Comprehensive Review of the Utility of Dynamic Contrast-Enhanced MRI for the Diagnosis and Treatment Assessment of Spinal Benign and Malignant Osseous Disease.

Conventional MRI is currently the preferred imaging technique for detection and evaluation of malignant spinal lesions. However, this technique is limited in its ability to assess tumor viability. Unlike conventional MRI, dynamic contrast-enhanced (DCE) MRI provides insight into the physiologic and hemodynamic characteristics of malignant spinal tumors and has been utilized in different types of spinal diseases. DCE has been shown to be especially useful in the cancer setting; specifically, DCE can discriminate between malignant and benign vertebral compression fractures as well as between atypical hemangiomas and metastases. DCE has also been shown to differentiate between different types of metastases. Furthermore, DCE can be useful in the assessment of radiation therapy for spinal metastases, including the prediction of tumor recurrence. This review considers data analysis methods utilized in prior studies of DCE-MRI data acquisition and clinical implications.

Dynamic Contrast Enhanced MR Perfusion and Diffusion-Weighted Imaging of Marrow-Replacing Disorders of the Spine: A Comprehensive Review.

Significant advancements in cancer treatment have led to improved survival rates for patients, particularly in the context of spinal metastases. However, early detection and monitoring of treatment response remain crucial for optimizing patient outcomes. Although conventional imaging methods such as bone scan, PET, MR imaging, and computed tomography are commonly used for diagnosing and monitoring treatment, they present challenges in differential diagnoses and treatment response monitoring. This review article provides a comprehensive overview of the principles, applications, and practical uses of dynamic contrast-enhanced MR imaging and diffusion-weighted imaging in the assessment and monitoring of marrow-replacing disorders of the spine.

T1-Weighted, Dynamic Contrast-Enhanced MR Perfusion Imaging Can Differentiate between Treatment Success and Failure in Spine Metastases Undergoing Radiation Therapy.

BACKGROUND AND PURPOSE: Current imaging techniques have difficulty differentiating treatment success and failure in spinal metastases undergoing radiation therapy. This study investigated the correlation between changes in dynamic contrast-enhanced MR imaging perfusion parameters and clinical outcomes following radiation therapy for spinal metastases. We hypothesized that perfusion parameters will outperform traditional size measurements in discriminating treatment success and failure. MATERIALS AND METHODS: This retrospective study included 49 patients (mean age, 63 [SD, 13] years; 29 men) with metastatic lesions treated with radiation therapy who underwent dynamic contrast-enhanced MR imaging. The median time between radiation therapy and follow-up dynamic contrast-enhanced MR imaging was 62 days. We divided patients into 2 groups: clinical success (n = 38) and failure (n = 11). Failure was defined as PET recurrence (n = 5), biopsy-proved (n = 1) recurrence, or an increase in tumor size (n = 7), while their absence defined clinical success. A Mann-Whitney U test was performed to assess differences between groups. RESULTS: The reduction in plasma volume was greater in the success group than in the failure group (-57.3% versus +88.2%, respectively; P < .001). When we assessed the success of treatment, the sensitivity of plasma volume was 91% (10 of 11; 95% CI, 82%-97%) and the specificity was 87% (33 of 38; 95% CI, 73%-94%). The sensitivity of size measurements was 82% (9 of 11; 95% CI, 67%-90%) and the specificity was 47% (18 of 38; 95% CI, 37%-67%). CONCLUSIONS: The specificity of plasma volume was higher than that of conventional size measurements, suggesting that dynamic contrast-enhanced MR imaging is a powerful tool to discriminate between treatment success and failure.

Dynamic Contrast-Enhanced MR Perfusion: Role in Diagnosis and Treatment Follow-Up in Patients with Vertebral Body Tumors.

Recent therapeutic advances have led to increased survival times for patients with metastatic disease. Key to survival is early diagnosis and subsequent treatment as well as early detection of treatment failure allowing for therapy modifications. Conventional MR imaging techniques of the spine can be at times suboptimal for identifying viable tumor, as structural changes and imaging characteristics may not differ pretreatment and posttreatment. Advanced imaging techniques such as DCE-MRI can allow earlier and more accurate noninvasive assessment of viable disease by characterizing physiologic changes and tumor microvasculature.

Delay of Aortic Arterial Input Function Time Improves Detection of Malignant Vertebral Body Lesions on Dynamic Contrast-Enhanced MRI Perfusion.

