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Biomedical subjects

B D Snyder

Publications and source records attributed to B D Snyder.

At least 19 recordsLinked to original sources
PubMed1992

Acute radicular pain as a presenting symptom in multiple sclerosis.

From December 1973 through November 1988, we cared for 11 patients who presented with acute radicular pain and in whom radicular compression was ruled out by imaging techniques. Eventually, multiple sclerosis was diagnosed and judged to be responsible for the acute radiculopathy. The patients (seven women, aged 18 to 40 years; median, 32 years) and four men (aged 23 to 34 years; median, 29 years) were followed up from 6 months to 15 years (mean, 4 years 11 months). They represent 3.9% of 282 newly diagnosed cases of multiple sclerosis during the same 15 years. A retrospective analysis of the characteristics of their illness and its evolution was conducted. Six had lumbosacral radiculopathies; three, cervical and two, thoracic. In six of the 11 patients, symptoms occurred in close relationship to trauma; seven had recurrent radicular pain; four had other pain syndromes; and three others, paroxysmal symptoms. One patient died of complications from multiple sclerosis 3 years after diagnosis. Three others were rated five or greater in the extended Kurtzke disability status scale during follow-up.

Adolescent↗
PubMed1989

Outcome data.

Explore the source record for details and available documents.

Health Maintenance Organizations↗
PubMed1988

Posterior cortical atrophy.

Five patients had progressive dementia heralded by disorders of higher visual function. All eventually developed alexia, agraphia, visual agnosia, and components of Balint's, Gerstmann's, and transcortical sensory aphasia syndromes. Memory, insight, and judgment were relatively preserved until late in the course. Predominant parieto-occipital atrophy was demonstrated on both computed tomography and magnetic resonance imaging in two of the patients; posterior circulation was normal by angiography in the three studied. To date, no pathologic specimen is available for study; speculations on the underlying pathologic condition include an atypical clinical variant of Alzheimer's disease, a lobar atrophy analogous to Pick's disease, or some previously unrecognized entity.

Aged↗
PubMed1987

Can embolic stroke be diagnosed on the basis of neurologic clinical criteria?

Diagnosis of embolic stroke is based on identification of a source of embolus (SOE) and on neurologic symptoms acknowledged as "clinical criteria." To test the validity of these criteria, we analyzed the symptoms at onset in 193 patients hospitalized after acute cerebral infarction. Patients were grouped according to identification of a cardiac SOE (106 patients), an arterial SOE (38 patients), or no SOE (49 patients). Cross-tabulations demonstrated that only rapidity and loss of consciousness at onset were associated with the presence of a cardiac SOE to a significant degree. Although these symptoms were highly specific for cardiac SOE, they were not sensitive. A distinct clinical neurologic profile from the symptoms and mode of onset was not identified.

Adult↗
PubMed1987

Trabecular bone remodeling around smooth and porous implants in an equine patellar model.

The objective of this investigation was to examine the stress-morphology relationships for trabecular bone around implants with different surface characteristics. Stainless steel spheres with either a polished surface or a sintered-bead porous coating were implanted unilaterally into equine patellae and maintained for a 6 month period. Stereological methods were used to quantify the trabecular bone morphology and finite element analyses were performed to predict the trabecular bone stresses. In general, the remodeling response around the smooth implants was greater than that around those porous implants that exhibited bone ingrowth. In accordance with these differences, the finite element models predicted greater changes in the stresses adjacent to the smooth implants due to the nonlinear boundary conditions. However, it did not appear that the trajectorial theory, in its simplest form, was applicable to the remodeling induced by the implants. A linear relationship between the change in bone areal density and the change in von Mises effective stress provides support for the hypothesis that the architecture of trabecular bone corresponds to an optimal structure. The results also demonstrated that, under certain circumstances, small changes in the stress state may result in large changes in the principal material orientation.

Animals↗
PubMed1987

Emergency carotid artery thrombectomy for postpartum hemiplegia.

The case of a 22-year-old patient who suffered from postpartum hemiplegia due to thrombosis of the internal carotid artery is reported. She was treated aggressively with pentobarbital coma, angiography, and thrombectomy and recovered with minimal deficit.

Adult↗
PubMed1987

Aneurysmal subarachnoid hemorrhage presenting as cardiorespiratory arrest.

Three cases of subarachnoid hemorrhage (SAH) due to ruptured developmental (berry) aneurysm are reported. Two patients presented with cardiac arrest and were successfully resuscitated, but the diagnosis of SAH was delayed and this most likely influenced poor final outcome. The third patient presented with irreversible respiratory arrest. The possible mechanisms responsible for SAH-triggered cardiac arrhythmia and/or respiratory arrest are discussed. Absence of previous cardiac history, persistent headache, focal neurologic findings (especially papilledema or subhyaloid hemorrhages) should warn the clinician of the possibility of SAH and warrant further neurologic investigation.

Arrhythmias, Cardiac↗
PubMed1986

Mannitol pharmacokinetics and serum osmolality in dogs and humans.

