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Biomedical subjects

F B Meyer

Publications and source records attributed to F B Meyer.

At least 127 records · Page 7Linked to original sources
PubMed1990

Extra-axial cavernous hemangiomas involving the dural sinuses.

Extra-axial cavernous hemangiomas are rare lesions previously associated with unacceptable mortality and morbidity rates that precluded surgical resection. The authors analyze the clinical presentation, surgical results, and histology of eight intrasinus cavernous hemangiomas: six located in the cavernous sinus, one in the petrosal sinus, and one in the torcula. Magnetic resonance imaging is the best radiographic test for surgical planning. Successful tumor removal was achieved in six cases with no mortality and low morbidity. In the remaining two patients, only subtotal resection was achieved because of massive hemorrhage in one and the misdiagnosis of a pituitary adenoma leading to a transsphenoidal approach in the other. For hemangiomas arising within the cavernous sinus, extradural removal of the sphenoid bone facilitated preservation of the neurovascular structures. Since the clinical and histological characteristics of these lesions are distinct from intra-axial cavernous hemangiomas, a more appropriate term may be "sinus cavernoma" to indicate that these lesions are primarily intrasinus in origin.

Adult↗
PubMed1990

Calcium antagonists and vasospasm.

A critical review of the clinical data supports the conclusion that nimodipine decreases the severity of neurologic deficits and improves outcome after subarachnoid hemorrhage. The mechanisms by which mortality and morbidity are reduced are still controversial. First, the frequency of vasospasm is not altered (Figs. 5 and 6). Second, the consistent reversal of vasospasm once present has not been demonstrated either angiographically or by noninvasive cerebral blood flow studies. These observations suggest that there is either modification of microcirculatory flow (i.e., dilation of pial conducting vessels or decreased platelet aggregation) or a direct neuronal protective effect. As suggested previously, support for either mechanism is not resolute, and further investigation is necessary. Currently, nimodipine has been the most thoroughly investigated calcium antagonist both from an experimental and clinical perspective. Oral administration has had few reported complications. Therefore, the benefit/risk ratio clearly supports the prophylactic use of this calcium antagonist in patients of all clinical grades after subarachnoid hemorrhage. Evidence also indicates that starting nimodipine after the onset of delayed ischemic deficits is of benefit. Finally, it can be predicted that in the future additional calcium antagonists with more selective vascular or neuronal effects will be developed for use in neurologic disorders.

Animals↗
PubMed1989

Cerebral aneurysms in childhood and adolescence.

In this study, 24 aneurysms occurring in 23 patients under the age of 18 years (mean 12 years) are analyzed. The male:female ratio was 2.8:1, and the youngest patient was 3 months old. Mycotic lesions and those associated with other vascular malformations were excluded. Forty-two percent of the aneurysms were located in the posterior circulation, and 54% were giant aneurysms. Presenting symptoms included subarachnoid hemorrhage in 13 and mass effect in 11. Several of these aneurysms were documented to rapidly increase in size over a 3-month to 2-year period of observation. All aneurysms were surgically treated: direct clipping was performed in 14; trapping with bypass in four; trapping alone in four; and direct excision with end-to-end anastomosis in two. The postoperative results were excellent in 21 aneurysms (87%), good in two (8%), and poor in one. The pathogenesis of cerebral aneurysms is reviewed.

Adolescent↗
PubMed1987

Intrasellar arachnoid cysts.

Thirteen pathologically documented intrasellar arachnoid cysts treated by transsphenoidal cyst excision and marsupialization were analyzed. Presenting symptoms included headache (7), visual loss (7), galactorrhea (4), and anterior pituitary dysfunction (2). Postoperatively, the 7 patients with visual loss and 4 with hyperprolactinemia improved. The 2 patients with anterior pituitary dysfunction did not improve and 2 additional patients required hormonal supplements. Based on this operative experience, the pathophysiology of these cysts is discussed. The indications for transsphenoidal exploration include the following: to relieve optic chiasm, pituitary stalk or gland compression, and to exclude the possibility of other sellar neoplasms.

Adenoma↗
PubMed1987

Focal cerebral ischemia: pathophysiologic mechanisms and rationale for future avenues of treatment.

Although approximately 500,000 patients suffer from a stroke each year in the United States, treatment of these patients to date has consisted primarily of prevention, supportive measures, and rehabilitation. The modification of experimental cerebral infarction by new pharmacologic agents, along with encouraging results from the restoration of blood flow to areas of focal ischemia in both laboratory and clinical trials, suggests that a more aggressive approach might be considered in selected patients with acute stroke.

Anticoagulants↗
PubMed1987

Treatment of experimental focal cerebral ischemia with mannitol. Assessment by intracellular brain pH, cortical blood flow, and electroencephalography.