Dynamic contrast-enhanced MRI (DCE) is an emerging modality in the study of vertebral body malignancies. DCE-MRI analysis relies on a pharmacokinetic model, which assumes that contrast uptake is simultaneous in the feeding of arteries and tissues of interest. While true in the highly vascularized brain, the perfusion of the spine is delayed. This delay of contrast reaching vertebral body lesions can affect DCE-MRI analyses, leading to misdiagnosis for the presence of active malignancy in the bone marrow. To overcome the limitation of delayed contrast arrival to vertebral body lesions, we shifted the arterial input function (AIF) curve over a series of phases and recalculated the plasma volume values (Vp) for each phase shift. We hypothesized that shifting the AIF tracer curve would better reflect actual contrast perfusion, thereby improving the accuracy of Vp maps in metastases. We evaluated 18 biopsy-proven vertebral body metastases in which standard DCE-MRI analysis failed to demonstrate the expected increase in Vp. We manually delayed the AIF curve for multiple phases, defined as the scan-specific phase temporal resolution, and analyzed DCE-MRI parameters with the new AIF curves. All patients were found to require at least one phase-shift delay in the calculated AIF to better visualize metastatic spinal lesions and improve quantitation of Vp. Average normalized Vp values were 1.78 ± 1.88 for zero phase shifts (P0), 4.72 ± 4.31 for one phase shift (P1), and 5.59 ± 4.41 for two phase shifts (P2). Mann-Whitney U tests obtained p-values = 0.003 between P0 and P1, and 0.0004 between P0 and P2. This study demonstrates that image processing analysis for DCE-MRI in patients with spinal metastases requires a careful review of signal intensity curve, as well as a possible adjustment of the phase of aortic AIF to increase the accuracy of Vp.

Semisupervised Training of a Brain MRI Tumor Detection Model Using Mined Annotations.

Background Artificial intelligence (AI) applications for cancer imaging conceptually begin with automated tumor detection, which can provide the foundation for downstream AI tasks. However, supervised training requires many image annotations, and performing dedicated post hoc image labeling is burdensome and costly. Purpose To investigate whether clinically generated image annotations can be data mined from the picture archiving and communication system (PACS), automatically curated, and used for semisupervised training of a brain MRI tumor detection model. Materials and Methods In this retrospective study, the cancer center PACS was mined for brain MRI scans acquired between January 2012 and December 2017 and included all annotated axial T1 postcontrast images. Line annotations were converted to boxes, excluding boxes shorter than 1 cm or longer than 7 cm. The resulting boxes were used for supervised training of object detection models using RetinaNet and Mask region-based convolutional neural network (R-CNN) architectures. The best-performing model trained from the mined data set was used to detect unannotated tumors on training images themselves (self-labeling), automatically correcting many of the missing labels. After self-labeling, new models were trained using this expanded data set. Models were scored for precision, recall, and F1 using a held-out test data set comprising 754 manually labeled images from 100 patients (403 intra-axial and 56 extra-axial enhancing tumors). Model F1 scores were compared using bootstrap resampling. Results The PACS query extracted 31 150 line annotations, yielding 11 880 boxes that met inclusion criteria. This mined data set was used to train models, yielding F1 scores of 0.886 for RetinaNet and 0.908 for Mask R-CNN. Self-labeling added 18 562 training boxes, improving model F1 scores to 0.935 (P < .001) and 0.954 (P < .001), respectively. Conclusion The application of semisupervised learning to mined image annotations significantly improved tumor detection performance, achieving an excellent F1 score of 0.954. This development pipeline can be extended for other imaging modalities, repurposing unused data silos to potentially enable automated tumor detection across radiologic modalities. © RSNA, 2022 Online supplemental material is available for this article.

Magnetic resonance spectroscopic imaging in gliomas: clinical diagnosis and radiotherapy planning.

The reprogramming of cellular metabolism is a hallmark of cancer diagnosis and prognosis. Proton magnetic resonance spectroscopic imaging (MRSI) is a non-invasive diagnostic technique for investigating brain metabolism to establish cancer diagnosis and IDH gene mutation diagnosis as well as facilitate pre-operative planning and treatment response monitoring. By allowing tissue metabolism to be quantified, MRSI provides added value to conventional MRI. MRSI can generate metabolite maps from a single volume or multiple volume elements within the whole brain. Metabolites such as NAA, Cho and Cr, as well as their ratios Cho:NAA ratio and Cho:Cr ratio, have been used to provide tumor diagnosis and aid in radiation therapy planning as well as treatment assessment. In addition to these common metabolites, 2-hydroxygluterate (2HG) has also been quantified using MRSI following the recent discovery of IDH mutations in gliomas. This has opened up targeted drug development to inhibit the mutant IDH pathway. This review provides guidance on MRSI in brain gliomas, including its acquisition, analysis methods, and evolving clinical applications.

