Diffusion-weighted magnetic resonance imaging for predicting the clinical outcome of comatose survivors after cardiac arrest: a cohort study

Abstract

Introduction: The aim of this study was to examine whether the patterns of diffusion-weighted imaging (DWI) abnormalities and quantitative regional apparent diffusion coefficient (ADC) values can predict the clinical outcome of comatose patients following cardiac arrest.

Methods: Thirty-nine patients resuscitated from out-of-hospital cardiac arrest were prospectively investigated. Within five days of resuscitation, axial DWIs were obtained and ADC maps were generated using two 1.5-T magnetic resonance scanners. The neurological outcomes of the patients were assessed using the Glasgow Outcome Scale (GOS) score at three months after the cardiac arrest. The brain injuries were categorised into four patterns: normal, isolated cortical injury, isolated deep grey nuclei injury, and mixed injuries (cortex and deep grey nuclei). Twenty-three subjects with normal DWIs served as controls. The ADC and percent ADC values (the ADC percentage as compared to the control data from the corresponding region) were obtained in various regions of the brains. We analysed the differences between the favourable (GOS score 4 to 5) and unfavourable (GOS score 1 to 3) groups with regard to clinical data, the DWI abnormalities, and the ADC and percent ADC values.

Results: The restricted diffusion abnormalities in the cerebral cortex, caudate nucleus, putamen and thalamus were significantly different between the favourable (n = 13) and unfavourable (n = 26) outcome groups. The cortical pattern of injury was seen in one patient (3%), the deep grey nuclei pattern in three patients (8%), the cortex and deep grey nuclei pattern in 21 patients (54%), and normal DWI findings in 14 patients (36%). The cortex and deep grey nuclei pattern was significantly associated with the unfavourable outcome (20 patients with unfavourable vs. 1 patient with favourable outcomes, P < 0.001). In the 22 patients with quantitative ADC analyses, severely reduced ADCs were noted in the unfavourable outcome group. The optimal cutoffs for the mean ADC and the percent ADC values determined by receiver operating characteristic (ROC) curve analysis in the cortex, caudate nucleus, putamen, and thalamus predicted the unfavourable outcome with sensitivities of 67 to 93% and a specificity of 100%.

Conclusions: The patterns of brain injury in early diffusion-weighted imaging (DWI) (less than or equal to five days after resuscitation) and the quantitative measurement of regional ADC may be useful for predicting the clinical outcome of comatose patients after cardiac arrest.

Figure 1

This figure shows the axial apparent diffusion coefficient maps indicating the 15 regions of interest. These regions were selected for quantitative measurement of the apparent diffusion coefficient values. (1) precentral cortex, (2) postcentral cortex, (3) frontal cortex, (4) frontal white matter, (5) parietal cortex, (6) parietal white matter, (7) caudate nucleus, (8) putamen, (9) thalamus, (10) temporal cortex, (11) temporal white matter, (12) occipital cortex, (13) occipital white matter, (14) pons, and (15) cerebellum.

Figure 2

Apparent diffusion coefficient map with colour shades (A), diffusion-weighted imaging (B) and T2-weighted image (C) from one representative patient at seven hours after cardiac arrest. Regions of low apparent diffusion coefficient (ADC) showed a blue colour; in contrast, regions of high ADC showed a white colour. The colour shades on the ADC maps identified the pixel showing the minimum ADC value in each brain region. A 3D cursor (arrow) was used to select the predefined spot (right thalamus) simultaneously in the three different sequences, and it can be easy to mark the area with the minimum ADC on the ADC maps based on the T2-weighted image (T2WI) and diffusion-weighted imaging (DWI). The circular region-of-interest (ROI) cursors were positioned on the areas with the minimum ADC in each brain region. Severely restricted diffusion within the ROIs was shown in the caudate nucleus (0.238 × 10^-3mm²/sec), putamen (0.299 × 10^-3mm²/sec), thalamus (0.290 × 10^-3mm²/sec), and occipital grey matter (0.184 × 10^-3mm²/sec) but not in the occipital white matter (0.712 × 10^-3mm²/sec).

Figure 3

Boxplot showing the distribution of the percent apparent diffusion coefficient values for the different brain regions of the control (white bars), favourable (striped bars), and unfavourable (grey bars) groups. The percent apparent diffusion coefficient (ADC) values were calculated using the mean normal control value of each brain region.