Biomedical subjects
Publications and source records attributed to J S Hahn.
We describe a term newborn with tuberous sclerosis who presented with a neonatal brain tumor, diagnosed as a subependymal giant cell astrocytoma. We compare the various imaging modalities used in the diagnosis of this tumor.
As a percentage of the gross national product, expenditures for health care in the United States are considerably larger than in Canada, even though one in seven Americans is uninsured whereas all Canadians have comprehensive health insurance. Among the sectors of health care, the difference in spending is especially large for physicians' services. In 1985, per capita expenditure was $347 in the United States and only $202 (in U.S. dollars) in Canada, a ratio of 1.72. We undertook a quantitative analysis of this ratio. We found that the higher expenditures per capita in the United States are explained entirely by higher fees; the quantity of physicians' services per capita is actually lower in the United States than in Canada. U.S. fees for procedures are more than three times as high as Canadian fees; the difference in fees for evaluation and management services is about 80 percent. Despite the large difference in fees, physicians' net incomes in the United States are only about one-third higher than in Canada. A parallel analysis of Iowa and Manitoba yielded results similar to those for the United States and Canada, except that physicians' net incomes in Iowa are about 60 percent higher than in Manitoba. Updating the analysis to 1987 on the basis of changes in each country between 1985 and 1987 yielded results similar to those obtained for 1985. We suggest that increased use of physicians' services in Canada may result from universal insurance coverage and from encouragement of use by the larger number of physicians who are paid lower fees per service. U.S. physicians' net income is not increased as much as the higher U.S. fees would predict, probably because of greater overhead expenses and the lower workloads of America's procedure-oriented physicians.
Bronchopulmonary dysplasia (BPD) is a chronic lung disease which occurs in premature infants who require prolonged mechanical ventilation and supplemental oxygen support. Infants with severe BPD often have neurological sequelae or early mortality. We have observed a pattern of delay in the maturation of cerebral electrical activity of some infants who have more severe forms of BPD. This delayed electroencephalographic (EEG) maturation or 'dysmaturity' is best recognized when the conceptional age (CA) of the premature infant approaches term and is characterized by the presence of EEG activity which normally disappears in premature infants by 36-37 weeks CA. We studied 36 infants with BPD who had serial EEGs and at least 1 EEG between 37 and 42 weeks CA. Dysmature EEGs were found in 23 infants. Unfavorable outcomes were found in 83% (19/23) of these infants, including 22% (5/23) mortality, and 61% (14/23) abnormal or suspect neurological outcome. Thirteen infants had EEGs which lacked dysmature features. Of these infants, 62% (8/13) had normal neurological outcome, and 38% (5/13) had unfavorable outcome (1 death, 2 abnormal, and 2 suspect). In 2 of the 5 infants with unfavorable outcomes without dysmature EEGs, a suppression-burst pattern (known to be associated with neurological sequelae) was found. The presence of dysmature patterns in the near-term or term EEG was associated with significantly less favorable outcome (P = 0.01). Several other clinical factors which were associated with dysmature EEGs are also discussed.
Forty patients (median age 49.6 years) were treated for primary gastrointestinal lymphoma between 1979 and 1989. There were twenty-three cases of gastric lymphoma and seventeen cases of intestinal lymphoma. Following surgery, seventeen patients received postoperative chemoradiotherapy (ACOP) by the sandwich technique, seven patients received postoperative radiotherapy, and sixteen patients did not receive any other form of adjuvant treatment. Nineteen patients were stage IE and twenty-one were stage IIE. Stage IE disease was more prevalent in the gastric lymphoma group than the intestinal lymphoma group (p less than 0.01). At a median follow-up of 17 months (1-102 + months), 17 of 19 stage IE patients and 15 of 21 stage IIE patients remained alive. The survival rate was 90% in the postoperative chemoradiotherapy group and 83.3% in the postoperative radiotherapy group at five years, and 42.7% in the surgery alone group at four years, which showed statistical significance (p less than 0.01, p less than 0.05, each). Statistically improved survival rates were achieved with a postoperative chemoradiotherapy modality in intestinal lymphoma (p less than 0.01), stage IIE (p less than 0.01), intermediate grade by NCI criteria (p less than 0.01), poorly differentiated lymphocytic lymphoma (p less than 0.05), and diffuse histiocytic lymphoma (p less than 0.01) according to Rappaport classification, compared to those of the surgically treated only group. Three local relapses occurred in the operation alone group, and one in the adjuvant radiotherapy group which occurred simultaneously with distant lymph node recurrence. The pathologic stage of all of these relapsed patients was stage IIE-2. These results suggest that adjuvant chemoradiotherapy in completely resected localized gastrointestinal non-Hodgkin's lymphoma can decrease local and systemic relapse resulting in long-term disease free survival and overall survival compared to operation alone.