T1-weighted Dynamic Contrast-enhanced MRI to Differentiate Nonneoplastic and Malignant Vertebral Body Lesions in the Spine.

Background Dynamic contrast agent-enhanced (DCE) perfusion MRI may help differentiate between nonneoplastic and malignant lesions in the spine. Purpose To investigate the correlation between fractional plasma volume (Vp), a parameter derived from DCE perfusion MRI, and histopathologic diagnosis for spinal lesions. Materials and Methods In this retrospective study, patients who underwent DCE perfusion MRI and lesion biopsy between May 2015 and May 2018 were included. Inclusion criteria were short time interval (<30 days) between DCE perfusion MRI and biopsy, DCE perfusion MRI performed before biopsy, and DCE perfusion MRI performed at the same spine level as biopsy. Exclusion criteria were prior radiation treatment on vertebrae of interest, poor DCE perfusion MRI quality, nondiagnostic biopsy, and extensive spinal metastasis or prior kyphoplasty. One hundred thirty-four lesions were separated into a nonneoplastic group (n = 51) and a malignant group (n = 83) on the basis of histopathologic analysis. Two investigators manually defined regions of interest in the vertebrae. DCE perfusion MRI parameter Vp was calculated by using the Tofts pharmacokinetic two-compartment model. Vp was quantified, normalized to adjacent normal vertebrae, and compared between the two groups. A Mann-Whitney U test and receiver operating characteristic analysis was performed to verify the difference in Vp between the nonneoplastic and malignant groups. Reproducibility was assessed by calculating the Cohen κ coefficient. Results One hundred patients (mean age, 65 years ± 11 [standard deviation]; 52 men) were evaluated. Vp was lower in nonneoplastic lesions versus malignant lesions (1.6 ± 1.3 vs 4.2 ± 3.0, respectively; P < .001). The sensitivity of Vp was 93% (77 of 83; 95% confidence interval [CI]: 85%, 97%), specificity was 78% (40 of 51; 95% CI: 65%, 89%), and area under the receiver operating characteristic curve was 0.88 (95% CI: 0.82, 0.95). Cohen κ coefficient suggested substantial agreement in both intra- (κ = 0.72) and interreader (κ = 0.70) reproducibility. Conclusion This study indicated that dynamic contrast agent-enhanced perfusion MRI parameter, fractional plasma volume, was able to differentiate between nonneoplastic spinal lesions and malignant lesions. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Haller in this issue.

Radiographic and clinical outcomes using intraoperative magnetic resonance imaging for transsphenoidal resection of pituitary adenomas.

OBJECTIVE: The utility and safety of intraoperative MRI (iMRI) for resection of pituitary adenomas is not clearly established in the context of advances in endoscopic approaches. The goal in this study was to evaluate the safety and efficacy of iMRI for pituitary adenoma resection, with endoscopic transsphenoidal (ETS) versus microscopic transsphenoidal (MTS) approaches. METHODS: Radiographic and clinical outcomes of all pituitary adenomas resected using iMRI between 2008 and 2017 at a single institution were retrospectively evaluated. RESULTS: Of 212 tumors treated, 131 (62%) underwent further resection based on iMRI findings, resulting in a significant increase in gross-total resection on postoperative MRI compared with iMRI (p = 0.0001) in both ETS and MTS groups. iMRI increased rates of gross-total resection for cavernous sinus invasion Knosp grades 1 and 2, but not in Knosp ≥ 3 across treatment groups (p < 0.0001). The extent of resection on postoperative MRI was significantly correlated with increased progression-free survival (p < 0.0001). Initial hormone remission off medical therapy was achieved in 64%, with a significantly higher rate of remission in tumors resected via the ETS approach (81%) compared with the MTS approach (55%) (p = 0.02). The rate of persistent new hormone deficit was low at 8%, including a 2.8% rate of permanent diabetes insipidus, and 45% of patients had improvement in preoperative hormone deficit following surgery. Serious postoperative complications including CSF leaks requiring reoperation were rare at 1%, with no postoperative infections. CONCLUSIONS: These results suggest that iMRI is a safe and effective method of increasing the extent of resection for pituitary adenomas while preserving hormone function. When paired with the endoscope, iMRI may offer the ability to tailor more aggressive removal of tumors while optimizing pituitary function, resulting in high rates of secretory hormone remission. Secretory tumors and adenomas with Knosp grade < 3 cavernous sinus invasion may benefit most from the use of iMRI.

