This study aimed to evaluate potential posttreatment changes in ADC values within the tissue surrounding the enhancing lesion, particularly in areas not exhibiting MRI characteristics of involvement. Additionally, the objective was to investigate the correlations among ADC values, treatment response, and survival outcomes in individuals diagnosed with gliomas. This retrospective study included a total of 49 patients that underwent either stereotactic biopsy or maximal surgical resection. Histologically confirmed as Grade III or IV gliomas, all cases adhered to the 2016 and 2021 WHO classifications, with subsequent radio-chemotherapy administered post-surgery. Patients were divided into two groups: short and long survival groups. Baseline and follow-up MRI scans were obtained on a 1.5 T MRI scanner. Two ROI circles were positioned near the enhancing area, one ROI in the NAWM ipsilateral to the neoplasm and another symmetrically in the contralateral hemisphere on ADC maps. At follow-up there was a significant difference in both ipsilateral and contralateral NAWM between the two groups, −0.0857 (p = 0.004) and −0.0607 (p = 0.037), respectively. There was a weak negative correlation between survival and ADC values in ipsilateral and contralateral NAWM at the baseline with the correlation coefficient −0.328 (p = 0.02) and −0.302 (p = 0.04), respectively. The correlation was stronger at the follow-up. The findings indicate that ADC values in normal-appearing white matter (NAWM) may function as a prognostic biomarker in patients with diffuse gliomas.

BACKGROUND:Virtual monoenergetic (VM) dual-energy computed tomography (DE-CT) enables grey-to-white matter contrast-to-noise ratio optimization, potentially increasing ischaemic brain oedema visibility. The aim of this study was to compare the diagnostic accuracy of VM and standard DE-CT reconstructions for early stroke detection.METHODS:Consecutive patients with non-contrast DE-CT of the brain scanned within 12 h of stroke symptom onset were prospectively included in the study. Patients with other significant brain pathology were excluded. Two radiologists jointly evaluated standard and VM reconstructions (from 40 to 190 keV at increments of 10 keV) for early stroke signs on a four-point Likert scale: (a) stroke definitely present, (b) stroke probably present, (c) probably no stroke, and (d) definitely no stroke. Follow-up imaging and clinical data served as the standard of reference. Diagnostic accuracy was evaluated by receiver operating characteristic analysis.RESULTS:Stroke incidence among 184 patients was 76%. In 64 patients follow-up imaging served as the standard of reference: ischemic brain oedema detection was significantly more accurate on VM reconstructions at 80 keV compared with standard DE-CT reconstructions (area under the curve (AUC) = 0.821 vs. AUC = 0.672, p = 0.002). The difference was most prominent within the first 3 h after symptom onset (at 11%, AUC = 0.819 vs. AUC = 0.709, p = 0.17) and in patients with National Institutes of Health Stroke Scale above 16 (at 37.5%, AUC = 1 vs. AUC = 0.625, p = 0.14).CONCLUSION:VM DE-CT reconstructions at 80 keV appear to be the optimal non-contrast CT technique for diagnosing early ischaemic stroke, particularly within the first 3 h after symptom onset and in severely ill patients.

Purpose Weighted average dual-energy computed tomography (DE-CT) reconstructions are considered a proxy of standard CT images of the brain, recommended for routine clinical use and used as a reference standard in DE-CT research. However, their image quality has not been assessed, which was the aim of our study. Methods Images from 81 consecutive patients who underwent both non-contrast single-energy (SE)-CT and DE-CT of the brain on the same scanner were retrospectively evaluated. Attenuation values (HU) and SD of grey matter/white matter (GM/WM) pairs, along with SD in the posterior fossa and subcalvarial region were measured. Four readers evaluated image noise, GM/WM contrast, posterior fossa and subcalvarial artefacts, as well as overall image quality. Results Weighted average DE-CT GM and WM HU were significantly lower and noise higher compared to SE-CT (GM HU 36.46 v. 41.82; WM HU 28.18 v. 29.94; GM SD 2.93 v. 2.49; and WM SD 3.16 v. 2.44, all p < 0.0001). After correcting the measured SE-CT noise for 37% higher acquisition dose, DE-CT GM noise became significantly lower (2.93 v. 3.11, p = 0.0121). Measured and dose corrected SE-CT GM/WM contrast-to-noise ratio was superior to weighted average DE-CT (3.42 and 2.74 v. 1.95, both p < 0.0001). Weighted average DE-CT had significantly less artifacts on qualitative analysis. Conclusion Weighted average DE-CT images of the brain yield less artefacts at 37% dose reduction and lower noise at SE-CT equivalent dose. Dose-adjusted GM/WM contrast-to-noise ratio of weighted average DE-CT with 0.4 weighting factor remains inferior to SE-CT images.

