Prognostication of ICU Patients by Providers with and without Neurocritical Care Training.

BACKGROUND: Predictions of functional outcome in neurocritical care (NCC) patients impact care decisions. This study compared the predictive values (PVs) of good and poor functional outcome among health care providers with and without NCC training. METHODS: Consecutive patients who were intubated for  ≥ 72 h with primary neurological illness or neurological complications were prospectively enrolled and followed for 6-month functional outcome. Medical intensive care unit (MICU) attendings, NCC attendings, residents (RES), and nurses (RN) predicted 6-month functional outcome on the modified Rankin scale (mRS). The primary objective was to compare these four groups' PVs of a good (mRS score 0-3) and a poor (mRS score 4-6) outcome prediction. RESULTS: Two hundred eighty-nine patients were enrolled. One hundred seventy-six had mRS scores predicted by a provider from each group and were included in the primary outcome analysis. At 6 months, 54 (31%) patients had good outcome and 122 (69%) had poor outcome. Compared with other providers, NCC attendings expected better outcomes (p < 0.001). Consequently, the PV of a poor outcome prediction by NCC attendings was higher (96% [95% confidence interval [CI] 89-99%]) than that by MICU attendings (88% [95% CI 80-93%]), RES (82% [95% CI 74-88%]), and RN (85% [95% CI 77-91%]) (p = 0.047, 0.002, and 0.012, respectively). When patients who had withdrawal of life-sustaining therapy (n = 67) were excluded, NCC attendings remained better at predicting poor outcome (NCC 90% [95% CI 75-97%] vs. MICU 73% [95% CI 59-84%], p = 0.064). The PV of a good outcome prediction was similar among groups (MICU 65% [95% CI 52-76%], NCC 63% [95% CI 51-73%], RES 71% [95% CI 55-84%], and RN 64% [95% CI 50-76%]). CONCLUSIONS: Neurointensivists expected better outcomes than other providers and were better at predicting poor functional outcomes. The PV of a good outcome prediction was modest among all providers.

Prognostic value of diffusion-weighted MRI for post-cardiac arrest coma.

OBJECTIVE: To validate quantitative diffusion-weighted imaging (DWI) MRI thresholds that correlate with poor outcome in comatose cardiac arrest survivors, we conducted a clinician-blinded study and prospectively obtained MRIs from comatose patients after cardiac arrest. METHODS: Consecutive comatose post-cardiac arrest adult patients were prospectively enrolled. MRIs obtained within 7 days after arrest were evaluated. The clinical team was blinded to the DWI MRI results and followed a prescribed prognostication algorithm. Apparent diffusion coefficient (ADC) values and thresholds differentiating good and poor outcome were analyzed. Poor outcome was defined as a Glasgow Outcome Scale score of ≤2 at 6 months after arrest. RESULTS: Ninety-seven patients were included, and 75 patients (77%) had MRIs. In 51 patients with MRI completed by postarrest day 7, the prespecified threshold of >10% of brain tissue with an ADC <650 ×10-6 mm2/s was highly predictive for poor outcome with a sensitivity of 0.63 (95% confidence interval [CI] 0.42-0.80), a specificity of 0.96 (95% CI 0.77-0.998), and a positive predictive value (PPV) of 0.94 (95% CI 0.71-0.997). The mean whole-brain ADC was higher among patients with good outcomes. Receiver operating characteristic curve analysis showed that ADC <650 ×10-6 mm2/s had an area under the curve of 0.79 (95% CI 0.65-0.93, p < 0.001). Quantitative DWI MRI data improved prognostication of both good and poor outcomes. CONCLUSIONS: This prospective, clinician-blinded study validates previous research showing that an ADC <650 ×10-6 mm2/s in >10% of brain tissue in an MRI obtained by postarrest day 7 is highly specific for poor outcome in comatose patients after cardiac arrest.

Contralateral Hemispheric Cerebral Blood Flow Measured With Arterial Spin Labeling Can Predict Outcome in Acute Stroke.

