Normal Diffusion-weighted Imaging Research Articles

Good outcome prediction after out-of-hospital cardiac arrest: A prospective multicenter observational study in Korea (the KORHN-PRO registry)

AimTo assess the ability of clinical examination, biomarkers, electrophysiology and brain imaging, individually or in combination to predict good neurological outcomes at 6 months after CA. MethodsThis was a retrospective analysis of the Korean Hypothermia Network Prospective Registry 1.0, which included adult out-of-hospital cardiac arrest (OHCA) patients (≥18 years). Good outcome predictors were defined as both pupillary light reflex (PLR) and corneal reflex (CR) at admission, Glasgow Coma Scale Motor score (GCS-M) >3 at admission, neuron-specific enolase (NSE) <17 µg/L at 24–72 h, a median nerve somatosensory evoked potential (SSEP) N20/P25 amplitude >4 µV, continuous background without discharges on electroencephalogram (EEG), and absence of anoxic injury on brain CT and diffusion-weighted imaging (DWI). ResultsA total of 1327 subjects were included in the final analysis, and their median age was 59 years; among them, 412 subjects had a good neurological outcome at 6 months. GCS-M >3 at admission had the highest specificity of 96.7% (95% CI 95.3–97.8), and normal brain DWI had the highest sensitivity of 96.3% (95% CI 92.9–98.4). When the two predictors were combined, the sensitivities tended to decrease (ranging from 2.7–81.1%), and the specificities tended to increase, ranging from81.3–100%. Through the explorative variation of the 2021 European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) prognostication strategy algorithms, good outcomes were predicted, with a specificity of 83.2% and a sensitivity of 83.5% in patients by the algorithm. ConclusionsClinical examination, biomarker, electrophysiology, and brain imaging predicted good outcomes at 6 months after CA. When the two predictors were combined, the specificity further improved. With the 2021 ERC/ESICM guidelines, the number of indeterminate patients and the uncertainty of prognostication can be reduced by using a good outcome prediction algorithm.

Silent Micro-Infarct in Carotid Artery Stenting: Who Has it and Why?

Carotid stenosis (CS) is one of the modifiable risk factors for stroke. We aimed to compare the postprocedural cerebral diffusion-weighted imaging (DWI) findings in cases of CS-related carotid plaques in terms of plaque morphology, degree of stenosis, and the use of a distal protection filter. We also used DWI to assess the asymptomatic cerebral embolism rates during carotid artery stending (CAS) operations performed for noncalcified versus calcified carotid plaques. Our study included 99 patients admitted to the Ankara City Hospital Stroke Center in 2022. All of our patients have been evaluated and scheduled for CAS as a result of a decision made by the council. Cases of stenosis of 50% in symptomatic patients and 70% in asymptomatic patients were included. The patients were grouped according to their Doppler ultrasonography results. All of the patients underwent DWI within the first 24 hours after the procedure, and then two groups of patients were compared. A statistically significant difference was found between the distributions of the presence of silent micro-infarcts on DWI in terms of plaque characteristics (p 0.001). In the patients with normal DWI findings, the percentage of calcified plaques was 38.7%, while the percentages of hypoechoic plaques, plaques with low echogenicity, and ulcerated plaques were 91.3%, 85.7%, and 78.8%, respectively. The rates of calcified plaques and ulcerated plaques differed in the group of patients with silent micro-infarcts. The rate of silent micro-infarcts was 61.3% in the patients with calcified plaques, 8.7% in those with hypoechoic plaques, 14.3% in those with low-echogenicity plaques, and 21.2% in those with ulcerated plaques. The study found that carotid stents implanted in calcified and ulcerated plaques had a higher correlation with the presence of periprocedural asymptomatic ipsilateral DWI findings than those implanted in hypoechoic plaques and low-echogenicity plaques.

Diffusion kurtosis imaging in patients with tissue-negative transient ischemic attack.