CADASIL (Cerebral Autosomal Dominant Arteriopathy with Sub-cortical Infarcts and Leukoencephalopathy) is an inherited form of cerebrovascular disease that occurs when the thickening of blood vessel walls blocks the flow of blood to the brain. T he disease primarily affects small blood vessels in the white matter of the brain. A mutation in the Notch3 gene alters the muscular walls in these small arteries. CADASIL is characterized by migraine headaches and multiple strokes progressing to dementia. Other symptoms include cognitive deterioration, seizures, vision problems, and psychiatric problems such as severe depression and changes in behavior and personality. Individuals may also be at higher risk of heart attack. Symptoms and disease onset vary widely, with signs typically appearing in the mid-30s. Some individuals may not show signs of the disease until later in life. CADASIL — formerly known by several names, including hereditary multi-infarct dementia — is one cause of vascular cognitive impairment (dementia caused by lack of blood to several areas of the brain). It is an autosomal dominant inheritance disorder, meaning that one parent carries and passes on the defective gene. Most individuals with CADASIL have a family history of the disorder. However, because the genetic test for CADASIL was not available before 2000, many cases were misdiagnosed as multiple sclerosis, Alzheimer's disease, or other neurodegenerative diseases. Qeios · Definition, November 11, 2019

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Preoperative identification of high-grade gliomas is critical to optimize treatment strategy and to predict prognosis. To determine whether perilesional apparent diffusion coefficient (ADC) values differ between highand low-grade tumors, we assessed water diffusivity within normal-appearing brain parenchyma (NABP) surrounding gliomas in twenty-one treatment-naive patients. This showed significantly lower mean and 25th percentile (Q1) ADC values in high- grade compared to low-grade gliomas respectively in the range of 10-25 and 10-30 mm away from combined tumor and surrounding T2 signal. Thus, perilesional ADC measurement may reflect the extent of tumor infiltration beyond the abnormality seen on conventional MRI.

The purpose of this study was to quantify how changing the amount of radiation used to perform routine head CT examinations (CTDIvol) affects visibility of key anatomical structures. Eight routine noncontrast head CT exams were selected from six CT scanners, each of which had a different CTDIvol setting (60 to 75 mGy). All exams were normal and two slices were selected for evaluation, one at the level of basal ganglia and the other at the fourth ventricle. Three experienced neuroradiologists evaluated the visibility of selected structures, including the putamen, caudate nucleus, thalamus, internal capsule, grey/white differentiation, and brainstem. Images were scored on a five-point scoring scheme (1, unacceptable, 3, satisfactory, and 5, excellent). Reader scores, averaged over the cases obtained from each scanner, were plotted as a function of the corresponding CTDIvol. Average scores for the fourth ventricle were 3.06 ± 0.83 and for the basal ganglia were 3.20 ± 0.86. No image received a score of 1. Two readers showed no clear trend of an increasing score with increasing CTDIvol. One reader showed a slight trend of increasing score with increasing CTDIvol, but the increase in score from a 25% increase in CTDIvol was a fraction of the standard deviation associated average scores. Collectively, results indicated that there were no clear improvements in visualizing neuroanatomy when CTDIvol increased from 60 to 75 mGy in routine head CT examinations. Our study showed no apparent benefit of using more than 60 mGy when performing routine noncontrast head CT examinations.

