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Biomedical subjects

W R Selman

Publications and source records attributed to W R Selman.

At least 37 records · Page 2Linked to original sources
PubMed1995

Cerebral arterial aneurysm formation and rupture in 20,767 elderly patients: hypertension and other risk factors.

Cerebral arterial aneurysms are common in the general population and their rupture is a catastrophic event. Considerable uncertainty remains concerning the conditions that predispose individuals to aneurysm formation or rupture. The role of systemic hypertension in aneurysm formation and rupture has been especially controversial. Demographic variables have rarely been addressed because of the small sample sizes in previous studies. The authors describe the demographics and prevalence of hypertension in 20,767 Medicare patients with an unruptured aneurysm and compared these to a random sample of the hospitalized Medicare population. The prevalence of hypertension in patients with unruptured aneurysms was 43.2% compared with 34.4% in the random sample. Patients who survived their initial hospitalization were separated into two groups: those with an unruptured cerebral aneurysm as the primary diagnosis and those with an unruptured cerebral aneurysm as a secondary diagnosis. Follow-up data for 18,119 patients were examined to determine the risk of subarachnoid hemorrhage (SAH) associated with age, gender, race, hypertension, insulin-dependent diabetes mellitus, and surgical treatment. For patients with an unruptured cerebral aneurysm as the primary diagnosis, hypertension was found to be a significant risk factor for future SAH (risk ratio: 1.46, 95% confidence interval (CI): 1.01-2.11), whereas surgical treatment (risk ratio: 0.29, 95% CI: 0.09-0.97) had a significant protective effect. Advancing age had a small but significant protective effect in both groups. Elderly patients identified with unruptured aneurysms are more likely to have coexisting hypertension than the general hospitalized population. In elderly patients hospitalized with an unruptured cerebral aneurysm as their primary diagnosis, hypertension is a risk factor for subsequent SAH, whereas surgical treatment is a protective factor against SAH.

Age Factors↗
PubMed1994

Immediate recovery of pituitary function after transsphenoidal resection of pituitary macroadenomas.

Mild hyperprolactinemia frequently accompanies the hypopituitarism associated with pituitary macroadenomas not secreting PRL. Because of this association, hypopituitarism was postulated to be due to compression of portal vessels. We postulate that resumption of hypothalamic control over pituitary function occurs immediately after adenomectomy. To test this hypothesis, we examined pituitary function before and after transsphenoidal adenomectomy in 26 ACTH-deficient patients and 23 subjects with normal adrenal and thyroidal functions (control group). Glucocorticoids, given only to ACTH-deficient subjects, were withdrawn 36 h after surgery. ACTH, cortisol, and PRL levels were measured twice daily in all patients. Both ACTH and PRL levels increased hours after surgery in controls and returned to baseline over 4 days. In all hypopituitary subjects, PRL levels decreased by 50% within hours of adenomectomy and remained so until discharge. ACTH levels, measured simultaneously, increased within hours in 17 of 26 hypopituitary patients, all of whom recovered normal adrenal function before discharge. Nine additional patients had low ACTH levels and required cortisol replacement. The reciprocal changes in PRL and ACTH levels measured simultaneously, hours after surgery, support the hypothesis that hypopituitarism is reversible and largely caused by compression of the protal vessels and the resulting interruption of delivery of hypothalamic hormones. The persistence of hypopituitarism in some patients suggests that ischemic necrosis of the anterior pituitary could limit recovery.

Adenoma↗
PubMed1994

Temporary vessel occlusion in spontaneously hypertensive and normotensive rats. Effect of single and multiple episodes on tissue metabolism and volume of infarction.

Temporary occlusion of an intracranial artery is frequently necessary in the surgical management of intracranial aneurysms, arteriovenous malformations, and tumors. While the risks of vessel damage associated with clip application have been lessened by improved design, the threat of ischemic damage remains. It is unclear whether multiple, brief periods of clip application are more or less safe than a single period of occlusion, and whether the underlying cerebrovascular status influences the outcome from either method. The effect of each of these paradigms (single: 1-hour occlusion; multiple: three 20-minute episodes separated by 10 minutes of reperfusion) on histopathological outcome was assessed in a middle cerebral artery (MCA) occlusion model using both normotensive and spontaneously hypertensive rats. The mean volume of infarction (+/- standard error of the mean) was not different between the single-ischemic (49.4 +/- 17.3 cu mm) and the multiple-ischemic (42.9 +/- 12.9 cu mm) episode groups of normotensive rats, whereas in the spontaneously hypertensive rats a significant difference existed between the volume of infarction for the single-occlusion group (126.7 +/- 18.7 cu mm) and the multiple-occlusion group (162.4 +/- 15.5 cu mm) (p < 0.05). The metabolic data obtained from spontaneously hypertensive animals did not provide an explanation for the larger infarction in that there were no significant differences between the single- and multiple-occlusion groups with respect to tissue glucose, adenosine triphosphate, or lactate levels. The results suggest that intermittent reperfusion may have different effects depending not only on the degree and duration of ischemia and reperfusion, but also on the underlying cerebrovascular status.