Perioperative management of endoscopic transsphenoidal pituitary surgery.

The contemporary embrace of endoscopic technology in the approach to the anterior skull base has altered the perioperative landscape for patients requiring pituitary surgery. Utility of a multi-disciplinary unit in management decisions facilitates the delivery of optimal care. Evolution of technology and surgical expertise in pituitary surgery mandates ongoing review of all components of the care central to these patients. The many areas of potential variability in the pre, intra and post-operative timeline of pituitary surgery are readily identifiable. Core undertakings and contemporary controversies in the peri-operative management of patients undergoing endoscopic transsphenoidal pituitary surgery are assessed against the available literature with a view to providing guidance for the best evidence-based practice.

A Potential Role For Apparent Diffusion Coefficient in the Diagnosis of Trilateral Retinoblastoma.

We attempted to investigate the potential role for apparent diffusion coefficient (ADC) to diagnose trilateral retinoblastoma (TRb) by retrospectively reviewing brain magnetic resonance images of retinoblastoma patients. Observations: The median ADC measured 620.95 for TRb (n=6) and 1238.5 for normal pineal gland in bilateral retinoblastoma (n=8). Monitoring ADC trends aided in establishing the appropriate diagnoses in 3 patients (2 TRb, 1 benign pineal cyst). Conclusions: Our results provide baseline reference data and describe the importance of downward trending ADC which should prompt consideration of TRb. Unchanged high/nonrestricted values (>1000) may distinguish those with benign pineal tissue and obviate invasive neurosurgical procedures.

Genetic variants and cognitive functions in patients with brain tumors.

BACKGROUND: Patients with brain tumors treated with radiotherapy (RT) and chemotherapy (CT) often experience cognitive dysfunction. We reported that single nucleotide polymorphisms (SNPs) in the APOE, COMT, and BDNF genes may influence cognition in brain tumor patients. In this study, we assessed whether genes associated with late-onset Alzheimer's disease (LOAD), inflammation, cholesterol transport, dopamine and myelin regulation, and DNA repair may influence cognitive outcome in this population. METHODS: One hundred and fifty brain tumor patients treated with RT ± CT or CT alone completed a neurocognitive assessment and provided a blood sample for genotyping. We genotyped genes/SNPs in these pathways: (i) LOAD risk/inflammation/cholesterol transport, (ii) dopamine regulation, (iii) myelin regulation, (iv) DNA repair, (v) blood-brain barrier disruption, (vi) cell cycle regulation, and (vii) response to oxidative stress. White matter (WM) abnormalities were rated on brain MRIs. RESULTS: Multivariable linear regression analysis with Bayesian shrinkage estimation of SNP effects, adjusting for relevant demographic, disease, and treatment variables, indicated strong associations (posterior association summary [PAS] ≥ 0.95) among tests of attention, executive functions, and memory and 33 SNPs in genes involved in: LOAD/inflammation/cholesterol transport (eg, PDE7A, IL-6), dopamine regulation (eg, DRD1, COMT), myelin repair (eg, TCF4), DNA repair (eg, RAD51), cell cycle regulation (eg, SESN1), and response to oxidative stress (eg, GSTP1). The SNPs were not significantly associated with WM abnormalities. CONCLUSION: This novel study suggests that polymorphisms in genes involved in aging and inflammation, dopamine, myelin and cell cycle regulation, and DNA repair and response to oxidative stress may be associated with cognitive outcome in patients with brain tumors.

Change in the cross-sectional area of the thecal sac following balloon kyphoplasty for pathological vertebral compression fractures prior to spine stereotactic radiosurgery.

