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Biomedical subjects

F A Simeone

Publications and source records attributed to F A Simeone.

At least 37 records · Page 2Linked to original sources
PubMed1987

Spontaneous subdural hygromas: a complication following craniofacial surgery.

We present a case report of symptomatic, spontaneous subdural hygromas complicating craniofacial resection of a malignant skull base tumor. This complication occurs after prolonged spinal drainage instituted to prevent cerebrospinal fluid fistulas secondary to insecure dural repair. We believe that this complication may be seen repeatedly as indications for craniofacial surgery in the elderly continue to expand.

Aged↗
PubMed1987

Whole mounted pressurized in vitro model for the study of cerebral arterial mechanics.

A whole mounted model for the study of smooth muscle mechanics is described which uses cylindrical sections of middle cerebral artery (MCA). One- to 2-cm sections of artery were cannulated, pressurized and perfused. Changes in the outer diameter of the artery were detected using an infrared photoelectric diameter gauge. MCA displayed spontaneous rhythmic contractions, which were initiated and sensitive to changing intraluminal pressure. Rhythmic activity was dependent upon the presence of Ca2+ in the bath, but not affected by phentolamine. Increasing pressure significantly reduced high (50, 70 and 125 mM) potassium-induced contractions, but not drug (serotonin, norepinephrine, histamine) induced contractions. The intraluminal surface of the MCA was significantly more sensitive to serotonin than the extraluminal surface. The above contractile responses are discussed in light of the advantages of this model over helical or ring preparations.

Animals↗
PubMed1987

Latency of the cortical component of the somatosensory evoked potential in relation to cerebral blood flow measured in the white matter of the cat brain during focal ischemia.

In a focal model of cerebral ischemia (middle cerebral artery (MCA) occlusion in the cat), the existence of a relationship between the latency from the onset of stimulation to the appearance of the cortical component of the somatosensory evoked response and blood flow was explored. White matter blood flow was determined in the left and right hemispheres under control conditions. During left MCA occlusion, the blood flow and the latency of the cortical component recorded from the right hemisphere deviated from their preexisting linear relationship obtained from plotting latency as a function of blood flow. In an effort to increase flow during focal ischemia, hemodilution and volume expansion with dextran 40 was used. Application of this technique only mildly increased blood flows and did not restore the correlation of latencies of the cortical component of the evoked response and blood flows observed before MCA occlusion. This finding suggests that latencies and blood flows are not correlated in the contralateral hemisphere during focal ischemia and only show a mild degree of relationship in the unperturbed brain. During ischemia, flow and electrical activities may not respond to the same stimuli and, if they do respond, it may not be unidirectionally. These findings are discussed in light of other reports on the Significance of the evoked response in monitoring cerebrovascular insults and the observation of diaschisis.

Animals↗
PubMed1987

Ocular ischemic syndrome: long-term ocular complications.

Acute retinal arterial occlusive events in the eye are generally easily recognized and the association with embolic material, often from ulcerative lesion of the ipsilateral carotid vessels, usually can be established by noninvasive imaging techniques. In contrast, chronic retinal and choroidal circulatory impairments from ophthalmic artery insufficiency is usually due to high-grade, hemodynamically-significant carotid occlusive disease which can be difficult to recognize because of the diverse clinical features and presentations. We present herein the experience of the senior author (LEM) in the diagnosis and management of these complex cases.

Aged↗
PubMed1986

Single stage composite resection and reconstruction of malignant anterior skull base tumors.

Operative morbidity, including osteomyelitis and meningeal and cerebral sepsis, remains high among patients undergoing the composite (bony and overlying soft tissue) resection of malignant skull base tumors. This is in part because of the poor wound healing afforded by free skin grafts and the poorly vascularized pericranial flaps routinely used to resurface the operative defect. In an effort to reduce the operative morbidity, single stage resection and reconstruction with distant vascularized flap tissue was performed in five consecutive patients who presented with malignant skull base tumors. We think that immediate flap reconstruction will allow skull base lesions previously considered unresectable or associated with a prohibitive complication rate to be safely resected. Case presentations illustrate operative techniques. The potential disadvantage of masking a tumor recurrence with immediate flap coverage is discussed.

Aged↗
PubMed1985

Transsphenoidal hypophysectomy: postsurgical CT findings.