Approximately 50-60% of patients with a clinical transient ischemic attack (TIA) do not have diffusion-weighted imaging (DWI) evidence of cerebral ischemia. The purpose of this study was to assess the added diagnostic value of diffusion kurtosis imaging (DKI) in the evaluation of patients with TIA who have normal DWI findings. From September 2014 to May 2017, a total of 179 consecutive patients with suspected TIA were eligible for enrollment in our study. The inclusion criteria were a confirmed diagnosis of TIA confirmed by a stroke neurologist, MRI (including DWI and DKI) within 24 h after symptom onset, no stroke history, and no DWI lesion. A follow-up DWI was performed to establish stroke recurrence within a period of 90 days. A total of 98 patients who had no lesions on the baseline DWI were included for data analysis. Of these 98 patients, 31 (31.6%) had positive findings on the initial DKI. In 29 of the 31 (93.5%) patients, the location of the abnormality observed on DKI was consistent with the clinical symptoms. During the 90-day follow-up period, 14 (14.3%) patients developed recurrent stroke. The prevalence of recurrent stroke was higher in the DKI-positive group than in the DKI-negative group (29.0% vs. 7.5%, p = 0.01). A comparison between the patients with and without recurrent stroke showed that an abnormality on the baseline DKI was associated with stroke recurrence. Furthermore, 8 of the 9 stroke patients in the DKI-positive group developed a new ischemic lesion in the artery territory corresponding to the initial DKI abnormality. The new findings suggest the predictive value of DKI on the recurrence of stroke in the patients with TIA who have negative findings on conventional DWI.

Seizure types associated with negative arterial spin labeling and positive diffusion-weighted imaging on peri-ictal magnetic resonance imaging

PurposeArterial spin labeling (ASL) and diffusion-weighted imaging (DWI) are useful for assessing hyperperfusion and cytotoxic edema, respectively, caused by acute seizures. This study investigated the clinical characteristics associated with normal ASL findings and DWI abnormalities in patients with acute seizures. MethodsOverall, 41 patients with ASL and DWI images that were obtained within 48 h of focal onset seizure diagnosis, due to epilepsy or acute symptomatic seizures, were divided into groups based on initial ASL findings (ASL-negative vs. ASL-positive), and DWI abnormalities (DWI-negative vs. DWI-positive). The diagnosis was made based on seizure semiology, electroencephalography, and conventional imaging modalities. ASL and DWI abnormalities were based on visual assessment. ResultsOf the 41 patients, eight (19.5%) displayed normal ASL findings. The proportion of patients with focal aware seizures (FAS) was significantly higher among ASL-negative patients (62.5%) than that in ASL-positive patients (15.2%); the proportion of patients with focal impaired awareness seizures (FIAS) was significantly lower among ASL-negative patients (12.5%) than that among ASL-positive patients (57.6%). Hyperintensity findings on DWI were observed in 12 patients (29.3%, DWI-positive). The proportion of patients with FIAS was significantly higher among DWI-positive patients (75.0%) than that among DWI-negative patients (37.9%). Multivariate analysis revealed that FAS and FIAS were associated with normal ASL findings (odds ratio [OR]: 21.37, P = 0.010) and DWI abnormalities (OR = 6.11, P = 0.028). ConclusionA diagnosis of seizures should not be excluded based on normal ASL findings, especially in patients with FAS. FIAS may be a risk factor for neuronal damage caused by seizure activity.

Should Primary Stroke Centers Perform Advanced Imaging?

Should Primary Stroke Centers Perform Advanced Imaging?

The diagnostic value of neurogranin in patients with carbon monoxide poisoning: Can it show early neurological damage?

