Utilidad de la resonancia magnética en el diagnóstico del stroke agudo / Usefulness of magnetic resonance imaging in the diagnosis of acute stroke

Resumen El ataque cerebrovascular (ACV) es la primera causa de discapacidad y la tercera causa de muerte en la Argentina y en el mundo. La etiología del stroke es isquémica en su mayoría (más del 80% de los casos), siendo las causas más frecuentes las lesiones isquémicas de pequeños vasos de tipo lacunar y las tromboembólicas debido a ateroesclerosis de grandes arterias o cardioembolia. Las secuencias utilizadas en nuestro protocolo de estudio incluyen DWI, FLAIR, angio-RM 3D-TOF, SWI y FSE-T1 (tiempo aproximado de exploración de 13 minutos). Pueden observarse diferentes hallazgos en cada una de estas secuencias que son orientativos para determinar la etiología subyacente y estimar el tiempo de evolución de la lesión. En la actualidad, la trombectomía mecánica se ha convertido en el tratamiento de elección en pacientes seleccionados con accidente cerebral isquémico agudo. La transformación hemorrágica es la complicación más temida luego de la terapia de reperfusión intraarterial. La técnica de difusión de la resonancia magnética (RM) posee una mayor sensibilidad para detectar lesiones isquémicas, permite sospechar la etiología según el patrón lesional y aporta información valiosa para la selección de los pacientes candidatos a la reperfusión arterial.

Abstract Stroke or cerebrovascular attack (CVA) is the first cause of disability and the third cause of death in Argentina and in the world. The etiology of strokes is mostly ischemic (more than 80% of cases), with the most frequent causes being lacunar-type ischemic lesions of small vessels and thromboembolic lesions due to atherosclerosis of large arteries or cardioembolism. The sequences used in our study protocol include DWI, FLAIR, angio-RM 3D-TOF, SWI, and FSE-T1 (approximate scan time of 13 minutes). Different findings can be observed in each of these sequences that are indicative to determine the underlying etiology and estimate the time of evolution of the lesion. Currently, mechanical thrombectomy has become the treatment of choice in selected patients with acute ischemic stroke. Hemorrhagic transformation is the most feared complication after intra-arterial reperfusion therapy. The diffusion magnetic resonance technique is more sensitive for detecting ischemic lesions, allows one to suspect the etiology based on the lesion pattern, and provides valuable information for the selection of patients who are candidates for arterial reperfusion.

Probabilistic Tractography Between Nucleus Accumbens and Other Reward-related Brain Areas in Malay Female Adolescents

@#Introduction: Studies show that adolescents are more reward sensitive compared to other age groups. The nucleus accumbens (NAcc) has been identified as a key brain area involved in reward through its connectivity to other reward-related brain areas. Our study aimed to characterise the white matter structural connectivity of nucleus accumbens with brain areas that are most often associated with reward in female adolescents. Methods: Fifteen healthy female Malay adolescents were recruited and underwent diffusion-weighted brain scanning. Two behaviour scales were also given to verify typical reward responsiveness. Then, probabilistic tractography and NAcc segmentation were performed on the data using FMRIB Software Library (FSL). Probabilistic tractography was performed to determine the relative connection probability of nucleus accumbens (NAcc) to areas shown to be associated with reward, namely amygdala, anterior cingulate cortex (ACC), medial orbitofrontal cortex (mOFC), hippocampus, ventrolateral prefrontal cortex (vlPFC) and dorsolateral prefrontal cortex (dlPFC). Connectivity-based segmentation of NAcc was performed to determine the spatial distribution of its connectivity with the target brain areas according to the highest connection probability. Results: The highest relative connection probability was found between NAcc to mOFC, while the NAcc parcellation showed the widest distribution of connection to mOFC compared to the other five targets on both sides of the brain. Conclusion: Our findings demonstrated the strongest structural connectivity and widest distribution between NAcc and mOFC compared with other brain areas related to reward. This study’s findings could be used as baseline to compare with people with atypical reward circuit problems.

