Publications by authors named "Callen A"

Amphibians are among the most threatened vertebrate taxa globally. Their global decline necessitates effective conservation actions to bolster populations across both the larval and adult stages. Constructing man-made ponds is one action proven to enhance reproduction in pond-breeding amphibians.

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Cerebrospinal fluid (CSF) leaks are a challenging condition characterized by the loss of CSF, leading to severe orthostatic headaches and other debilitating symptoms. Diagnosis and management require a multifaceted approach involving clinical evaluation, imaging, and various treatment modalities to improve patient outcomes and quality of life.

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With large wildfires becoming more frequent, we must rapidly learn how megafires impact biodiversity to prioritize mitigation and improve policy. A key challenge is to discover how interactions among fire-regime components, drought and land tenure shape wildfire impacts. The globally unprecedented 2019-2020 Australian megafires burnt more than 10 million hectares, prompting major investment in biodiversity monitoring.

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Background And Purpose: Spontaneous intracranial hypotension (SIH) due to CSF venous fistula (CVF) is increasingly recognized as a secondary cause of headaches, with symptoms often overlapping with primary headache syndromes such as migraine. While brain MRI studies have focused on features indicative of SIH, findings that support an alternate headache etiology, such as the bifrontal white matter hyperintensities (WMH) often seen in migraines, have not been explored in this context. This study assesses 1) the quantity and distribution of WMH and 2) the presenting clinical features in patients with and without CVF found on dynamic decubitus CT myelography (dCTM).

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Article Synopsis
  • Spontaneous intracranial hypotension is primarily caused by spinal CSF leaks, mostly reported in adults, but this report focuses on its occurrence in children.
  • Recent advances in specialized myelography techniques have improved the localization of these leaks, yet there's been limited research in the pediatric population due to the rarity of the condition and concerns about invasive procedures.
  • This study reviews pediatric cases with spontaneously occurring spinal CSF leaks, identifying similar leak types found in adults, and demonstrates that advanced imaging techniques can effectively pinpoint and aid in the treatment of these leaks.
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  • Deep gray matter (DGM) atrophy and lesions are prevalent in multiple sclerosis (MS), particularly in relapsing-remitting MS (RRMS), with a higher incidence of thalamic lesions.
  • An optimized automated segmentation technique using 7 T MRI revealed significant DGM volume loss in MS patients compared to healthy controls, particularly in the caudate region.
  • The study found strong correlations between DGM atrophy, white matter lesions, and physical disability, suggesting that DGM abnormalities are closely linked to the severity of disability in RRMS.
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Spinal CSF leak care has evolved during the past several years due to pivotal advances in its diagnosis and treatment. To the reader of the (), it has been impossible to miss the exponential increase in groundbreaking research on spinal CSF leaks and spontaneous intracranial hypotension (SIH). While many clinical specialties have contributed to these successes, the neuroradiologist has been instrumental in driving this transformation due to innovations in noninvasive imaging, novel myelographic techniques, and image-guided therapies.

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Although 7 T MRI research has contributed much to our understanding of multiple sclerosis (MS) pathology, most prior data has come from small, single-center studies with varying methods. In order to truly know if such findings have widespread applicability, multicenter methods and studies are needed. To address this, members of the North American Imaging in MS (NAIMS) Cooperative worked together to create a multicenter collaborative study of 7 T MRI in MS.

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Objective: To identify distinct clinical or imaging subtypes of spontaneous intracranial hypotension (SIH) due to spinal cerebrospinal fluid (CSF) venous fistula (CVF).

Background: Spontaneous intracranial hypotension is classically understood to present clinically with an orthostatic headache and stereotyped brain magnetic resonance imaging (MRI) findings; however, most prior literature examining clinical and brain MRI features of SIH has focused on all types of spinal CSF leaks concurrently. This study aimed to evaluate whether data support the possibility of internally consistent subtypes based on brain imaging features and clinical symptoms analogous to those seen in primary headache syndromes.

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Introduction: The presence of psychiatric comorbidity in some neurological disorders is common. A bi-directional influence between some psychiatric and neurological disorders has been discussed, but not widely studied. There is an absence of literature on the typology and rates of neurology consultations in different types of psychiatric inpatients.

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Background And Objectives: Spinal CSF leaks lead to spontaneous intracranial hypotension (SIH). While International Classification of Headache Disorders, Third Edition (ICHD-3) criteria necessitate imaging confirmation or low opening pressure (OP) for SIH diagnosis, their sensitivity may be limited. We offered epidural blood patches (EBPs) to patients with symptoms suggestive of SIH, with and without a documented low OP or confirmed leak on imaging.

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Infarcts from cerebral air embolism are rare events with potentially catastrophic clinical consequences. The imaging features of cerebral air embolism are not well-defined in the literature. We report a novel constellation of MR imaging findings of cerebral arterial air emboli-induced infarcts in a series of 6 patients.

