Vasospasm after subarachnoid hemorrhage: utility of perfusion CT and CT angiography on diagnosis and management

Abstract

Purpose: To evaluate the utility of perfusion CT (PCT) combined with CT angiography (CTA) for the diagnosis and management of vasospasm, by using conventional digital subtraction angiography (DSA) as the gold standard.

Methods: We retrospectively identified 27 patients with acute subarachnoid hemorrhage who had undergone CTA/PCT, DSA, and transcranial Doppler (TCD) ultrasonography within a time interval of 12 hours of one another. The patients' charts were reviewed for treatment of vasospasm. CTA, PCT, TCD, and DSA examinations were independently reviewed and quantified for vasospasm. PCT thresholds, CTA findings, noncontrast CT (NCT) hypodensities, and TCD thresholds were evaluated for accuracy, sensitivity, and specificity, as well as for negative (NPV) and positive predictive values (PPV) in the prediction of angiographic vasospasm and endovascular treatment, considering DSA as the gold standard.

Results: Thirty-five CTA/PCT, TCD, and DSA examinations were performed on these 27 patients. A total of 123 arterial territories in 11 patients demonstrated angiographic vasospasm. Six patients underwent endovascular therapy. CTA qualitative assessment and PCT-derived mean transit time (MTT) with a threshold at 6.4 seconds represented the most accurate (93%) combination for the diagnosis of vasospasm, whereas MTT considered alone represented the most sensitive parameter (NPV, 98.7%). A cortical regional cerebral blood flow value </=39.3 (mL x 100 g(-1)x min(-1)) represented the most accurate (94.8%) indicator for endovascular therapy. PCT had significantly higher PPV (89.9%) than TCD (62.9%).

Conclusions: A CT survey combining CTA and PCT represents an accurate screening test in patients with suspected vasospasm. However promising, the value of PCT for selecting the best management strategy in such patients will need to be further investigated.

Figures

Fig 1.

Patient transferred at day 8 to our neurovascular ICU from an outside institution after coiling of a ruptured ACom aneurysm. NCT obtained at the admission of the patient in our neurovascular ICU demonstrated extensive residual SAH and suspicious loss of gray-white matter contrast in the left superior frontal gyrus (white arrows). The tip of a right ventricular drain catheter is also visible. On PCT, significantly abnormal brain perfusion in the distribution of the anterior and inferior branches of the left (and also, to a lesser extent, right) ACA (arrowheads) and of the right posterior MCA branches is seen primarily on MTT and TTP maps. The rCBF was also slightly decreased in the same territories, whereas rCBV was mainly preserved (it is lowered only in the left superior frontal gyrus [star]). CTA confirmed the suspicion of moderate vasospasm of both A2 and A3 segments of the ACA (arrows), ultimately verified by gold-standard DSA. No abnormality of the right posterior MCA branches was identified. The artifacts created by the coils on the CTA images, obscuring the A1 segments bilaterally and interfering with their evaluation, are noteworthy. Endovascular therapy (intra-arterial verapamil) was performed in the ACA territories during the DSA.

Fig 2.

Patient transferred to our neurovascular ICU from an outside institution at day 4 after rupture of an ACom aneurysm (arrow). Admission TCD ultrasonography demonstrated increased absolute FV of 135 cm/s in ACAs. A CTA and PCT survey were obtained to rule out vasospasm; the PCT was completely normal and the CTA demonstrated the ACom aneurysm (arrow), but no vasospasm. DSA was performed determine the configuration of the aneurysm and to determine the best therapeutic strategy (endovascular coiling vs neurosurgical clipping). It confirmed the absence of vasospasm. TCD false-positive results were most likely related to the triple H (hypertensive, hypervolemic, hemodilutional) therapy undergone by the patient at the time of the TCD examination.