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Biomedical subjects

D O Davis

Publications and source records attributed to D O Davis.

At least 19 recordsLinked to original sources
PubMed1992

Contrast-enhanced MR imaging performed after successful lumbar disk surgery: prospective study.

A prospective study was undertaken to establish the normal spectrum and timing of gadolinium-enhanced magnetic resonance (MR) imaging findings in 15 patients who had resolution of symptoms after successful lumbar disk surgery. Enhancement of the facet joints (in 88% of disk levels) and paraspinal muscles (100%) decreased gradually after surgery. Enhancement of the decompressed nerve root tracked proximally toward the conus medullaris in 62% at 3 weeks and was absent in all by 6 months postoperatively. Areas of intermediate signal intensity with peripheral enhancement and mass effect were seen on T1-weighted images at the site of the original disk herniation in 38% at 3 weeks and 12% at 3 months, despite complete relief of leg pain. These results reveal that even in successfully treated (asymptomatic) patients, residual mass effect on the neural elements may frequently simulate a recurrent or residual disk fragment. There is an orderly progression of imaging changes during the first 6 months after lumbar surgery that limits the interpretation of MR examinations during that period.

Adult↗
PubMed1992

Postoperative diskitis: distinguishing early MR imaging findings from normal postoperative disk space changes.

To distinguish early magnetic resonance (MR) imaging findings in postoperative diskitis from normal postoperative changes, a prospective study was performed in 15 asymptomatic patients (17 disk levels) who underwent uncomplicated lumbar diskectomy and seven patients with proved postoperative diskitis. On postoperative MR images, four of the asymptomatic patients had a finding that could also be seen in patients with diskitis. Gadolinium enhancement was useful in making the distinction and occurred as follows: (a) vertebral bone marrow: all seven diskitis patients and one asymptomatic patient; (b) disk space: five diskitis patients and three asymptomatic patients; and (c) posterior anulus fibrosus: all seven diskitis patients and 13 asymptomatic patients (14 of 17 levels). This entire triad of findings, which is strongly suggestive of postoperative diskitis, was not seen in any of the asymptomatic patients. Changes in the disk space and adjacent bone marrow on pre- and post-contrast MR images after routine diskectomy are uncommon and should not be assumed to be normal postoperative changes without careful consideration and analysis for early diskitis.

Adult↗
PubMed1992

A prospective and blinded investigation of magnetic resonance imaging of the knee. Abnormal findings in asymptomatic subjects.

To evaluate magnetic resonance imaging (MRI) of meniscal, ligamentous, and bony abnormalities in patients without clinical symptoms, scans were performed on 74 asymptomatic volunteers without histories or symptoms of knee injury. Before review by three radiologists in an independent and blinded fashion, the scans were mixed with 26 MRI scans from symptomatic patients. Sixteen percent of the asymptomatic volunteers had meniscal abnormalities consistent with a tear. The prevalence of MRI findings of a meniscal tear increased from 13% in individuals younger than 45 years of age to 36% in those older than 45. An additional 30% of the volunteers showed meniscal abnormalities consisting of a linear area of increased MR signal not communicating with a meniscal edge, which was not interpreted to represent a tear. The high incidence of abnormal MRI findings in asymptomatic subjects underscores the danger of relying on a diagnostic test without careful correlation with clinical signs and symptoms. These findings also emphasize the importance of access to relevant clinical data when interpreting MRI scans of the knee.

Adolescent↗
PubMed1991

Gd-DTPA-enhancement magnetic resonance imaging of the cavernous sinus.

Based upon our experiences with 7 cases and a literature review a survey is provided on the possibilities and limitations of preoperative diagnosis of space-occupying lesions of the cavernous sinus using MRI with Gd-DTPA enhancement. Advantages are, that in many cases arteriography is no longer necessary, and that the diagnostic sensitivity is higher as compared with CT. The pattern of enhancement does not allow for histological distinction among the various lesions.

Adult↗
PubMed1990

Abnormal magnetic-resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation.

We performed magnetic resonance imaging on sixty-seven individuals who had never had low-back pain, sciatica, or neurogenic claudication. The scans were interpreted independently by three neuro-radiologists who had no knowledge about the presence or absence of clinical symptoms in the subjects. About one-third of the subjects were found to have a substantial abnormality. Of those who were less than sixty years old, 20 per cent had a herniated nucleus pulposus and one had spinal stenosis. In the group that was sixty years old or older, the findings were abnormal on about 57 per cent of the scans: 36 per cent of the subjects had a herniated nucleus pulposus and 21 per cent had spinal stenosis. There was degeneration or bulging of a disc at at least one lumbar level in 35 per cent of the subjects between twenty and thirty-nine years old and in all but one of the sixty to eighty-year-old subjects. In view of these findings in asymptomatic subjects, we concluded that abnormalities on magnetic resonance images must be strictly correlated with age and any clinical signs and symptoms before operative treatment is contemplated.