Adenosine Triphosphate↗
PubMed1994

Early reversal of acidosis and metabolic recovery following ischemia.

Tissue acidosis is believed to be a key element in ischemic injury of neural tissue. The goal of this study was to determine whether persisting postischemic acidosis or the extent of acidosis would affect metabolic recovery following an ischemic event. Intracellular pH (pHi), adenosine triphosphate, phosphocreatine, and lactate levels were measured in the cerebral cortex during the early stages of reperfusion, following either 5 or 10 minutes of global ischemia in both normo- and hyperglycemic gerbils. A total of 130 gerbils were injected with a solution containing 1.5 ml Neutral Red (1%) (+/- 2.5 gm/kg glucose); 30 minutes later, the gerbils were placed under halothane anesthesia, and the carotid arteries were occluded for either 5 or 10 minutes. The brains were frozen in liquid nitrogen at 0, 15, 30, 60, and 120 seconds after reperfusion; they were sectioned and the block face was photographed to determine the pHi by using Neutral Red histophotometry. At the conclusion of the ischemia, the pHi in all groups had decreased significantly from a control value of 7.05 +/- 0.03) (mean +/- standard error of the mean). In normoglycemic brains, the pHi values fell to 6.71 +/- 0.04 and 6.68 +/- 0.11 after 5 and 10 minutes of ischemia, respectively. Hyperglycemic brains were more acidotic; values fell to 6.57 +/- 0.10 and 6.52 +/- 0.24 after 5 and 10 minutes of ischemia, respectively. Lactate levels were approximately fivefold greater than those of control tissue in normoglycemic brains, while lactate levels in hyperglycemic brains were increased eightfold. The adenosine triphosphate and phosphocreatine levels were depleted at the end of ischemia in all groups. After 2 minutes of reflow activity, the pHi levels in both normo- and hyperglycemic brains were restored to those of control values in the '5-minute ischemic group, while the pHi levels remained significantly depressed in the 10-minute ischemic group. Restoration of high-energy phosphates was similar in normoglycemic brains regardless of ischemic duration, recovering to only 20% of the restoration obtained in control tissue at 2 minutes. In hyperglycemic brains, however, there was complete recovery of high-energy phosphates by 2 minutes of reflow activity following 5 minutes of ischemia. Extending the ischemic period to 10 minutes in hyperglycemic brains slowed the rate of metabolic recovery to that observed in normoglycemic brains. The results indicate that the reflow period permits the rapid restoration of pHi levels substantially before the normalization of primary energetic compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Acidosis↗
PubMed1992

Evaluation of experimental early acute cerebral ischemia before the development of edema: use of dynamic, contrast-enhanced and diffusion-weighted MR scanning.

The ability of dynamic, contrast-enhanced, magnetic susceptibility-weighted scanning to delineate early experimental acute cerebral infarction was compared with that of heavily T2-weighted and diffusion-weighted spin echo scanning. Spontaneously hypertensive rats, which had undergone right middle cerebral artery occlusion, were studied from 15 min to 3 h post ligation on a 1.5-T clinical whole-body imager. In contrast to the diffusion- and T2-weighted spin echo scans, the dynamic, contrast-enhanced technique clearly and consistently delineated the nonperfused regions as early as 15 min post ligation.

Acute Disease↗
PubMed1992

Glutamate-induced energetic stress in hippocampal slices: evidence against NMDA and glutamate uptake as mediators.

The introduction of exogenous glutamate to normally respiring hippocampal slices produced substantial reductions in ATP, phosphocreatine (PCr) and intracellular pH (pHi) when the concentration exceeded 1 mM. These changes were not prevented by addition of MK-801 (an NMDA receptor antagonist), nor were they mimicked by NMDA or high potassium. In addition, the glutamate-induced metabolic alterations were not prevented by addition of aspartate-b-hydroxymate or sodium substitution by choline, both of which should inhibit high-affinity sodium-dependent glutamate uptake. These results suggest that glutamate alone can produce marked energetic stress in neural tissue, even when glucose and oxygen are maintained at control levels; and that the energetic stress does not appear to be specifically mediated by NMDA-induced depolarization, or by high-affinity uptake of glutamate.