Carbon monoxide poisoning is a toxicological emergency that causes neurological complications. High serum neurogranin can be detected in acute or chronic conditions where brain tissue is damaged. This study aimed to investigate the diagnostic value of serum neurogranin level and its role in demonstrating neurological damage in patients admitted to the emergency department with carbon monoxide poisoning. The study was conducted prospectively on patients with carbon monoxide poisoning (patient group) and healthy volunteers (control group). Demographic characteristics and serum neurogranin level of all participants and symptoms at admission, neurological examination findings, laboratory results, and Diffusion-Weighted Magnetic Resonance Imaging results of the patient group were recorded. We used an independent sample t-test to compare neurogranin levels and bivariate correlation analysis to compare the relationship between serum neurogranin levels and data belonging to the patient group. Sixty eight participants (patient group, n = 36; control group, n = 32) were included in the study. Serum neurogranin level was significantly higher in patients with carbon monoxide poisoning (0.31 ± 0.16 ng/ml) compared to control group (0.22 ± 0.10 ng/ml) (p = 0.015). The mean Glasgow Coma Scale of the patients with carbon monoxide poisoning was 14.59 ± 0.23, and of Diffusion Weighted Magnetic Resonance Imaging results were completely normal in 94.4% (n = 34). There was no correlation between serum neurogranin level and Diffusion Weighted Magnetic Resonance Imaging results (r = -0.011; p = 0.953). Serum neurogranin level may be a new diagnostic biomarker in patients admitted to the emergency department with carbon monoxide poisoning. The high serum neurogranin levels detected in patients with normal diffusion-weighted imaging after carbon monoxide poisoning suggest that there is neurological damage in these patients, even if imaging methods cannot detect it.

History of Hypertension Is Associated With MR Hypoperfusion in Chinese Inpatients With DWI-Negative TIA.

Objectives: The present study aimed to examine the prevalence of and risk factors for magnetic resonance (MR) perfusion abnormality in a Chinese population with transient ischemic attack (TIA) and normal diffusion-weighted imaging (DWI) findings.Methods: Patients with TIA admitted to our stroke center between January 2015 and October 2017 were recruited to the present study. MRI, including both DWI and perfusion-weighted imaging (PWI), was performed within 7 days of symptom onset. Time to maximum of the residue function (Tmax) maps were evaluated using the RAPID software (Ischemaview USA, Version 4.9) to determine hypoperfusion. Multivariate analysis was used to assess perfusion findings, clinical variables, medical history, cardio-metabolic, and the ABCD2 scores (age, blood pressure, clinical features, symptom duration, and diabetes).Results: Fifty-nine patients met the inclusion criteria. The prevalence of MR perfusion Tmax ≥ 4 s ≥ 0 ml and ≥ 10 mL were 72.9% (43/59) and 42.4% (25/59), respectively. Multivariate analyses revealed that history of hypertension is an independent factor associated with MR perfusion abnormality (Tmax ≥ 4 s ≥ 10 mL) for Chinese patients with TIA (P = 0.033, adjusted OR = 4.11, 95% CI = 1.12–15.11). Proximal artery stenosis (>50%) tended to lead to a larger PW lesion on MRI (p = 0.067, adjusted OR = 3.60, 95% CI = 0.91–14.20).Conclusion: Our results suggest that the prevalence of perfusion abnormality is high as assessed by RAPID using the parametric Tmax ≥ 4 s. History of hypertension is a strong predictor of focal perfusion abnormality as calculated by RAPID on Tmax map of TIA patients with negative DWI findings.

Diffusion pseudonormalization and clinical outcome in term neonates with hypoxic-ischemic encephalopathy.

Pseudonormalization of diffusion-weighted magnetic resonance imaging (MRI) can lead to underestimation of brain injury in newborns with hypoxic-ischemic encephalopathy (HIE), posing a significant problem. We have noticed that some neonates show pseudonormalization negativity on diffusion-weighted imaging. To compare pseudonormalization negativity with clinical outcomes. Seventeen term neonates with moderate or severe HIE underwent therapeutic hypothermia. They were examined by MRI twice at mean ages of 3days and 10days. We evaluated the presence of restricted diffusion, and also the presence or absence of pseudonormalization, by diffusion-weighted imaging at the time of the second MRI, and correlated the results with clinical outcome. DWI demonstrated no abnormality in seven neonates. Among the 10 neonates with abnormal diffusion-weighted imaging findings, 2 were positive for pseudonormalization and 8 were negative. Among neonates with normal diffusion-weighted imaging findings and with positivity for pseudonormalization, none had major disability. Among the eight neonates with pseudonormalization negativity, all but one, who was lost to follow-up, had major disability. Abnormal diffusion-weighted imaging with pseudonormalization negativity might be predictive of severe brain injury and major disability. The second-week MRI is important for the judgment of pseudonormalization.