OBJECTIVEPercutaneous vertebral augmentation procedures such as vertebroplasty and kyphoplasty are often performed in cancer patients to relieve mechanical axial-load pain due to pathological collapse deformities. The collapsed vertebrae in these patients can be associated with varying degrees of spinal canal compromise that can be worsened by kyphoplasty. In this study the authors evaluated changes to the spinal canal, in particular the cross-sectional area of the thecal sac, following balloon kyphoplasty (BKP) prior to stereotactic radiosurgery (SRS).METHODSThe authors retrospectively reviewed the records of all patients with symptomatic vertebral compression fractures caused by metastatic disease who underwent kyphoplasty prior to single-fraction SRS. The pre-BKP cross-sectional image, usually MRI, was compared to the post-BKP CT myelogram required for radiation treatment planning. The cross-sectional area of the thecal sac was calculated pre- and postkyphoplasty, and intraprocedural CT imaging was reviewed for epidural displacement of bone fragments, tumor, or polymethylmethacrylate (PMMA) extravasation. The postkyphoplasty imaging was also evaluated for evidence of fracture progression or fracture reduction.RESULTSAmong 30 consecutive patients, 41 vertebral levels were treated with kyphoplasty, and 24% (10/41) of the augmented levels showed a decreased cross-sectional area of the thecal sac. All 10 of these vertebral levels had preexisting epidural disease and destruction of the posterior vertebral body cortex. No bone fragments were displaced posteriorly. Minor epidural PMMA extravasation occurred in 20% (8/41) of the augmented levels but was present in only 1 of the 10 vertebral segments that showed a decreased cross-sectional area of the thecal sac postkyphoplasty.CONCLUSIONSIn patients with preexisting epidural disease and destruction of the posterior vertebral body cortex who are undergoing BKP for pathological fractures, there is an increased risk of further mass effect upon the thecal sac and the potential to alter the SRS treatment planning.

Resting-State Functional Magnetic Resonance Imaging and Probabilistic Diffusion Tensor Imaging Demonstrate That the Greatest Functional and Structural Connectivity in the Hand Motor Homunculus Occurs in the Area of the Thumb.

The primary hand motor region is classically believed to be in the "hand knob" area in the precentral gyrus (PCG). However, hand motor task-based activation is often localized outside this area. The purpose of this study is to investigate the structural and functional connectivity driven by different seed locations corresponding to the little, index, and thumb in the PCG using probabilistic diffusion tractography (PDT) and resting-state functional magnetic resonance imaging (rfMRI). Twelve healthy subjects had three regions of interest (ROIs) placed in the left PCG: lateral to the hand knob (thumb area), within the hand knob (index finger area), and medial to the hand knob (little finger area). Connectivity maps were generated using PDT and rfMRI. Individual and group level analyses were performed. Results show that the greatest hand motor connectivity between both hemispheres was obtained using the ROI positioned just lateral to the hand knob in the PCG (the thumb area). The number of connected voxels in the PCG between the two hemispheres was greatest in the lateral-most ROI (the thumb area): 279 compared with 13 for the medial-most ROI and 9 for the central hand knob ROI. Similarly, the highest white matter connectivity between the two hemispheres resulted from the ROI placed in the lateral portion of PCG (p < 0.003). The maximal functional and structural connectivity of the hand motor area between hemispheres occurs in the thumb area, located laterally at the "hand knob." Thus, this location appears maximal for rfMRI and PDT seeding of the motor area.

Radiographic patterns of recurrence and pathologic correlation in malignant gliomas treated with bevacizumab.

Interpretation of MRI abnormalities in patients with malignant gliomas (MG) treated with bevacizumab is challenging. Recent reports describe quantitative analyses of diffusion-weighted imaging abnormalities not available in standard clinical settings, to differentiate tumor recurrence from treatment necrosis. We retrospectively reviewed bevacizumab treated MG patients who underwent surgery or autopsy to correlate radiographic recurrence patterns with pathologic findings. 32 patients with MG (26 glioblastoma, three anaplastic astrocytoma and three anaplastic oligodendroglioma) were identified. Recurrence patterns: local enhancing (n = 23), distant enhancing (n = 1), nonenhancing (n = 7) and leptomeningeal (n = 1). HISTOLOGY: tumor (n = 25), mixed tumor/necrosis (n = 5) and all necrosis (n = 2). On diffusion-weighted imaging, 5/32 had restricted diffusion (three mixed and two necrosis). Irrespective of radiographic recurrence pattern, tumor was found in 94% of cases. Restricted diffusion correlated with necrosis.

Diffusion Tensor Imaging Shows Corpus Callosum Differences between High-Grade Gliomas and Metastases.

