therapy. For patients undergoing treatment, the rate of favorable outcome was 57.3 % (500/872 patients; 95 % CI 54.1 - 60.6 %) following administration of CCBs, 94.1 % (16/17 patients; 95 % CI 82.9 - 100.0 %) following endovascular intervention, and 54.8 % (51/93 patients; 95 % CI 44.7 - 65.0 %) following dopamine-induced hypertension. Of note, the endovascular group had the highest rate of favorable outcome but was also the smallest sample size (n = 17). Patients who received tailored therapeutic intervention for PTV had a higher rate of favorable outcome than patients who did not receive tailored therapy: 57.7 % (567/982 patients; 95 % CI 54.1 - 60.8 %) versus 52.0 % (470/903 patients; 95 % CI 48.8 - 55.3 %), respectively.

CONCLUSIONS

The available data suggests that tailored therapeutic intervention of PTV results in a favorable outcome. While endovascular intervention of PTV had the highest rate of favorable outcome, both CCB administration and dopamine-induced hypertension had similar lower rates of favorable outcome.

Arterial Spin Labeling Perfusion of the Brain: Emerging Clinical Applications

Arterial spin labeling (ASL) is a magnetic resonance (MR) imaging technique used to assess cerebral blood flow noninvasively by magnetically labeling inflowing blood. In this article, the main labeling techniques, notably pulsed and pseudocontinuous ASL, as well as emerging clinical applications will be reviewed. In dementia, the pattern of hypoperfusion on ASL images closely matches the established patterns of hypometabolism on fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) images due to the close coupling of perfusion and metabolism in the brain. This suggests that ASL might be considered as an alternative for FDG, reserving PET to be used for the molecular disease-specific amyloid and tau tracers. In stroke, ASL can be used to assess perfusion alterations both in the acute and the chronic phase. In arteriovenous malformations and dural arteriovenous fistulas, ASL is very sensitive to detect even small degrees of shunting. In epilepsy, ASL can be used to assess the epileptogenic focus, both in peri- and interictal period. In neoplasms, ASL is of particular interest in cases in which gadolinium-based perfusion is contraindicated (eg, allergy, renal impairment) and holds promise in differentiating tumor progression from benign causes of enhancement. Finally, various neurologic and psychiatric diseases including mild traumatic brain injury or posttraumatic stress disorder display alterations on ASL images in the absence of visualized structural changes. In the final part, current limitations and future developments of ASL techniques to improve clinical applicability, such as multiple inversion time ASL sequences to assess alterations of transit time, reproducibility and quantification of cerebral blood flow, and to measure cerebrovascular reserve, will be reviewed. ^© RSNA, 2016 Online supplemental material is available for this article.

Ultrasound and dynamic functional imaging in vascular cognitive impairment and Alzheimer's disease

BACKGROUND

The vascular contributions to neurodegeneration and neuroinflammation may be assessed by magnetic resonance imaging (MRI) and ultrasonography (US). This review summarises the methodology for these widely available, safe and relatively low cost tools and analyses recent work highlighting their potential utility as biomarkers for differentiating subtypes of cognitive impairment and dementia, tracking disease progression and evaluating response to treatment in various neurocognitive disorders.

METHODS

At the 9th International Congress on Vascular Dementia (Ljubljana, Slovenia, October 2015) a writing group of experts was formed to review the evidence on the utility of US and arterial spin labelling (ASL) as neurophysiological markers of normal ageing, vascular cognitive impairment (VCI) and Alzheimer's disease (AD). Original articles, systematic literature reviews, guidelines and expert opinions published until September 2016 were critically analysed to summarise existing evidence, indicate gaps in current knowledge and, when appropriate, suggest standards of use for the most widely used US and ASL applications.

RESULTS

Cerebral hypoperfusion has been linked to cognitive decline either as a risk or an aggravating factor. Hypoperfusion as a consequence of microangiopathy, macroangiopathy or cardiac dysfunction can promote or accelerate neurodegeneration, blood-brain barrier disruption and neuroinflammation. US can evaluate the cerebrovascular tree for pathological structure and functional changes contributing to cerebral hypoperfusion. Microvascular pathology and hypoperfusion at the level of capillaries and small arterioles can also be assessed by ASL, an MRI signal. Despite increasing evidence supporting the utility of these methods in detection of microvascular pathology, cerebral hypoperfusion, neurovascular unit dysfunction and, most importantly, disease progression, incomplete standardisation and missing validated cut-off values limit their use in daily routine.

