A Volumetric Method for Quantification of Cerebral Vasospasm in a Murine Model of Subarachnoid Hemorrhage

Automated Grading of Cerebral Vasospasm to Standardize Computed Tomography Angiography Examinations After Subarachnoid Hemorrhage

Background: Computed tomography angiography (CTA) is frequently used with computed tomography perfusion imaging (CTP) to evaluate whether endovascular vasospasm treatment is indicated for subarachnoid hemorrhage patients with delayed cerebral ischemia. However, objective parameters for CTA evaluation are lacking. In this study, we used an automated, investigator-independent, digital method to detect vasospasm, and we evaluated whether the method could predict the need for subsequent endovascular vasospasm treatment. Methods: We retrospectively reviewed the charts and analyzed imaging data for 40 consecutive patients with subarachnoid hemorrhages. The cerebrovascular trees were digitally reconstructed from CTA data, and vessel volume and the length of the arteries of the circle of Willis and their peripheral branches were determined. Receiver operating characteristic curve analysis based on a comparison with digital subtraction angiographies was used to determine volumetric thresholds that indicated severe vasospasm for each vessel segment. Results: The automated threshold-based volumetric evaluation of CTA data was able to detect severe vasospasm with high sensitivity and negative predictive value for predicting cerebral hypoperfusion on CTP, although the specificity and positive predictive value were low. Combining the automated detection of vasospasm on CTA and cerebral hypoperfusion on CTP was superior to CTP or CTA alone in predicting endovascular vasospasm treatment within 24 h after the examination. Conclusions: This digital volumetric analysis of the cerebrovascular tree allowed the objective, investigator-independent detection and quantification of vasospasms. This method could be used to standardize diagnostics and the selection of subarachnoid hemorrhage patients with delayed cerebral ischemia for endovascular diagnostics and possible interventions.

Volumetric analysis of intracranial vessels: a novel tool for evaluation of cerebral vasospasm

PURPOSE

Together with other diagnostic modalities, computed tomography angiography (CTA) is commonly used to indicate endovascular vasospasm treatment after subarachnoid hemorrhage (SAH), despite the fact that objective, user-independent parameters for evaluation of CTA are lacking. This exploratory study was designed to investigate whether quantification of vasospasm by automated volumetric analysis of the middle cerebral artery M1 segment from CTA data could be used as an objective parameter to indicate endovascular vasospasm treatment.

METHODS

We retrospectively identified SAH patients who underwent transcranial Doppler sonography (TCD), CTA, and CT perfusion (CTP), with or without subsequent endovascular treatment. We determined vessel volume/vessel length of the M1 segments from CTA data and used receiver operating characteristic curve analysis to determine the optimal threshold of vessel volume to predict vasospasm requiring endovascular treatment. In addition, blinded investigators independently analyzed TCD, CTA, and CTP data.

RESULTS

Of 45 CTA examinations with corresponding CTP and TCD examinations (24 SAH patients), nine indicated the need for endovascular vasospasm treatment during examination. In our patients, vessel volume < 5.8 µL/mm was moderately sensitive but fairly specific to detect vasospasm requiring endovascular treatment (sensitivity, 67%; specificity, 78%; negative predictive value (NPV), 89%; positive predictive value (PPV), 46%). For CTA, CTP, and TCD, we found NPVs of 96%, 92%, and 89%, PPVs of 40%, 35%, and 35%, sensitivities of 89%, 78%, and 67%, and specificities of 67%, 64%, and 69%, respectively.

CONCLUSION

Vessel volumes could provide a new objective parameter for the interpretation of CTA data and could thereby improve multimodal assessment of vasospasm in SAH patients.

Large Vessel Vasospasm Is Not Associated with Cerebral Cortical Hypoperfusion in a Murine Model of Subarachnoid Hemorrhage

Clinical studies on subarachnoid hemorrhage (SAH) have shown discrepancies between large vessel vasospasm, cerebral perfusion, and clinical outcome. We set out to analyze the contribution of large vessel vasospasm to impaired cerebral perfusion and neurological impairment in a murine model of SAH. SAH was induced in C57BL/6 mice by endovascular filament perforation. Vasospasm was analyzed with microcomputed tomography, cortical perfusion by laser SPECKLE contrast imaging, and functional impairment with a quantitative neuroscore. SAH animals developed large vessel vasospasm, as shown by significantly lower vessel volumes of a 2.5-mm segment of the left middle cerebral artery (MCA) (SAH 5.6 ± 0.6 nL, sham 8.3 ± 0.5 nL, p < 0.01). Induction of SAH significantly reduced cerebral perfusion of the corresponding left MCA territory compared to values before SAH, which only recovered partly (SAH vs. sham, 15 min 35.7 ± 3.1 vs. 101.4 ± 10.2%, p < 0.01; 3 h, 85.0 ± 8.6 vs. 121.9 ± 13.4, p < 0.05; 24 h, 75.3 ± 4.6 vs. 110.6 ± 11.4%, p < 0.01; 72 h, 81.8 ± 4.8 vs. 108.5 ± 14.5%, n.s.). MCA vessel volume did not correlate significantly with MCA perfusion after 72 h (r = 0.34, p = 0.25). Perfusion correlated moderately with neuroscore (24 h: r = - 0.58, p < 0.05; 72 h: r = - 0.44, p = 0.14). There was no significant correlation between vessel volume and neuroscore after 72 h (r = - 0.21, p = 0.50). In the murine SAH model, cerebral hypoperfusion occurs independently of large vessel vasospasm. Neurological outcome is associated with cortical hypoperfusion rather than large vessel vasospasm.