Background The evaluation of children with suspected ventriculoperitoneal shunt (VPS) malfunction has evolved into a diagnostic dilemma. This patient population is vulnerable not only to the medical risks of hydrocephalus and surgical complications but also to silent but harmful effects of ionizing radiation secondary to imaging used to evaluate shunt efficacy and patency. The combination of increased medical awareness regarding ionizing radiation and public concern has generated desire to reduce the reliance on head computed tomography (CT) for the evaluation of VPS malfunction. Many centers have started to investigate the utility of low-dose CT scans and alternatives, such as fast magnetic resonance imaging for the investigation of VP shunt malfunction in order to keep radiation exposure as low as reasonably achievable. This pilot study hopes to add to the armamentarium available to the clinician charged with evaluating this challenging patient population by testing the feasibility of a limited CT protocol as an alternative to a full head CT examination. Objective To evaluate the efficacy of a limited head CT protocol compared with a complete head CT for the evaluation of children presenting to the pediatric emergency department with suspected shunt malfunction. Methods We retrospectively reviewed all pediatric patients who received a head CT for suspected VPS malfunction evaluation at a tertiary care children's hospital from January 2001 through January 2013. Children were included in the pilot study if they had at least 2 CT scans in this study period interpreted by a specific senior attending neuroradiologist. For each patient enrolled, a limited series was generated from the most recent CT scan by selecting four representative axial slices based on the sagittal scout image. These 4 slices where selected at the level of the fourth ventricle, third ventricle, basal ganglia level, and lateral ventricles, respectively. A blinded, senior attending neuroradiologist first reviewed the limited 4-slice CT data set and was asked to determine if the ventricular system had increased, decreased, or remained stable. Subsequently, the neuroradiologist compared their interpretation of the limited examination with the official report from the full CT data set as the standard of reference as well as the interpretation of the most recent prior scan. Results Forty-six patients (age range, 2 months to 18 years; average age, 6.4 years (SD, 4.2), 54% male) were included in the study. Forty-four of 46 (95.7%) limited CT scans matched the official report of the full CT scan. No cases of increased ventricular size were missed (100% positive predictive value for increased ventricular size). The use of a limited head CT (4 axial images) instead of a complete head CT (average of 31 axial images in our studied patients) confers a radiation dose reduction of approximately 87%. Conclusions Our pilot study demonstrates that utilization of limited head CT scan in the evaluation of children with suspected VP shunt malfunction is a feasible strategy for the evaluation of the ventricular size. Further prospective and multidisciplinary studies are needed to evaluate the reliability of limited head CT for the clinical evaluation of VP shunt malfunction.

Background: Intracranial atherosclerosis is a leading cause of stroke, but little is known about the composition of the intracranial atherosclerotic lesion and how intracranial plaque morphology is related to the risk of stroke. High-resolution magnetic resonance imaging (HR MRI) has been used in patients with extracranial carotid atherosclerosis as an invivo tool to identify, with high-interrater agreement, histologically defined plaque components (i.e., intraplaque hemorrhage, fibrous cap, and lipid core), which have been shown to be predictors of recurrent stroke. With careful imaging the components ofatherosclerotic plaque can be visualized in the intracranial arteries using HRMRI, but there are no reports of reproducibility or interrater reliability. Methods/Study design: The Characterization of intracranial atherosclerotic stenosis using high-resolution MRI (CHIASM) study is a single-center NIH-funded prospective observational study, to (1) demonstrate high -interrater agreement for identifying intracranial plaque components on HR MRI, (2) determine the frequency of these components in symptomatic versus asymptomatic plaques, and (3) estimate the 1-year rate of stroke in the territory of high-risk plaque components. CHIASM will recruit 90 patients with 50-99% intracranial atherosclerosis to undergo HRMRI of the intracranial artery plaque at enrollment and 1-year follow-up. Both symptomatic and asymptomatic subjects will be recruited. Conclusion: Determination of good interrater reliability is an important first step in the development of HR MRI as a tool to predict risk in patients with intracranial atherosclerosis. This study will inform the design of future multicenter studies to determine the prevalence and prognosis of intracranial atherosclerotic plaque components. Such studies could lead to new understanding of the pathophysiological mechanisms of cerebral ischemia in patients with atherosclerotic intracranial stenosis, improvements in risk stratification, and potentially to new treatments of this common and serious disease.