The relationship between mannitol pharmacokinetics and changes in serum osmolality were studied in dogs and humans. Four human subjects each received between 0.5 and 0.7 g/kg of mannitol as an i.v. infusion given over 15 min. Intravenous bolus doses of 0.5, 1.0 and 1.5 g/kg were given to each of five animals. Serial determinations of serum osmolality and serum mannitol concentrations were then performed. Mannitol disposition was best described using a biexponential equation and assuming a two-compartment, open model with elimination from the central compartment. For human subjects, the mean (+/- S.D.) distribution half-life was 2.11 +/- 2.67 min and the elimination half-life was 71.15 +/- 27.02 min. The volume of distribution was 0.47 +/- 0.50 liters/kg and total body clearance was 7.15 +/- 10.23 ml X min-1 X kg-1. The disposition of mannitol in dogs is similar to that observed in humans. Mannitol clearance was independent of dose whereas the central compartment volume was significantly larger (P less than .005) in animals receiving the 1.5-g/kg dose. The volume change is probably due to a rapid, uncompensated shift of water from intracellular to extracellular space. There was a strong positive correlation (r = 0.90) between mannitol concentration and serum osmolality changes. However, neither maximum serum mannitol concentration nor maximum serum osmolality increased proportionately with dose. Only the 1.5-g/kg dose produced a sustained elevation of serum osmolality, confirming that larger doses are more likely to result in prolonged hypertonic dehydration.

Adult↗
PubMed1985

Stress analysis of a condylar knee tibial component: influence of metaphyseal shell properties and cement injection depth.

We generated three-dimensional finite element models of the proximal tibia with an implanted tibial component. The component features a cobalt-chromium tray with four short vertical posts and a porous-coated surface for improved fixation to polymethylmethacrylate (PMMA). We examined the stresses after varying: the structural rigidity of the metaphyseal cortical shell; the surface area of the cobalt-chromium tray; and the depth of pressure-injected PMMA bone cement. Our results indicate that previous finite element models of prosthetic tibial components have overestimated the structural contribution of the metaphyseal cortical shell by a factor of approximately 6. A standard size tray, in contrast to a tray that extends to the cortical shell, does not significantly alter the axial load distribution but could result in bone resorption beyond the tray periphery. An important consequence of the component peg locations is that they direct the compressive stresses into dense regions of trabeculae that run from the subchondral articular surface to the metaphyseal-diaphyseal junction. The use of a modified von Mises failure criterion suggests that at excessive load levels the most likely location of material failure is at the bone cement-trabecular bone interface immediately distal to the fixation posts. Due to its added rigidity, injection of cement beyond the fixation posts results in slightly increased stresses in this region, but these stress increases are compensated for by an increased strength of the cement-bone composite.

Bone Cements↗
PubMed1979

Delayed meningitis following stapes surgery.

Perilymphatic fistulae, developing even years after stapedectomy, open a communication between the perilymph and middle ear. These fistulae constitute a potential pathway for flora of the middle ear to invade the subarachnoid space by way of the cochlear aqueduct. Our patient developed pneumococcal meningitis 14 months after stapedectomy. The history of stapedectomy in a patient with meningitis is an indication for reexploration+ion of the operative site. The appearance of fistula symptoms in patients who have had stapedectomy indicates a high risk for development of intracranial infection.

Ear, Middle↗
PubMed1978

Isolated benign cerebral vasculitis.

A young woman south medical care for headache, nausea, and evolving focal neurologic signs. The CSF was normal; cerebral angiography showed segmental narrowing and irregularity of intraparenchymal arterioles. Isolated cerebral vasculitis was the clinical diagnosis made by careful exclusion; the illness reponded well to steroids and there was later angiographic evidence of healing.

Adult↗
PubMed1978

Behavioral toxicity of anesthetic gases.

Operating room personnel were studied for evidence of acute reversible or chronic cumulative cognitive dysfunction as measured by psychometric testing. In comparison with matched controls, no acute reversible deficits were noted in a relatively unpolluted operating room environment. There were only 2 marginally significant test differences between the control and operating room groups; however, control subjects did better than operating room personnel on 16 of 18 tests at both the beginning and end of the work week. Analyses of the deficit patterns and correlations with years of operating room exposure only weakly support the hypothesis that the test differences are due to toxic exposure.

Adult↗
PubMed1977

Neurology in the psychiatry Boards.

On the basis of his experience as an examiner, the author discusses the problems encountered in assessing psychiatrists' abilities in clinical neurology for certification by the American Board of Psychiatry and Neurology. Hoping to stimulate discussion among trainees, training programs, and the Board, he outlines five paradigms designed to survey neurological knowledge and skill potentially needed by psychiatrists in various situations; these are reduced to specific topics on which Board candidates should be questioned. Relationships between training and examination expectations are discussed.

Achievement↗
PubMed1977

Neurologic status and prognosis after cardiopulmonary arrest: I. A retrospective study.

A retrospective survey of survivors of cardiorespiratory arrest included 34 patients. Twenty-one had a good outcome neurologically and 13 were seriously impaired. Depth and duration of postarrest coma correlated significantly with poor neurologic function. Seventy percent of the seriously impaired patients never regained consciousness and none emerged from coma within 5 days; 90 percent of patients with good outcome were alert within 18 hours after resuscitation. Coma motor unresponsiveness, absent pupillary light reflexes, and absent oculocephalic responses were closely associated with dismal prognosis for neurologic functioning. This retrospective study cannot provide a basis for discontinuation of life support at any specific time.

Adult↗
PubMed1977

Cervical myelopathy complicating cerebral angiography. Report of a case and review of the literature.

Transverse cervical myelopathy, at C-6 level, followed injection of Renografin-60 into the right thyrocervical trunk during cerebral angiography. Review of the literature yielded only two cases in which attempted posterior fossa angiography resulted in cervical myelopathy. Two more cases were found. In one, cervical myelopathy occurred during aortography in a patient with coractation of the aorta, and in the other it followed mediastinal angiography. Summation of anoxia, hemorrhage, and cellular toxicity is responsible for spinal cord necrosis following arterial injection of contrast material.

Adult↗