Pamela Schaefer - Academia.edu (original) (raw)

Papers by Pamela Schaefer

IDKD Springer series, 2024

Spontaneous ICH is usually intraparenchymal or subarachnoid in location. Intraparenchymal hemorrh... more Spontaneous ICH is usually intraparenchymal or subarachnoid in location. Intraparenchymal hemorrhages, encompassing lobar or centrally located hematomas, have diverse underlying causes, with cerebral amyloid angiopathy, characterized by lobar hemorrhage, being the most common. Hypertension is the second most common cause with a predilection for the basal ganglia, pons, and cerebellum. Subarachnoid hemorrhage is linked to aneurysm rupture in 85% of cases. Other relatively common causes of spontaneous intracranial hemorrhage include hemorrhagic conversion of ischemic infarction, cerebral arteriovenous malformations, dural arteriovenous fistulas, venous sinus thrombosis, cavernous malformations, reversible cerebral vasoconstriction syndrome, coagulopathy, and underlying tumors. Computed tomography followed by CT angiography is used for initial assessment of spontaneous ICH. However, MRI is more sensitive than CT for the detection of ICH and plays an important role in their etiology characterization. In this paper, the authors present a logical approach to imaging spontaneous intracranial hemorrhage including identifying prognostic factors, determining etiology, and establishing treatment.

Archives of neurology, Jul 1, 2000

Background: Most patients initially seen with a clini- cal syndrome consistent with a small-penet... more Background: Most patients initially seen with a clini- cal syndrome consistent with a small-penetrator infarct (SPI) also harbor multiple, chronic, hyperintense, white matter lesions on conventional magentic resonance imaging (ie, T2-weighted image (T2WI) and fluid- attenuation inversion recovery (FLAIR) imaging). Diffusion-weighted imaging (DWI) can identify the clinically relevant &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;index infarction&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; in such circum- stances, since it differentiates between acute and

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) is useful in diagnosing bacterial brain ... more BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) is useful in diagnosing bacterial brain abscesses, but DWI features of fungal brain abscesses have not been characterized. Because fungal abscesses are not purulent, we hypothesized that their DWI characteristics are distinct from those of bacterial abscesses. METHODS: We reviewed clinical, neuropathologic and neuroimaging findings of patients with fungal brain infections due to Aspergillus (n ‫؍‬ 6), Rhizopus (n ‫؍‬ 1), or Scedosporium (n ‫؍‬ 1) species. DWI and apparent diffusion coefficient (ADC) maps were obtained before definitive diagnosis and antifungal therapy. ADC ratios (lesion/contralateral white matter) were calculated. RESULTS: Two patients had a rapidly progressive, fatal course, with cerebritis and acute inflammation; fungal organisms were largely restricted to vessels. Lesions were predominantly nonenhancing and had heterogeneous foci of restricted diffusion. Six patients with subacute neurologic presentations had acute or chronic inflammation, capsule formation, focal necrosis, and fungal organisms disseminated throughout the lesion. Their abscesses were ring enhancing. In five, lesions had restricted diffusion in the central nonenhancing portions. The sixth patient had a lesion with a peripheral rim of restricted diffusion but elevated central diffusion; histopathology showed early abscess formation. Mean ADC for all lesions was 0.33 ؎ 0.06 ؋ 10 ؊3 mm 2 /s, with an average ADC ratio of 0.43. CONCLUSION: Fungal cerebral abscesses may have central restricted diffusion similar to that of bacterial abscesses but with histologic features of acute or chronic inflammation and necrosis rather than suppuration. Altered water diffusion in these lesions likely reflects highly proteinaceous fluid and cellular infiltration. Cerebral abscess is a well-described condition in immunocompromised patients (1). Abscesses may be secondary to bacterial, fungal, or parasitic organisms. These lesions often produce complex clinical and radiologic findings and require prompt recognition and treatment to avoid a fatal neurologic outcome. MR imaging is a sensitive and specific technique for the diagnosis of pyogenic bacterial abscess. Typi

