American Journal of Neuroradiology

BACKGROUND AND PURPOSE: Degenerative changes are commonly found in spine imaging but often occur in pain-free individuals as well as those with back pain. We sought to estimate the prevalence, by age, of common degenerative spine conditions by performing a systematic review studying the prevalence of spine degeneration on imaging in asymptomatic individuals. MATERIALS AND METHODS: We performed a systematic review of articles reporting the prevalence of imaging findings (CT or MR imaging) in asymptomatic individuals from published English literature through April 2014. Two reviewers evaluated each manuscript. We selected age groupings by decade (20, 30, 40, 50, 60, 70, 80 years), determining age-specific prevalence estimates. For each imaging finding, we fit a generalized linear mixed-effects model for the age-specific prevalence estimate clustering in the study, adjusting for the midpoint of the reported age interval. RESULTS: Thirty-three articles reporting imaging findings for 3110 asymptomatic individuals met our study inclusion criteria. The prevalence of disk degeneration in asymptomatic individuals increased from 37% of 20-year-old individuals to 96% of 80-year-old individuals. Disk bulge prevalence increased from 30% of those 20 years of age to 84% of those 80 years of age. Disk protrusion prevalence increased from 29% of those 20 years of age to 43% of those 80 years of age. The prevalence of annular fissure increased from 19% of those 20 years of age to 29% of those 80 years of age. CONCLUSIONS: Imaging findings of spine degeneration are present in high proportions of asymptomatic individuals, increasing with age. Many imaging-based degenerative features are likely part of normal aging and unassociated with pain. These imaging findings must be interpreted in the context of the patient's clinical condition.

SUMMARY: Resting-state fMRI measures spontaneous low-frequency fluctuations in the BOLD signal to investigate the functional architecture of the brain. Application of this technique has allowed the identification of various RSNs, or spatially distinct areas of the brain that demonstrate synchronous BOLD fluctuations at rest. Various methods exist for analyzing resting-state data, including seed-based approaches, independent component analysis, graph methods, clustering algorithms, neural networks, and pattern classifiers. Clinical applications of resting-state fMRI are at an early stage of development. However, its use in presurgical planning for patients with brain tumor and epilepsy demonstrates early promise, and the technique may have a future role in providing diagnostic and prognostic information for neurologic and psychiatric diseases.

Susceptibility-weighted imaging (SWI) is a new neuroimaging technique, which uses tissue magnetic susceptibility differences to generate a unique contrast, different from that of spin density, T1, T2, and T2*. In this review (the first of 2 parts), we present the technical background for SWI. We discuss the concept of gradient-echo images and how we can measure local changes in susceptibility. Armed with this material, we introduce the steps required to transform the original magnitude and phase images into SWI data. The use of SWI filtered phase as a means to visualize and potentially quantify iron in the brain is presented. Advice for the correct interpretation of SWI data is discussed, and a set of recommended sequence parameters for different field strengths is given.

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state coupled with a unique CT or MR imaging appearance. Recognized in the setting of a number of complex conditions (preeclampsia/eclampsia, allogeneic bone marrow transplantation, organ transplantation, autoimmune disease and high dose chemotherapy) the imaging, clinical and laboratory features of this toxic state are becoming better elucidated. This review summarizes the basic and advanced imaging features of PRES, along with pertinent features of the clinical and laboratory presentation and available histopathology. Many common imaging/clinical/laboratory observations are present among these patients, despite the perception of widely different associated clinical conditions.

PURPOSE: To describe a technique for percutaneous vertebroplasty of osteoporotic vertebral body compression fractures and to report early results of its use. METHODS: The technique was used over a 3-year period in 29 patients with 47 painful vertebral fractures. The technique involves percutaneous puncture of the involved vertebra(e) via a transpedicular approach followed by injection of polymethylmethacrylate (PMMA) into the vertebral body. RESULTS: The procedure was technically successful in all patients, with an average injection amount of 7.1 mL PMMA per vertebral body. Two patients sustained single, nondisplaced rib fractures during the procedure; otherwise, no clinically significant complications were noted. Twenty-six patients (90%) reported significant pain relief immediately after treatment. CONCLUSION: Vertebroplasty is a valuable tool in the treatment of painful osteoporotic vertebral fractures, providing acute pain relief and early mobilization in appropriate patients.