Background and Purpose- Imaging is frequently used to select acute stroke patients for intra-arterial therapy. Quantitative cerebral blood flow can be measured noninvasively with arterial spin labeling magnetic resonance imaging. Cerebral blood flow levels in the contralateral (unaffected) hemisphere may affect capacity for collateral flow and patient outcome. The goal of this study was to determine whether higher contralateral cerebral blood flow (cCBF) in acute stroke identifies patients with better 90-day functional outcome. Methods- Patients were part of the prospective, multicenter iCAS study (Imaging Collaterals in Acute Stroke) between 2013 and 2017. Consecutive patients were enrolled after being diagnosed with anterior circulation acute ischemic stroke. Inclusion criteria were ischemic anterior circulation stroke, baseline National Institutes of Health Stroke Scale score ≥1, prestroke modified Rankin Scale score ≤2, onset-to-imaging time <24 hours, with imaging including diffusion-weighted imaging and arterial spin labeling. Patients were dichotomized into high and low cCBF groups based on median cCBF. Outcomes were assessed by day-1 and day-5 National Institutes of Health Stroke Scale; and day-30 and day-90 modified Rankin Scale. Multivariable logistic regression was used to test whether cCBF predicted good neurological outcome (modified Rankin Scale score, 0-2) at 90 days. Results- Seventy-seven patients (41 women) met the inclusion criteria with median (interquartile range) age of 66 (55-76) yrs, onset-to-imaging time of 4.8 (3.6-7.7) hours, and baseline National Institutes of Health Stroke Scale score of 13 (9-20). Median cCBF was 38.9 (31.2-44.5) mL per 100 g/min. Higher cCBF predicted good outcome at day 90 (odds ratio, 4.6 [95% CI, 1.4-14.7]; P=0.01), after controlling for baseline National Institutes of Health Stroke Scale, diffusion-weighted imaging lesion volume, and intra-arterial therapy. Conclusions- Higher quantitative cCBF at baseline is a significant predictor of good neurological outcome at day 90. cCBF levels may inform decisions regarding stroke triage, treatment of acute stroke, and general outcome prognosis. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02225730.

The neuron specific enolase (NSE) ratio offers benefits over absolute value thresholds in post-cardiac arrest coma prognosis.

INTRODUCTION: Serum neuron-specific enolase (NSE) levels have been shown to correlate with neurologic outcome in comatose survivors of cardiac arrest but use of absolute NSE thresholds is limited. This study describes and evaluates a novel approach to analyzing NSE, the NSE ratio, and evaluates the prognostic utility of NSE absolute value thresholds and trends over time. METHODS: 100 consecutive adult comatose cardiac arrest survivors were prospectively enrolled. NSE levels were assessed at 24, 48, and 72 h post-arrest. Primary outcome was the Glasgow Outcome Score (GOS) at 6 months post-arrest; good outcome was defined as GOS 3-5. Absolute and relative NSE values (i.e. the NSE ratio), peak values, and the trend in NSE over 72 h were analyzed. RESULTS: 98 patients were included. 42 (43%) had a good outcome. Five good outcome patients had peak NSE >33 µg/L (34.9-46.4 µg/L). NSE trends between 24 and 48 h differed between outcome groups (decrease by 3.0 µg/L (0.9-7.0 µg/L) vs. increase by 13.4 µg/L (-3.7 to 69.4 µg/L), good vs. poor, p = 0.004). The 48:24 h NSE ratio differed between the good and poor outcome groups (0.8 (0.6-0.9) vs. 1.4 (0.8-2.5), p = 0.001), and a 48:24 h ratio of ≥1.7 was 100% specific for poor outcome. CONCLUSIONS: The NSE ratio is a unique method to quantify NSE changes over time. Values greater than 1.0 indicate increasing NSE and may be reflective of ongoing neuronal injury. The NSE ratio obviates the need for an absolute value cut-off.

Quantitative EEG Metrics Differ Between Outcome Groups and Change Over the First 72 h in Comatose Cardiac Arrest Patients.