Initial diffusion-weighted MRI and long-term neurologic outcomes in charcoal-burning carbon monoxide poisoning

Context: This study assessed the results of diffusion-weighted imaging (DWI) at presentation for acute charcoal-burning carbon monoxide (CO) poisoning and investigated whether the initial DWI results can predict long-term neurologic outcomes.Methods: The study included 128 patients who suffered from CO poisoning after burning charcoal and underwent DWI. These patients were divided into two groups based on imaging results: a normal DWI group and an abnormal DWI group. Data regarding clinical courses and long-term neurologic outcomes (persistent severe neurologic sequelae) were collected and compared.Results: The rate of abnormal DWI findings at presentation was 23.4%, and the most common site of abnormalities was the globus pallidus. All lesions in abnormal DWI had decreased apparent diffusion coefficient (ADC) values. The long-term neurologic state was assessed at a median follow-up of 19.5 months, and the frequency of poor long-term neurologic outcome was significantly higher in the abnormal DWI group (40.0% in the abnormal DWI group vs. 1.0% in the normal DWI group; p < .001). Abnormal DWI (odds ratio [OR]): 31.3, 95% confidence interval [CI]: 2.5–397) and old age (OR 1.1, 95% CI: 1.001–1.13) were independent factors for poor long-term neurologic outcomes, whereas the Glasgow Coma Scale score at presentation (OR: 0.7, 95% CI: 0.6–0.9) was negatively associated with the risk of poor long-term neurologic outcome.Conclusions: In cases involving CO poisoning due to charcoal burning, DWI at presentation may help predict the long-term neurological outcome after discharge.

Diffusion-weighted imaging for evaluating inflammatory activity in Crohn\u2019s disease: comparison with histopathology, conventional MRI activity scores, and faecal calprotectin

ABSTRACTPurposeTo evaluate whether the extent of enteric diffusion-weighted imaging (DWI) signal abnormality reflects inflammatory burden in Crohn’s disease (CD), and to compare qualitative and quantitative grading.Methods69 CD patients (35 male, age 16–78) undergoing MR enterography with DWI (MRE-D) and the same-day faecal calprotectin (cohort 1) were supplemented by 29 patients (19 male, age 16–70) undergoing MRE-D and terminal ileal biopsy (cohort 2). Global (cohort 1) and terminal ileal (cohort 2) DWI signal was graded (0 to 3) by 2 radiologists and segmental apparent diffusion coefficient (ADC) calculated. Data were compared to calprotectin and a validated MRI activity score [MEGS] (cohort 1), and a histopathological activity score (eAIS) (cohort 2) using nonparametric testing and rank correlation.ResultsPatients with normal (grades 0 and 1) DWI signal had lower calprotectin and MEGS than those with abnormal signal (grades 2 and 3) (160 vs. 492 μg/l, p = 0.0004, and 3.3 vs. 21, p < 0.0001), respectively. Calprotectin was lower if abnormal DWI affected <10 cm of small bowel compared to diffuse small and large bowel abnormality (236 vs. 571 μg, p = 0.009). The sensitivity and specificity for active disease (calprotectin > 120 μg/l) were 83% and 52%, respectively. There was a negative correlation between ileal MEGS and ADC (r = −0.41, p = 0.017). There was no significant difference in eAIS between qualitative DWI scores (p = 0.42). Mean ADC was not different in those with and without histological inflammation (2077 vs. 1622 × 10−6mm2/s, p = 0.10)ConclusionsQualitative grading of DWI signal has utility in defining the burden of CD activity. Quantitative ADC measurements have poor discriminatory ability for segmental disease activity.

