Dynamic perfusion computed tomography in the diagnosis of cerebral vasospasm

OBJECTIVE: The aim of the study was to correlate absolute cerebral blood flow (CBF) and mean transient time (MTT) measured by dynamic perfusion computed tomographic (PCT) scanning with the clinical course, vasospasm severity, and perfusion abnormality in patients with cerebral vasospasm after aneurysmal subarachnoid hemorrhage. METHODS: Forty-six patients with vasospasm after aneurysmal subarachnoid hemorrhage had 63 PCT images obtained during the course of vasospasm. All patients had transcranial Doppler measurements, 28 had an angiography study, and 38 had ^99mTc single-photon emission computed tomographic imaging performed in conjunction with the PCT scan. RESULTS: The average minimal regional CBF (rCBF) and maximal regional MTT in patients with delayed ischemic deficit were significantly different in comparison with patients without delayed ischemic deficit (22.6 ± 11.2 cm³/100 g/min versus 45.2 ± 21.3 cm³/100 g/min, P < 0.001; 7.3 ± 2.5 s versus 3.3 ± 1.7 s, P < 0.05). The average minimal rCBF and maximal regional MTT in middle cerebral vascular territories in which severe middle cerebral artery vasospasm was measured by transcranial Doppler were significantly different in comparison with middle cerebral vascular territories in which no vasospasm was measured by transcranial Doppler (29.3 ± 1.7 cm³/100 g/min versus 54.1 ± 25.4 cm ³/100 g/min, P < 0.01; 4.5 ± 2.4 s versus 2.8 ± 1.1 P < 0.001). The average minimal rCBF and maximal rMTT in vascular territories with estimated severe hypoperfusion on single-photon emission computed tomographic imaging were significantly different in comparison with values in vascular territories with unimpaired perfusion as estimated by single-photon emission computed tomographic imaging (18.9 ± 6.9 cm³/100 g/min versus 54.2 ± 23.4 cm³/100 g/min, P < 0.001, 0.001; 8.1 ± 1.9 s versus 2.5 ± 0.39 s, P < 0.001). CONCLUSION: The present study suggests that, in general, quantitative measurements of rCBF and regional MTT by PCT show high concordance rates with the clinical course, vasospasm severity, and hemodynamic impairments in patients with cerebral vasospasm aneurysmal subarachnoid hemorrhage.