Posterior reversible encephalopathy syndrome (PRES) is a neurotoxic state accompanied by a unique brain imaging pattern typically associated with a number of complex clinical conditions including: preeclampsia/eclampsia, allogeneic bone marrow transplantation, solid organ transplantation, autoimmune diseases and high dose cancer chemotherapy. The mechanism behind the developing vasogenic edema and CT or MR imaging appearance of PRES is not known. Two theories have historically been proposed: 1) Severe hypertension leads to failed auto-regulation, subsequent hyperperfusion, with endothelial injury/vasogenic edema and; 2) vasoconstriction and hypoperfusion leads to brain ischemia and subsequent vasogenic edema. The strengths/weaknesses of these hypotheses are reviewed in a translational fashion including supporting evidence and current available imaging/clinical data related to the conditions that develop PRES. While the hypertension/hyperperfusion theory has been most popular, the conditions associated with PRES have a similar immune challenge present and develop a similar state of T-cell/endothelial cell activation that may be the basis of leukocyte trafficking and systemic/cerebral vasoconstriction. These systemic features along with current vascular and perfusion imaging features in PRES appear to render strong support for the older theory of vasoconstriction coupled with hypoperfusion as the mechanism.

SUMMARY: Increasing detection of unruptured intracranial aneurysms, catastrophic outcomes from subarachnoid hemorrhage, and risks and cost of treatment necessitate defining objective predictive parameters of aneurysm rupture risk. Image-based computational fluid dynamics models have suggested associations between hemodynamics and intracranial aneurysm rupture, albeit with conflicting findings regarding wall shear stress. We propose that the "high-versus-low wall shear stress" controversy is a manifestation of the complexity of aneurysm pathophysiology, and both high and low wall shear stress can drive intracranial aneurysm growth and rupture. Low wall shear stress and high oscillatory shear index trigger an inflammatory-cell-mediated pathway, which could be associated with the growth and rupture of large, atherosclerotic aneurysm phenotypes, while high wall shear stress combined with a positive wall shear stress gradient trigger a mural-cell-mediated pathway, which could be associated with the growth and rupture of small or secondary bleb aneurysm phenotypes. This hypothesis correlates disparate intracranial aneurysm pathophysiology with the results of computational fluid dynamics in search of more reliable risk predictors.

We evaluated the temporal and anatomic relationships between changes in diffusion-weighted MR image signal intensity, induced by unilateral occlusion of the middle cerebral artery in cats, and tissue perfusion deficits observed in the same animals on T2-weighted MR images after administration of a nonionic intravascular T2 shortening agent. Diffusion-weighted images obtained with strong diffusion-sensitizing gradient strengths (5.6 gauss/cm, corresponding to gradient attenuation factor, b, values of 1413 sec/mm2) displayed increased signal intensity in the ischemic middle cerebral artery territory less than 1 hr after occlusion, whereas T2-weighted images without contrast usually failed to detect injury for 2-3 hr after stroke. After contrast administration (0.5-1.0 mmol/kg by Dy-DTPA-BMA, IV), however, T2-weighted images revealed perfusion deficits (relative hyperintensity) within 1 hr after middle cerebral artery occlusion that corresponded closely to the anatomic regions of ischemic injury shown on diffusion-weighted MR images. Close correlations were also found between early increases in diffusion-weighted MR image signal intensity and disrupted phosphorus-31 and proton metabolite levels evaluated with surface coil MR spectroscopy, as well as with postmortem histopathology. These data indicate that diffusion-weighted MR images more accurately reflect early-onset pathophysiologic changes induced by acute cerebral ischemia than do T2-weighted spin-echo images.