BACKGROUND: Forty to sixty-six percent of patients resuscitated from cardiac arrest remain comatose, and historic outcome predictors are unreliable. Quantitative spectral analysis of continuous electroencephalography (cEEG) may differ between patients with good and poor outcomes. METHODS: Consecutive patients with post-cardiac arrest hypoxic-ischemic coma undergoing cEEG were enrolled. Spectral analysis was conducted on artifact-free contiguous 5-min cEEG epochs from each hour. Whole band (1-30 Hz), delta (δ, 1-4 Hz), theta (θ, 4-8 Hz), alpha (α, 8-13 Hz), beta (ß, 13-30 Hz), α/δ power ratio, percent suppression, and variability were calculated and correlated with outcome. Graphical patterns of quantitative EEG (qEEG) were described and categorized as correlating with outcome. Clinical outcome was dichotomized, with good neurologic outcome being consciousness recovery. RESULTS: Ten subjects with a mean age = 50 yrs (range = 18-65) were analyzed. There were significant differences in total power (3.50 [3.30-4.06] vs. 0.68 [0.52-1.02], p = 0.01), alpha power (1.39 [0.66-1.79] vs 0.27 [0.17-0.48], p < 0.05), delta power (2.78 [2.21-3.01] vs 0.55 [0.38-0.83], p = 0.01), percent suppression (0.66 [0.02-2.42] vs 73.4 [48.0-97.5], p = 0.01), and multiple measures of variability between good and poor outcome patients (all values median [IQR], good vs. poor). qEEG patterns with high or increasing power or large power variability were associated with good outcome (n = 6). Patterns with consistently low or decreasing power or minimal power variability were associated with poor outcome (n = 4). CONCLUSIONS: These preliminary results suggest qEEG metrics correlate with outcome. In some patients, qEEG patterns change over the first three days post-arrest.

Depression one year after hemorrhagic stroke is associated with late worsening of outcomes.

BACKGROUND: Poststroke depression is the most common psychiatric sequelae of stroke, and it's independently associated with increased morbidity and mortality. Few studies have examined depression after intracranial hemorrhage (ICH). OBJECTIVE: To investigate the relationship between depression, ICH and outcomes. METHODS: A substudy of the prospective Diagnostic Accuracy of MRI in Spontaneous Intracerebral Hemorrhage (DASH) study, we included 89 subjects assessed for depression 1 year after hemorrhage. A Hamilton Depression Rating Scale score >10 defined depression. Univariate, multivariable, and trend analyses evaluated relationships between depression, clinical, radiographic, and inflammatory factors and modified Rankin score (mRS) at 90 days and one year. RESULTS: Prevalence of depression at one year was 15%. Depression was not associated with hematoma volumes, presence of IVH or admission NIHSS, nor with demographic factors. Despite this, depressed patients had worse 1-year outcomes (p = 0.004) and were less likely to improve between 3 and 12 months, and more likely to worsen (p = 0.042). CONCLUSION: This is the first study to investigate depression one year after ICH. Post-ICH depression was common and associated with late worsening of disability unrelated to initial hemorrhage severity. Further research is needed to understand whether depression is caused by worsened disability, or whether the converse is true.

Functional Neurologic Outcomes Change Over the First 6 Months After Cardiac Arrest.

OBJECTIVES: To determine the longitudinal changes in functional outcome and compare ordinal outcome scale assessments in comatose cardiac arrest survivors. DESIGN: Prospective observational study of comatose cardiac arrest survivors. Subjects who survived to 1 month were included. SETTING: Academic medical center ICU. PATIENTS: Ninety-eight consecutive patients who remained comatose after resuscitation from cardiac arrest; 45 patients survived to 1 month. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients' functional neurologic outcomes were assessed by phone call or in-person clinic visit at 1, 3, 6, and 12 months postcardiac arrest using the modified Rankin Scale, Glasgow Outcome Scale, and Barthel Index. A "good" outcome was defined as modified Rankin Scale 0-3, Barthel Index 70-100, and Glasgow Outcome Scale 4-5. Changes in dichotomized outcomes and shifts on each outcome scale were analyzed. The mean age of survivors was 51 ± 19 years and 18 (40%) were women. Five (19%) out of 26 patients with data available at all timepoints improved to good modified Rankin Scale outcome and none worsened to poor outcome between postarrest months 1 and 6 (p = 0.06). Thirteen patients (50%) improved on the modified Rankin Scale by 1-3 points and four (15%) worsened by 1-2 points between months 1 and 6 (overall improvement by 0.5 points; 95% CI, 0-1; p = 0.04). From postarrest months 6 to 12, there was no change in the number of patients with good versus poor outcomes. The modified Rankin Scale and Barthel Index were more sensitive to detecting changes in outcome than the Glasgow Outcome Scale. CONCLUSIONS: In initially comatose cardiac arrest survivors, improvements in functional status occur over the first 6 months after the event. There was no significant change in outcome between postarrest months 6 and 12. The modified Rankin Scale is a sensitive outcome scale in this population.