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Purpose Of Review: This review focuses on the challenges of diagnosing and treating spontaneous intracranial hypotension (SIH), a condition caused by spinal CSF leakage. It emphasizes the need for increased awareness and advocates for early and thoughtful use of empirical epidural blood patches (EBPs) in suspected cases.

Recent Findings: SIH diagnosis is hindered by variable symptoms and inconsistent imaging results, including normal brain MRI and unreliable spinal opening pressures.

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Background And Purpose: CSF venous fistula leads to spontaneous intracranial hypotension. The exact mechanisms underlying the development of CSF venous fistula remain unclear: Some researchers have postulated that underlying chronic intracranial hypertension may lead to damage to spinal arachnoid granulations, given that many patients with CSF venous fistulas have an elevated body mass index (BMI). However, individuals with higher BMIs are also more prone to spinal degenerative disease, and individuals with CSF venous fistulas also tend to be older.

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Background And Purpose: The inaugural "Spinal CSF Leak: Bridging the Gap" Conference was organized to address the complexities of diagnosing and treating spinal CSF leaks. This event aimed to converge the perspectives of clinicians, researchers, and patients with a patient-centered focus to explore the intricacies of spinal CSF leaks across 3 main domains: diagnosis, treatment, and aftercare.

Materials And Methods: Physician and patient speakers were invited to discuss the varied clinical presentations and diagnostic challenges of spinal CSF leaks, which often lead to misdiagnosis or delayed treatment.

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Article Synopsis
  • A report studied how a special imaging test called 18 F-PBR06-PET can help find signs of brain cell problems in people with multiple sclerosis (MS).
  • The study looked at 30 scans from 22 MS patients and compared their results with 8 healthy people to see how effective different treatments were.
  • Results showed MS patients had higher brain activity scores than healthy people, and even though stronger treatments helped reduce this activity, it still wasn't completely normal, linking it to their symptoms and brain changes.
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The cerebral cortex is vital for the processing and perception of sensory stimuli. In the somatosensory axis, information is received primarily by two distinct regions, the primary (S1) and secondary (S2) somatosensory cortices. Top-down circuits stemming from S1 can modulate mechanical and cooling but not heat stimuli such that circuit inhibition causes blunted perception.

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Purpose Of The Study: Posterior cortical atrophy is a clinico-radiographical syndrome that presents with higher-order visual dysfunction and is most commonly due to Alzheimer's disease. Understanding factors associated with atypical presentations of Alzheimer's disease, such as posterior cortical atrophy (PCA), holds promise to shape our understanding of AD pathophysiology. Thus, we aimed to compare MRI evidence of lobar microbleeds (LMBs) in posterior cortical atrophy (PCA) syndrome to typical AD (tAD) and to assess and compare MRI evidence of cerebral amyloid angiopathy (CAA) in each group.

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Background And Purpose: Cerebral venous sinus thrombosis (CVST) is an underrecognized cause of morbidity in acute traumatic brain injury (TBI). Radiologic diagnosis is challenging in the setting of concurrent extra-axial injury and a lack of standardized diagnostic criteria. The prevalence of traumatic thrombosis versus compression is unknown.

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Background And Purpose: CSF-venous fistula can be diagnosed with dynamic decubitus CT myelography. This study aimed to analyze the temporal characteristics of CSF-venous fistula visualization on multiphase decubitus CT myelography.

Materials And Methods: A retrospective, multisite study was conducted on patients diagnosed with CSF-venous fistula at 2 institutions between June 2017 and February 2023.

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Threatened species monitoring can produce enormous quantities of acoustic and visual recordings which must be searched for animal detections. Data coding is extremely time-consuming for humans and even though machine algorithms are emerging as useful tools to tackle this task, they too require large amounts of known detections for training. Citizen scientists are often recruited via crowd-sourcing to assist.

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We describe a novel patient-positioning device for dynamic CT myelography. Dynamic CT myelography requires angling the patient's spine to distribute dense contrast along the dependent thecal sac. The proposed device is constructed of a low-density reinforced polymer frame and can be raised or lowered to various heights with a hand-operated mechanism, allowing precise adjustment of the spinal angle and control of the contrast bolus, increasing the safety, reproducibility, and sensitivity of dynamic CT myelography.

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Background And Purpose: CSF-to-venous fistulas contribute to spontaneous intracranial hypotension. CT-guided fibrin occlusion has been described as a minimally invasive treatment strategy; however, its reproducibility across different institutions remains unclear. This multi-institution study evaluated the clinical and radiologic outcomes of CT-guided fibrin occlusion, hypothesizing a correlation among cure rates, fibrin injectate spread, and drainage patterns.

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