Feasibility and validity of monitoring subarachnoid hemorrhage by a noninvasive MRI imaging perfusion technique: Pulsed Arterial Spin Labeling (PASL)

Brain damage evaluation via arterial spin labeling perfusion imaging for patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

Subarachnoid hemorrhage (SAH) is a neurological condition with an annual incidence of 6-22 per 100,000. Despite many advances in diagnosis, the rates of mortality and morbidity in patients remain high. The most important reason for this is complications accompanied by perfusion changes. The aim of our study was to show the perfusion changes with arterial spin labelling (ASL) after SAH.

MATERIALS AND METHODS

In this prospective study, 23 patients diagnosed with aneurysmal SAH were evaluated by ASL perfusion imaging between days 1-3 and 8-10. The mean signal intensities (SI) of both hemispheres from the anterior cerebral artery, middle cerebral artery, and basal ganglia were measured manually according to the region of interest. The relationship between the SI values calculated for both cerebral hemispheres, complications, and grading scales of the side with more intense (ipsilateral) and less (contralateral) bleeding were evaluated.

RESULTS

There was a significant difference in the ipsilateral/contralateral SI ratio (SIIps/ConBGin) (p = 0.015) among all ASL values, including the basal ganglia between days 0-3 and 8-10. There was a significant negative correlation between ASL parameters and rating scale scores. Additionally, when the SIIps/ConBGinDay0-3 ratio cut-off value was ≤ 0.72, the sensitivity and specificity were 57.1% and 100.0%, respectively, in predicting non-fatal complications, and the sensitivity and specificity in predicting all complications, including death, were 55.6% and 100.0%, respectively.

CONCLUSION

Global or regional perfusion decrease can be shown using ASL, with or without the development of vasospasm, without the need for exogenous contrast agent use.

Arterial spin labeling in neonatal magnetic resonance imaging - first experience and new observations

Purpose

Arterial spin labeling (ASL) is a noninvasive non-contrast technique of perfusion imaging that uses endogenous water from the blood as the perfusion tracer, with very scant data on its use in neonates. The authors present the added value of ASL in the examined babies in their own material and discuss it in the light of the existing literature.

Material and methods

During the first 10 months after the purchase of a new magnetic resonance imaging (MRI) scanner, 123 neonates were examined using it in an MR-compatible incubator, 117 of them had brain MRI, and in 104 ASL was incorporated in the routine protocol, which resulted in prolongation of the study time by approximately 4 minutes. 3D ASL sequence uses Pulsed Continuous Arterial Spin Labeling (PCASL; aka pseudo continuous) technique.

Results

The quality of the cerebral blood flow (CBF) maps was good in all cases but 2 because all the babies were sedated. Apart from the knowledge about normal perfusion patterns in the preterm and term neonatal brains, the use of ASL sequence provided important additional information in 11 cases (10.8%): increased CBF correlating with electroencephalographic seizure localization in otherwise normal MRI (n = 1), increased CBF in the cortex without clinical information about seizures and with posthaemorrhagic changes (n = 1), increased CBF in the brain stem and decreased in the upper parts of the brain (n = 2), probably reflecting the homeostatic mechanism which allows preferential perfusion of the vital structures of the brain stem, hypoperfusion (n = 1) or hypoperfusion with peripheral hyperperfusion (n = 1) in the area of stroke, hypoperfusion of the posterior areas of the brain in the presence of subarachnoid or epidural haemorrhage (n = 3), significantly increased CBF in the presumed nidus of arteriovenous malformation causing haemorrhage (n = 1), and lack of perfusion in the supratentorial compartment in a case of suspected brain death (n = 1).

Conclusions

Our short experience but relatively large volume of material encourages the use of ASL in routine neonatal MRI as a useful and non-time-consuming tool providing additional important clinical information in a significant percentage of cases.

How to diagnose delayed cerebral ischaemia and symptomatic vasospasm and prevent cerebral infarction in patients with subarachnoid haemorrhage

PURPOSE OF REVIEW

Delayed cerebral ischaemia (DCI) complicates the clinical course of patients with subarachnoid haemorrhage (SAH) in 20--30% and substantially worsens outcome. In this review, we describe a multimodal diagnostic approach based on underlying mechanisms of DCI and provide treatment options with a special focus on the most recently published literature.