Relationship between cortex and pulvinar abnormalities on diffusion-weighted imaging in status epilepticus.

The aim of this study was to analyze the pattern of magnetic resonance diffusion-weighted imaging (DWI) findings in status epilepticus in terms of clinical characteristics. Participants comprised 106 patients with status epilepticus who were admitted to our hospital and underwent DWI. Forty-five patients (42.5 %) showed abnormal findings on DWI and were divided into two groups, comprising 26 patients (24.5 %) with cortex lesions alone and 19 patients (17.9 %) with cortex and pulvinar lesions in the same hemisphere. A long duration of status epilepticus (>120 min) tended to be more prevalent among patients with cortex and pulvinar lesions (57.9 %) than among patients with cortex lesions alone (30.8 %) by univariate and multivariate analyses. Todd's palsy tended to be more frequent in patients with abnormalities on DWI (24/45, 53.3 %) than in patients with normal DWI (21/61, 34.4 %). Six of the 26 patients with cortex lesions alone (23.1 %) had taken anti-epileptic drugs before the attack compared to none of the 19 patients with both cortex and pulvinar lesions. The trend toward a longer duration of status epilepticus in patients with both cortex and pulvinar lesions favors a spreading pattern of seizure discharge from cortex to pulvinar via cortico-pulvinar pathways, and anti-epileptic drugs might, to some extent, prevent spreading of seizure discharge from cortex to pulvinar. In addition, existence of high-intensity areas on DWI at the onset of epilepsy may be a predictive factor for the occurrence of Todd's palsy.

Diffusion weighted imaging of nasopharyngeal adenoid hypertrophy.

Diffusion-weighted imaging (DWI) could be helpful for the differentiation of malignant and benign entities. Nasopharyngeal adenoid hypertrophy (NAH) is a typical benign lesion. DWI appearances of this lesion have not been reported previously. To identify and to analyse DWI findings of NAH. We analyzed 688 MR investigations of the head performed at our institution. Magnetic resonance imaging (MRI) was obtained at a 1.5 T MRI device. Beside normal standard sequences DWI was obtained using a multislice single-shot echo-planar sequence. DWI was performed with b values of 0, 500, and 1000 s/mm(2). The mean whole lesion ADC value was 0.83 ± 0.12 × 10(-3) mm(2) s(-1) (median, 0.82 × 10(-3) mm(2) s(-1); range, 0.58-1.45 × 10(-3) mm(2) s(-1)). The mean ADC value of solid areas of NAH was 0.59 ± 0.11 × 10(-3) mm(2) s(-1) (range, 0.36-0.84 × 10(-3) mm(2) s(-1)). Although NAH is a benign lesion, it shows low ADC values both in childhood and in adults. This finding should be kept in mind to avoid possible misinterpretations as a malignant lesion.

Evaluation of different mathematical models for diffusion-weighted imaging of normal prostate and prostate cancer using high b-values: a repeatability study.

To evaluate monoexponential, stretched exponential, kurtosis, and biexponential models for diffusion-weighted imaging (DWI) of normal prostate and prostate cancer (PCa), using b-values up to 2000 s/mm(2) , in terms of fitting quality and repeatability. Eight healthy volunteers and 16 PCa patients underwent a total of four repeated 3T DWI examinations using 16 and 12 b-values, respectively. The highest b-value was 2000 s/mm(2) . The normalized mean signal intensities of regions of interest, placed in normal tissue and PCa using anatomical images and prostatectomy sections, were fitted using the four models. The fitting quality was evaluated using Akaike information criteria and F-ratio. Repeatability of the fitted parameters was evaluated using intraclass correlation coefficient ICC(3,1). The biexponential model provided the best fit to normal prostate and PCa DWI data. The parameters of the monoexponential, kurtosis, and stretched exponential (with the exception of the α parameter) models had higher ICC(3,1) values compared with the biexponential model. The kurtosis model provided a better fit to DWI data of normal prostate and PCa than the monoexponential model, whereas these models had comparable reliability and repeatability based on ICC(3,1) values. Considering the model fit and repeatability, the kurtosis model seems to be the preferred model for characterization of normal prostate and PCa DWI using b-values up to 2000 s/mm(2) .