Transsphenoidal surgery produces changes in the paranasal sinuses and sella that should be familiar to radiologists in view of the frequency of this type of surgery. Some of these changes, such as soft-tissue-density debris in the sinuses, are transient. Fat and other packing material identifiable in the sinuses and sella after surgery is permanent. The procedure is associated with a variety of complications that are readily detectable by computed tomography (CT). These include bleeding, compression of parasellar structures by packing material, cerebrospinal fluid leaks, and pneumocephalus. After a transsphenoidal procedure, with or without follow-up radiation therapy, residual enhancing intrasellar and parasellar lesions may still be identified.

Adult↗
PubMed1984

Correlative aspects of hypervolemic hemodilution: low-molecular-weight dextran infusions after experimental cerebral arterial occlusion.

Unilateral clipping of cerebral arteries in eight dogs reduced regional cortical blood flow (rCoBF) without altering cardiac output (CO) or intracranial pressure (ICP) and resulted in 10% hemispheric infarction. In ten dogs, total blood volume (TBV), CO, rCoBF in the region of the occluded artery, and ICP increased while the hematocrit (Hct) decreased following two low-molecular-weight dextran (D40) infusions. Hemispheric infarction was 4%. The CO, rCoBF, and ICP correlated directly with TBV, but inversely with Hct, while rCoBF correlated positively with CO. Two similar hemodiluting D40 infusions in nine control dogs raised TBV, CO, and ICP but not rCoBF. The CO, rCoBF, and ICP correlated positively with TBV but inversely with Hct while rCoBF correlated with CO. Thus, hypervolemic hemodilution with D40 enhances collateral perfusion to acutely ischemic regions of brain distal to segmental arterial occlusions and concomitantly augments CO and ICP. Correlations between CO and cerebral blood flow after D40 infusion may be secondary to lowered Hct.

Animals↗
PubMed1984

Experimental hypervolemic hemodilution: physiological correlations of cortical blood flow, cardiac output, and intracranial pressure with fresh blood viscosity and plasma volume.

Rheological, cerebrovascular, and cardiovascular alterations induced by serial plasma volume (PV) expansion were evaluated in splenectomized dogs. Seven dogs received two infusions of autologous plasma within 120 minutes; each infusion equaled 20% of the respective dog's total blood volume (TBV). The PV increased 31% and then another 26% after the two respective infusions, and the hematocrit (Hct) was obligatorily decreased by 22% during the experiment. The fresh blood viscosity at the shear rate of 10 sec-1 varied inversely with the TBV and the PV and correlated directly with the Hct after these plasma infusions. Cardiac output (CO) increased 71% after the two infusions without significant alterations in mean arterial blood pressure. Additionally, CO was inversely related to both Hct and blood viscosity. Although the 15% rise in regional cortical blood flow (rCoBF) in the territory of the middle cerebral artery did not reach statistical significance, the rCoBF was related inversely to both Hct and blood viscosity and directly to TBV, PV, and CO after the plasma infusions. Cortical vascular resistance (CVR) decreased 18% after the two infusions. The CVR correlated inversely with PV and directly with Hct and blood viscosity. Our data suggest that hypervolemic hemodilution with expansion of PV increases CO more than cerebral blood flow in normal brain. Fresh blood viscosity seems to be a major factor determining CO and cerebral perfusion after IV expansion. This study adds support to the hypothesis that reductions of blood viscosity account for the direct relationship between cerebral blood flow and CO observed after intravascular volume expansion with hemodiluting agents. Hypervolemic hemodilution with plasma reduces CVR, possibly secondary to its effect on blood viscosity, and also raises intracranial pressure.

Animals↗
PubMed1984

Alteration of somatosensory evoked potentials in response to global ischemia.

The somatosensory evoked potential (SEP) measured in response to median nerve stimulation was correlated with cortical and white matter cerebral blood flow (CBF), adenosine triphosphate (ATP), and lactate levels in 14 cats subjected to graded hemorrhagic hypotension following bilateral carotid artery ligation. Three additional cats served as controls. Regional CBF was determined by the hydrogen clearance method, and the time for conduction of the sensory stimulus from the thalamus to the cortex (the thalamocortical conduction time), was used to assess SEP latency changes. A reproducible sequence of changes occurred in the SEP as ischemia developed. There was an early conduction delay that correlated well with mild white matter ischemia. Amplitude reductions in the SEP began as significant cortical ischemia occurred. The cortical SEP was abolished when white matter CBF and ATP fell to critical levels.

