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Biomedical subjects

K Silver

Publications and source records attributed to K Silver.

At least 55 records · Page 3Linked to original sources
PubMed1994

Human interindividual variability--a major source of uncertainty in assessing risks for noncancer health effects.

For noncancer effects, the degree of human interindividual variability plays a central role in determining the risk that can be expected at low exposures. This discussion reviews available data on observations of interindividual variability in (a) breathing rates, based on observations in British coal miners; (b) systemic pharmacokinetic parameters, based on studies of a number of drugs; (c) susceptibility to neurological effects from fetal exposure to methyl mercury, based on observations of the incidence of effects in relation to hair mercury levels; and (d) chronic lung function changes in relation to long-term exposure to cigarette smoke. The quantitative ranges of predictions that follow from uncertainties in estimates of interindividual variability in susceptibility are illustrated.

Disease Susceptibility↗
PubMed1994

Benign familial nocturnal alternating hemiplegia of childhood.

In infancy, two brothers developed recurrent attacks of alternating or bilateral hemiplegia arising exclusively out of sleep. The episodes were terminated by even brief sleep. Neither child had hypotonia, dystonic attacks, paroxysmal eye movement abnormalities, or other features characteristic of the now-classic form of alternating hemiplegia of childhood (AHC). The development of the brothers has so far remained normal. Both parents have a history of migraine. In the older boy, magnetic resonance spectroscopy (MRS) of muscle showed increased inorganic phosphate similar to what is found in children with AHC. In the younger brother and parents, MRS of muscle was normal. Other investigations were unrevealing. Flunarizine greatly reduced the duration of attacks. This genetically determined disorder represents a specific entity that is probably migraine-related and is easily misdiagnosed as AHC. Because of its benign course, particularly as far as mental development is concerned, it must be distinguished from classic AHC, which has a terrible prognosis.

Adult↗
PubMed1994

Medical treatment of Rasmussen's syndrome (chronic encephalitis and epilepsy): effect of high-dose steroids or immunoglobulins in 19 patients.

We treated 19 patients with Rasmussen's syndrome (chronic encephalitis and epilepsy)--a rare progressive disorder of unknown etiology causing focal epilepsy, hemiparesis, and intellectual deterioration--with intravenous immunoglobulins, high-dose steroids, or both, to control seizures and improve the end point of the disease. Ten of 17 patients receiving steroids, and eight of nine patients receiving immunoglobulins, had some reduction of seizure frequency in the short term. Improvement in hemiparesis was slight. The effect of these drugs in ameliorating the end point of the disease in the long term remains unknown, and further multicenter studies with standardized protocols are warranted.

Adolescent↗
PubMed1993

Evidence for mitochondrial dysfunction in patients with alternating hemiplegia of childhood.

Phosphorus magnetic resonance spectra of resting muscle were obtained from 4 patients with alternating hemiplegia of childhood. All patients had abnormally high resonance intensities from inorganic phosphate and an abnormally low calculated cytosolic phosphorylation potential. Two of the 4 patients had abnormally low resonance intensities from phosphocreatine and an abnormally high calculated cytosolic free adenosine diphosphate concentration. These abnormalities are indicative of mitochondrial dysfunction. The combination of a central nervous system disorder and evidence of mitochondrial dysfunction in muscle suggests that alternating hemiplegia of childhood may represent a previously unrecognized phenotype of mitochondrial disease.

Adenosine Diphosphate↗
PubMed1993

Pulmonary artery hypertension in severe aortic stenosis: incidence and mechanism.

We investigated the incidence and mechanism of pulmonary artery hypertension (PAH) in a consecutive series of patients with aortic stenosis who were undergoing diagnostic cardiac catheterization. Forty-five patients with severe aortic stenosis were divided into two groups: group 1 comprised 13 patients (29%) with PAH (pulmonary artery systolic pressure > 50 mm Hg); group 2 comprised 32 patients (71%) without PAH. Group 1 patients had a higher incidence of congestive heart failure, a lower left ventricular ejection fraction and cardiac index, and more mitral regurgitation as compared with group 2 patients. Of the 13 group 1 patients, 8 had a transpulmonary gradient (pulmonary artery mean pressure--pulmonary capillary wedge pressure) > or = 10 mm Hg, consistent with reactive PAH. We conclude that PAH frequently accompanies aortic stenosis and is often reactive.