Respiratory syncytial virus-related encephalitis: magnetic resonance imaging findings with diffusion-weighted study: response to a “letter to the editor”

Dear Sir, We thank Dr. Donmez for his comments on our publication in Neuroradiology [1], and we would like to make the following comments in reply. He noted that the normal diffusion-weighted imaging (DWI) of our cases may not be associated with a good prognosis if brain magnetic resonance imaging (MRI) with diffusion study was performed in the subacute phase of cytotoxic edema, in which restricted diffusion start to diminish and apparent diffusion coefficient (ADC) values increase. We agree with him that timing is important in brain MRI with diffusion study in patients with encephalitis, and DWI may be less sensitive when there is a time delay between the onset of the disease and imaging. In all three of our cases, the pediatric physicians decided to performDWIwithin the first 12 h and conventional brainMRI within the first 3 days immediately after meaningful neurologic symptom onset. There was no definite restriction on the diffusion study including ADC map in our cases. So we could not find the evidence of cytotoxic edema induced by encephalitis at acute phase in our cases by using diffusion study [2]. As we expected, these patients showed favorable outcome with supportive management. In a previous report, enterovirus 71-related encephalomyelitis with brainMRI and DWI study, we experienced that four of five patients did not reveal definite restriction on the diffusion study, who gradually recovered with conservative treatment without sequelae. But, one case with restricted diffusion in the lesion of the hippocampus showed the atrophic change on follow-up study [3]. Consequently, we consider that no definite restriction on the diffusion study in the early phase of the RSV-related encephalitis may provide evidence for the reversibility of the lesion, which is not progressed to cytotoxic edema and it is associated with favorable outcomes [4, 5]. As Dr. Donmez commented, DWI is superior to conventional MRI in detecting irreversible cytotoxic edema especially at acute phase of encephalitis. However, it may be less sensitive at later phase due to dynamic pathologic changes. It is needed to be considered and discussed at further study.

Respiratory syncytial virus-related encephalitis: magnetic resonance imaging findings with diffusion-weighted study

Dear Editor, I have read the article “Respiratory syncytial virus-related encephalitis: magnetic resonance imaging findings with diffusion-weighted study” by Park, A. et al. with interest [1]. The authors aim to describe the diffusion-weighted imaging (DWI) findings, which showed normal results. As far as I could understand, the DWI showed no increased diffusion as well as no restriction. This is interesting because apart from the prognosis, there may be either restriction due to lymphocytic infiltration which is more common or increased diffusion due to vascular congestion, generalized, or local edema in cases of encephalitis [2]. The prognosis may be poor in cases which show diffusion restriction, but good outcome can also be seen in cases with increased diffusion as well as in patients with no diffusion abnormality such as in this study group; the most important point for good prognosis is the absence of cytotoxic edema which affects gray matter neurons. Timing is important in imaging of patients with encephalitis as the pathology itself is very dynamic, especially in the pediatric group. The reason of the normal DWI may be related