Animals↗
PubMed1991

Rapid metabolic failure in spontaneously hypertensive rats after middle cerebral artery ligation.

The metabolic characteristics of the penumbral region were examined in spontaneously hypertensive rats one hour after permanent middle cerebral artery occlusion. The effect of hyperglycemia on this region was examined by providing a glucose load prior to occlusion. The depressed concentrations of adenosine triphosphate and elevated levels of lactate in the penumbral region were similar to those found in the ischemic focus. The purported neuroprotective effect of hyperglycemia in the penumbral region was not reflected in an increased high-energy phosphate level in the penumbral region. The rapid deterioration of the metabolic status of this region in this strain of rat suggests that the increased consistency of infarction may come at the expense of the penumbral region, and thus this model may not be well suited for the study of metabolic changes and perhaps even therapeutic intervention.

Adenosine Triphosphate↗
PubMed1990

The evolution of focal ischemic damage: a metabolic analysis.

Focal cerebral ischemia in the rat was induced by left middle cerebral artery occlusion. The area of ischemia was determined by infusion of a qualitative perfusion indicator, neutral red. The temporal evolution of alterations in regional energy metabolism was assessed by direct microquantitative histochemical analysis of high-energy phosphates, glucose, glycogen, and lactate content of the tissue. Perfusion analyses demonstrated a perifocal region of diminished, but not absent perfusion up to 6 hr after occlusion. By 24 hr, there was an abrupt demarcation between perfused and nonperfused regions. Profound metabolic alterations were seen as early as 20 min after occlusion. Although there was an area of intermediate metabolic derangement in the more medial portions of the lateral ipsilateral cortex up to 6 hr, by 24 hr there was an abrupt transition from normal to abnormal cortex. No evidence of metabolic recovery was seen in this model of permanent occlusion.

Adenosine Triphosphate↗
PubMed1990

Impairment of metabolic recovery with increasing periods of middle cerebral artery occlusion in rats.

We examined the consequences of reflow on metabolic recovery following increasing periods of focal ischemia. The middle cerebral artery of 21 Sprague-Dawley rats was occluded with a snare ligature for 1, 2, or 6 hours followed by 5, 4, or 0 hours of reflow, respectively (seven rats in each group). All animals were injected with neutral red for visual confirmation that the affected regions were reperfused. The brains were frozen in situ, and the concentrations of adenosine triphosphate, phosphocreatine, glycogen, and lactate were determined in those areas corresponding to the normally perfused medial ipsilateral cortex, the perifocal region, and the ischemic focus. Values for the 6 hours' occlusion with no reflow group served as a control to demonstrate restoration of metabolite concentrations. In both groups with reflow, the levels of high-energy phosphates were greater than control, but this effect of reflow was primarily significant for the group with 1 hour's occlusion (p less than 0.05). The levels of glycogen and lactate provided additional evidence that the extent of metabolite restoration was graded; following 2 hours of occlusion, metabolite recovery was compromised (p less than 0.05). Our data strongly support the concept that the window of opportunity for effective treatment of focal ischemia by reperfusion is narrow (of short duration).

Adenosine Triphosphate↗
PubMed1990

Improvement of pituitary function after surgical decompression for pituitary tumor apoplexy.