BACKGROUND AND PURPOSE: Endoluminal reconstruction with flow diverting devices represents a novel constructive technique for the treatment of cerebral aneurysms. We present the results of the first prospective multicenter trial of a flow-diverting construct for the treatment of intracranial aneurysms. MATERIALS AND METHODS: Patients with unruptured aneurysms that were wide-necked (> 4 mm), had unfavorable dome/neck ratios (<1.5), or had failed previous therapy were enrolled in the PITA trial between January and May 2007 at 4 (3 European and 1 South American) centers. Aneurysms were treated with the PED with or without adjunctive coil embolization. All patients underwent clinical evaluation at 30 and 180 days and conventional angiography 180 days after treatment. Angiographic results were adjudicated by an experienced neuroradiologist at a nonparticipating site. RESULTS: Thirty-one patients with 31 intracranial aneurysms (6 men; 42-76 years of age; average age, 54.6 years) were treated during the study period. Twenty-eight aneurysms arose from the ICA (5 cavernous, 15 parophthalmic, 4 superior hypophyseal, and 4 posterior communicating segments), 1 from the MCA, 1 from the vertebral artery, and 1 from the vertebrobasilar junction. Mean aneurysm size was 11.5 mm, and mean neck size was 5.8 mm. Twelve (38.7%) aneurysms had failed (or recurred after) a previous endovascular treatment. PED placement was technically successful in 30 of 31 patients (96.8%). Most aneurysms were treated with either 1 (n = 18) or 2 (n = 11) PEDs. Fifteen aneurysms (48.4%) were treated with a PED alone, while 16 were treated with both PED and embolization coils. Two patients experienced major periprocedural stroke. Follow-up angiography demonstrated complete aneurysm occlusion in 28 (93.3%) of the 30 patients who underwent angiographic follow-up. No significant in-construct stenosis (≥ 50%) was identified at follow-up angiography. CONCLUSIONS: Intracranial aneurysm treatment with the PED is technically feasible and can be achieved with a safety profile analogous to that reported for stent-supported coil embolization. PED treatment elicited a very high rate (93%) of complete angiographic occlusion at 6 months in a population of the most challenging anatomic subtypes of cerebral aneurysms.

SUMMARY: Susceptibility-weighted imaging (SWI) has continued to develop into a powerful clinical tool to visualize venous structures and iron in the brain and to study diverse pathologic conditions. SWI offers a unique contrast, different from spin attenuation, T1, T2, and T2* (see Susceptibility-Weighted Imaging: Technical Aspects and Clinical Applications, Part 1). In this clinical review (Part 2), we present a variety of neurovascular and neurodegenerative disease applications for SWI, covering trauma, stroke, cerebral amyloid angiopathy, venous anomalies, multiple sclerosis, and tumors. We conclude that SWI often offers complementary information valuable in the diagnosis and potential treatment of patients with neurologic disorders.

BACKGROUND AND PURPOSE: To examine the influence of age and sex on T1 relaxation and volume in brain and upper cervical cord using MP2RAGE, which offers high contrast-to-noise ratio, uniform tissue contrast, and superior anatomical resolution alongside T1 mapping. This provides an accurate analysis of the magnitude of the effects of these covariates on the outcomes. MATERIALS AND METHODS: 208 MP2RAGE scans from the Max Planck Institute Leipzig Mind-Brain-Body LEMON dataset were segmented and labeled using FreeSurfer and Spinal Cord Toolbox. The influences of age and sex on dependent variables were analyzed using linear regression and group difference were compared using the Mann-Whitney U test. RESULTS: T1 values of cortical gray matter (GM), cerebral white matter (WM), thalamus, caudate, putamen, hippocampus, amygdala, and anterior corpus callosum (CC) varied significantly with age. Cortical GM and cervical C1 T1 showed statistical significance with sex, with latter lower in the females compared to males. T1 values of the posterior CC were significantly lower than the anterior portion. GM, WM, thalamus, caudate, putamen, hippocampus and anterior CC volumes were significantly affected by age. Spine cross-sectional area (CSA) showed statistically significant differences with sex but not age. CONCLUSIONS: T1, regional brain volumes, and spinal CSA vary according to anatomical location, age, and sex, reflecting physiological differences associated with aging and sex. These results can operate as a normative baseline to gauge the magnitude of effect of these covariates on future studies in health or disease.