IMPORTANCE Intracranial arterial stenosis (ICAS) and small vessel disease (SVD) may coexist. There are limited data on the frequency and risk factors for coexistent SVD and the effect of SVD on stroke recurrence in patients receiving medical treatment for ICAS. OBJECTIVE To investigate the frequency and risk factors for SVD and the effect of SVD on stroke recurrence in patients with ICAS. DESIGN, SETTING, AND PARTICIPANTS A post hoc analysis of the Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) study, a prospective, multicenter clinical trial. Among 451 participants, 313 (69.4%) had baseline brain magnetic resonance imaging scans read centrally for SVD that was defined by any of the following: old lacunar infarction, grade 2 to 3 on the Fazekas scale (for high-grade white matter hyperintensities), or microbleeds. Patient enrollment in SAMMPRIS began November 25, 2008, and follow-up ended on April 30, 2013. Data analysis for the present study was performed from May 13, 2014, to July 29, 2015. MAIN OUTCOMES AND MEASURES Risk factors in patients with vs without SVD and the association between SVD and other baseline risk factors with any ischemic stroke and ischemic stroke in the territory of the stenotic artery determined using proportional hazards regression. RESULTS Of 313 patients, 155 individuals (49.5%) had SVD noted on baseline magnetic resonance imaging. Variables that were significantly higher in patients with SVD, reported as mean (SD), included age, 63.5 (10.5) years (P < .001), systolic blood pressure, 149 (22) mm Hg (P < .001), glucose level, 130 (50) mg/dL (P = .03), and lower Montreal Cognitive Assessment scores (median, ≥24 [interquartile range, 20-26]; P = .02).Other significant variables were the number of patients with diabetes mellitus (88 of 155 [56.8%]; P = .003), coronary artery disease (46 [29.7%]; P = .004), stroke before the qualifying event (59 [38.1%]; P < .001), old infarct in the territory of the stenotic intracranial artery (88 [56.8%]; P < .001), and receiving antithrombotic therapy at the time of the qualifying event (109 [70.3%]; P = .005). The association between SVD and any ischemic stroke was nearly significant in the direction of a higher risk (18 [23.7%]); P = .07) for patients with SVD. On bivariate analysis, SVD was not associated with an increased risk on multivariable analyses (hazard ratio, 1.7 [95% CI, 0.8-3.8]; P = .20). In addition, SVD was not associated with an increased risk of stroke in the territory on either bivariate or multivariable analyses. CONCLUSIONS AND RELEVANCE Although SVD is common in patients with ICAS, the presence of SVD on baseline magnetic resonance imaging is not independently associated with an increased risk of stroke in patients with ICAS. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00576693.

The submandibular gland is one of the most frequently affected salivary gland in IgG4-related systemic disease, usually demonstrate homogeneous attenuation on CT imaging as reported, but without much pathological comparison of many cases. This article is to investigate and analyze the typical CT findings and pathologic characteristics of IgG4-related systemic disease (IgG4-RSD) of submandibular gland. A retrospective analysis of the preoperative CT findings in patients with IgG4-RSD of submandibular glands who underwent surgical resection between January 2010 and February 2014 was performed. Twenty patients (16 women) were identified, with a mean age of 58.1±10.2 years. All patients presented with painless submandibular gland swelling. Diffuse gland enlargement, with clear margins and homogeneous density, was found on non-enhanced CT scans in all cases. There were no calcifications or stones within the involved glands. Based on contrast-enhanced CT appearance the patients could be divided into two groups: 11 cases showed homogeneous gland enhancement; and multiple hyperenhancing foci, with a crazy-paving pattern, were detected in 9 cases, which were in consistent with the pathologic findings. The maximum submandibular gland diameter on transverse images was significantly larger (P=0.008) in patients with crazy-paving appearance (32±4 mm) compared to patients with homogeneous enhancement (28±3 mm). It is concluded that the submandibular glands with IgG4-RSD can be characterized by either homogenous appearance or crazy-paving pattern on contrast-enhanced CT imaging.