CONCLUSIONS

US and ASL are promising tools with excellent temporal resolution, which will have a significant impact on our understanding of the vascular contributions to VCI and AD and may also be relevant for assessing future prevention and therapeutic strategies for these conditions. Our work provides recommendations regarding the use of non-invasive imaging techniques to investigate the functional consequences of vascular burden in dementia.

Computed tomography angiography source images closely reflect the integrity of collateral circulation

BACKGROUND

We studied the interplay between collateral circulation, the location of the thrombus and infarct extent based on evaluation of CT angiography source images (CTA-SI) in predicting the clinical outcome of patients treated with intravenous thrombolytic therapy (<3h) in a retrospective cohort.

METHODS

Anterior circulation occlusion was detected with CTA in 105 patients. The site of the occlusion was recorded, collaterals were assessed with Collateral Score (CS) and Alberta Stroke Program Early CT Score (ASPECTS) was evaluated from CTA-SI, and entered into logistic regression analysis to predict favorable clinical outcome (three-month modified Rankin Scale 0-2).

RESULTS

CTA-SI ASPECTS was highly correlated with CS (Spearman's rho=0.63, P=0.01). Not a single patient with good collaterals (CS 2-4) had a poor CTA-SI scan (ASPECTS 0-7). The mean CTA-SI ASPECTS score became progressively lower when the status of the collateral circulation deteriorated (ANOVA P<0.001). In univariate analysis a good CTA-SI scan at the admission predicted favorable three-month outcome (P<0.001). In a multivariate model containing CTA-SI ASPECTS, CS and the site of the occlusion along with significant clinical parameters, CTA-SI ASPECTS was rendered non-significant (P=0.43) in the presence of CS.

CONCLUSIONS

CTA-SI and CS convey overlapping information. CTA-SI is not a significant predictor of the clinical outcome three months after intravenous thrombolysis when the other CTA-based parameters, CS and the clot location, are considered simultaneously. CTA-SI may have a role in the assessment of the extent of irreversible ischemic changes at admission if contrast injection and image acquisition protocols are designed suitably.

Imaging-based selection in acute ischemic stroke trials - a quest for imaging sweet spots

Ischemic stroke is a very heterogeneous disease that limits the efficacy of acute stroke treatments. Future trials will require advanced imaging to select patients for specific treatments. The most well-established imaging tools are the use of CT to exclude hemorrhage and diffusion-weighted MRI to demonstrate ischemia. While perfusion imaging is one option for patient selection, it has unresolved issues, including standardization and validation, that limit its value. As an alternative to mismatch when addressing stroke, one needs to know the size of the initial irreversible lesion (core), the presence and site/extent of occlusion (clot), and presence of leptomeningeal back filling and Willisian filling (collaterals). These can be summarized as the "3C" approach of core, clot, and collateral interpretation, which together can represent an imaging sweet spot, particularly for time-efficient endovascular treatment trial design.

[Grading of adults primitive glial neoplasms using arterial spin-labeled perfusion MR imaging]

PURPOSE

We investigated the relationship between tumor blood-flow measurement based on perfusion-imaging by arterial spin-labeling (ASL) and histopathologic findings in adults' primitive glial tumours.

PATIENTS AND METHODS

Thus, 40 primitive brain tumors (8 low-grade and 32 high-grade gliomas according to the Sainte-Anne classification) were imaged using pulsed (n=19) or continuous (n=21) ASL. Relative cerebral blood flow (rCBF=tumoral blood flow/normal cerebral blood flow) between high- and low-grade gliomas were compared.

RESULTS

Using pulsed ASL, differences in mean rCBF were observed in high- and low-grade gliomas although no significant (respectively 1.95 and 1.5). Using continuous ASL, mean rCBF were significantly higher for high-grade than for low-grade gliomas (P<0.05). High-grade gliomas could be discriminated using a CBF threshold of 1.18, with a sensitivity of 88%, specificity of 60%, predictive positive value of 88%, and predictive negative value of 60%.

CONCLUSION

ASL-based perfusion provides a quantitative, non-invasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating CBF. ASL is a suitable method for gliomas initial staging and could be useful to identify intermediate tumoral evolution.