Prognostic value of a qualitative brain MRI scoring system after cardiac arrest.

BACKGROUND AND PURPOSE: To develop a qualitative brain magnetic resonance imaging (MRI) scoring system for comatose cardiac arrest patients that can be used in clinical practice. METHODS: Consecutive comatose postcardiac arrest patients were prospectively enrolled. Routine MR brain sequences were scored by two independent blinded experts. Predefined brain regions were qualitatively scored on the fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences according to the severity of the abnormality on a scale from 0 to 4. The mean score of the raters was used. Poor outcome was defined as death or vegetative state at 6 months. RESULTS: Sixty-eight patients with 88 brain MRI scans were included. Median time from the arrest to the initial MRI was 77 hours (IQR 58-144 hours). At 100% specificity, the "cortex score" performed best in predicting unfavorable outcome with a sensitivity of 55%-60% (95% CI 41-74) depending on time window selection. When comparing the "cortex score" with historically used predictors for poor outcome, MRI improved the sensitivity for poor outcome over conventional predictors by 27% at 100% specificity. CONCLUSIONS: A qualitative MRI scoring system helps assess hypoxic-ischemic brain injury severity following cardiac arrest and may provide useful prognostic information in comatose cardiac arrest patients.

Natural history and prognostic value of corticospinal tract Wallerian degeneration in intracerebral hemorrhage.

BACKGROUND: The purpose of this study was to define the incidence, imaging characteristics, natural history, and prognostic implication of corticospinal tract Wallerian degeneration (CST-WD) in spontaneous intracerebral hemorrhage (ICH) using serial MR imaging. METHODS AND RESULTS: Consecutive ICH patients with supratentorial ICH prospectively underwent serial MRIs at 2, 7, 14, and 21 days. MRIs were analyzed by independent raters for the presence and topographical distribution of CST-WD on diffusion-weighted imaging (DWI). Baseline demographics, hematoma characteristics, ICH score, and admission National Institute of Health Stroke Score (NIHSS) were systematically recorded. Functional outcome at 3 months was assessed by the modified Rankin Scale (mRS) and the motor-NIHSS. Twenty-seven patients underwent 93 MRIs; 88 of these were serially obtained in the first month. In 13 patients (48%), all with deep ICH, CST-WD changes were observed after a median of 7 days (interquartile range, 7 to 8) as reduced diffusion on DWI and progressed rostrocaudally along the CST. CST-WD changes evolved into T2-hyperintense areas after a median of 11 days (interquartile range, 6 to 14) and became atrophic on MRIs obtained after 3 months. In univariate analyses, the presence of CST-WD was associated with poor functional outcome (ie, mRS 4 to 6; P=0.046) and worse motor-NIHSS (5 versus 1, P=0.001) at 3 months. CONCLUSIONS: Wallerian degeneration along the CST is common in spontaneous supratentorial ICH, particularly in deep ICH. It can be detected 1 week after ICH on DWI and progresses rostrocaudally along the CST over time. The presence of CST-WD is associated with poor motor and functional recovery after ICH.

Serum neuron-specific enolase levels from the same patients differ between laboratories: assessment of a prospective post-cardiac arrest cohort.