American Journal of Neuroradiology, 1998

Our purpose was to determine the clinical feasibility of quantitative threedimensional functional... more Our purpose was to determine the clinical feasibility of quantitative threedimensional functional CT in patients with hyperacute stroke. METHODS: Twenty-two patients who underwent clinically indicated CT angiography were studied: nine patients had no stroke, eight had mature stroke, and five had hyperacute stroke (less than 3 hours since ictus). Maps were obtained of perfused cerebral blood volume (PBV), and CT angiograms were generated by using standard techniques. RESULTS: Normal PBV values (mean ؎ SEM) were 4.6 ؎ 0.15% in the gray matter, 1.75 ؎ 0.09% in the white matter, 2.91 ؎ 0.20% in the cerebellum, 3.18 ؎ 0.10% in the caudate, 2.84 ؎ 0.23% in the putamen, 2.92 ؎ 0.29% in the thalamus, and 1.66 ؎ 0.03% in the brain stem. For patients with mature stroke, ischemic changes were visible on noncontrast, contrastenhanced, and PBV scans. In patients with hyperacute stroke, ischemic changes were either absent or subtle before contrast administration, but became apparent on contrastenhanced scans. Quantitative PBV maps confirmed reduced regional perfusion. CT angiograms in the hyperacute group showed occlusion of vessels in locations appropriate to the PBV deficits seen. CONCLUSION: Quantitative three-dimensional functional CT is feasible for patients with hyperacute stroke. It is performed by using helical CT techniques, and yields measures of cerebrovascular physiological function, which are useful in this patient population. Methods Quantitative maps of cerebral perfusion were obtained retrospectively from data sets that were collected in an unselected

The New England Journal of Medicine, Mar 12, 2009

Severe headaches associated with hypertension developed in a 36-year-old woman 10 days after deli... more Severe headaches associated with hypertension developed in a 36-year-old woman 10 days after delivery of twins by cesarean section; initial brain magnetic resonance imaging (MRI) and computed tomographic examinations were normal. Headaches persisted despite antihypertensive medications; a seizure and an episode of aphasia and hemiparesis occurred. Repeated MRI and magnetic resonance angiography showed posterior white-matter changes on T2-weighted sequences and multifocal narrowing and dilatation of intracranial arteries. A diagnostic procedure was performed.

Cerebrovascular Diseases, 2002

Objective: Diffusion-weighted imaging (DWI) conveys temporal as well as anatomic information abou... more Objective: Diffusion-weighted imaging (DWI) conveys temporal as well as anatomic information about brain infarction, and is therefore well suited to identify ischemic injury that has occurred simultaneously, or closely linked in time, with a transient ischemic attack (TIA). We aimed to determine the proportion and clinical characteristics of patients with TIA who harbor infarction(s) on DWI. Methods: Using T2-weighted imaging (T2-WI), fast fluid attenuated inversion recovery (FLAIR), and DWI, we studied 57 consecutive patients presenting with acute focal neurologic symptoms lasting less than 24 h. Results: A hyperintense DWI lesion was identified in a vascular territory appropriate to the symptoms in 27 patients (47%). Lesions judged to be clinically appropriate on T2-WI and FLAIR overlapped with a DWI lesion in 41 and 48% of patients, respectively. Independent predictors of infarction on DWI were previous nonstereotypic TIAs, presentation with motor symptoms, and identified stroke mechanism. Conclusion: DWI establishes that recent infarction occurs in almost half of patients with the clinical syndrome of TIA and this subgroup is more likely to harbor an underlying cardiac or cerebrovascular abnormality.