RECENT FINDINGS

Symptomatic vasospasm refers to clinical deterioration in the presence of vasospasm whereas DCI constitutes multiple causes. Pathophysiologic mechanisms underlying DCI range beyond large vessel vasospasm from neuroinflammation, to microthromboembolism, impaired cerebral autoregulation, cortical spreading depolarizations and many others. The current definition of DCI can be challenged by these mechanisms. We propose a pragmatic approach using a combination of clinical examination, cerebral ultrasonography, neuroimaging modalities and multimodal neuromonitoring to trigger therapeutic interventions in the presence of DCI. In addition to prophylactic nimodipine and management principles to improve oxygen delivery and decrease the brain metabolic demand, other specific interventions include permissive hypertension, intra-arterial application of calcium channel blockers and in selected patients angioplasty.

SUMMARY

The complex pathophysiology underlying DCI urges for a multimodal diagnostic approach triggering targeted interventions. Novel treatment concepts still have to be proven in large trials.

Temporal evolution of cerebral computed tomography perfusion after acute subarachnoid hemorrhage: a prospective cohort study

Background

Changes in cerebral perfusion occur in subarachnoid hemorrhage that possibly relate to clinical presentation and complications.

Purpose

To evaluate changes in computed tomography perfusion (CTP) parameters between the acute and subacute stage of subarachnoid hemorrhage. To analyze correlation of these parameters to SAH severity and delayed cerebral ischemia.

Material and Methods

Cerebral CT perfusion was assessed in a prospective cohort of 44 patients with acute subarachnoid hemorrhage at < 72 h (CTP1) and 8–10 days (CTP2), using the mean of all regions of interest. Regions of interest were located at arterial territories of the anterior, middle, and posterior cerebral artery and basal ganglia and midpons cerebellar hemispheres. Linear regression models (univariable and multivariable) were used to explore the association between changes in perfusion parameters (absolute and relative differences) and relevant clinical data.

Results

Worse perfusion parameters on the first 72 h were correlated with poor admission clinical scores: cerebral blood flow positively correlated with Glasgow Coma Scale (rS = 0.398, P = 0.008), and negatively correlated with Hunt & Hess scale (rS = −0.348, P = 0.020) and World Federation of Neurosurgeons scale (rS = −0.384, P = 0.010). Cerebral blood volume positively correlated with Glasgow Coma Scale (rS = 0.332, P = 0.028) and negatively correlated with World Federation of Neurosurgeons scale (rS = −0.353, P = 0.019). Mean transit time negatively correlated with Glasgow Coma Scale (rS = −0.415, P = 0.005) and positively correlated with Hunt & Hess scale (rS = 0.471, P = 0.001) and World Federation of Neurosurgeons scale (rS = 0.386, P = 0.010) scores. There were no differences between absolute CTP1/CTP2 parameters. Patients with delayed cerebral ischemia had ΔTmax mean decrease of 2.08 s (95% CI = −4.04–−0.12; P = 0.038).

Conclusion

Early cerebral hypoperfusion correlates with poor clinical grade at admission in subarachnoid hemorrhage and with higher amounts of blood. Tmax was decreased at 8–10 days, in patients with delayed cerebral ischemia, which may favor the application value of Tmax in signaling delayed cerebral ischemia.

Magnetic Resonance Imaging in Aneurysmal Subarachnoid Hemorrhage: Current Evidence and Future Directions

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with an unacceptably high mortality and chronic disability in survivors, underscoring a need to validate new approaches for treatment and prognosis. The use of advanced imaging, magnetic resonance imaging (MRI) in particular, could help address this gap given its versatile capacity to quantitatively evaluate and map changes in brain anatomy, physiology and functional activation. Yet there is uncertainty about the real value of brain MRI in the clinical setting of aSAH.

METHODS

In this review, we discuss current and emerging MRI research in aSAH. PubMed was searched from inception to June 2017, and additional studies were then chosen on the basis of relevance to the topics covered in this review.

RESULTS

Available studies suggest that brain MRI is a feasible, safe, and valuable testing modality. MRI detects brain abnormalities associated with neurologic examination, outcomes, and aneurysm treatment and thus has the potential to increase knowledge of aSAH pathophysiology as well as to guide management and outcome prediction. Newer pulse sequences have the potential to reveal structural and physiological changes that could also improve management of aSAH.

CONCLUSION

Research is needed to confirm the value of MRI-based biomarkers in clinical practice and as endpoints in clinical trials, with the goal of improving outcome for patients with aSAH.

Arterial spin-labeling perfusion imaging of childhood encephalitis: correlation with seizure and clinical outcome

PURPOSE

In childhood encephalitis, perfusion abnormalities have been infrequently reported to associate with clinical status. We investigated whether perfusion abnormalities correlated with seizure and clinical outcome in encephalitis.

