Association between a quantitative CT scan measure of brain edema and outcome after cardiac arrest

Abstract

Background Cerebral edema is one physical change associated with brain injury and decreased survival after cardiac arrest. Edema appears on computed tomography (CT) scan of the brain as decreased x-ray attenuation by gray matter. This study tested whether the gray matter attenuation to white matter attenuation ratio (GWR) was associated with survival and functional recovery. Methods Subjects were patients hospitalized after cardiac arrest at a single institution between 1/1/2005 and 7/30/2010. Subjects were included if they had non-traumatic cardiac arrest and a non-contrast CT scan within 24 hours after cardiac arrest. Attenuation (Hounsfield Units) was measured in gray matter (caudate nucleus, putamen, thalamus, and cortex) and in white matter (internal capsule, corpus callosum and centrum semiovale). The GWR was calculated for basal ganglia and cerebrum. Outcomes included survival and functional status at hospital discharge. Results For 680 patients, 258 CT scans were available, but 18 were excluded because of hemorrhage (10), intravenous contrast (3) or technical artifact (5), leaving 240 CT scans for analysis. Lower GWR values were associated with lower initial Glasgow Coma Scale motor score. Overall survival was 36%, but decreased with decreasing GWR. The average of basal ganglia and cerebrum GWR provided the best discrimination. Only 2/58 subjects with average GWR<1.20 survived and both were treated with hypothermia. The association of GWR with functional outcome was completely explained by mortality when GWR<1.20. Conclusions Subjects with severe cerebral edema, defined by GWR<1.20, have very low survival with conventional care, including hypothermia. GWR estimates pre-treatment likelihood of survival after cardiac arrest.

Combination of Initial Neurologic Examination, Quantitative Brain Imaging and Electroencephalography to Predict Outcome After Cardiac Arrest

“…While it is our protocol for comatose patients to CT imaging and cEEG monitoring, a large proportion were excluded due to CT image quality, timing of CT, and rapid awakening. 17 This rate of exclusion is similar to prior work. 17 These exclusions may be one reason for the low sensitivity seen for predicting poor outcome and the lower good neurologic outcome rate found in the PCAC II cohort.…”

“…17 This rate of exclusion is similar to prior work. 17 These exclusions may be one reason for the low sensitivity seen for predicting poor outcome and the lower good neurologic outcome rate found in the PCAC II cohort. Another limitation is the lack of standard definition of malignant cEEG.…”

“…[20][21][22] Prior work has examined prognostic tests such as neurologic examination, SSEP, biomarkers, EEG, brain CT, and MRI in isolation. [9][10][11][12][13][14][15][16][17][18] Recent work has tested predictive value of multiple modalities, but the ideal combination is not known. [28][29][30][31][32] Importantly, not all tests are necessary for all patients and some facilities may not offer all of these modalities.…”

“…GWR was calculated by an investigator blinded to clinical information as previously reported. 17 Briefly, Hounsfield Units (HU) were recorded at the basal ganglia level; caudate nucleus, putamen, genu of corpus callosum, and posterior limb of internal capsule and also recorded at the cerebrum level; the medial cortex and medial white matter at the level of the centrum semiovale and high convexity area. Average gray matter to white matter ratio (aGWR) was calculated as the mean of the Basal Ganglia GWR and Cerebrum GWR.…”

“…[9][10][11][12][13][14][15][16][17][18][19] The combination of multiple modalities is recommended because no single test short of physical examination meeting brain death criteria can predict neurologic outcome correctly. [20][21][22] We previously reported that combining the initial neurologic examination with continuous EEG (cEEG) was superior to any individual test for predicting outcome after CA.…”