BACKGROUND: The efficacy of middle meningeal artery embolization (MMAE) for chronic subdural hematoma (cSDH) has heightened interest in imaging biomarkers that may reflect neomembrane activity, predict recurrence, and identify patients most likely to benefit from treatment. Characterization of hematoma internal architecture, referred to as the imaging phenotype, may provide indirect information regarding the biological activity and maturation of the neomembrane. However, imaging phenotype has not been incorporated into randomized trials or validated treatment-selection algorithms, and standardized definitions and reporting remain lacking. METHODS: The American Society of Functional Neuroradiology Clinical Practice Committee developed this State of Practice statement through expert consensus and review of the available literature. KEY MESSAGE: Noncontrast CT (NCCT) remains the primary imaging modality for cSDH assessment. Hematoma burden should be characterized by maximum thickness measured perpendicular to the inner table, midline shift, and, when appropriate, volume. Volume may be estimated using the ABC/2 formula, whereas segmentation is more accurate for irregular, crescentic, or multiloculated collections when available. Internal architecture should be described using the Nakaguchi framework of homogeneous, laminar, separated, and trabecular phenotypes, with mixed or transitional features explicitly reported. Advanced techniques, including dual-energy CT, photon-counting CT, MRI, and arterial spin labeling, may provide information regarding membrane activity but are supported by limited, largely single-center evidence and currently have a problem-solving rather than routine role. Standardized reporting and prospective validation are needed before imaging phenotype or advanced-imaging biomarkers can guide treatment selection.

Transcranial MR-guided high-intensity focused ultrasound (HIFU) thermoablation is an established incisionless image-guided treatment for movement disorders; however, neuroradiologist involvement in clinical decision-making and procedural workflows is highly variable and site-specific. Transcranial low-intensity focused ultrasound (LIFU) is a rapidly evolving non-invasive, image-guided technology for neuromodulation and blood-brain barrier disruption. Compared with HIFU, the optimal protocol, therapeutic mechanism, and safety limits remain uncertain for LIFU. Despite these gaps, LIFU has significant potential for neuropsychiatric and neuro-oncologic diseases. Familiarity with transcranial ultrasound principles and the pivotal role of CT and MR imaging for targeting and evaluating outcomes is increasingly important for neuroradiologists. This review uses HIFU as a clinical model to illustrate the integration of imaging into focused ultrasound workflows. We then discuss LIFU with respect to technical factors, imaging considerations, safety, and limitations. We highlight its emerging applications, including neuromodulation, targeted drug delivery, and liquid biopsy. Finally, we conclude by summarizing key knowledge gaps, outlining future directions, and proposing strategies to more actively engage neuroradiologists in this emerging field.