METHODS

We retrospectively analyzed the MR studies of 77 pediatric patients with encephalitis. Pseudo-continuous arterial spin-labeling (ASL) imaging was performed on a 3-T scanner. The patients were divided into five groups according to ASL perfusion imaging pattern: normal perfusion (NP), focal hypoperfusion (Lf), extreme global hypoperfusion (LE), focal hyperperfusion (Hf), and extreme global hyperperfusion (HE). Clinical outcome at 3 weeks was dichotomized to unfavorable or favorable outcome according to the Glasgow outcome scale. Multivariate logistic regression was conducted to predict unfavorable outcome and presence of seizure separately, based on explanatory variables including age, sex, and ASL pattern.

RESULTS

Twenty-seven (35%) patients were designated as in group Hf, five (7%) in group Lf, 11 (14%) in group LE, none in group HE, and 34 (44%) in group NP. Multivariate logistic regression analysis showed that ASL pattern was significantly associated with unfavorable outcome (P = 0.005) and with presence of seizure (P = 0.005). For ASL pattern, group LE was 17.31 times as likely to have an unfavorable outcome as group NP (odds ratio confidence interval [CI] 3.084, 97.105; P = 0.001). Group Hf was 6.383 times as likely to have seizure as group NP (CI 1.765, 23.083; P = 0.005).

CONCLUSIONS

In childhood encephalitis, patients with extreme global hypoperfusion had poor neurological outcome and those with focal hypoperfusion were more likely to have seizure.

Complication rate of intraarterial treatment of severe cerebral vasospasm after subarachnoid hemorrhage with nimodipine and percutaneous transluminal balloon angioplasty: Worth the risk?

BACKGROUND AND PURPOSE

Delayed cerebral ischemia (DCI) is a complication of aneurysmal subarachnoid hemorrhage (SAH). Arterial cerebral vasospasm (CVS) is discussed as the main pathomechanism for DCI. Due to positive effects of per os nimodipine, intraarterial nimodipine application is used in patients with DCI. Further, percutaneous transluminal balloon angioplasty (PTA) is applied in focal high-grade spasm of intracranial arteries. However, clinical benefits of those techniques are unconfirmed in randomized trials so far, and complications might occur. We analyzed the occurrence of new infarcts in patients with severe CVS treated intra-arterially to assess benefits and risks of those techniques in a large single-center collective.

MATERIALS AND METHODS

All imaging and clinical data of 88 patients with CVS after SAH and 188 procedures of intraarterial nimodipine infusion and additional PTA in selected cases (18 patients, 20 PTA procedures) treated at our institution were reviewed. In the event of new infarcts after endovascular treatment of CVS, infarct patterns were analyzed to determine the most probable etiology.

RESULTS

Fifty-three percent of patients developed new cerebral infarction after intraarterial nimodipine and additional PTA in selected cases. Hereunder 47% were caused by persisting CVS. In 6% of patients, 3% of procedures respectively, new infarcts occurred due to complications of the intraarterial treatment including thromboembolism and arterial dissection. Of those, 3% of patients, 2% of procedures respectively, were assigned to thrombembolic complications of digital substraction angiography for intraarterial nimodipine. 17% of all patients treated with PTA (3/18=17%) showed infarction as a complication of PTA (15% of all PTA procedures). In 1% of patients, etiology of new infarction remained unclear.

CONCLUSION

Ischemic complications occur in about 6% of patients treated intraarterially for CVS, 3% of procedures respectively. Further, to date a benefit for patients treated with this therapy could not be proven. Therefore, intraarterial treatment of CVS should be performed only in carefully selected cases.

Default Mode Network Perfusion in Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The etiology of altered consciousness in patients with high-grade aneurysmal subarachnoid hemorrhage (SAH) is not thoroughly understood. We hypothesized that decreased cerebral blood flow (CBF) in brain regions critical to consciousness may contribute.

METHODS

We retrospectively evaluated arterial-spin labeled (ASL) perfusion magnetic resonance imaging (MRI) measurements of CBF in 12 patients with aneurysmal SAH admitted to our neurocritical care unit. CBF values were analyzed within gray matter nodes of the default mode network (DMN), whose functional integrity has been shown to be necessary for consciousness. DMN nodes studied were the bilateral medial prefrontal cortices, thalami, and posterior cingulate cortices. Correlations between nodal CBF and admission Glasgow Coma Scale (GCS) score, admission Hunt and Hess (HH) class, and GCS score at the time of MRI (MRI GCS) were tested.

