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Biomedical subjects

K R Davis

Publications and source records attributed to K R Davis.

At least 73 records · Page 4Linked to original sources
PubMed1984

Interdural cyst of the lumbosacral region.

The purpose of this report is to call attention to the clinical, myelographic, and computed tomographic appearance of a very rare type of dural cyst within the lumbosacral spinal canal. We report this condition in three unrelated boys who presented with symptoms of cauda equina compression. Our experience suggests that these cysts are congenital in origin. Anatomically, the cyst wall consisted of a dura-like layer without arachnoid. There was a small ventral defect allowing incomplete communication with the compressed subarachnoid space. Cerebrospinal fluid-like fluid accumulated within the interdural cyst as a result of this communication. Treatment consisted of obliteration of the point of entry between cyst and subarachnoid space in all cases and partial cyst wall excision in one case. After operation, the two patients who had presented with long-standing sphincter disturbance had partial improvement in function and the child with a pain syndrome was completely relieved of symptoms.

Cauda Equina↗
PubMed1984

Intravenous digital subtraction angiography of arteriosclerotic vertebrobasilar disease.

Intravenous digital subtraction angiography (DSA) was performed in 111 patients with vertebrobasilar ischemia. Ninety percent of the vertebral images were of diagnostic quality; 23% of the basilar images were good quality and 53% fair quality; and 58% of the posterior cerebral images were poor. Compared with selective film arteriography in 23 patients, DSA tended to underestimate the degree of atheromatous disease. Segments of the basilar artery were often poorly seen, which could result in false-negative errors. DSA can provide a general assessment of atheromatous disease of the brachiocephalic vessels, including the vertebral and carotid arteries, and in many cases can exclude occlusion or critical stenosis of the vertebrobasilar system. However, it does not adequately image the posterior cerebral or cerebellar artery.

Basilar Artery↗
PubMed1984

Evaluation of multiplanar reconstruction in CT recognition of lumbar disk disease.

Axial computed tomographic (CT) images were compared with sagittal and coronal reformations and myelograms in 60 patients to evaluate the diagnostic usefulness of multiplanar reconstructions for the recognition of lumbar disk disease. The axial CT scans were most sensitive and specific. The sagittal scans were helpful in evaluating the neural foramina, the size of the disk bulge into the spinal canal, especially at L5-S1, and patients with spondylolisthesis. The coronal images were the least informative, although they contributed to the evaluation of lumbar nerve roots. The myelograms and the sagittal images were equally useful in the detection of herniated disk, but axial scans were superior to either. It was concluded that reformatted sagittal and coronal images are not required if all axial images are normal. However, when uncertainty exists or complex anatomy is being evaluated, reformatted images may be helpful, particularly for reassurance.

Evaluation Studies as Topic↗
PubMed1984

Obliteration of experimental aneurysms in dogs with isobutyl-cyanoacrylate.

Experimental cervical carotid aneurysms in dogs are obliterated with isobutyl-cyanoacrylate ( IBCA ) injected under direct vision into the aneurysm. Reflux of IBCA into the artery was prevented by inflating either a latex or a Silastic balloon in the carotid artery at the level of the neck of the aneurysm. This balloon was introduced through a catheter advanced into the common carotid artery by femoral catheterization. The Silastic balloon was found to be much more effective than the latex balloon in preventing spillage of IBCA into the lumen.

Animals↗
PubMed1984

Clinical neuroimaging approaches to cerebrovascular diseases.

Because of the importance of therapeutic implications, strokes must first be differentiated into ischemic or hemorrhagic; although such differentiation is often suggested clinically, it usually must be verified by computed axial tomography (CT scan). This discussion reflects this first, broad subdivision of strokes into ischemic or hemorrhagic; within these two subdivision, further discussion is related to specific etiopathologic processes.

Brain↗
PubMed1983

Bragg-peak proton-beam therapy for arteriovenous malformations of the brain.

Patients with arteriovenous malformations of the brain, who are subject to disabling or fatal recurrent hemorrhage, seizures, severe headache, and progressive neurologic deficits, may be considered unsuitable for conventional therapies (craniotomy with excision or embolization), usually because of the location, size, or operative risk of the lesion. We have treated such patients with stereotactic Bragg-peak proton-beam therapy and report the follow-up of 74 of the first 75, 2 to 16 years after treatment. Proton-beam therapy is intended to induce subendothelial deposition of collagen and hyaline substance, which narrows the lumens of small vessels and thickens the walls of the malformation during the first 12 to 24 months after the procedure. Two deaths from hemorrhage occurred in the first 12 months after treatment, but no lethal or disabling hemorrhages occurred after this interval. Seizures, headaches, and progressive neurologic deficits were in most cases arrested or improved. Bragg-peak proton-beam therapy appears to be a useful technique for treatment of intracranial arteriovenous malformations, especially those that are unsuitable for treatment by other methods.

Adolescent↗
PubMed1983

Leucinal inhibits brain aminopeptidase activity and potentiates analgesia induced by leu-enkephalen.

L-Leucinal, a transition state analog inhibitor or kidney leucine amino-peptidases, was found to serve as a competitive inhibitor of soluble aminopeptidase activity from rat brain (Ki = 22 microM). Simultaneous intracisternal administration of leucinal and leu-enkephalin produced dose-dependent analgesia in the hot plate test in mice, in concentrations at which neither L-leucinal nor leu-enkephalin alone elicited a significant response. simultaneous administration of leucinal and beta-endorphin also resulted in potentiation of beta-endorphin's analgesic activity. Leucinal did not enhance the antinociceptive response to neurotensin or to [D-ala2]-met-enkephalinamide, which are structurally resistant to the action of brain aminopeptidases.