BACKGROUND: In comatose post-cardiac arrest patients, a serum neuron-specific enolase (NSE) level of >33 µg/L within 72 h was identified as a reliable marker for poor outcome in a large Dutch study (PROPAC), and this level was subsequently adopted in an American Academy of Neurology practice parameter. Later studies reported that NSE >33 µg/L is not a reliable predictor of poor prognosis. To test whether different clinical laboratories contribute to this variability, we compared NSE levels from the laboratory used in the PROPAC study (DLM-Nijmegen) with those of our hospital's laboratory (ARUP) using paired blood samples. METHODS: We prospectively enrolled cardiac arrest patients who remained comatose after resuscitation. During the first 3 days, paired blood samples for serum NSE were drawn at a median of 10 min apart. After standard preparation for each lab, one sample was sent to ARUP laboratories and the other to DLM-Nijmegen. RESULTS: Fifty-four paired serum samples from 33 patients were included. Although the serum NSE measurements correlated well between laboratories (R = 0.91), the results from ARUP were approximately 30% lower than those from DLM-Nijmegen. Therapeutic hypothermia did not affect this relationship. Two patients had favorable outcomes after hypothermia despite NSE levels measured by DLM-Nijmegen as >33 µg/L. CONCLUSIONS: Absolute serum NSE levels of comatose cardiac arrest patients differ between laboratories. Any specific absolute cut-off levels proposed to prognosticate poor outcome should not be used without detailed data on how neurologic outcomes correspond to a particular laboratory's method, and even then only in conjunction with other prognostic variables.

Magnetic resonance imaging profile of blood-brain barrier injury in patients with acute intracerebral hemorrhage.

BACKGROUND: Spontaneous intracerebral hemorrhage (ICH) is associated with blood-brain barrier (BBB) injury, which is a poorly understood factor in ICH pathogenesis, potentially contributing to edema formation and perihematomal tissue injury. We aimed to assess and quantify BBB permeability following human spontaneous ICH using dynamic contrast-enhanced magnetic resonance imaging (DCE MRI). We also investigated whether hematoma size or location affected the amount of BBB leakage. METHODS AND RESULTS: Twenty-five prospectively enrolled patients from the Diagnostic Accuracy of MRI in Spontaneous intracerebral Hemorrhage (DASH) study were examined using DCE MRI at 1 week after symptom onset. Contrast agent dynamics in the brain tissue and general tracer kinetic modeling were used to estimate the forward leakage rate (K(trans)) in regions of interest (ROI) in and surrounding the hematoma and in contralateral mirror-image locations (control ROI). In all patients BBB permeability was significantly increased in the brain tissue immediately adjacent to the hematoma, that is, the hematoma rim, compared to the contralateral mirror ROI (P<0.0001). Large hematomas (>30 mL) had higher K(trans) values than small hematomas (P<0.005). K(trans) values of lobar hemorrhages were significantly higher than the K(trans) values of deep hemorrhages (P<0.005), independent of hematoma volume. Higher K(trans) values were associated with larger edema volumes. CONCLUSIONS: BBB leakage in the brain tissue immediately bordering the hematoma can be measured and quantified by DCE MRI in human ICH. BBB leakage at 1 week is greater in larger hematomas as well as in hematomas in lobar locations and is associated with larger edema volumes.

A comparison of cooling techniques to treat cardiac arrest patients with hypothermia.

Introduction. We sought to compare the performance of endovascular cooling to conventional surface cooling after cardiac arrest. Methods. Patients in coma following cardiopulmonary resuscitation were cooled with an endovascular cooling catheter or with ice bags and cold-water-circulating cooling blankets to a target temperature of 32.0-34.0°C for 24 hours. Performance of cooling techniques was compared by (1) number of hourly recordings in target temperature range, (2) time elapsed from the written order to initiate cooling and target temperature, and (3) adverse events during the first week. Results. Median time in target temperature range was 19 hours (interquartile range (IQR), 16-20) in the endovascular group versus. 10 hours (IQR, 7-15) in the surface group (P = .001). Median time to target temperature was 4 (IQR, 2.8-6.2) and 4.5 (IQR, 3-6.5) hours, respectively (P = .67). Adverse events were similar. Conclusion. Endovascular cooling maintains target temperatures better than conventional surface cooling.

Natural history of perihematomal edema after intracerebral hemorrhage measured by serial magnetic resonance imaging.