Animals↗
PubMed1984

A study of computer-assisted tomography. II. Comparison of metrizamide myelography and computed tomography in the diagnosis of herniated lumbar disc and spinal stenosis.

One hundred twenty-two patients with surgically confirmed pathology consisting of either herniated lumbar disc, spinal stenosis, or both were included in this investigation. For each of these patients, preoperative metrizamide myelography and computerized tomography were performed. Each myelogram and CT scan was read blindly so that the neuroradiologist interpreting the study had no knowledge of the patient's surgical pathology, clinical examination, nor any knowledge of the interpretation of the other preoperative test. A painstaking attempt was made to describe precisely both the exact nature of the preoperative myelogram and CT scan interpretations. The correlations between the preoperative interpretation of each test and the observed surgical findings then were analyzed statistically. Based upon this analysis, myelography was found to be more accurate than computed tomography in the diagnosis of herniated lumbar disc (83% vs. 72%). In the diagnosis of spinal stenosis, myelography was slightly more accurate than computed tomography (93% vs. 89%). Based upon the results of this study, the authors conclude that metrizamide myelography is more accurate than computed tomography in the diagnosis of both herniated lumbar disc and spinal stenosis and remains the diagnostic study of choice for these conditions. Furthermore, metrizamide myelography gives the added advantage of visualizing the thoracolumbar junction and, thus, affords the opportunity to diagnose occult spinal tumors.

False Negative Reactions↗
PubMed1983

Hypervolemic hemodilution in experimental focal cerebral ischemia. Elevation of cardiac output, regional cortical blood flow, and ICP after intravascular volume expansion with low molecular weight dextran.

Cerebrovascular and cardiac alterations evoked by intravascular volume expansion with low molecular weight dextran (LMD, molecular weight 40,000), an advocated adjunct in the clinical prevention or therapy of acute stroke and cerebral vasospasm, were studied in splenectomized dogs. Clipping of the right distal internal carotid artery and the proximal middle cerebral artery (MCA) in eight dogs decreased regional cortical blood flow (rCoBF) by 58% without changing cardiac output (CO), and caused 10% +/- 5% (SE) hemispheric infarction. Ten other dogs underwent similar cerebral arterial occlusion and were infused twice with LMD within 2 hours; each infusion equaled 20% of the respective dog's total blood volume. Both CO and rCoBF in the territory of the occluded MCA increased significantly by 119% +/- 13% and 42% +/- 6%, respectively. following the two LMD infusions. Although the mean arterial blood pressure was unaltered, the hematocrit decreased significantly and the intracranial pressure (ICP) increased significantly. The mean hemispheric infarction in these 10 treated dogs was 4% +/- 2%. Another nine dogs underwent arterial manipulation without clipping. Two hemodiluting LMD infusions, similar to those in the 10 dogs, significantly elevated CO and ICP but not rCoBF. These data suggest that hypervolemic hemodilution with LMD effectively elevates collateral perfusion to ischemic regions of brain distal to occluded MCA segments and concomitantly raises the CO and ICP.

Animals↗
PubMed1983

Clinical usefulness of CT scanning in the diagnosis and treatment of lumbar spine disease.

CT scanning of the lumbar spine is in its infancy. Nevertheless, it has had a remarkable effect on the way we evaluate and treat patients. The principal advantages are the following: (1) If the scan alone in the diagnostic work-up of patients with lumbar disc herniation and correlative neurologic deficit. (2) The CT scan aids in the screening of patients with back and leg pain who did not have a neurologic deficit. It may determine the need for further studies such as myelography. (3) CT has become helpful in the evaluation of patients with lumbar spinal stenosis and may replace myelography when greater experience is garnered. (4) CT is of great value in the evaluation of the lumbar spine previously operated on and may provide diagnostic information unavailable on the myelogram because of dural scar formation, arachnoiditis, and so on. (5) Future comparative studies probably will indicate greater accuracy with CT scanning than with myelography, and consequently, the overall diagnostic acumen in the treatment of patients with lumbar spine disease will be improved.

Humans↗