Evaluation of the association between silent ischemic lesions and stent design in carotid stenting applications

SUMMARY OBJECTIVE: Minor ischemic events and silent ischemic lesions are more common in carotid stenting than in endarterectomy. These silent ischemic lesions are also associated with stroke risk and cognitive impairment, so it is important to understand the factors that increase the risk and develop strategies to reduce the risk. We aimed to evaluate the association between carotid stent design and silent ischemic lesion development. METHODS: The files of the patients who underwent carotid stenting between January 2020 and April 2022 were scanned. Patients with diffusion MR images taken within the postoperative 24 h were included in the study, while those undergoing acute stent placement were excluded. The patients were divided into two groups: those with open-cell stents and those with closed-cell stents. RESULTS: A total of 65 patients, including 39 patients undergoing open-cell stenting and 26 patients undergoing closed-cell stenting, were included in the study. There was no significant difference in demographic data and vascular risk factors between the groups. New ischemic lesions were detected in 29 (74.4%) patients in the open-cell stent group and 10 (38.4%) patients in the closed-cell stent group and were significantly higher in the open-cell group. There was no significant difference between the two groups in terms of major and minor ischemic events and stent restenosis at the 3-month follow-up. CONCLUSION: The rate of new ischemic lesion development was found to be significantly higher in carotid stent procedures performed with an open-cell Protégé stent than in those performed with a closed-cell Wallstent stent.

The Role of Double Inversion Recovery Imaging in Acute Ischemic Stroke

PURPOSE: The purpose of this study was to investigate if double inversion recovery (DIR) imaging can have a role in the evaluation of brain ischemia, compared with diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) imaging. MATERIALS AND METHODS: Sixty-seven patients within 48 hours of onset, underwent MRI scans with FLAIR, DWI with b-value of 0 (B0) and 1000 s/mm², and DIR sequences. Patients were categorized into four groups: within three hours, three to six hours, six to 24 hours, and 24 to 48 hours after onset. Lesion-to-normal ratio (LNR) value was calculated and compared among all sequences within each group, by the Friedman test and conducted among all groups, for each sequence by the Kruskal-Wallis test. In qualitative assessment, signal intensity changes of DIR, B0, and FLAIR based on similarity with DWI and image quality of each sequence, were graded on a 3-point scale, respectively. Scores for detectability of lesions were compared by the McNemar's test. RESULTS: LNR values from DWI were higher than DIR, but not statistically significant in all groups (P > 0.05). LNR values of DIR were significantly higher than FLAIR within 24 hours of onset (P < 0.05). LNR values were significantly different between, before, and after six hours onset time for DIR (P = 0.016), B0 (P = 0.008), and FLAIR (P = 0.018) but not for DWI (P = 0.051). Qualitative analysis demonstrated that detectability of DIR was higher, compared to that of FLAIR within 4.5 hours and six hours of onset (P < 0.05). Also, the DWI quality score was lower than that of DIR, particularly relative to infratentorial lesions. CONCLUSION: DIR provides higher detectability of hyperacute brain ischemia than B0 and FLAIR, and does not suffer from susceptibility artifact, unlike DWI. So, DIR can be used to replace evaluation of the FLAIR-DWI mismatch.

Assessment of Cervical Cancer with a Parameter-Free Intravoxel Incoherent Motion Imaging Algorithm

OBJECTIVE: To evaluate the feasibility of a parameter-free intravoxel incoherent motion (IVIM) approach in cervical cancer, to assess the optimal b-value threshold, and to preliminarily examine differences in the derived perfusion and diffusion parameters for different histological cancer types. MATERIALS AND METHODS: After Institutional Review Board approval, 19 female patients (mean age, 54 years; age range, 37–78 years) gave consent and were enrolled in this prospective magnetic resonance imaging study. Clinical staging and biopsy results were obtained. Echo-planar diffusion weighted sequences at 13 b-values were acquired at 3 tesla field strength. Single-sliced region-of-interest IVIM analysis with adaptive b-value thresholds was applied to each tumor, yielding the optimal fit and the optimal parameters for pseudodiffusion (D*), perfusion fraction (F(p)) and diffusion coefficient (D). Monoexponential apparent diffusion coefficient (ADC) was calculated for comparison with D. RESULTS: Biopsy revealed squamous cell carcinoma in 10 patients and adenocarcinoma in 9. The b-value threshold (median [interquartile range]) depended on the histological type and was 35 (22.5–50) s/mm² in squamous cell carcinoma and 150 (100–150) s/mm² in adenocarcinoma (p < 0.05). Comparing squamous cell vs. adenocarcinoma, D* (45.1 [25.1–60.4] × 10⁻³ mm²/s vs. 12.4 [10.5–21.2] × 10⁻³ mm²/s) and F(p) (7.5% [7.0–9.0%] vs. 9.9% [9.0–11.4%]) differed significantly between the subtypes (p < 0.02), whereas D did not (0.89 [0.75–0.94] × 10⁻³ mm²/s vs. 0.90 [0.82–0.97] × 10⁻³ mm²/s, p = 0.27). The residuals did not differ (0.74 [0.60–0.92] vs. 0.94 [0.67–1.01], p = 0.32). The ADC systematically underestimated the magnitude of diffusion restriction compared to D (p < 0.001). CONCLUSION: The parameter-free IVIM approach is feasible in cervical cancer. The b-value threshold and perfusion-related parameters depend on the tumor histology type.