Radiology, 1999

To evaluate the diagnostic accuracy of diffusion-weighted magnetic resonance (MR) imaging perform... more To evaluate the diagnostic accuracy of diffusion-weighted magnetic resonance (MR) imaging performed within 6 hours of the onset of stroke symptoms. The authors reviewed the patient records and images from all patients hospitalized in a 10-month period in whom diffusion-weighted imaging was performed within 6 hours of the onset of strokelike symptoms (n = 22). Analyses included comparison of the initial interpretation of the diffusion-weighted images with the final clinical diagnosis; blinded reviews of computed tomographic (CT) scans and conventional and diffusion-weighted images; and determination of lesion contrast-to-noise ratios (CNRs). Diffusion-weighted images indicated stroke in 14 patients, all of whom had a final diagnosis of acute stroke. Diffusion-weighted images were negative in eight patients, all of whom had a final clinical diagnosis other than stroke (100% sensitivity, 100% specificity, chi 2 = 23.00, P < .0001). Blinded reviews yielded 100% sensitivity and 86% specificity for diffusion-weighted MR imaging (chi 2 = 15.43, P < .0005); 18% sensitivity and 100% specificity for conventional MR imaging (chi 2 = 2.85, P > .2); and 45% sensitivity and 100% specificity for CT (chi 2 = 4.40, P > .10). Lesion percentage CNRs were 77% for diffusion-weighted imaging, 5.5% for CT, 9.8% for T2-weighted MR imaging, and 3.1% for proton-density-weighted MR imaging (P < .002 for diffusion-weighted imaging vs others). Diffusion-weighted MR imaging is highly accurate for diagnosing stroke within 6 hours of symptom onset and is superior to CT and conventional MR imaging.

Neurology, Jun 1, 1999

Background: Diffusion-weighted MRI (DWI) represents a major advance in the early diagnosis of acu... more Background: Diffusion-weighted MRI (DWI) represents a major advance in the early diagnosis of acute ischemic stroke. When abnormal in patients with stroke-like deficit, DWI usually establishes the presence and location of ischemic brain injury. However, this is not always the case.Objective: To investigate patients with stroke-like deficits occurring without DWI abnormalities in brain regions clinically suspected to be responsible.Methods: We identified 27 of 782 consecutive patients scanned when stroke-like neurologic deficits were still present and who had normal DWI in the brain region(s) clinically implicated. Based on all the clinical and radiologic data, we attempted to arrive at a pathophysiologic diagnosis in each.Results: Best final diagnosis was a stroke mimic in 37% and a cerebral ischemic event in 63%. Stroke mimics (10 patients) included migraine, seizures, functional disorder, transient global amnesia, and brain tumor. The remaining patients were considered to have had cerebral ischemic events: lacunar syndrome (7 patients; 3 with infarcts demonstrated subsequently) and hemispheric cortical syndrome (10 patients; 5 with TIA, 2 with prolonged reversible deficits, 3 with infarction on follow-up imaging). In each of the latter three patients, the regions destined to infarct showed decreased perfusion on the initial hemodynamically weighted MRI (HWI).Conclusions: Normal DWI in patients with stroke-like deficits should stimulate a search for nonischemic cause of symptoms. However, more than one-half of such patients have an ischemic cause as the best clinical diagnosis. Small brainstem lacunar infarctions may escape detection. Concomitant HWI can identify some patients with brain ischemia that is symptomatic but not yet to the stage of causing DWI abnormality.

Stroke, May 1, 1997

Background The pathophysiology of eclampsia remains unclear. While the majority of patients devel... more Background The pathophysiology of eclampsia remains unclear. While the majority of patients develop reversible T2 hyperintense signal abnormalities on MR scans and reversible neurological deficits, some patients do develop infarctions (permanent T2 hyperintense abnormalities) and permanent neurological impairment. Routine MRI cannot prospectively differentiate between these two patient groups. Echo-planar diffusion-weighted imaging, however, is a new technique that clearly differentiates between cytotoxic and vasogenic edema. Case Description A 30-year-old woman developed symptoms consistent with eclampsia 24 hours after delivering premature twins. An MRI demonstrated extensive, diffuse T2 hyperintense signal abnormalities involving subcortical white matter and adjacent gray matter with a posterior predominance, consistent with either infarction or hypertensive ischemic encephalopathy. Diffusion-weighted images demonstrated increased diffusion, consistent with vasogenic edema and hypertensive ischemic encephalopathy. Conclusions Unlike routine MRI, diffusion-weighted imaging reliably differentiates between vasogenic edema and cytotoxic edema. Consequently, in eclamptic patients diffusion-weighted imaging can afford clear differentiation between hypertensive ischemic encephalopathy and infarction, two very different entities with very different treatment protocols. Diffusion-weighted imaging should be performed in all eclamptic patients and should greatly affect their management.