Adult↗
PubMed1990

Abnormal magnetic-resonance scans of the cervical spine in asymptomatic subjects. A prospective investigation.

Previous investigations with plain radiography, myelography, and computed tomography have shown that degenerative disease of the cervical spine frequently occurs in the absence of clinical symptoms. We studied the magnetic resonance-imaging scans of sixty-three volunteers who had no history of symptoms indicative of cervical disease. The scans were mixed randomly with thirty-seven scans of patients who had a symptomatic lesion of the cervical spine, and all of the scans were interpreted independently by three neuroradiologists. The scans were interpreted as demonstrating an abnormality in 19 per cent of the asymptomatic subjects: 14 per cent of those who were less than forty years old and 28 per cent of those who were older than forty. Of the subjects who were less than forty, 10 per cent had a herniated nucleus pulposus and 4 per cent had foraminal stenosis. Of the subjects who were older than forty, 5 per cent had a herniated nucleus pulposus; 3 per cent, bulging of the disc; and 20 per cent, foraminal stenosis. Narrowing of a disc space, degeneration of a disc, spurs, or compression of the cord were also recorded. The disc was degenerated or narrowed at one level or more in 25 per cent of the subjects who were less than forty years old and in almost 60 per cent of those who were older than forty. The prevalence of abnormal magnetic-resonance images of the cervical spine as related to age in asymptomatic individuals emphasizes the dangers of predicating operative decisions on diagnostic tests without precisely matching those findings with clinical signs and symptoms.

Adult↗
PubMed1988

Updated assessment and current classification of spinal meningeal cysts.

The classification of spinal meningeal cysts (MC's) in the literature is indistinct, confusing, and in certain categories histologically misleading. Based on a series of 22 cases, the authors propose a classification comprising three categories: spinal extradural MC's without spinal nerve root fibers (Type I); spinal extradural MC's with spinal nerve root fibers (Type II); and spinal intradural MC's (Type III). Although water-soluble myelography may disclose a filling defect for all three categories, computerized tomographic myelography (CTM) is essential to reveal communication between the cyst and the subarachnoid space. Communication demonstrated by CTM allows accurate diagnosis of a spinal MC and rules out other mass lesions. Magnetic resonance imaging appears useful as an initial study to identify an intraspinal cystic mass. Final characterization is based on operative inspection and histological examination for all three categories.

Adolescent↗
PubMed1987

Delayed postoperative dural arteriovenous malformations. Report of two cases.

The authors present two cases of dural arteriovenous malformations (AVM's) that developed at the site of previous suboccipital craniectomies. No other cases of delayed postoperative dural AVM's have been reported. Congenital and acquired dural AVM's are discussed, with reference to the similarity between postoperative dural AVM's and traumatic dural AVM's. Embolization is recommended in selected cases where the arterial supply is primarily from the external carotid system.

Aged↗
PubMed1987

Toxoplasma encephalitis in patients with acquired immune deficiency syndrome: diagnosis and response to therapy.

Although Toxoplasma gondii is the most commonly recognized cause of central nervous system mass lesions in patients with acquired immune deficiency syndrome, published investigations have provided little information about criteria for diagnosis of toxoplasmosis or the response to therapy. In this series the method of diagnosis and response to therapy were assessed in 14 patients who had evidence for toxoplasmosis based on routine histopathology, immunoperoxidase staining, or mouse inoculation. These patients presented with clinical and radiologic findings that did not clearly distinguish them from patients with other infectious or neoplastic processes. Excisional biopsies usually showed tachyzoites on routine histology, but needle biopsies were usually negative unless mouse inoculation or immunoperoxidase staining was employed. Response to pyrimethamine and sulfadiazine therapy was often prompt, but therapy had to be continued for long periods of time to maintain a clinical response, and no alternative regimen of one or more drugs appeared to be effective in patients unable to tolerate both pyrimethamine and sulfadiazine.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Pituitary adenomas: high-resolution MR imaging at 1.5 T.

