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

Abstract

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 40.4 mL/100 g/min and 3.78 seconds, 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, 0.32 seconds for MTT difference and 1.31 seconds 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.

Introduction

Delayed cerebral ischemia (DCI) is a devastating complication following aneurysmal subarachnoid hemorrhage (aSAH). It typically occurs in the time-window (4–14 days after aneurysm rupture) and is associated with significant morbidity and mortality in patients who survive the first days [1], [2]. In clinical practice, DCI can first present as clinical deterioration including new neurologic deficits, a gradual decrease in consciousness or both and then can reverse or develop into cerebral infarction which increases the risk of poor outcome [3], [4]. Therefore, if DCI can be found in the early stage of clinical deterioration, the treatment can be performed actively and the prognosis for DCI patients may be improved. However, the diagnosis of DCI is often difficult and clinical deterioration can also be caused by other etiologies than DCI, such as rebleeding, postoperative complications, infection, metabolic disturbances or hydrocephalus. Previously, transcranial Doppler sonography (TCD), digital subtraction angiography or CT angiography was frequently used to indicate the emergence of DCI by diagnosing cerebral large artery spasm, but the vasospasm is only moderately associated with DCI [5], [6], [7]. Better diagnostic tests, which can identify regions of potential brain ischemia instead of vasospasm to diagnose DCI, are therefore needed.

Computed tomography perfusion (CTP), a noninvasive and less time consuming screening method, can diagnose DCI by detecting cerebral regions of hypoperfusion, and several studies support the use of CTP parameters to quantitatively evaluate cerebral hemodynamics [7], [8], [9], [10], [11]. Furthermore, it has been confirmed that CTP on admission cannot be used to predict DCI, but CTP can diagnose DCI within the time-window [3]. Therefore, we believe that it is a great help to improve the prognosis of SAH patients, if DCI can be identified in the early stage of its time-window. In this study, we evaluated the diagnostic accuracy of each CTP parameter for DCI during the early stage of the time-window (4–6 days after SAH).