Journal of Child Neurology, Jun 1, 1998

20. Deonna TW, Roulet E, Fontan D, Marcoz JP: Speech and oromotor deficits of epileptic origin in... more 20. Deonna TW, Roulet E, Fontan D, Marcoz JP: Speech and oromotor deficits of epileptic origin in benign partial epilepsy of childhood with rolandic spikes (BPERS). Neuropediatrics 1993;24:83-87. 21. Hirsch E, Marescaux C, Maquet P, et al: Landau-Kleffner syndrome: A clinical and EEG study of five cases. Epilepsia 1990;31:756-767. 22. Holmes GL, McKeever M, Saunders Z: Epileptiform activity in aphasia of childhood: An epiphenomenon? EpiLepsia 1981;22:631-639. 23. Deonna T, Beaumanoir A, Gaillard F, et al: Acquired aphasia in childhood with seizure dirsorders: A heterogenous syndrome. Neuropediatrics 1997;8:263-273. 24. Gascon G, Victor D, Lombroso CT: Language disorders, convulsive disorder, and electroencephalographic abnormalities. Acquired syndrome in children. Arch Neurol 1973;28:156-162. 25. Deonna T, Ziegler AL: Adult follow-up of the acquired aphasiaepilepsy syndrome in childhood. Report of 7 cases. Neuropediatrics 1989; 20:132-138.

American Journal of Neuroradiology, Sep 1, 2005

BACKGROUND AND PURPOSE: Conventional MR imaging findings are considered to be inadequate for reli... more BACKGROUND AND PURPOSE: Conventional MR imaging findings are considered to be inadequate for reliably distinguishing radiation necrosis from tumor recurrence in patients with glioma. Despite this belief, we hypothesized that certain conventional MR imaging findings, alone or in combination, though not definitive, may favor one or another of these diagnoses in proton beam-treated patients with new enhancing lesions on serial scanning. METHODS: MR imaging findings (axial T1-, T2-, and post-gadolinium T1-weighted) of 27 proton beam radiation therapy patients with high-grade gliomas were retrospectively reviewed. Entry criteria included new MR imaging enhancing lesions after treatment and histologically unequivocal biopsy proof of diagnosis. Readers rated corpus callosum involvement, midline spread, subependymal spread, new discrete multiple enhancing foci, a "spreading wavefront" appearance, and septum pellucidum involvement. Statistical analysis was by the Fisher exact test. RESULTS: Corpus callosum involvement in combination with multiple other findings was highly associated with progressive glioma. These combinations included involvement of the corpus callosum with multiple enhancing foci (P ‫؍‬ .02), involvement of the corpus callosum with crossing the midline and multiple enhancing lesions (P ‫؍‬ .04), and involvement of the corpus callosum with subependymal spread and multiple enhancing lesions (P ‫؍‬ .01). CONCLUSIONS: In proton beam-treated patients with glioma, corpus callosum involvement, in conjunction with multiple enhancing lesions with or without crossing of the midline and subependymal spread, favors predominant glioma progression. Overall, combinations of enhancement patterns were more likely than individual patterns to distinguish necrosis from predominant tumor progression. Together with clinical and functional imaging findings, these results may assist in determining the need for biopsy. The distinction between radiation necrosis and recurrent high-grade glioma remains a challenge despite advanced imaging techniques such as perfusion-and diffusion-weighted MR imaging (1-5), MR spectroscopy (6), and positron emission tomography (7-9). MR imaging characteristics of high-grade tumor classically include intravenous contrast enhancement, mass effect, and associated vasogenic edema (10). Unfortunately, radiation necrosis entails the same