BACKGROUND AND PURPOSE: knowledge on the natural history and clinical impact of perihematomal edema (PHE) associated with intracerebral hemorrhage is limited. We aimed to define the time course, predictors, and clinical significance of PHE measured by serial magnetic resonance imaging. METHODS: patients with primary supratentorial intracerebral hemorrhage ≥ 5 cm(3) underwent serial MRIs at prespecified intervals during the first month. Hematoma (H(v)) and PHE (E(v)) volumes were measured on fluid-attenuated inversion recovery images. Relative PHE was defined as E(v)/H(v). Neurologic assessments were performed at admission and with each MRI. Barthel Index, modified Rankin scale, and extended Glasgow Outcome scale scores were assigned at 3 months. RESULTS: twenty-seven patients with 88 MRIs were prospectively included. Median H(v) and E(v) on the first MRI were 39 and 46 cm(3), respectively. Median peak absolute E(v) was 88 cm(3). Larger hematomas produced a larger absolute E(v) (r(2)=0.6) and a smaller relative PHE (r(2)=0.7). Edema volume growth was fastest in the first 2 days but continued until 12 ± 3 days. In multivariate analysis, a higher admission hematocrit was associated with a greater delay in peak PHE (P=0.06). Higher admission partial thromboplastin time was associated with higher peak rPHE (P=0.02). Edema volume growth was correlated with a decline in neurologic status at 48 hours (81 vs 43 cm(3), P=0.03) but not with 3-month functional outcome. CONCLUSIONS: PHE volume measured by MRI increases most rapidly in the first 2 days after symptom onset and peaks toward the end of the second week. The timing and magnitude of PHE volume are associated with hematologic factors. Its clinical significance deserves further study.

Sedation confounds outcome prediction in cardiac arrest survivors treated with hypothermia.

BACKGROUND: Therapeutic hypothermia is commonly used in comatose survivors' post-cardiopulmonary resuscitation (CPR). It is unknown whether outcome predictors perform accurately after hypothermia treatment. METHODS: Post-CPR comatose survivors were prospectively enrolled. Six outcome predictors [pupillary and corneal reflexes, motor response to pain, and somatosensory-evoked potentials (SSEP) >72 h; status myoclonus, and serum neuron-specific enolase (NSE) levels <72 h] were systematically recorded. Poor outcome was defined as death or vegetative state at 3 months. Patients were considered "sedated" if they received any sedative drugs ≤ 12 h prior the 72 h neurological assessment. RESULTS: Of 85 prospectively enrolled patients, 53 (62%) underwent hypothermia. Furthermore, 53 of the 85 patients (62%) had a poor outcome. Baseline characteristics did not differ between the hypothermia and normothermia groups. Sedative drugs at 72 h were used in 62 (73%) patients overall, and more frequently in hypothermia than in normothermia patients: 83 versus 60% (P = 0.02). Status myoclonus <72 h, absent cortical responses by SSEPs >72 h, and absent pupillary reflexes >72 h predicted poor outcome with a 100% specificity both in hypothermia and normothermia patients. In contrast, absent corneal reflexes >72 h, motor response extensor or absent >72 h, and peak NSE >33 ng/ml <72 h predicted poor outcome with 100% specificity only in non-sedated patients, irrespective of prior treatment with hypothermia. CONCLUSIONS: Sedative medications are commonly used in proximity of the 72-h neurological examination in comatose CPR survivors and are an important prognostication confounder. Patients treated with hypothermia are more likely to receive sedation than those who are not treated with hypothermia.

Temporal and spatial profile of brain diffusion-weighted MRI after cardiac arrest.