Diagnostic and Prognostic Value of Multimodal MRI in Transient Ischemic Attack

The clinical diagnosis of transient ischemic attack is highly subjective, and the risk prediction after transient ischemic attack using the clinical parameters still remains unsatisfactory. We aimed to investigate the diagnostic and prognostic value of multimodal magnetic resonance imaging in transient ischemic attack patients. We prospectively performed diffusion-weighted imaging, perfusion-weighted imaging, and intracranial and extracranial magnetic resonance angiogram within 72 h of symptom onset in 162 transient ischemic attack patients defined by the classical time-based definition. Follow-up diffusion-weighted imaging was obtained three-days later in patients who did not exhibit lesions on the initial diffusion-weighted imaging. The occurrence of clinical events (transient ischemic attack or stroke) three-months after the initial transient ischemic attack was recorded, and the ABCD2 and ABCD3-I scores were calculated. The clinical and imaging parameters were compared between patients with and without initial diffusion-weighted imaging lesion, clinical events, and follow-up diffusion-weighted imaging lesions. Abnormalities were present on diffusion-weighted imaging, perfusion-weighted imaging, and magnetic resonance angiogram in 38·9%, 44·1%, and 51·9% of patients, respectively. Diffusion-weighted imaging plus perfusion-weighted imaging explained 64·8%, and the addition of magnetic resonance angiogram explained 74% of the transient ischemic attack symptoms. The initial diffusion-weighted imaging positivity was associated with longer time from symptom onset to magnetic resonance imaging examination (odds ratio, 1·039; 95% confidence interval, 1·008-1·071; P=0·013). On follow-up diffusion-weighted imaging, new lesions were found in 46·7% of the patients who initially showed normal diffusion-weighted imaging findings. Initial perfusion-weighted imaging abnormality predicted the appearance of follow-up diffusion-weighted imaging lesion (chi-square=7·774, P=0·005). During the three-months follow-up, 23 patients (14·2%) experienced subsequent transient ischemic attack (n=16) or stroke (n=7). Symptomatic magnetic resonance angiogram abnormality (odds ratio, 12·667; 95% confidence interval, 2·859-56·110; P=0·001) was the only independent factor associated with clinical events with a sensitivity of 91·3% and specificity of 54·7% (C statistics, 0·73). None with initially normal multimodal magnetic resonance imaging findings developed subsequent clinical events. Approximately three-quarter of transient ischemic attack is associated with multimodal magnetic resonance imaging abnormality. Initial perfusion-weighted imaging abnormality predicts newly developed diffusion-weighted imaging lesions, and symptomatic magnetic resonance angiogram abnormality seems to be the most important predictor for subsequent clinical events. Multimodal magnetic resonance imaging appears to be useful in assessing transient ischemic attack and predicting outcome in these patients.

Total mismatch in anterior circulation stroke patients before thrombolysis

Our aim was to estimate the prevalence of negative diffusion-weighted imaging (DWI) with total perfusion-diffusion mismatch in a large series of anterior circulation stroke patients treated with thrombolysis and to describe the characteristics of these patients. From January 2006 to December 2010, a retrospective search was made for total perfusion-diffusion (PWI-DWI) mismatch patterns on pretreatment 1.5-T MRI scans of 166 consecutive thrombolyzed patients taken<4.5 h after onset of anterior stroke. A total mismatch profile corresponded to an absence of initial DWI signal changes with hypoperfusion (T(max)>6 s) on PWI. Clinical and MRI characteristics were compared between DWI+ and DWI- patients. Five (3%) patients had a normal initial DWI. All had stable substantial clinical deficits (NIHSS scores ≥ 6) and large perfusion abnormalities - in other words, 'total mismatch' - and infarcts in the acutely hypoperfused area on follow-up imaging. While DWI- and DWI+ patients did not significantly differ in any of the pretreatment imaging or clinical variables except for the extent of PWI-DWI mismatch, DWI- patients had lower NIHSS scores at 24 h, and were more likely to show early neurological improvement (Δ0-24 h NIHSS ≥ 8) and good outcomes (mRS ≤ 2) at the time of hospital discharge. Total mismatch i.e. failure of DWI to reveal any ischemic tissue despite a large perfusion defect, can be observed before thrombolysis even in stroke patients with stable substantial neurological deficits. However, this rare MRI profile is associated with a favorable outcome after thrombolysis.