Interburst intervals (IBIs) are quiescent periods of cerebral activity, which normally occur in the electroencephalograms (EEGs) of premature infants. Although it is generally felt that the duration of these intervals shorten with increasing conceptional age (CA), no systemic studies of IBIs have been done in a large group of normal premature infants with long-term follow-up and using multichannel routine EEGs. In this study, we measured the IBIs, using defined criteria, in 36 premature infants who were normal at 3 years. The IBIs were measured in 104 EEGs, obtained from these infants, using standard recording techniques. Mean and the maximum IBIs were calculated. IBI duration decreased with increasing CA, although this trend was not very prominent when very restrictive criteria for measurement of IBI length were used. Less restrictive criteria for defining an IBI led to trends which are similar to those of previous studies. Various clinical factors, such as mild encephalopathies, small intraventricular/subependymal hemorrhages, mild bronchopulmonary dysplasia, or patent ductus arteriosus did not significantly alter IBI durations. Comparison with other techniques of IBI measurement and recording are discussed. The longest period of continuous activity during a routine recording was also measured and was found to increase with increasing CA.
Of 78 children identified with hemolytic-uremic syndrome at the Children's Hospital, Boston, from 1976 to 1986, 16 patients (20.5%) had neurological manifestations during their hospitalization. The most common manifestations were significant alterations in consciousness (coma, stupor) in 12 patients, and either generalized or partial seizures in ten patients. Others included hemiplegia (4 patients), decerebrate posturing (3), cortical blindness (2), hallucinations (1), and dystonic posturing (1). Cranial computed tomographic scans were abnormal in eight of 11 patients scanned. The abnormalities included diffuse cerebral edema (4 patients), large vessel infarctions (3), diffuse multiple small infarcts (4), and multiple hemorrhages (1). Five patients died as a result of their central nervous system complications, and six had neurological sequelae at discharge. Five patients recovered and at discharge had no evidence of neurological dysfunction.
It is widely held that a glutamate-like toxin that resembles N-methyl-D-aspartate may be responsible for the death of nerve cells seen after severe neurological insults including stroke, seizures, and degenerative disorders, such as Huntington disease, Alzheimer disease, and the amyotrophic lateral sclerosis-parkinsonism-dementia complex found on Guam. One puzzling fact about these maladies is the differential vulnerability of specific groups of neurons peculiar to each condition. We report here that an identified population of central neurons, rat retinal ganglion cells, are resistant to the neurotoxic effects of millimolar concentrations of glutamate under otherwise normal culture conditions. Patch-clamp experiments show that this resistance is associated with a very small ionic current response to N-methyl-D-aspartate. Varying the ionic milieu by increasing the extracellular Ca2+ concentration, however, results in a striking increase in glutamate-induced cell death in this population. Under these conditions, Mg2+ or the amino acid antagonist MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo-(alpha,gamma)-cyclohepten-5 ,10-imine maleate], blockers of N-methyl-D-aspartate receptor-coupled ion channels, completely abrogate the lethal effects of glutamate. These findings strongly suggest that Ca2+ entry through N-methyl-D-aspartate-activated channels is responsible for this type of neuronal death and suggest strategies that may be clinically useful in the treatment of various neurological disorders.
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We examined the differences in the economic performance of 80 matched pairs of investor-owned chain and not-for-profit hospitals in eight states during 1978 and 1980, and considered how their operating strategies might affect their relative success in a more price-conscious market. We found that total charges (adjusted for case mix) and net revenues per case were both significantly higher in the investor-owned chain hospitals, mainly because of higher charges for ancillary services; there were no significant differences between the two groups of hospitals in regard to patient-care costs per case (adjusted for case mix), but the investor-owned hospitals had significantly higher administrative overhead costs; investor-owned hospitals were more profitable; investor-owned hospitals had fewer employees per occupied bed but paid more per employee; investor-owned hospitals had funded more of their capital through debt and had significantly higher capital costs in proportion to their operating costs; and the two groups did not differ in patient mix, as measured by their Medicare case-mix indexes or the proportions of their patients covered by Medicare or Medicaid. We conclude that investor-owned chain hospitals generated higher profits through more aggressive pricing practices rather than operating efficiencies - a result not unexpected in view of past cost-based reimbursement policies. Recent changes in these policies are creating new pressures for cost control and moderation in charges, to which both types of hospitals must adapt. Neither type has a clear-cut advantage in the ability to make the necessary changes.