BACKGROUND AND PURPOSE: The corpus callosum (CC) has an important role in regulating interhemispheric transfer and is thought to be instrumental in contralateral brain reorganization in patients with brain tumors, as suggested by a previous study reporting callosal differences between language dominance groups through diffusion tensor imaging (DTI) characteristics. The purpose of this study was to explore the structural differences in the CC between high-grade gliomas (HGGs) and metastatic tumors (METs) using the DTI characteristics of fractional anisotropy (FA), mean diffusivity (MD), and axial diffusivity (AD). METHODS: HGG (n = 30) and MET (n = 20) subjects with Magnetic Resonance Imaging (MRI) scans including DTI were retrospectively studied. The tumor and CC were segmented using the 3-dimensional T1-weighted scans to determine their volumes. The region of interest (ROI; mean volume of the ROI = 3,090 ± 464 mm3 ) of the body of the CC was overlaid onto the DTI parametric maps to obtain the averaged FA, MD, and AD values. RESULTS: There were significant differences in the distributions of FA and MD values between the two patient groups (mean FA for HGG/MET = .691/.646, P < .05; mean MD for HGG/MET = .894×10-3 mm 2/ second /.992×10-3 mm2 /second, P < .01), while there was no correlation between the DTI parameters and the anatomical volumes. CONCLUSION: These results suggest that there is more contralateral brain reorganization in HGG patients than MET patients and that neither the tumor nor callosal volume impact the degree of contralateral brain reorganization.

Intracranial metastasis in fibrolamellar hepatocellular carcinoma.

Fibrolamellar hepatocellular carcinoma (FLHCC) is a rare liver malignancy in adolescents and young adults. Surgery is the mainstay of therapy for primary and metastatic disease. Most patients relapse, with development of both local and distant metastases. Brain metastases from solid tumors are rare in the pediatric and young adult population. Here, we document three patients with brain metastases from FLHCC, confirmed by histology and molecular characterization of the chimeric fusion DNAJB1-PRKACA, each necessitating neurosurgical intervention. These observations highlight the ability of FLHCC to metastasize to the brain and suggest the need for surveillance neuroimaging for patients with advanced-stage disease.

Calcifying pseudoneoplasm of the spine: imaging and pathological features.

Calcifying pseudoneoplasms of the neuraxis are extremely rare calcified lesions that can occur anywhere in the central nervous system. These non-neoplastic lesions have been reported to arise both in the brain and spine with similar frequency and can be found intra-axially as well as extra-axially. The associated symptoms are generally due to mass effect rather than local invasion as calcifying pseudoneoplasms of the neuraxis are usually considered to be benign non-infiltrative lesions. We report a unique case of a 67-year-old male patient who developed lower extremity weakness and gait instability with imaging and histological features of calcifying pseudoneoplasm of the neuraxis occurring in the spine with adhesive features and intradural extension. Calcifying pseudoneoplasms are benign, slow-growing masses that can present with a wide variety of symptoms depending on the size and location of the tumor. The differential diagnosis for these entities can be narrowed taking into consideration relevant imaging features as well as important clinical information.

Corticosteroid therapy and severity of vasogenic edema in posterior reversible encephalopathy syndrome.

BACKGROUND: Posterior reversible encephalopathy syndrome (PRES) is a variable cerebrovascular syndrome associated with hypertension and autoregulatory failure. Steroids have been reported to both precipitate and treat PRES. We sought to determine the prevalence of steroid therapy at the time of PRES and to assess the relationship between steroid therapy and extent of vasogenic edema. METHODS: We performed a retrospective review of radiology reports between 2008 and 2014 from two academic medical centers to identify cases of PRES. Clinical and radiographic data were collected. Descriptive statistics were used to determine the prevalence of corticosteroid therapy at the time of PRES onset and the latency from steroid initiation to PRES onset. The association between steroid therapy and extent of vasogenic edema was assessed in multiple regression models. RESULTS: We identified 99 cases of PRES in 96 patients. The median age was 55years (IQR 30-65) and 74% were women. Steroid therapy at time of PRES onset was identified in 44 of 99 cases. Excluding patients on chronic therapy, the median duration of steroid exposure before PRES onset was 6 (IQR, 3-10) days. Steroid therapy was not associated with extent of vasogenic edema in unadjusted or linear and logistic regression models adjusted for age, sex, and maximum systolic blood pressure on day of onset. CONCLUSION: Corticosteroid therapy, often of brief duration, frequently preceded the onset of PRES and was not associated with severity of vasogenic edema.