The Value of Repetitive CT Perfusion for Detection of Cerebral Vasospasm-related Hypoperfusion after Aneurysmal Subarachnoid Hemorrhage

Aim: Cerebral infarction in the context of vasospasm after aneurysmal subarachnoid hemorrhage remains a severe complication. Therefore, early diagnosis of misery perfusion is crucial. It has already been shown that hypoperfused brain areas can be detected with CT perfusion (CTP) in patients with acute clinical deterioration. Aim of this study was to evaluate, if a single CTP at time of neurological deterioration is sufficient or if serial CTP examinations are needed to reliably detect the areas at risk. In addition, the perfusion parameters with the highest specifity and sensitivity were determined.

Methods: A retrospective analysis of all CTP examinations in selected patients with SAH was performed. Patients with CTP within 24 hours after aneurysm treatment (baseline CTP) and follow up CTP in the vasospasm phase were included. Two groups were divided – patients with and without acute neurological deterioration. The following CTP parameters were analyzed for predefined brain regions: Mean Transit Time (MTT), Time To Peak (TTP), Time To Drain (TTD), Cerebral Blood Flow (CBF) and Cerebral Blood Volume (CBV). CTP parameter thresholds for (i) changes compared with the baseline CTP, (ii) absolute values at the time point of deterioration and (iii) between-hemisphere differences at time of deterioration were determined. Sensitivities and specifities were calculated. Statistical analysis was performed using receiver operator characteristics (ROC) curves and multivariate analysis.

Results: Fifty-six patients were finally included – 33 with and 23 without neurological deterioration. CTP parameters MTT, TTP and TTD showed the highest sensitivities and specifities for the symptomatic territory in the acute CTP. Threshold values were 4.15 second for MTT, 10.16 second for TTP and 4.7 second for TTD. Similar results were seen for inter-hemispheric comparisons with highest sensitivities and specifities for MTT, TTP and TTD. Comparison of CTP parameters at time of clinical deterioration with a baseline examination yielded no additional diagnostic gain. Regarding all categories, TTD provided the highest sensitivity and specifity.

Conclusion: CTP parameters MTT, TTP and TTD offer the highest sensitivities and specifities in the detection of critically perfused brain regions. Based on our data, we conclude that baseline CTP does not provide additional diagnostic information and, therefore, one CTP in acute neurological deterioration is sufficient.