RESULTS

Spearman's correlation coefficients were not significant when comparing admission GCS, admission HH, and MRI GCS versus nodal CBF (p > 0.05). However, inter-rater reliability for nodal CBF was high (r = 0.71, p = 0.01).

CONCLUSIONS

In this retrospective pilot study, we did not identify significant correlations between CBF and admission GCS, admission HH class, or MRI GCS for any DMN node. Potential explanations for these findings include small sample size, ASL data acquisition at variable times after SAH onset, and CBF analysis in DMN nodes that may not reflect the functional integrity of the entire network. High inter-rater reliability suggests ASL measurements of CBF within DMN nodes are reproducible. Larger prospective studies are needed to elucidate whether decreased cerebral perfusion contributes to altered consciousness in SAH.

Advanced MRI Measures of Cerebral Perfusion and Their Clinical Applications

Cerebral blood flow measurement by magnetic resonance imaging perfusion (MRP) techniques is broadly applied to patients with acute ischemic stroke, vasospasm following aneurysmal subarachnoid hemorrhage, chronic arterial steno-occlusive disease, cervical atherosclerotic disease, and primary brain neoplasms. MRP may be performed using an exogenous tracer, most commonly gadolinium-based intravenous contrast, or an endogenous tracer, such as arterial spin labeling (ASL) or intravoxel incoherent motion (IVIM). Here, we review the technical basis of commonly performed MRP techniques, the interpretation of MRP imaging maps, and how MRP provides valuable clinical information in the triage of patients with cerebral disease.

CT perfusion diagnoses delayed cerebral ischemia in the early stage of the time-window after aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

It has been acknowledged that delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (SAH) can be diagnosed by CT perfusion (CTP) in the DCI time-window. We evaluated the diagnostic accuracy of CTP for DCI during the early stage of the time-window.

MATERIALS AND METHODS

We prospectively enrolled patients with aneurysmal SAH. DCI was defined as both new cerebral infarction and clinical deterioration after SAH. CTP was performed by using a standardized protocol with predefined regions of interest in 4 to 6 days after SAH. We quantitatively evaluated the diagnostic accuracy of eight CTP parameters (4 for absolute parameters and 4 for relative parameters). The receiver operator characteristic (ROC) curves of all parameters were generated and the optimal threshold values were derived for the calculation of sensitivities and specificities.

RESULTS

Fifty-three patients were enrolled and 20 patients were diagnosed with DCI. In the analysis of absolute CTP parameters, CBF and MTT had areas under the curve (AUC) >0.75 and the optimal threshold value was 40.4mL/100g/min and 3.78seconds, respectively. Through the evaluation of relative CTP parameters, all 4 parameters had AUC >0.75 and the optimal threshold value was 0.9 for CBV ratio, 0.85 for CBF ratio, 0.32seconds for MTT difference and 1.31seconds for TTP difference.

CONCLUSIONS

Besides two absolute CTP parameters (CBV and TTP), all six CTP parameters can be used as good diagnostic tests for DCI in the early stage of the time-window.

Cerebrovascular reactivity in the caudate nucleus, lentiform nucleus and thalamus in patients with carotid artery disease

BACKGROUND AND PURPOSE

To assess the effect of unilateral large vessel disease upon the cerebral hemodynamic autoregulatory status in the basal ganglia of patients with steno-occlusive internal carotid artery (ICA) disease.

MATERIALS AND METHODS

Twenty-five healthy volunteers and 38 patients with a unilateral symptomatic steno-occlusive ICA lesion and were investigated; 20 with a stenosis >50% and 18 with an occlusion. Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were assessed with pseudo-continuous arterial spin labeling (ASL) magnetic resonance (MR) imaging before and after administration of acetazolamide.

RESULTS

When compared to controls, the CVR in patients with ICA stenosis was significantly lower in the middle cerebral artery (MCA) territory (P<0.05), and in the caudate (P<0.05) and lentiform nucleus (P<0.05) of the hemisphere ipsilateral to the stenosis. The CVR in the caudate nucleus contralateral to the stenosis was significantly lower (P<0.05) as well. In patients with ICA occlusion, the CVR in the hemisphere ipsilateral to the occlusion as well as in the contralateral hemisphere was significantly lower in the MCA territory (P<0.05), the caudate (P<0.05) and lentiform nucleus (P<0.05), and in the thalamus (P<0.05).

CONCLUSION

Perfusion ASL MR imaging shows impaired cerebral hemodynamic autoregulation of the basal ganglia in patients with steno-occlusive ICA disease both in the hemisphere ipsilateral as well as in the hemisphere contralateral to the stenosis or occlusion.