Stroke, Aug 1, 2010

Background and Purpose-The purpose of this study was to determine whether acute diffusion-weighte... more Background and Purpose-The purpose of this study was to determine whether acute diffusion-weighted imaging (DWI) and mean transit time (MTT) lesion volumes and presenting National Institutes of Health Stroke Scale (NIHSS) can identify patients with acute ischemic stroke who will have a high probability of good and poor outcomes. Methods-Fifty-four patients with acute ischemic stroke who had MRI within 9 hours of symptom onset and 3-month follow-up with modified Rankin scale were evaluated. Acute DWI and MTT lesion volumes and baseline NIHSS scores were calculated. Clinical outcomes were considered good if the modified Rankin Scale was 0 to 2. Results-The 33 of 54 (61%) patients with good outcomes had significantly smaller DWI lesion volumes (Pϭ0.0001), smaller MTT lesion volumes (PϽ0.0001), and lower NIHSS scores (PϽ0.0001) compared with those with poor outcomes. Receiver operating characteristic curves for DWI, MTT, and NIHSS relative to poor outcome had areas under the curve of 0.889, 0.854, and 0.930, respectively, which were not significantly different. DWI and MTT lesion volumes predicted outcome better than mismatch volume or percentage mismatch. All patients with a DWI volume Ͼ72 mL (13 of 54) and an NIHSS score Ͼ20 (6 of 54) had poor outcomes. All patients with an MTT volume of Ͻ47 mL (16 of 54) and an NIHSS score Ͻ8 (17 of 54) had good outcomes. Combining clinical and imaging thresholds improved prognostic yield (70%) over clinical (43%) or imaging (54%) thresholds alone (Pϭ0.01). Conclusions-Combining quantitative DWI and MTT with NIHSS predicts good and poor outcomes with high probability and is superior to NIHSS alone.

European Radiology Experimental

Flow-related artifacts have been observed in highly accelerated T1-weighted contrast-enhanced wav... more Flow-related artifacts have been observed in highly accelerated T1-weighted contrast-enhanced wave-controlled aliasing in parallel imaging (CAIPI) magnetization-prepared rapid gradient-echo (MPRAGE) imaging and can lead to diagnostic uncertainty. We developed an optimized flow-mitigated Wave-CAIPI MPRAGE acquisition protocol to reduce these artifacts through testing in a custom-built flow phantom. In the phantom experiment, maximal flow artifact reduction was achieved with the combination of flow compensation gradients and radial reordered k-space acquisition and was included in the optimized sequence. Clinical evaluation of the optimized MPRAGE sequence was performed in 64 adult patients, who all underwent contrast-enhanced Wave-CAIPI MPRAGE imaging without flow-compensation and with optimized flow-compensation parameters. All images were evaluated for the presence of flow-related artifacts, signal-to-noise ratio (SNR), gray-white matter contrast, enhancing lesion contrast, and ima...

American Journal of Neuroradiology, 2021

American Journal of Neuroradiology, 2020

Annals of Neurology, 2020

Many patients with severe coronavirus disease 2019 (COVID‐19) remain unresponsive after surviving... more Many patients with severe coronavirus disease 2019 (COVID‐19) remain unresponsive after surviving critical illness. Although several structural brain abnormalities have been described, their impact on brain function and implications for prognosis are unknown. Functional neuroimaging, which has prognostic significance, has yet to be explored in this population. Here we describe a patient with severe COVID‐19 who, despite prolonged unresponsiveness and structural brain abnormalities, demonstrated intact functional network connectivity, and weeks later recovered the ability to follow commands. When prognosticating for survivors of severe COVID‐19, clinicians should consider that brain networks may remain functionally intact despite structural injury and prolonged unresponsiveness. ANN NEUROL 2020;88:851–854