Hypopituitarism is a major manifestation of pituitary adenoma apoplexy. We postulated that the acute deterioration in pituitary function may be caused by compression of portal vessels and the pituitary stalk, secondary to a sudden increase in intrasellar contents. If this were the case, one would predict improvement in pituitary function to occur after surgical decompression. We studied pituitary function in eight patients presenting with the clinical syndrome of pituitary adenoma apoplexy before and on multiple occasions after urgent surgical decompression. Partial or complete hypopituitarism was seen in all subjects at the time of presentation. Serum cortisol levels were inappropriately low (5.9 +/- 1.4 micrograms/dL; 162.8 +/- 38 nmol/L) for the degree of stress in seven patients and appropriately elevated in only one subject (55.3 micrograms/dL; 1525.7 nmol/L). High normal increments in cortisol levels were noted in three subjects given test doses of cosyntropin. Patients were given glucocorticoids before, during, and for 2 days after surgery. Serum cortisol concentrations measured on or after the third day when glucocorticoids had already been stopped were normal in seven subjects and consistently low in one. These seven subjects were discharged on no replacement and were subsequently documented by dynamic testing to have normal pituitary-adrenal function. Gonadal function improved in two of four men and in one of two women who had hypogonadism on presentation. Improvement in thyroid function was documented in two of three subjects with preoperative hypothyroidism. Gradual improvement and almost complete resolution of the neuroophthalmological abnormalities occurred days to weeks after decompression. These observations demonstrate that urgent surgical decompression after pituitary tumor apoplexy was associated with improvement not only in neurological defects but also in pituitary function. The rapid improvement in pituitary function indicates not only that the hypopituitarism was reversible, but also that it might be caused by compression of the portal circulation and pituitary stalk by the sudden increase in intrasellar contents.

Adrenocorticotropic Hormone↗
PubMed1990

Intracranial aneurysms: evaluation by MR angiography.

The purpose of this study was to compare the accuracy of a volume gradient-echo MR angiography (MRA) technique with that of intraarterial digital subtraction angiography (IA DSA) in the identification of intracranial aneurysms. The intracranial vasculature was examined in 47 patients by MRA and compared with IA DSA findings in 19 of these patients who had saccular or giant intracranial aneurysms. The remaining 28 patients, in whom no aneurysm was found, served as a control group. MRA was performed with the use of a velocity-compensated gradient-echo sequence (TR = 40-50/TE = 7-15) with a 15 degrees flip angle. The sensitivity and specificity were calculated for the evaluation of the cine 3D reconstructions (cine MRA) only, cine MRA + inspection of the individual partitions, and cine MRA + individual partitions + spin-echo studies. Of 21 aneurysms, of which three were missed in two patients, the sensitivity varied from 67% for cine MRA only to 86% for the cine MRA + partitions + spin-echo studies; of the 19 patients, among whom it was assumed that the diagnosis of any one aneurysm in a patient would lead to angiography and detection of additional aneurysms, the sensitivity varied from 73% for the cine MRA only to 95% for the cine MRA + partitions + spin-echo studies. The results of this study suggest that MRA can define the circle of Willis sufficiently to allow detection of intracranial aneurysms as small as 3-4 mm. MRA holds promise as a truly noninvasive screening examination of intracranial vasculature in patients at risk for aneurysms.

Adolescent↗
PubMed1990

Intracranial aneurysms: evaluation by MR angiography.

The purpose of this study was to compare the accuracy of a volume gradient-echo MR angiography (MRA) technique with that of intraarterial digital subtraction angiography (IA DSA) in the identification of intracranial aneurysms. The intracranial vasculature was examined in 47 patients by MRA and compared with IA DSA findings in 19 of these patients who had saccular or giant intracranial aneurysms. The remaining 28 patients, in whom no aneurysm was found, served as a control group. MRA was performed with the use of a velocity-compensated gradient-echo sequence (TR = 40-50/TE = 7-15) with a 15 degree flip angle. The sensitivity and specificity were calculated for the evaluation of the cine 3D reconstructions (cine MRA) only, cine MRA + inspection of the individual partitions, and cine MRA + individual partitions + spin-echo studies. Of 21 aneurysms, of which three were missed in two patients, the sensitivity varied from 67% for cine MRA only to 86% for the cine MRA + partitions + spin-echo studies; of the 19 patients, among whom it was assumed that the diagnosis of any one aneurysm in a patient would lead to angiography and detection of additional aneurysms, the sensitivity varied from 73% for the cine MRA only to 95% for the cine MRA + partitions + spin-echo studies. The results of this study suggest that MRA can define the circle of Willis sufficiently to allow detection of intracranial aneurysms as small as 3-4 mm. MRA holds promise as a truly noninvasive screening examination of intracranial vasculature in patients at risk for aneurysms.

Adolescent↗
PubMed1989

Intracranial circulation: preliminary clinical results with three-dimensional (volume) MR angiography.