Congenital anomalies are important to consider in the differential of head and neck masses in children. These lesions can present as palpable cystic masses, draining sinuses, or fistulae. Thyroglossal duct cysts are most common, followed by branchial cleft anomalies and dermoid cysts. Lymphatic malformations are typically found in the posterior neck and may not respect the fascial planes. Other vascular malformations can be differentiated based on their US, MRI, and CT features. Hemangiomas are by far the most common pediatric neck neoplasms, with teratomas and nerve sheath tumors as the other common benign masses. Head and neck malignancy is rare in children, with lymphomas, rhabdomyosarcomas, and carcinomas occurring in decreasing frequency. CTand MR imaging are excellent modalities for detection of deep-space infections; however they are not very reliable for the distinction between abscesses and inflammatory mass (cellulitis). The pediatric airway is primarily assessed by endoscopy, while imaging may offer additional information when needed, including virtual endoscopy. External and internal laryngotracheal trauma is best assessed with CT, which plays an increasingly important role in patient management. Dedicated lower-dose pediatric CT protocols and newer low-dose scanners are valuable in minimizing radiation exposure. Practical Embryology of the Neck The anatomic structures of the neck are predominantly derived from the branchial (pharyngeal) apparatus, which consists of paired arches, clefts, pouches, and membranes (Fig. 1). The branchial arches are the embryologic precursors of the ear and the muscles, blood vessels, bones, cartilage, and mucosal lining of the face, neck, and pharynx. Five pairs of arches form on either side of the pharyngeal foregut, in a craniocaudal sequence, from day 22 to 29 of the embryological development; they correspond to the primitive vertebrate gill bars (branchial arches) 1, 2, 3, 4, and 6. Arch 5 either never forms or promptly degenerates in humans. Each arch is composed of a central core of mesoderm, lined externally by ectoderm and internally by endoderm, and contains a central cartilage, muscle element, an arch-specific cranial nerve that innervates the muscle, and an aortic arch artery. The surface ectoderm invaginates between the arches, creating four pairs of branchial clefts (or grooves), which are apposed by branchial pouches, formed by foregut endoderm evaginations. Therefore, the first and the second pharyngeal arches are separated by the first clefts and pouches, the second and the third arches by the second clefts and pouches, and so on. In fish, this process leads to gill slits, which never become perforated in humans. Instead, thin branchial membranes remain at the junction of each pharyngeal cleft and pouch. These membranes consist of three layers, with mesoderm separating the ectoderm from the endoderm (Sadler 2012; Grevellec and Tucker 2010). *Email: puz3@yahoo.com *Email: rumbolz@musc.edu Pediatric Neuroradiology DOI 10.1007/978-3-662-46258-4_65-1 # Springer-Verlag Berlin Heidelberg 2015

Background: High-resolution MRI (HRMRI) is a promising tool for studying intracranial atherosclerotic disease (ICAD) in-vivo, but its use to understand the pathophysiology of ICAD has been limited by a lack of correlation between MRI signal characteristics and pathology in intracranial arteries. Description of case: A patient with symptomatic left cavernous carotid stenosis underwent 3T HRMRI and died 4 days later. In-vivo HRMRI and postmortem histopathology images were compared. MRI signal characteristics consistent with atherosclerotic plaque composed of lipid and loose matrix, fibrous tissue, and calcium were correlated with pathology findings. Intraplaque hemorrhage was not present on HRMRI or pathology. Conclusions: This report demonstrates correlation between atherosclerotic plaque components visualized on 3T HRMRI images obtained in-vivo and pathological specimens of a symptomatic ICAD plaque, providing an important step in developing HRMRI as an in-vivo research tool to understand ICAD pathology.

This report describes a case of successful percutaneous direct-puncture ethanol embolization, followed by vertebroplasty, of an aggressive vertebral hemangioma (VH) involving two adjacent thoracic vertebral levels. In this case, the 78-year-old male patient presented with a 6-month history of progressive paraparesis due to spinal cord compression by a T8–T9 VH with an extensive epidural component. Follow-up demonstrated epidural component shrinkage with complete regression of symptoms at 3 months. This case suggests that exclusive percutaneous treatment may be considered for symptomatic VH even when two adjacent vertebral levels are affected.

We present a percutaneous modified technique to access large thoracic vertebral body lytic lesions, to increase the volume of tumor accessible to ablation, prior to cement augmentation. Tumor ablation and cavity creation-assisted percutaneous vertebroplasty was considered a palliative measure for structural stabilization in plasmocytoma involvement of the entire T8 vertebral body. Given the extent of osteolysis bilateral combined transpedicular and extrapedicular access to the vertebral body was undertaken to maximize the volume of cavity creation within the tumor. The combined transpedicular and extrapedicular access was feasible, uncomplicated, and successful in reaching all the quadrants of the anterior two thirds of the vertebral body. Slow, fluoroscopically monitored injection of high-viscosity cement resulted in a successful, desired cement distribution into the anterior two thirds of the vertebral body, spanning superior to inferior endplates, providing structural stability, in the absence of venous or epidural leakage. The technical modification described in this case yielded positive results while overcoming some of the limitations of the existing coblation device. This approach may offer an option for cement augmentation of extensive vertebral body lytic lesions, at increased risk for tumor displacement and extra-vertebral cement leakage.