The magnetic resonance (MR) images of 28 patients with surgically confirmed pituitary adenomas were retrospectively evaluated. The examinations were performed on a 1.5-T superconducting MR system using a multisection spin-echo technique with 3-mm-thick sections and a 256 X 256 matrix. T1- and T2-weighted images were obtained in sagittal and coronal planes. The MR findings were correlated with detailed operative reports and diagrams. There were 11 microadenomas and 17 macroadenomas. Ten of the microadenomas and all of the macroadenomas were accurately localized and their extent delineated, particularly on T1-weighted coronal sections. Adenomas typically appeared hypointense on T1-weighted coronal sections. The appearance on T2-weighted images was variable, and generally the lesions were less well seen. Involvement of parasellar structures, particularly the optic chiasm and cavernous sinuses, was accurately depicted. Cyst formation and hemorrhage could be characterized in some instances. In general, there was excellent correlation between MR imaging and operative findings.

Adenoma↗
PubMed1986

Intracranial lesions: flow-related enhancement on MR images using time-of-flight effects.

Many physico-anatomic variables and instrument parameters influence the relative magnetic resonance signal intensity of vascular channels. The interaction of these mechanisms is complex, but their composite effects can be accounted for by two main categories of flow phenomena: time-of-flight effects and spin-phase changes. Of these two mechanisms only the time-of-flight effect known as flow-related enhancement produces augmentation of intravascular signal. Flow-related enhancement can potentially provide positive contrast of diagnostic value in terms of anatomic depiction of vascular detail as well as physiologic characterization of blood flow. The authors have used a single-section, selectively irradiated, spin-echo pulse sequence to maximize flow-related enhancement within a variety of intracranial lesions, as a supplement to their regular imaging. The technique was found to be diagnostically useful in improving the conspicuity of vascular lesions, in determining vessel patency, in distinguishing flow void from calcification, and in obtaining semiquantitative information about flow dynamics.

Brain Diseases↗
PubMed1979

Acute isodense epidural hematoma on computed tomography.

Computed tomography (CT) has proven to be invaluable in the diagnosis of craniocerebral injuries. Acute epidural hematomas have been described as having a characteristic appearance on CT of a lenticular shaped area of blood density most commonly situated over the cerebral convexity. This case demonstrates an acute epidural hematoma that is essentially isodense with brain tissue.

Adult↗
PubMed1979

Cranial CT findings in patients with meningomyelocele.

The association between meningomyelocele and various cranial abnormalities, particularly Chiari II malformation is well established. Cranial CT scans in 47 patients with meningomyelocele proved to be a safe and effective method of elucidating the type and extent of anatomic abnormalities associated with this disorder, and evaluating and following the degree of hydrocephalus seen in these patients. Of the 47 patients, 43 (92%) showed CT findings indicative of an abnormally low fourth ventricle, the hallmark finding in Chiari II malformation. In 67% the fourth ventricle was not visualized, and in 25% it was directly visualized in an abnormally caudal position. Other findings included hydrocephalus (85%), a striking and possibly unique heart-shaped psuedomass in the posterior fossa (58%), and abnormal configuration of the lateral ventricles ("vampire bat" configuration). Calvarial abnormalities, in particular lacunar skull, were also noted at CT.

Abnormalities, Multiple↗
PubMed1979

Subdural hematomas: an unusual appearance on computed tomography.

It may at times be difficult to separate supra- from infratentorial and intra- from extraaxial pathology on the basis of axial transverse computed tomography (CT) scans. Coronal CT scans may be quite useful in more accurate localization of compartments. Three head injured patients with subdural hematomas were studied with axial transverse CT scans. In addition to the typical appearance of subdural hematomas, unusually shaped areas of increased attenuation were noted in the region of the tentorium cerebelli separate from the mass of the subdural collection. Coronal scans confirmed the supratentorial, extraaxial collection as an extension of the subdural hematoma into the supratentorial subdural space.

Cerebral Ventriculography↗
PubMed1978

Utilization and cost-effectiveness of cranial computed tomography at a university hospital.

This study prospectively surveyed the utilization of cranial computed tomography (CCT) at The George Washington University Hospital over a 12-month period. Of 3,070 CCT scans studied, 1,098 (35%) resulted in a positive clinically important diagnosis for an overall case finding cost of $800. Within each of 25 individual indications for scanning, classified on the basis of the patient's most specific sign or symptom, case finding costs varied from a low of $411 for patients in coma to $3,500 for patients with headaches as their only indication for CT scanning. Within two diagnostic categories, malignant brain tumors and cerebral aneurysms, there was significant agreement (p less than 0.001) between the prescanning diagnosis and the result on CCT. Overall there was also close agreement (correlation coefficient = 0.706) between the rank listing of the 25 indications for scanning compiled prior to CCT with that obtained after the scanning results were known.

Adolescent↗