BACKGROUND AND PURPOSETo evaluate an ultrafast 3D-FLAIR sequence using Wave-CAIPI encoding (Wave-... more BACKGROUND AND PURPOSETo evaluate an ultrafast 3D-FLAIR sequence using Wave-CAIPI encoding (Wave-FLAIR) compared to standard 3D-FLAIR in the visualization and volumetric estimation of cerebral white matter lesions in a clinical setting.MATERIALS AND METHODS42 consecutive patients underwent 3T brain MRI including standard 3D-FLAIR (acceleration factor R=2, scan time TA=7:15 minutes) and resolution-matched ultrafast Wave-FLAIR sequences (R=6, TA=2:45 minutes for the 20-ch coil; R=9, TA=1:50 minutes for the 32-ch coil) as part of clinical evaluation for demyelinating disease. Automated segmentation of cerebral white matter lesions was performed using the Lesion Segmentation Tool in SPM. Student’s t-test, intra-class correlation coefficient (ICC), relative lesion volume difference (LVD) and Dice similarity coefficients (DSC) were used to compare volumetric measurements between sequences. Two blinded neuroradiologists evaluated the visualization of white matter lesions, artifact and over...

Frontiers in Neurology, 2020

Results: Wave-CAIPI post-contrast T1 SPACE was non-inferior to the standard T1 SPACE for visualiz... more Results: Wave-CAIPI post-contrast T1 SPACE was non-inferior to the standard T1 SPACE for visualization of enhancing lesions (P < 0.01) and offered equivalent diagnostic quality performance and only marginally higher background noise compared to the standard sequence. Goncalves Filho et al. Brain Metastases Evaluation With Post-contrast Wave-T1-SPACE Conclusions: Our findings suggest that Wave-CAIPI post-contrast T1 SPACE provides equivalent visualization of pathology and overall diagnostic quality with three times reduced scan time compared to the standard 3D T1 SPACE.

American Journal of Neuroradiology, 2017

BACKGROUND AND PURPOSE: The development of new MR imaging scanners with stronger gradients and im... more BACKGROUND AND PURPOSE: The development of new MR imaging scanners with stronger gradients and improvement in coil technology, allied with emerging fast imaging techniques, has allowed a substantial reduction in MR imaging scan times. Our goal was to develop a 10-minute gadolinium-enhanced brain MR imaging protocol with accelerated sequences and to evaluate its diagnostic performance compared with the standard clinical protocol. MATERIALS AND METHODS: Fifty-three patients referred for brain MR imaging with contrast were scanned with a 3T scanner. Each MR image consisted of 5 basic fast precontrast sequences plus standard and accelerated versions of the same postcontrast T1WI sequences. Two neuroradiologists assessed the image quality and the final diagnosis for each set of postcontrast sequences and compared their performances. RESULTS: The acquisition time of the combined accelerated pre-and postcontrast sequences was 10 minutes and 15 seconds; and of the fast postcontrast sequences, 3 minutes and 36 seconds, 46% of the standard sequences. The 10-minute postcontrast axial T1WI had fewer image artifacts (P Ͻ .001) and better overall diagnostic quality (P Ͻ .001). Although the 10-minute MPRAGE sequence showed a tendency to have more artifacts than the standard sequence (P ϭ .08), the overall diagnostic quality was similar (P ϭ .66). Moreover, there was no statistically significant difference in the diagnostic performance between the protocols. The sensitivity, specificity, and accuracy values for the 10-minute protocol were 100.0%, 88.9%, and 98.1%. CONCLUSIONS: The 10-minute brain MR imaging protocol with contrast is comparable in diagnostic performance with the standard protocol in an inpatient motion-prone population, with the additional benefits of reducing acquisition times and image artifacts. ABBREVIATIONS: GRAPPA ϭ generalized autocalibrating partially parallel acquisition; GRE ϭ gradient-echo; SE ϭ spin-echo