BACKGROUND AND PURPOSE: Contralateral dural supply may leave residual membrane perfusion after unilateral middle meningeal artery embolization (MMAE) for unilateral chronic subdural hematoma (cSDH). We compared unilateral and bilateral MMAE selected as initial standalone treatment, focusing on index-admission surgical rescue and other clinically relevant outcomes. MATERIALS AND METHODS: This retrospective cohort included patients treated at 16 centers worldwide from 2018 through 2025. The primary endpoint was index-admission surgical rescue. The original 3:1 and confirmatory 1:1 propensity-matched analyses used prespecified baseline covariates. A composite sensitivity outcome of any retreatment was also examined post hoc. RESULTS: Among 600 patients, 546 underwent unilateral and 54 bilateral MMAE. Bilateral cases had lower baseline radiographic severity and more often underwent general anesthesia and selective distal embolization. Index-admission surgical rescue occurred in 9.5% of unilateral and 0% of bilateral cases (p<0.001), with corresponding rates of 10.6% versus 0% after 3:1 matching (p<0.001) and 11.1% versus 0% after 1:1 matching (p<0.001). The post-hoc composite of any retreatment did not differ in the unmatched cohort (p=0.37), 3:1 cohort (p=0.56), or 1:1 cohort (>0.99). Other outcomes showed no statistically significant between-group differences, but postdischarge follow-up was incomplete. CONCLUSIONS: Overall retreatment did not differ between groups, although bilateral MMAE was associated with fewer index-admission surgical rescues. These observational data identify, but do not validate, angiographically documented contralateral supply as a candidate selection marker for prospective evaluation but do not establish a benefit of bilateral treatment or support routine bilateral MMAE.

BACKGROUND: Acute ischaemic stroke (AIS) remains a major cause of disability and mortality worldwide. Endovascular treatment (EVT) is the standard of care for large vessel occlusion, yet a favourable neurological outcome is not achieved in all patients. Edaravone dexborneol (ED) has been proposed as an adjuvant therapy during EVT procedures. However, its clinical impact has not been systematically synthesized. METHODS: This systematic review and meta-analysis was conducted in accordance with the PRISMA guidelines. PubMed, Web of Science, Scopus, ClinicalTrials.gov, Cochrane Central, and Embase were searched from inception to March 2026. Randomized and non-randomized studies comparing ED versus non-ED (placebo) controls in AIS patients undergoing mechanical thrombectomy (MT) were included. The primary outcomes of this study were excellent and good neurological outcomes at 90 days, measured with the modified Rankin Scale. A random-effects meta-analysis was performed, with robust sensitivity analyses to explore heterogeneity. RESULTS: Seven studies were included, of which three were randomized. For the primary outcomes, there was no significant difference in the proportion of patients with excellent (mRS 0-1: OR 1.14; 95% CI 0.95 to 1.36; p = 0.17) or good neurological outcome (mRS 0-2: OR 1.34; 95% CI 0.97 to 1.85; p = 0.08). The incidence of symptomatic intracranial hemorrhage (sICH) was similar between groups (OR 0.73; 95% CI 0.50 to 1.07; p = 0.11). Prediction intervals crossed the null for all efficacy outcomes. No significant differences were observed in mortality at 90 days (p = 0.51). However, in pooled adjusted analyses, ED was associated with a modest increase in good neurological outcome (aOR 1.46; 95% CI 1.13 to 1.90; p = 0.004). CONCLUSION: Unadjusted analyses show no significant benefit of ED in reducing mortality, symptomatic bleeding events, or improving functional recovery. However, pooled adjusted estimates suggest a modest improvement in good neurological outcomes (mRS 0-2). Wide prediction intervals crossing the null indicate that the current evidence is preliminary, and confirmation in adequately powered trials is needed before routine clinical adoption.