The Effect of Pulsatility Index on Infarct Volume in Acute Lacunar Stroke

PURPOSE: Lacunar stroke, in the context of small vessel disease, is a type of cerebral infarction caused by occlusion of a penetrating artery. Pulsatility index (PI) is an easily measurable parameter in Transcranial Doppler ultrasound (TCD) study. PI reflects distal cerebral vascular resistance and has been interpreted as a surrogate marker of small vessel disease. We hypothesized that an increased PI, a marker of small vessel disease, might be associated with a larger infarct volume in acute lacunar stroke. MATERIALS AND METHODS: This study included 64 patients with acute lacunar stroke who underwent TCD and brain MRI. We evaluated the association between the mean PI value of bilateral middle cerebral arteries and infarct volume on diffusion-weighted MRI using univariate and multivariate linear regression. RESULTS: The mean infarct volume and PI were 482.18±406.40 mm3 and 0.86±0.18, respectively. On univariate linear regression, there was a significant positive association between PI and infarct volume (p=0.001). In the multivariate model, a single standard deviation increase of PI (per 0.18) was associated with an increase of 139.05 mm3 in infarct volume (95% confidence interval, 21.25 to 256.85; p=0.022). CONCLUSION: We demonstrated that PI was an independent determinant of infarct volume in acute lacunar stroke. The PI value measured in acute stroke may be a surrogate marker of the extent of ischemic injury.

Usefulness of Diffusion Tensor Tractography in Pediatric Epilepsy Surgery

PURPOSE: This study was conducted to assess the clinical relevance of diffusion tensor tractography (DTT) in pre- and post-operative evaluations of childhood epilepsy surgery. MATERIALS AND METHODS: Seventy-two patients who received epilepsy surgery between March 2004 and July 2008 were retrospectively analyzed (M : F=40 : 32, ages of 3 months to 24 years, mean age=8.9 years). DTT was performed using a 3.0 T scanner and single-shot spin-echo echo-planar imaging with 32-different diffusion gradient directions. We reviewed the data focusing on the type of surgery, final pathological diagnosis, and how the DTT data were clinically used. RESULTS: The most common form of childhood epilepsy surgery was complete resection of an epileptogenic lesion (n=52, 72.2%). The reported etiologies included cortical dysplasia (n=32, 44.4%), hippocampal sclerosis (n=9, 12.5%), brain tumors (n=7, 9.7%), and non-pathologic lesions (n=4, 5.6%) in the final diagnoses. Twenty-one dysplastic cortexes and four brain tumors involved an approximal relationship with the corticospinal tract (n=18), optic radiation (n=2), and arcuate fasciculus (n=5). Additionally, although DTT demonstrated white matter tracts clearly, DTT in the hippocampal sclerosis did not provide any additional information. In cases of callosotomy (n=18, 25%), post-operative DTT was utilized for the evaluation of complete resection in all patients. DTT information was not used in functional hemispherectomy (n=2, 2.8%). CONCLUSION: Preoperatively, DTT was a useful technique in cases of cortical dysplasia and brain tumors, and in cases with callosotomy, postoperatively. DTT should be included among the routine procedures performed in management of epilepsy.

Acute Spinal Cord Infarction: Diffusion-Weighted MR Imaging: Case Report

STUDY DESIGN: A case report. OBJECTIVE: We present a rare case of acute spinal cord infarction and usefulness of diffusion weighted MR imaging. SUMMARY OF LITERATURE REVIEW: T1-weighted and T2-weighted images are often normal in a patient with acute spinal cord infarction. MATERIAL AND METHODS: An 82-year-old presented with acute onset of paraplegia and urinary retention. His symptoms developed 6 days ago without any trauma. He had a history of vertebroplasty due to compression fracture of 12th thoracic vertebral body 6 years ago. There was no evidence of spinal cord compression on routine T1-and T2-weighted MRI. RESULTS: In diffusion-weighted MRI, a high intensity signal intensity lesion in the spinal cord and conus medullaris was observed. CONCLUSION: We report an example for the usefulness of diffusion-weighted image for early and accurate diagnosis of acute spinal cord infarction.

Can Early Ischemic Lesion Recurrence on Diffusion-Weighted MRI Affect Functional Outcome after Acute Ischemic Stroke?