Intracellular brain pH, cortical blood flow (CBF), and electrocorticograms were recorded in regions of severe and moderate ischemia in 10 control rabbits and 10 rabbits given mannitol, 1 gm/kg, after occlusion of a major branch of the middle cerebral artery. Pooling the data from all 20 animals, preocclusion CBF was 46.4 +/- 3.6 ml/100 gm/min and intracellular brain pH was 7.01 +/- 0.04 (means +/- standard error of the means). Although mannitol administration mildly improved CBF in regions of severe ischemia, this increase was not sufficient to prevent metabolic deterioration as assessed by brain pH. However, in regions of moderate ischemia, CBF improved significantly with mannitol and the gradual decline in brain pH observed in control animals was prevented. For example, in the treated moderate ischemia sites 4-hour postocclusion CBF and pH values were 31.8 ml/100 gm/min and 6.89 +/- 0.09, respectively, as compared to control values of 14.3 ml/100 gm/min and 6.75 +/- 0.06. These results suggest that mannitol may be of benefit in stabilizing regions of moderate, but not severe, ischemia after vessel occlusion.

Animals↗
PubMed1986

Inhibition of electrically induced seizures by a dihydropyridine calcium channel blocker.

Nimodipine, a calcium channel blocker with high affinity for central dihydropyridine Ca2+ channels, produced a dose-dependent suppression of electrically induced seizures in the rabbit. Verapamil, a diphenylalkylamine which acts at peripheral Ca2+ channels, was ineffective. Phenytoin was less effective than nimodipine. These results suggest that calcium flux into neurons may be a biochemical precipitant for seizure genesis. Centrally acting calcium channel blockers may prove to be a new class of anticonvulsants.

Animals↗
PubMed1986

Selective central nervous system calcium channel blockers--a new class of anticonvulsant agents.

Current research suggests that Ca2+ flux into the neuron may be a critical factor in the genesis of seizures. We report herein the influence of nimodipine, a selective central nervous system calcium channel blocker, in 60 rabbits with seizures that had been induced through ischemia, postischemia reperfusion, pentylenetetrazol, and bicuculline. In 30 animals subjected to 4 hours of ischemia, 9 of the 15 control animals had seizures in comparison with 1 of the 15 treated animals (P less than 0.005). Five animals with reperfusion seizures demonstrated similar results. In 10 animals in which a convulsant was applied topically to both cerebral hemispheres, unilateral intracarotid injection of nimodipine arrested seizures in that hemisphere alone, whereas the control contralateral hemisphere continued to have electrical seizure activity (P less than 0.001). Both placebo and verapamil were ineffective. These results suggest that Ca2+ influx is a common biochemical precipitant for various types of experimental seizures. Selective central nervous system calcium channel blockers may prove to be a new class of anticonvulsant agents.

Animals↗
PubMed1986

Intracellular brain pH, indicator tissue perfusion, electroencephalography, and histology in severe and moderate focal cortical ischemia in the rabbit.

Intracellular brain pH and indicator tissue perfusion were measured with a lipid-soluble, pH-sensitive fluorescent indicator in 10 rabbits who had either severe or moderate focal ischemia depending on whether the middle cerebral artery was occluded at its main trunk or bifurcation. Preocclusion tissue indicator perfusion was 50.1 ml/100 g/min and intracellular brain pH was 7.03. In severe focal ischemia, immediate postocclusion tissue perfusion was 12.7 ml/100 g/min and intracellular brain pH was 6.64. Four hours after occlusion, the perfusion was 5.2 ml/100 g/min and intracellular brain pH was 6.08. There was EEG and histological confirmation of infarction. In the moderate focal ischemia group, immediate postocclusion flow was 20.0 ml/100 g/min and intracellular brain pH was 6.92. At 3 h, postocclusion tissue perfusion was 22.6 ml/100 g/min and intracellular brain pH was 6.86. Therefore, for the first 3 h, this ischemic penumbra was stable. At the fourth hour, both cerebral tissue perfusion and intracellular brain pH worsened. This suggests that the ischemic penumbra is a dynamic state. The rabbit is a good experimental model for the production of both severe and moderate focal ischemia.

Animals↗
PubMed1986

Emergency carotid endarterectomy for patients with acute carotid occlusion and profound neurological deficits.

Emergency revascularization procedures for patients with acute stroke are controversial. Thirty-four patients with acute internal carotid artery occlusion documented at the time of emergency endarterectomy were analyzed. Before operation, all these patients had profound neurological deficits including hemiplegia and aphasia. There was a 94% success rate in restoring patency. In follow-up, nine patients (26.5%) had a normal neurological exam, four (11.8%) had a minimal deficit, 10 (29.4%) had a moderate hemiparesis, which was improved over their preoperative deficit, 4 (11.8%) remained hemiplegic, and seven (20.6%) died. The natural history of patients with acute carotid occlusion and profound neurological deficits is dismal. In comparison, 13 patients (38%) made a dramatic recovery. The surgical mortality rate compares favorably with the natural history. Good collateral flow was a good prognostic factor, while a simultaneous middle cerebral artery embolus was associated with a poorer prognosis. An emergency carotid endarterectomy may be indicated in selected patients with acute internal carotid artery occlusion with profound neurological deficits. Full preoperative angiography may identify those patients who would benefit from surgical intervention and reduce the operative mortality rate.