Acute Disease↗
PubMed1993

Proton MR spectroscopic characterization of differences in regional brain metabolic abnormalities in mitochondrial encephalomyopathies.

Localized brain proton MR spectra were acquired from patients with different mitochondrial encephalomyopathies (myoclonus epilepsy with ragged-red fibers [MERRF], Kearns-Sayre syndrome [KSS], and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes [MELAS]). The regional brain metabolic abnormalities in patients with these syndromes showed different features consistent with the distinct phenotypes. In MERRF, only one of four patients showed an increase in the lactate/creatine resonance intensity ratio (an index of impairment of oxidative metabolism) in spectra from central (supraventricular) or occipital brain volumes, and this was small. There were significant decreases in N-acetylaspartate/creatine (a measure of neuronal loss or dysfunction) in central cerebral volumes of demented patients and, more prominently, in occipital volumes. In the one patient in whom it was studied, the cerebellum also showed a decreased N-acetylaspartate/creatine. Spectra from two patients with KSS both showed large (four- to sevenfold) increases in lactate/creatine and large decreases in N-acetylaspartate/creatine in central brain volumes. Yet another pattern of regional metabolic abnormality was present in the MELAS syndrome, where proton spectroscopic imaging demonstrated focal localization of abnormally increased lactate/creatine and decreased N-acetylaspartate/creatine to the regions of the stroke-like lesions on conventional MR images. Serial studies emphasized that the regional metabolic abnormalities in MELAS are highly variable as the stroke-like lesions appear and evolve.

Aspartic Acid↗
PubMed1993

Alternating hemiplegia of childhood: a study of 10 patients and results of flunarizine treatment.

Alternating hemiplegia of childhood is a rare syndrome characterized by onset before 18 months of age of frequent attacks of alternating paralysis, transient ocular palsies, nystagmus, choreoathetosis, and autonomic dysfunction. We describe features of 10 patients followed for up to 27 years. The mechanism of alternating hemiplegia remains unknown but an association to migraine is suspected because of the strong family history of migraine and aura symptoms in some patients. We treated nine patients with flunarizine, a calcium channel blocker, for up to 5 years; they showed a reduction in duration of the hemiplegic attacks, but the episodes ceased completely in only one patient. With long-term follow-up, the persistent motor, movement, and cognitive deficits are more apparent. It is not certain if the flunarizine alters this course.

Adolescent↗
PubMed1993

Inflammatory myopathy and Walker-Warburg syndrome: etiologic implications.

Walker-Warburg syndrome is a well delineated clinical entity with characteristic brain and eye anomalies. Recent diagnostic surveys have revealed that muscular dystrophy is an obligatory feature of this syndrome. We report a patient with an inflammatory myopathy that preceded dystrophic changes. While reports of parental consanguinity and multiple affected sibships strongly suggest an autosomal recessive genetic basis for this syndrome, previous pathological analyses of the CNS have suggested an inflammatory process. Our case supports both the notion of an aberrant inflammatory process that is likely under genetic control or etiologic heterogeneity (phenocopies) underlying this syndrome.

Brain↗
PubMed1992

Left ventricular mass quantitation using single-phase cardiac magnetic resonance imaging.