Aminopeptidases↗
PubMed1983

Nuclear magnetic resonance imaging in central nervous system disease.

From the preliminary work of many investigators, it appears that proton nuclear magnetic resonance (NMR) imaging will have wide application in the diagnostic assessment (and potential management) of patients with vascular, neoplastic, and demyelinating diseases of the central nervous system (CNS). Findings in isolated cases and small series suggest that NMR imaging may play a role in the evaluation of patients with other CNS conditions including hydrocephalus, malformations, infections, developmental and metabolic disorders, and degenerative processes. Because of the dynamic nature of disease processes involving the CNS, the precise meaning of NMR image parameters (rho, T1, and T2) remains unclear. A comprehensive study correlating NMR images in neurologic disease with precise neuropathologic examination is required. In the future, with accurate quantitative measurements of these NMR parameters, in vivo imaging may provide insight into the dynamic nature of neurologic disease.

Central Nervous System Diseases↗
PubMed1983

The relation of cerebral vasospasm to the extent and location of subarachnoid blood visualized by CT scan: a prospective study.

In 41 cases of verified ruptured saccular aneurysm, we prospectively predicted the presence or absence of delayed symptomatic cerebral vasospasm. CT criteria quantifying the extent and location of subarachnoid blood (developed in our previous retrospective study) were used in this prospective series of patients. Twenty-two patients had recognizable subarachnoid clots larger than 3 X 5 mm or layers of blood more than 1 mm thick (measured on reproduced images). In 20 of the 22 patients with severe significant clot or thick layer, severe vasospasm was correctly predicted and localized (2 false positives). In 19 patients with no blood, or diffuse blood, or blood outside the subarachnoid space, the absence of severe vasospasm was correctly predicted in 14 (5 false negatives). All of the false-positive and false-negative cases could be explained by inadequate CT technique. The data indicate that the extent and location of blood in the subarachnoid space determine the severity and location of vasospasm and that patients in jeopardy of developing symptomatic cerebral vasospasm can now be identified. Early preventive measures may now be assessed more accurately.

Adult↗
PubMed1982

Definitive radiation therapy for chordoma and chondrosarcoma of base of skull and cervical spine.

Proton-beam radiation therapy has been developed for the treatment of chordomas or sarcomas of bone or soft tissue that abut the central nervous system. The authors report the results of treatment of 10 patients, six with chordoma, three with chondrosarcoma, and one with a neurofibrosarcoma. Local control has been achieved for all patients (with, however, one marginal failure) with a follow-up period ranging from 2 months to 6 years. High doses of radiation, up to 76 Cobalt Gray Equivalents (CGE), have been delivered without significant morbidity. In particular, no neurological sequelae have been observed.

Adult↗
PubMed1982

A neuroradiologic approach to the patient with a diagnosis of subarachnoid hemorrhage.

If early CT confirms the presence of subarachnoid hemorrhage, no intratemporal clot is present, and the patient is neurologically normal, surgery is planned in approximately eight to ten days. The first angiogram is performed just before surgery. If that angiogram shows severe vasospasm, surgery is deferred for approximately five to seven days. If the initial angiogram clearly shows the anatomy of the aneurysm and completely visualizes the intracranial circulation, it does not need to be repeated. If the initial angiogram is incomplete, then all vessels are studied prior to surgery. In cases of middle cerebral artery aneurysm with temporal clot, an angiogram is obtained early. In the future, early complete angiography followed by surgery may be possible in those patients with little blood on the initial CT scan. Those patients are not considered to be in jeopardy of developing severe vasospasm.

Cerebral Angiography↗
PubMed1981

Toxic and teratogenic effects of selected aromatic amines on embryos of the amphibian Xenopus laevis.

Evaluations of the toxic and teratogenic effects of four aromatic amines, acridine, aniline, pyridine, and quinoline, have been made on amphibian (Xenopus laevis) embryos. For toxicity testing, the embryos were divided into three groups according to stage of development: Group I were mid-blastulae, Group II were tailbud embryos, and Group III were swimming larvae. Of the amines tested, acridine and quinoline were the most toxic, followed by aniline and pyridine. Ninety six hr LC50 values for acridine, quinoline, aniline, and pyridine were 4.5, 95, 150, and 1090 mg/L, respectively, for Group III larvae. Except for acridine, where embryos in all three groups were about equally affected, those in Group II were less sensitive to the other amines than those in Groups I and III. Group I embryos were exposed to all four amines to determine their teratogenicity. The amines were ranked in order to decreasing teratogenicity: acridine, quinoline, aniline, and pyridine having 96-hr EC50 values of 2.4, 29, 370, and 1200 mg/L, respectively. Electron microscopic examination of Group III larvae exposed to these amines reveals pathology of the spinal cord and musculature. This damage was correlated with immobility of the larvae. The uptake of acridine was followed in larvae (Group III) exposed to 5 mg/L and was found to reach a maximum level of about 85 mg/g wet weight in about one hr. Depuration kinetics were characterized by a rapid loss of 70% of the total acridine within 45 min. Acridine was undetectable after two hr. These data suggest that acridine, aniline, and quinoline have toxic and teratogenic effects at sufficiently low concentrations as to make them potential environmental hazards.

Acridines↗
PubMed1981

Computed tomography of intracranial aspergillosis.

Cranial computed tomography (CT) scans were analyzed in five patients with autopsy documented intracranial aspergillosis. All infections occurred in immunocompromised hosts. Our findings included subtle low attenuation abnormalities, minimal mass effect, and poor contrast enhancement without ring configuration, in the clinical setting of lethargy, fever, and pulmonary infection. The benign CT picture did not clearly depict the aggressive intracranial parenchymal destruction.

Adult↗