BACKGROUND AND PURPOSE: Ischemic lesion recurrence on diffusion-weighted imaging (DWI-LR) is a frequently observed phenomenon after acute ischemic stroke. However, no study has elucidated the impact of DWI-LR on functional outcome. METHODS: Among a consecutive series of patients who presented with focal symptoms or signs compatible with stroke within 48 hours from the onset over a 50-month period, those who had relevant ischemic lesions on initial DWI and underwent follow-up DWI within 14 days after the onset were enrolled in this study. As outcome variables, the scores on the modified Rankin Disability Scale (mRDS) at 3 months and 1 year were measured prospectively and dichotomized into good (0-2) vs. poor (3-6). When calculating odds ratios (ORs), adjustment was performed for age, previous stroke, initial score on the NIH Stroke Scale, stroke subtype, and IV thrombolysis. RESULTS: Among those 786 patients finally enrolled in this study, 221 (28.1%) had DWI-LR. For a poor outcome at 3 months, the crude ORs of any, symptomatic, and asymptomatic DWI-LR were 2.70 [95% confidence interval (CI), 1.96 to 3.72], 10.03 (95% CI, 4.39 to 22.96), and 2.04 (95% CI, 1.44 to 2.88), respectively. With adjustment, the OR of symptomatic DWI-LR was 6.44 (95% CI, 2.50 to 16.57), whereas those of any and asymptomatic DWI-LR lost their statistical significance: 1.44 (95% CI, 0.94 to 2.20) and 1.04 (95% CI, 0.65 to 1.65), respectively. Analyzing with the 1-year outcome produced similar results. CONCLUSIONS: This study shows that symptomatic early lesion recurrence can affect functional outcome after acute ischemic stroke, whereas an asymptomatic one may not.

A Case of Encephalitis with a Reversible Splenial Lesion on a Diffusion Weighted MRI Image

Reversible splenial lesion may occur in encephalitis rarely. A 21-year-old man was admitted with viral encephalitis. High signal on the diffusion MRI and low signal on the ADC map image was showed in the splenium. As the patient improved, the lesion suggestive of cytotoxic edema was completely resolved one month later. Although the concrete pathophysiology of focal cytotoxic edema in encephalitis is unclear yet, MRI is valuable diagnostic tool to manage encephalitis in the view of prognosis.

Neuroendovascular Therapy-Current Technical Advancement / 대한뇌혈관학회지

This article surveys current technical advancement in neuroendovascular therapy. The technical advancement happens not only in the field of products of microcatheter and guide wire but in the field of diagnosis. In the local intraarterial fibrinolysis, diffusion weighted MR imaging allows us more precise patient selection. In the atherosclerotic lesions, stent is clinically available. Some types of stent can be used in intracranial arteries. In the acutely ruptured aneurysm, intraanerysmal embolization using Guglielmi detachable coil followed by intratechal tissue-type plasminogen activator reduced occurring rate of vasospasm. In the wide neck aneurysm, neck plasty technique brings us better results. Neuroendovascular therapy is still evolving supported by such technical advancement.

Comparison of Perfusion- and Diffusion-weighted MRI in Acute Ischemic Stroke

BACKGROUND: Perfusion imaging (PI) of magnetic resonance imaging (MRI) uses the signal loss that occurs during dynamic tracking of the first pass of intravenous paramagnetic contrast agent. Then different hemodynamic measurements can be calculated and displayed as perfusion maps. Diffusion-weighted imaging (DWI) measures diffusional movement of water molecules within the brain and it can identify acute ischemic injury or cytotoxic edema. We evaluated clinical usefulness of PI and DWI in acute ischemic stroke. METHODS: Fifteen patients with clinical diagnosis of acute cerebral infarction were imaged with PI, DWI, and magnetic resonance angiogram (MRA) including FLAIR within 24 hours after onset. Comparisons were made between infarct volumes measured by DWI and PI using the parameters including relative mean transit time (rMTT) map, relative cerebral blood volume (rCBV) map, and relative cerebral blood flow (rCBF) map. RESULTS: Two patterns were found. rMTT map in PI lesion is larger than in the DWI lesion (n=7/15), and rMTT map in PI lesion is the same size or smaller than in DWI lesion (n=8/15). The former pattern was shown in cases with severe stenosis or occlusion of the major cerebral artery (MCA, PCA, or ICA) on MRA. The majority of latter pattern was lacunes (n=6/8). Also, we found presence of infarction cores surrounded by hypoperfused areas in rMTT map in acute largearterial territorial infarction. CONCLUSIONS: Perfusion- and Diffusion- weighted MRIs may be useful in differentiating large-arterial territorial infarction from lacunes.