Background Early results of the Stenting and Aggressive Medical Management for Preventing Recurrent stroke in Intracranial Stenosis trial showed that, by 30 days, 33 (14.7%) of 224 patients in the stenting group and 13 (5.8%) of 227 patients in the medical group had died or had a stroke (percentages are product limit estimates), but provided insufficient data to establish whether stenting offered any longer-term benefit. Here we report the long-term outcome of patients in this trial.Methods We randomly assigned (1:1, stratified by centre with randomly permuted block sizes) 451 patients with recent transient ischaemic attack or stroke related to 70-99% stenosis of a major intracranial artery to aggressive medical management (antiplatelet therapy, intensive management of vascular risk factors, and a lifestyle-modification programme) or aggressive medical management plus stenting with the Wingspan stent. The primary endpoint was any of the following:stroke or death within 30 days after enrolment, ischaemic stroke in the territory of the qualifying artery beyond 30 days of enrolment, or stroke or death within 30 days after a revascularisation procedure of the qualifying lesion during follow-up. Primary endpoint analysis of between-group differences with log-rank test was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT 00576693.Findings During a median follow-up of 32.4 months, 34 (15%) of 227 patients in the medical group and 52 (23%) of 224 patients in the stenting group had a primary endpoint event. The cumulative probability of the primary endpoints was smaller in the medical group versus the percutaneous transluminal angioplasty and stenting (PTAS) group (p=0.0252). Beyond 30 days, 21 (10%) of 210 patients in the medical group and 19 (10%) of 191 patients in the stenting group had a primary endpoint. The absolute differences in the primary endpoint rates between the two groups were 7.1% at year 1 (95% CI 0.2 to 13.8%; p=0.0428), 6.5% at year 2 (-0.5 to 13.5%; p=0.07) and 9.0% at year 3 (1.5 to 16.5%; p=0.0193). The occurrence of the following adverse events was higher in the PTAS group than in the medical group:any stroke (59 [26%] of 224 patients vs 42 [19%] of 227 patients; p=0.0468) and major haemorrhage (29 [13%] of 224 patients vs 10 [4%] of 227 patients; p=0.0009).Interpretation The early benefit of aggressive medical management over stenting with the Wingspan stent for high-risk patients with intracranial stenosis persists over extended follow-up. Our findings lend support to the use of aggressive medical management rather than PTAS with the Wingspan system in high-risk patients with atherosclerotic intracranial arterial stenosis.

BACKGROUND:There are limited data on the specific mechanisms of stroke in patients with intracranial atherosclerotic stenosis (ICAS). We undertook this study to describe infarct patterns and likely mechanisms of stroke in a large cohort of patients with ICAS, and to evaluate the relationship of these infarct patterns to angiographic features (collaterals, stenosis location and stenosis severity). METHODS:We evaluated infarct patterns in the territory of a stenotic intracranial artery on neuroimaging performed at baseline and during follow-up if a recurrent stroke occurred in patients enrolled in the Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) trial. We defined the likely mechanism of stroke (artery-to-artery embolism, perforator occlusion, hypoperfusion or mixed) according to the site of ICAS and based on the infarct patterns on neuroimaging. Collaterals were assessed using American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) grades, and stenosis severity using the WASID trial's measurement technique. We evaluated the association of infarct patterns with angiographic features using χ(2) tests. RESULTS:The likely mechanisms of stroke based on the infarct patterns at baseline in the 136 patients included in the study were artery-to-artery embolism (n = 69; 50.7%), perforator occlusion (n = 34; 25%), hypoperfusion (n = 12; 8.8%) and mixed (n = 21; 15.5%). Perforator-occlusive infarcts were more frequent in the posterior circulation, and mixed patterns were more prevalent in the anterior circulation (both p < 0.01). Most of the mixed patterns in the anterior circulation combined small pial or scattered multiple cortical infarcts with infarcts in border-zone regions, especially the cortical ones. Isolated border-zone infarcts were not significantly associated with a poor grading for collaterals or the severity of stenosis. Among 47 patients with a recurrent infarct during follow-up, the infarct patterns suggested an artery-to-artery embolic mechanism in 29 (61.7%). CONCLUSIONS:Artery-to-artery embolism is probably the most common mechanism of stroke in both the anterior and the posterior circulations in patients with ICAS. An extension of intracranial atherosclerosis at the site of stenosis into adjacent perforators also appears to be a common mechanism of stroke, particularly in the posterior circulation, whereas hypoperfusion as the sole mechanism is relatively uncommon. Further research is important to accurately establish the specific mechanisms of stroke in patients with ICAS, since preliminary data suggest that the underlying mechanism of stroke is an important determinant of prognosis.