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An 8-year-old boy developed anaphylaxis after receiving his maintenance dose of immunotherapy and proceeded to display the signs and symptoms of serum sickness. These consisted of fever, arthralgia, arthritis, urticaria followed by a hemorrhagic palpable rash, edema, lymphadenopathy, splenomegaly, abdominal pain, proteinuria, and neurologic manifestations consistent with vascular compromise of the posterior cerebral circulation. A skin biopsy specimen revealed perivascular infiltrates of lymphocytes and few polymorphonuclear neutrophils. The timing of events in this patient suggests that immunotherapy initiated a chain of events beginning with anaphylaxis and leading to serum sickness. It is hypothesized that the enhanced vascular permeability that accompanied the anaphylaxis allowed immune complexes that may have preexisted in the circulation to deposit in the blood vessels of the patient. These complexes may or may not have been related to the immunotherapy itself. Because antihistamines are known to prevent the induction of serum sickness, early and aggressive treatment of anaphylaxis during immunotherapy may prevent the occurrence of immune complex disease.
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Neonatal meningitis is associated with significant neurologic sequelae. Previous studies from our laboratory and others demonstrated electroencephalography (EEG) to be a useful tool in predicting long-term neurologic outcome in at-risk neonates. We, therefore, retrospectively studied 29 infants with culture-proved neonatal meningitis who died in the neonatal period or survived to follow-up at a mean of 34.4 months. Seventy-five EEGs were obtained during the acute phase of infection; the degree of EEG background abnormality proved to be an accurate predictor of outcome. Infants who had normal or mildly abnormal backgrounds had normal outcomes, whereas those with markedly abnormal EEGs died or manifested severe neurologic sequelae at follow-up. When the EEG was considered with the presence or absence of seizures and the level of consciousness, an accurate prediction of neurologic outcome was obtained in 27 infants (93%). Although the EEG patterns were generally nonspecific, some abnormalities, such as positive rolandic sharp waves, persistent hemispheric or focal voltage attenuation, suggested more specific pathology (i.e., deep white matter necrosis, large-vessel infarction and abscess, respectively). EEG was also valuable for the recognition of subtle and subclinical seizures. Therefore, we conclude that EEG is a valuable tool for predicting the long-term prognoses of infants with neonatal meningitis.
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Hypermedia systems allow storage of huge collections of information from a wide variety of sources and afford immediate and random access to the collections. While providing unprecedented possibilities for storing and disseminating information, hypermedia systems have the potential to confuse the developer and the user alike with a multitude of intricacies. When hypermedia are being used in the teaching/learning process, they can cause cognitive overload and disorientation, if not designed properly. One way to resolve these problems is to develop system and content flowcharts. Although developing system and content flowcharts seems to be time-consuming work, it saves time and energy over the long run. Furthermore, it promotes efficiency.
BACKGROUND AND PURPOSE: Although holoprosencephaly has been known for many years, few detailed analyses have been performed in a large series of patients to outline the range of morphology in this disorder, particularly regarding the deep gray nuclear structures. We reviewed a large patient cohort to elucidate the combinations of morphologic aberrations of the deep gray nuclei and to correlate those findings with recent discoveries in embryology and developmental neurogenetics. METHODS: A retrospective review of the imaging records of 57 patients (43 MR studies and 14 high-quality CT studies) to categorize the spectrum of deep gray nuclear malformations. The hypothalami, caudate nuclei, lentiform nuclei, thalami, and mesencephalon were graded as to their degree of noncleavage. Spatial orientation was also evaluated, as was the relationship of the basal ganglia to the diencephalic structures and mesencephalon. The extent of noncleavage of the various nuclei was then assessed for statistical association. RESULTS: In every study on which it could be accurately assessed, we found some degree of hypothalamic noncleavage. Noncleavage was also common in the caudate nuclei (96%), lentiform nuclei (85%), and thalami (67%). Complete and partial noncleavage were more common in the caudate nuclei than in the lentiform nuclei. The degree of thalamic noncleavage was uniformly less than that in the caudate and lentiform nuclei. Abnormalities in alignment of the long axis of the thalamus were seen in 71% of cases, and were associated with degree of thalamic noncleavage; 27% of patients had some degree of mesencephalic noncleavage. CONCLUSION: The hypothalamus and caudate nuclei are the most severely affected structures in holoprosencephaly, and the mesencephalic structures are more commonly involved than previously thought in this "prosencephalic disorder." These findings suggest the lack of induction of the most rostral aspects of the embryonic floor plate as the cause of this disorder.