The authors assessed the clinical utility of a magnetic resonance angiography technique in the evaluation of intracranial circulation. Eighteen patients with a low likelihood of cerebrovascular disease (control group) and 40 patients with suspected cerebrovascular disease were imaged with a FISP (fast imaging with steady precession) sequence (repetition time of 50 msec, echo time of 15 msec, velocity compensation in the read and section-select directions with acceleration compensation in the read direction, 15 degrees anisotropic volume, and a 1.25-mm partition thickness). Ninety-four percent of images in the control group and 72% of images in the group with cerebrovascular disease were considered useful for diagnosis. This technique can provide accurate images of intracranial circulation and can be performed in conjunction with two-dimensional spin-echo or gradient-echo imaging. It was most useful in the evaluation of patent intracranial aneurysms, vessel displacement, and large-vessel occlusive disease. Disadvantages included limited field of view, persistent signal voids, limited spatial resolution, and inadequate depiction of lesions with slow flow.

Adolescent↗
PubMed1989

Three-dimensional (volume) gradient-echo imaging of the carotid bifurcation: preliminary clinical experience.

This study was designed to test the accuracy of magnetic resonance (MR) imaging with a FLASH (fast low-angle shot) 40 degrees volume pulse sequence by comparing it with intraarterial digital subtraction angiography (DSA) in patients with suspected carotid artery stenoses. Fifteen patients referred for evaluation of anterior circulation in cerebrovascular disease composed the pilot group. Twelve patients underwent correlative intraarterial DSA examinations. The FLASH volume sequence, with an echo time of 7.7 seconds, produced high-signal-intensity vascular images for 28 of 30 bifurcations. Of the 24 carotid bifurcations studied with DSA, 22 were depicted with MR angiography. Among the depicted bifurcations, 21 showed good correlation with the DSA images. These included four of four normal bifurcations, three of three with mild stenosis, four of four with moderate stenosis, eight of nine with severe stenosis, and two of two with occlusions. With respect to ulceration, three of four MR angiographic studies showed good correlation with DSA images. This preliminary experience indicates that the method is reproducible and capable of delineating carotid lesions in patients and that it can be performed in conjunction with conventional spin-echo imaging of the brain with only a small increase in patient examination time.

Adult↗
PubMed1989

Magnetic resonance angiography of the extracranial carotid arteries and intracranial vessels: a review.

MRI is uniquely suited for evaluation of vascular structures due to its sensitivity to a variety of flow-related phenomena. Recent work has demonstrated that high quality magnetic resonance angiograms (MRA) of the carotid arteries and intracranial vasculature can be achieved by using gradient-echo techniques with short echo times. These MRAs are displayed like conventional arteriograms, but are acquired in a noninvasive fashion with a minimal increase in examination time. We used MRA to visualize 50 of 54 carotid bifurcations tested, with good correlation to the intra-arterial angiograms. We examined the intracranial vasculature in over 40 patients, and demonstrated aneurysms, vascular malformations, and occlusions.

Blood Vessels↗
PubMed1989

Herniation of the suprasellar visual system and third ventricle into empty sellae: morphologic and clinical considerations.

Intrasellar herniation of the optic nerve, optic chiasm, optic tract (suprasellar visual system, SVS), and anteroinferior third ventricle can occur into primary or secondary empty sellae. The anatomic part of this study evaluated the appearance of the SVS in subjects with normal sellae (n = 52), the patterns and prevalence of SVS herniation in enlarged primary empty sellae (n = 24), and the patterns of intrasellar herniation of the SVS in secondary empty sellae (n = 8). The clinical part of this study was to correlate the visual status with the anatomic patterns of the intrasellar herniated SVS. High-resolution MR and CT were used to define the anatomy. MR was superior to CT in all groups in defining accurately the SVS relationship to the sella turcica. In the normal group, the SVS invariably had a straight-line appearance formed by the optic nerve, optic chiasm, and floor of the third ventricle and was above the sella. The SVS was herniated in three of 24 enlarged primary empty sellae. A difference in the appearance of the hypothalamic and infundibular recesses in the primary empty sella group with SVS herniation (dilated recesses and formation of an obtuse angle) and in the secondary empty sella group with SVS herniation (nondilated recesses and formation of an acute angle) was observed. Visual disturbances in primary empty sellae with SVS herniation were present in two of three subjects. Visual disturbances may be absent or minimal in primary empty sellae and secondary empty sellae with herniation of the SVS. Progression of the symptoms--visual field defects, optic atrophy, and loss of vision--is not inevitable. There was no correlation between the severity of visual symptoms and the degree of herniation of the SVS in either the primary or secondary sellae. We found that intrasellar herniation of the SVS into a primary or secondary empty sella is well delineated with MR, and MR should facilitate decisions concerning surgery or therapy. Visual disturbances proved to be an unreliable indicator of herniation.

Adult↗