BACKGROUND AND PURPOSE: Idiopathic Normal Pressure Hydrocephalus is characterized by gait disturbance, cognitive impairment, and urinary incontinence. Symptom improvement can be achieved by shunt surgery, especially regarding gait difficulties. This study investigated whether CSF volumetry can define postoperative target values associated with clinical improvement and, secondly, predict potential non-response or overdrainage complications. MATERIALS AND METHODS: Forty-seven patients with iNPH were prospectively followed for three years after shunt surgery. Quantitative MRI was performed at baseline and at 3, 12, and 36 months postoperatively. Automatic segmentation yielded ventricular volume, subarachnoid CSF volume, ratio of ventricular and total CSF volume and ratio of total brain volume and intracranial volume. Clinical outcome was assessed using the Hellström iNPH scale. Patients were classified as responders and non-responders and further subdivided with and without overdrainage complications. RESULTS: Eighty-seven percent of patients were classified as responders. Responders demonstrated a 26% reduction in ventricular volume(139 ml at baseline and 102 ml at three years) accompanied by a >60% improvement in iNPH score. The ventricular/total CSF ratio decreased from 0.34 to 0.25. Non-responders exhibited low ratios already at baseline, due to a significantly higher subarachnoid CSF volume. Overdrainage-related postural headaches were associated withlow subarachnoid CSF volume, younger age, higher baseline iNPH score, and higher BPV/ICV ratio. Aggregate z-scores combining multiple baseline metrics improved discrimination between responders, non-responders, and patients at risk for overdrainage. CONCLUSIONS: Baseline volumetry may provide target values and risk stratification for shunt surgery in iNPH. Responders showed a reduction of ventricular volume to ∼100 ml and ventricle/total CSF ratio to ∼0.25. High subarachnoid CSF volumes at baseline, however, was associated with poor response, while low subarachnoid CSF volume indicated an increased risk of postural headache. Quantitative CSF segmentation may improve patient selection and postoperative management in iNPH.

Low-intensity focused ultrasound (LIFU) is an emerging, noninvasive neuromodulation technique with a growing evidence base and set of applications. LIFU uses low-energy acoustic waves that are focused to a focal volume in the millimeter range and transiently modulate neuronal activity in targeted cortical and subcortical brain structures. Unlike high-intensity focused ultrasound (HIFU), which is designed to cause thermal ablation of the target tissue, LIFU is intended to modulate neuronal activity rather than ablate tissue. In this article, we review the technical background, clinical applications, and safety of LIFU from neuroimaging and neurointerventional perspectives.

INTRODUCTION: Neuromodulation of the thalamic centromedian nucleus (CM) is an established therapy for epilepsy and been applied for pain, Tourette syndrome, and disorders of consciousness. Accurate targeting remains challenging because CM is poorly visualized on conventional MRI sequences, necessitating reliance on indirect targeting approaches. Although advanced MRI sequences, such as magnetization-prepared rapid acquisition of two gradient echoes (MP2RAGE) and white matter null (WMn), have been explored, they fail to reliably delineate the boundary between CM and lateral thalamus, a region associated with optimal stimulation outcomes, particularly in epilepsy. Quantitative susceptibility mapping (QSM) has emerged as a promising technique for differentiating thalamic nuclei based on tissue magnetic susceptibility. OBJECTIVE: The purpose of this study was to evaluate visualization of CM using QSM, assess contrast between CM and adjacent nuclei, and indirectly compare across WMn and MP2RAGE. METHODS: This retrospective study included patients with solitary cerebral cavernous malformations, not involving the thalamus, who underwent surveillance MRI including QSM (n=24). WMn sequences were obtained from a separate cohort of patients with epilepsy (n=16). MP2RAGE sequences were acquired from healthy individuals (n=24). All sequences were registered to the MNI152 template space and compared with the Morel histological atlas. Normalized intensity differences, contrast-to-noise ratios (CNR), and signal-to-noise ratios (SNR) were calculated for CM and neighboring nuclei. RESULTS: On QSM, CM was hypointense to medial and posterior thalamus and hyperintense relative to motor thalamus. Median CNR on QSM (P<0.05) relative to CM was highest for medial pulvinar (median 2.9, interquartile range 1.6-4.7) and ventral lateral thalamus (1.6, 0.6-2.3). Highest overall CNR was seen on WMn for PuM (3.4, 3.0-4.0). SNR on QSM was highest for anterior pulvinar (2.4, 1.1-3.6) and highest overall SNR was on on MP2RAGE for PuA (20.8, 17.3-24.3). In an indirect comparison across independent cohorts, QSM showed greater lateral thalamic contrast than WMn and MP2RAGE, but lower overall SNR. CONCLUSION: QSM allows visualization of CM including the lateral border poorly seen on other sequences, and may be useful as a complementary sequence for direct targeting of CM.