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Biomedical subjects

William G Bradley

Publications and source records attributed to William G Bradley.

11 recordsLinked to original sources
PubMed2006

Idiopathic normal pressure hydrocephalus may be a "two hit" disease: benign external hydrocephalus in infancy followed by deep white matter ischemia in late adulthood.

PURPOSE: To determine if normal pressure hydrocephalus (NPH) could result from decreased resorption of cerebrospinal fluid (CSF) by the arachnoidal villi, leading to benign external hydrocephalus [BEH] in infancy, followed by deep white matter ischemia (DWMI) in late adulthood (the more hydrophilic environment increasing resistance to CSF flow through the extracellular space (ECS) of the brain). MATERIALS AND METHODS: CSF outflow via the fourth ventricle and the ECS of the brain was mathematically modeled using a parallel electrical circuit analog. The apparent diffusion coefficient (ADC) was measured as a surrogate of the amount of water in the ECS in normals, patients with symptomatic NPH, and patients with dilated ventricles without symptoms of NPH ("pre-NPH"). RESULTS: The electrical circuit model demonstrates increasing ventricular volume with increasing resistance to flow through the ECS of the brain. ADC measurements performed in the centrum semiovale are significantly higher in patients with NPH and "pre-NPH" than in age-matched controls (P<0.05), controlling for the same degree of DWMI indicating increased fluid in the ECS of the brain. CONCLUSION: The electrical circuit analog and finding of increased periventricular ADC support the theory that NPH is a "two hit" disease.

Aged↗
PubMed2005

The ependymal "Dot-Dash" sign: an MR imaging finding of early multiple sclerosis.

BACKGROUND AND PURPOSE: Corpus callosum lesions are of specific interest in the evaluation of suspected multiple sclerosis in brain MR imaging. Using thin-section sagittal fluid-attenuated inversion recovery images, researchers have shown that the finding of "subcallosal striations" correlates significantly with the diagnosis of multiple sclerosis. Using the same MR imaging technique, we describe a finding of ependymal irregularity that we call the "Dot-Dash" sign, which we believe to be associated with early multiple sclerosis. METHODS: Sagittal 2-mm fast fluid-attenuated inversion recovery images were obtained in 70 patients. Thirty-five patients had multiple sclerosis according to the Poser criteria, and 35 were age-matched controls. The images were reviewed in a blinded fashion by an experienced neuroradiologist for the presence or absence of the Dot-Dash sign. RESULTS: The correlation between the Dot-Dash sign and definite clinical multiple sclerosis is highly significant (P < .001), with a sensitivity of 91.4% and a specificity of 65.7%. In the age group of < or =50 years, the sensitivity was 95.7% and the specificity, 71.9%. CONCLUSION: The Dot-Dash sign of ependymal irregularity on thin-section sagittal fluid-attenuated inversion recovery images is an early marker for multiple sclerosis, which is particularly useful in the younger patient. This finding appears to be more sensitive for early lesion detection than any other multiple sclerosis imaging finding yet described in the literature.

Adolescent↗
PubMed2004

Increased intracranial volume: a clue to the etiology of idiopathic normal-pressure hydrocephalus?

BACKGROUND AND PURPOSE: The etiology of idiopathic normal-pressure hydrocephalus (NPH) is unknown. The purpose of this study was to examine the hypothesis that NPH begins in infancy as benign external hydrocephalus due to decreased uptake of CSF by the arachnoid villi. Since this occurs before the sutures fuse, a secondary hypothesis is that the intracranial volumes of patients with NPH should be larger than those of healthy individuals. METHODS: Intracranial volumes of 51 patients with clinically suspected NPH were compared with those of age- and sex-matched control subjects. All patients underwent phase-contrast CSF velocity MR imaging. They had aqueductal CSF stroke volumes of at least 60 microL, which was 50% higher than previously published normal values. Intracranial volumes were measured and compared between groups. RESULTS: The average intracranial volume for men with NPH (n = 22) was 1682 mL compared with 1565 for male control subjects (n = 55). The NPH volume averaged 118 mL (7.5%) larger than the control volume (P = .003). The average intracranial volume for women with NPH (n = 29) was 1493 mL compared with 1405 mL for female control subjects (n = 55). The NPH volume was 88 mL (6.3%) larger than the control volume (P = .002). CONCLUSION: Patients with NPH have intracranial volumes significantly larger than normal, suggesting that the initial insult occurs before the sutures fuse at 1 year of age. The patients somehow remain asymptomatic until their later years, when a second insult must occur, leading to symptomatic NPH.

Aged↗
PubMed2003

Head position modulates activity in the human parietal eye fields.

For us to interact with our environment we need to know where objects are around us, relative to our body. In monkeys, a body-centered map of visual space is known to exist within the parietal eye fields. This map is formed by the modulation of retinal responses by gain fields to gaze position. In humans, no map of body-centered space has yet been discovered but clinical data suggest that the right parietal lobe is predominantly responsible for visuospatial function. Using functional MRI, we have been able to demonstrate that an area in the intraparietal sulcus of humans has properties very similar to the parietal eye fields of monkeys. This area demonstrates BOLD signal changes related to the visual, saccadic, and memory components of saccade tasks that are analogous to the visual, saccadic, and memory responses of neurons within the parietal eye fields of monkeys. More importantly, the amount of signal change seen in this region is modulated by head position relative to the body, suggesting that a gain field dependent body-centered representation of space exists bilaterally within the parietal lobes in humans.

Adult↗
PubMedDate not supplied

Image Interpretation Session: Sunday, November 27, 2005.

The Sunday afternoon Image Interpretation Session has been a high point of the annual meeting of the Radiological Society of North America for over 65 years. A panel of five experts has been selected, representing the very best from the fields of neurologic, abdominal, thoracic, pediatric, and musculoskeletal radiology. Each panelist will dazzle us with an insightful analysis of two difficult cases in their area of expertise. The panelists are to be lauded for their bravery in subjecting their diagnostic acumen to the scrutiny of the thousands of radiologists in the audience. The cases, representing a diverse spectrum of diseases and disease manifestations, were selected from recent clinical imaging studies performed at the Stanford University Medical Center or the Lucille Salter Packard Children's Hospital. This session celebrates the skills of diagnostic radiologists worldwide, who are called on daily to amalgamate disparate clinical information with complex imaging data into focused differential diagnoses and effective treatment planning. We hope that these cases will serve to illustrate the central role that expert image interpretation plays in the care of patients. We welcome our audience of RSNA attendees, readers of RadioGraphics, and cyberspace denizens to join with our experts in solving these medical puzzles and to enjoy the excitement of unraveling the unknown.

Adolescent↗