Magnetic resonance imaging (MRI) has been used to measure left ventricular (LV) mass in animals with superior accuracy. However, its use in cardiac patients has been limited by the long total scan times necessitated by imaging the heart at end-diastole at each of 8 to 10 slice locations. Recent canine studies showed that LV mass may be determined accurately, with considerable timesavings, by use of sequential images throughout the cardiac cycle (single-phase MRI). Twenty normal subjects underwent spin-echo MRI to determine the relationship between LV mass computed from single-phase MRI and results obtained from the more time-consuming end-diastolic MRI (which was used as the reference standard for this study). The left ventricle was spanned with 2 interleaved series of 5 short-axis 1 cm thick slices. 5 images, evenly spaced throughout the cardiac cycle, were obtained at each slice location in all subjects. LV mass ranged from 86 to 198 g. Although end-diastolic LV mass exceeded single-phase results by an average of 5 g (p less than 0.002), there was a close correlation between the 2 (slope = 0.99; r = 0.96). Although LV mass derived from end-diastolic images exceeded single-phase results, this difference is unlikely to be clinically significant and is small compared with the standard error of echocardiographic methods. Furthermore, when the order in which single-phase images were selected was reversed, there was improved agreement with end-diastolic MRI.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart↗
PubMed1992

Syndrome of microcephaly, Brachmann-de Lange-like facial changes, severe metatarsus adductus, and developmental delay: mild Brachmann-de Lange syndrome?

We report on 4 individuals (3 sibs and their father) with a syndrome of growth retardation, microcephaly, minor facial anomalies reminiscent of a mild Brachmann-de Lange syndrome (BDLS), severe metatarsus adductus, developmental delay, and unusual dermatoglyphics. The syndrome, which seems to be inherited as an autosomal dominant trait with variable expressivity, resembles mild BDLS.

Adult↗
PubMed1992

How useful is the WAIS-R in closed head injury assessment?

The present study examined whether head-injury assessment findings based on the WAIS could be generalized to the WAIS-R. It also investigated whether WAIS-R findings from individuals with focal mass lesions could be generalized to closed-head-injured patients with mass lesions. Subjects were 71 CHI patients assessed with the WAIS-R an average of 1.38 years post-injury. Results were not always consistent with previous research. Patients with left or right mass lesion loci did not exhibit previously reported Verbal IQ-Performance IQ discrepancies.

Adult↗
PubMed1992

Brain dysgenesis and congenital intracerebral calcification associated with 3-hydroxyisobutyric aciduria.

Monozygotic male twins born to nonconsanguineous parents had dysmorphic facial features, microcephaly, migrational brain disorder, and congenital intracerebral calcification. They excreted excessive amounts of 3-hydroxyisobutyric acid, a metabolite of valine, and had evidence of impaired oxidative metabolism and metabolic acidosis. The level of 3-hydroxyisobutyrate in stored samples of midtrimester amniotic fluid was found to be high. The association of 3-hydroxyisobutyric aciduria with brain dysgenesis is a newly recognized mendelian disorder; its recurrence in a family at risk is potentially avoidable by prenatal diagnosis.

Amniotic Fluid↗
PubMed1991

Mucolipidosis type IV: clinical manifestations and natural history.

The clinical manifestations and psychomotor development of five patients with mucolipidosis IV (MLIV) from three Ashkenazi-Jewish families are reported. The presenting symptoms were hypotonia, developmental delay, corneal clouding, and puffy eyelids. Four of the patients had convergent strabismus and none progressed beyond a developmental age of 15 months. One patient died of aspiration at 17 years while the oldest patient entered puberty at 20 years, developed a coarse face at 30 years, and is now 32 years old. Histopathological studies in four patients showed storage changes characteristic of MLIV.

Adolescent↗
PubMed1991

Magnetic resonance imaging shows specific abnormalities in the MELAS syndrome.

The MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) can be difficult to identify. We report MRI abnormalities that we believe are specific to this disorder in three patients with complete or partial MELAS syndrome. The patients all showed an unusual pattern on T2-weighted MRI with multifocal areas of hyperintense signal confined to the cortex of the cerebrum, cerebellum, and adjacent white matter. Some images suggested selective cortical involvement of deeper layers only. Deep white matter was relatively spared, distinguishing this from usual cerebrovascular disease or the edema after status epilepticus. Specificity of these findings is further suggested by a good correlation of these findings with the previously described unique postmortem brain pathology of MELAS.

Acidosis, Lactic↗