Aged↗
PubMed1986

Temporal lobectomy in children with epilepsy.

The results of temporal lobectomy for medically refractory seizures are analyzed in 29 boys and 21 girls with a mean age of 15.8 years. The average age at onset of seizures was 7.5 years, and the time between onset and surgery averaged 8.3 years. Postoperatively, 27 patients (54%) were seizure-free, 12 patients (24%) had only occasional auras without loss of consciousness, five patients (10%) had fewer seizures, and six (12%) were unchanged. Therefore, 78% were essentially seizure-free and 88% benefited significantly from the operation. There was no significant change in the Wechsler Intelligence Scale scores before and after surgery; however, the shorter the time between seizure onset and surgery, the greater the likelihood of improvement in verbal and perceptual intelligence quotient. Social outcome was significantly improved, and a large percentage of patients were either in school or actively employed. Early consideration of temporal lobectomy in children with medically refractory seizures is recommended.

Adolescent↗
PubMed1986

Carotid body tumors: a subject review and suggested surgical approach.

Carotid body tumors are a rare but potentially difficult surgical entity. Their pathology, physiology, and natural history are reviewed along with surgical results reported in the literature. A surgical approach for removal of these tumors is presented which differs significantly from the recommended techniques in that emphasis is placed on intraoperative monitoring of cerebral blood flow, the the selective use of shunts, a tumor-adventitial plane of dissection, preservation of the carotid artery complex, and mobilization of the parotid gland. Thirteen cases using these techniques are reviewed. The mortality rate and the incidence of cerebrovascular sequelae were both 0%. The major morbidity consisted of injury to the lower cranial nerves in five patients (39%) with tumors larger than 5 cm in length.

Adult↗
PubMed1986

Effect of nimodipine on intracellular brain pH, cortical blood flow, and EEG in experimental focal cerebral ischemia.

Intracellular brain pH, cortical blood flow, and electroencephalograms (EEG's) were recorded in severely and moderately ischemic regions in 10 control and 10 nimodipine-treated rabbits prior to and following major branch occlusion of the middle cerebral artery (MCA). Preocclusion cortical blood flow was 51 ml/100 gm/min and intracellular brain pH was 7.01 in both the control and the treated animals. After MCA occlusion, the severely ischemic regions in the control group showed initial and 4-hour postocclusion flows of 12.7 and 5.2 ml/100 gm/min with a brain pH of 6.64 and 6.08, respectively. In animals given nimodipine after MCA occlusion, blood flow increased from 10.5 to 18.8 ml/100 gm/min, with an associated elevation in intracellular brain pH from 6.57 to 6.91. Comparable findings were observed in areas of moderate ischemia. Improvements in cortical blood flow, intracellular brain pH, and EEG attenuations produced by nimodipine were all statistically significant. Inspection of the cortex revealed reversal of cortical pallor and small-vessel spasm following treatment with nimodipine. It is hypothesized that nimodipine exerts its effects through reversal of ischemia-induced secondary vasoconstriction, and that this drug may be an important adjunctive treatment for patients with focal cerebral ischemia.

Animals↗
PubMed1985

Emergency embolectomy for acute occlusion of the middle cerebral artery.

Twenty cases treated with emergency embolectomy for acute occlusion of the middle cerebral artery were reviewed. There were 10 males and 10 females, with an average age of 55 years. The left middle cerebral artery was involved in 17 patients and the right in three. Flow was restored in 16 patients (75%). The embolus originated in the heart in seven, the carotid artery in seven, the aorta in three, an aneurysm in one, and an indeterminate source in two. It was technically most difficult to achieve patency with atheromatous emboli from the aorta. Two patients (10%) had an excellent result with no neurological deficit, five (25%) were left with a minimal deficit but were employable, seven (35%) had a fair result but were still independent and employable, four (20%) did poorly, and two (10%) died. Patients with an associated ipsilateral carotid artery occlusion did poorly. Collateral flow, as judged from preoperative angiograms, was the best predictor of outcome.

Acute Disease↗
PubMed1984

Benign tumors of the foramen magnum.

The authors reviewed 102 documented cases of benign extramedullary tumors of the foramen magnum treated at their institution between 1924 and 1982. There was 78 meningiomas, 23 neurofibromas, and one teratoma. Approximately 40% of the patients had a normal neurological examination upon first evaluation. The most frequent presenting complaints were suboccipital neck pain, dysesthesias, gait disturbances, weakness, and hand clumsiness. The average time from initial symptoms to diagnosis was 2 1/4 years. The most common findings included hyperreflexia, arm or hand weakness, Babinski sign, spastic gait, sensory loss, and 11th cranial nerve involvement. Based on these cases, an attempt is made to distinguish foramen magnum tumors from other disease entities by a grouping of signs and symptoms. There is no clinical finding that is pathognomonic. Metrizamide computerized tomography scanning and Pantopaque myelography have been the radiographic tests most commonly used to evaluate the foramen magnum. Recent experience suggests that nuclear magnetic resonance scanning will be a very useful noninvasive means of evaluating the foramen magnum region.

Adolescent↗