Acute-stage diffusion-weighted magnetic resonance imaging for predicting outcome of poor-grade aneurysmal subarachnoid hemorrhage

Abstract

We investigated the role of acute-stage diffusion-weighted images (DWIs) for predicting outcome of poor-grade subarachnoid hemorrhage (SAH). This study included 38 patients with poor-grade SAH who underwent DWI within 24 h after onset. DWI findings were divided into three groups on the basis of lesion area: none (N), spotty (S, <or=10 mm(2)), or areal (A, >10 mm(2)). We evaluated the correlation between preoperative DWI findings and clinical outcome, and the characteristics of DWI abnormalities. DWI abnormalities were revealed in 81.6% of cases (group S 34.2%; group A 47.3%). All patients in groups N and S and 73.3% of patients in group A were treated radically. For those patients without rerupture, favorable outcomes were achieved in 100% of group N, 53.8% of group S, and 0% of group A. Abnormal lesions on initial DWI, which resulted in permanent lesions, showed a mean apparent diffusion coefficient ratio to the control value of 0.71, which was significantly lower than 0.95 observed in reversible lesions (P<0.01). We recommend radical treatment for even poor-grade SAH as long as the preoperative DWI shows no or only spotty lesions. DWI may provide an objective means to estimate the outcome of poor-grade SAH.

Figure 1

Radiological findings on admission. (A–D) A representative patient in group A. (E–H) A representative patient in group S. (A and E) Computed tomography (CT) scans showing subarachnoid hemorrhage but no obvious lesions in the cerebral parenchyma. (B and F) Diffusion-weighted images showing abnormal high-intensity areal lesions in the right temporal lobe and the bilateral paramedian frontal lobes (arrows) in B and an abnormal high-intensity spotty lesion in the right paramedian frontal lobe (arrow) in F. Arrowheads indicate subarachnoid clots, referring to CT scan. (C and G) T2-weighted images showing no abnormal lesion in the brain parenchyma. (D and H) Apparent diffusion coefficient (ADC) maps of B and F, respectively, showing heterogeneous ADC reduction in the high-intensity lesions on DWI (arrows) in D, and decreased ADC in the spotty lesion (arrow) in H.

Figure 2

Illustrative cases in ROI analysis for ADC values. (A–C) A patient in group A (Case A-2, see also Figure 3A and Table 4). (D–F) A patient in group S (Case S-10, see also Figure 3B and Table 4). (A and D) Diffusion-weighted images (DWI) on admission. (B and E) Apparent diffusion coefficient (ADC) maps of A and D, respectively. ROIs (white empty boxes, 5 mm² each) were placed to cover the entire abnormal high-intensity lesions on the initial DWI except for hematoma. To obtain the control ADC value of the patient, several white empty circles were placed on the apparently normal white matter in the frontal, temporal, parietal, and occipital lobes. (C and F) T2-weighted images in the chronic stage corresponding to A and D, respectively. Most of the abnormal lesions on the initial DWI corresponded to high-intensity lesions on T2-weighted image, but some DWI lesions resulted in apparently normal (iso-intense) finding. Asterisk indicates intracerebral hematoma cavities.

Figure 3

Graphs showing the mean apparent diffusion coefficient (ADC) ratios on admission in relation to resulting findings on the chronic T2-weighed images (A) group A (n=11) and (B) group S (n=11). The ADC ratio was calculated for each regions of interest (ROI) as the mean ADC value of the ROI divided by the control ADC value of the patient obtained from apparently normal white matter regions. Black squares indicate mean ADC ratios of the ROIs, which result in high-intensity regions on the chronic T2-weighted images (HIR, high-intensity region). Number of ROIs for each black square was between 5 to 282 depending on patients. White squares indicate mean ADC ratios of the ROIs, which resulted in the iso-intensity regions on the chronic T2-weighted images (IIR, iso-intensity region). Number of ROIs for each white square was between 5 and 230 depending on patients. Note that some patients had regions corresponding either HIR or IIR only. (C) Comparison of mean ADC ratios between regions that eventually fell into high- (black squares) or iso-intensity (white squares) regions on chronic T2-weighted images. All ADC ratios in A and B were plotted and averaged. The mean ADC ratio for regions that appeared as high–intensity regions on the chronic T2-weighted image (HIR, 0.713±0.022) is lower than that of regions appeared as iso-intensity in the chronic image (IIR, 0.947±0.011) (P<0.01). Error bars indicate standard deviations. Details of ADC value and ratio in each patient have been provided in Table 4.