BACKGROUND AND PURPOSE: Diffusion-weighted magnetic resonance imaging of the brain is a promising technique to help predict functional outcome in comatose survivors of cardiac arrest. We aimed to evaluate prospectively the temporal-spatial profile of brain apparent diffusion coefficient changes in comatose survivors during the first 8 days after cardiac arrest. METHODS: Apparent diffusion coefficient values were measured by 2 independent and blinded investigators in predefined brain regions in 18 good- and 15 poor-outcome patients with 38 brain magnetic resonance imaging scans and were compared with those of 14 normal controls. The same brain regions were also assessed qualitatively by 2 other independent and blinded investigators. RESULTS: In poor-outcome patients, cortical structures, in particular the occipital and temporal lobes, and the putamen exhibited the most profound apparent diffusion coefficient reductions, which were noted as early as 1.5 days and reached a nadir between 3 and 5 days after the arrest. Conversely, when compared with normal controls, good-outcome patients exhibited increased diffusivity, in particular in the hippocampus, temporal and occipital lobes, and corona radiata. By qualitative magnetic resonance imaging readings, 1 or more cortical gray matter structures were judged to be moderately to severely abnormal in all poor-outcome patients except for the 3 patients imaged within 24 hours after the arrest. CONCLUSIONS: Brain diffusion-weighted imaging changes in comatose, postcardiac arrest survivors in the first week after the arrest are region and time dependent and differ between good- and poor-outcome patients. With increasing use of magnetic resonance imaging in this context, it is important to be aware of these relations.

Prognostic value of brain diffusion-weighted imaging after cardiac arrest.

OBJECTIVE: Outcome prediction is challenging in comatose postcardiac arrest survivors. We assessed the feasibility and prognostic utility of brain diffusion-weighted magnetic resonance imaging (DWI) during the first week. METHODS: Consecutive comatose postcardiac arrest patients were prospectively enrolled. AWI data of patients who met predefined specific prognostic criteria were used to determine distinguishing apparent diffusion coefficient (ADC) thresholds. Group 1 criteria were death at 6 months and absent motor response or absent pupillary reflexes or bilateral absent cortical responses at 72 hours or vegetative at 1 month. Group 2 criterion was survival at 6 months with a Glasgow Outcome Scale score of 4 or 5 (group 2A) or 3 (group 2B). The percentage of voxels below different ADC thresholds was calculated at 50 x 10(-6) mm(2)/sec intervals. RESULTS: Overall, 86% of patients underwent DWI. Fifty-one patients with 62 brain DWIs were included. Forty patients met the specific prognostic criteria. The percentage of brain volume with an ADC value less than 650 to 700 x 10(-6)mm(2)/sec best differentiated between Group 1 and Groups 2A and 2B combined (p < 0.001), whereas the 400 to 450 x 10(-6)mm(2)/sec threshold best differentiated between Groups 2A and 2B (p = 0.003). The ideal time window for prognostication using DWI was between 49 and 108 hours after the arrest. When comparing DWI in this time window with the 72-hour neurological examination, DWI improved the sensitivity for predicting poor outcome by 38% while maintaining 100% specificity (p = 0.021). INTERPRETATION: Quantitative DWI in comatose postcardiac arrest survivors holds promise as a prognostic adjunct.

Automated method for generating the arterial input function on perfusion-weighted MR imaging: validation in patients with stroke.

BACKGROUND AND PURPOSE: The choice of arterial input function (AIF) can have a profound effect on the blood flow maps generated on perfusion-weighted MR imaging (PWI). Automation of this process could substantially reduce operator dependency, increase consistency, and accelerate PWI analysis. We created an automated AIF identification program (auto-AIF) and validated its performance against conventional manual methods. METHODS: We compared the auto-AIF against manually derived AIFs from multisection PWIs of 22 patients with stroke. Time to peak, curve width, curve height, and voxel location determined with both techniques were compared. The time to maximum of the tissue residue function (Tmax) and cerebral blood flow (CBF) were computed on a per-pixel basis for each AIF. Spatial patterns of 528 map pairs were compared by computing Pearson correlation coefficients between maps generated with each method. RESULTS: All auto-AIF-derived PWI map parameters, including bolus peak, width, and height, were consistently superior to manually derived ones. Reproducibility of the auto-AIF-based Tmax maps was excellent (r = 1.0). Paired Tmax maps and CBF maps from both techniques were well correlated (r = 0.82). Time to identify the AIF was significantly shorter with the auto-AIF method than with the manual technique (mean difference, 72 seconds; 95% confidence interval: 54, 89 seconds). CONCLUSION: An automated program that identifies the AIF is feasible and can create reliably reproducible and accurate Tmax and CBF maps. Automation of this process could reduce PWI analysis time and increase consistency and may allow for more effective use of PWI in the evaluation of acute stroke.