Accuracy of Diffusion-Weighted Imaging in the Diagnosis of Stroke in Patients With Suspected Cerebral Infarct

The accuracy of diffusion-weighted imaging (DWI) for the diagnosis of acute cerebral ischemia among patients with suspected ischemic stroke arriving to an emergency room has not been studied in depth. DWI was performed in 712 patients with acute or subacute focal symptoms that suggested an acute ischemic stroke (AIS), 609 of them with AIS. DWI demonstrated a sensitivity of 90% and specificity of 97%, a positive likelihood ratio of 31 and a negative likelihood ratio of 0.1 for detecting AIS. The overall accuracy was 95%. Of those patients who demonstrated abnormal DWI studies, 99.5% were AIS patients, and of those patients with normal DWI studies 63% were stroke mimics. DWI is accurate in detecting AIS in unselected patients with suspected AIS; a negative study should alert for nonischemic conditions.

Clinical Use of Computed Tomographic Perfusion for the Diagnosis and Prediction of Lesion Growth in Acute Ischemic Stroke

Computed tomography perfusion (CTP) mapping in research centers correlates well with diffusion-weighted imaging (DWI) lesions and may accurately differentiate the infarct core from ischemic penumbra. The value of CTP in real-world clinical practice has not been fully established. We investigated the yield of CTP-derived cerebral blood volume (CBV) and mean transient time (MTT) for the detection of cerebral ischemia and ischemic penumbra in a sample of acute ischemic stroke (AIS) patients. We studied 165 patients with initial clinical symptoms suggestive of AIS. All patients had an initial noncontrast head CT, CTP, CT angiogram (CTA), and follow-up magnetic resonance imaging (MRI) of the brain. The obtained perfusion images were used for image processing. CBV, MTT, and DWI lesion volumes were visually estimated and manually traced. Statistical analysis was conducted using R and SAS software. All normal DWI sequences had normal CBV and MTT studies (N=89). Seventy-three patients had acute DWI lesions. CBV was abnormal in 23.3% and MTT was abnormal in 42.5% of these patients. There was a high specificity (91.8%) but poor sensitivity (40.0%) for MTT maps predicting positive DWI. The Spearman correlation was significant between MTT and DWI lesions (ρ=0.66; P>.0001) only for abnormal MTT and DWI lesions >0 cc. CBV lesions did not correlate with final DWI. In real-world use, acute imaging with CTP did not predict stroke or DWI lesions with sufficient accuracy. Our findings argue against the use ofCTP for screening AIS patients until real-world implementations match the accuracy reported from specialized research centers.

Concurrent acute brain infarcts in patients with monocular visual loss

Embolism from a proximal source to the retinal circulation could be a sign of embolism from the same source to the hemispheric circulation. We sought to determine the frequency of acute brain infarcts on diffusion-weighted imaging (DWI) in patients with monocular visual loss of presumed ischemic origin (MVL). We retrospectively studied 129 consecutive patients with MVL secondary to retinal ischemia. All patients underwent DWI, comprehensive ophthalmologic and neurologic examination, and diagnostic evaluations for the underlying etiology. Statistical analyses explored univariate and multivariate predictors of DWI evidence of acute brain infarcts. DWI revealed concurrent acute brain infarct(s) in 31 of the 129 patients (24%). The probability of positive DWI was higher in embolic versus nonembolic MVL (28 vs 8%, p = 0.04), in MVL characterized by permanent visual loss versus transient symptoms (33 vs 18%, p = 0.04), and in MVL associated with concurrent hemispheric symptoms versus isolated MVL (53 vs 20%, p < 0.01). Patients with positive DWI were more likely to harbor a major underlying etiology as compared to those with normal DWI (odds ratio, 3.7; 95% confidence interval, 1.5-9.4). This study demonstrates that MVL does not always represent an isolated disease of the retina; approximately 1 of every 4 patients with MVL demonstrates acute brain infarcts on DWI. Because patients with concurrent brain infarcts are more likely to exhibit a cardiac or vascular source of embolism, imaging evidence of brain injury in patients with MVL may be a useful marker to guide the timing and extent of diagnostic examinations.