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Biomedical subjects

G A Meyer

Publications and source records attributed to G A Meyer.

At least 19 recordsLinked to original sources
PubMed1995

Cervical carcinoma: determination of recurrent tumor extent versus radiation changes with MR imaging.

PURPOSE: To evaluate the effectiveness of magnetic resonance (MR) imaging for assessment of the present and extent of tumor recurrence as determined with pathologic and surgical findings. MATERIALS AND METHODS: MR findings were retrospectively examined in 37 patients with a history of cervical carcinoma. Inter- and intraobserver variability was analyzed. Surgical or pathologic results were acquired in 34 of these patients; the remaining three patients were clinically followed up for at least 4 years. RESULTS: MR imaging allowed correct detection of recurrent tumor in 18 of 21 patients who had histologically documented recurrence. It helped correctly exclude recurrent disease in 15 of 16 patients. Sensitivity and specificity for detection of recurrence was 86% and 94%, respectively. Good intra- and interobserver agreement was demonstrated. CONCLUSION: MR imaging is a useful modality for differentiation of recurrent cervical carcinoma from radiation changes. Determination of the extent of recurrence with MR imaging may offer clinical assistance in the selection of optimal therapy.

Adenocarcinoma↗
PubMed1995

Moraxella (Branhamella) catarrhalis bacteremia in children. A report of two patients and review of the literature.

We report two cases of Moraxella catarrhalis (M. catarrhalis) bacteremia in apparently healthy children. One patient had bilateral otitis media and the other had pharyngitis and sinusitis; both patients had uncomplicated clinical courses. A literature review revealed 22 reported cases of M. catarrhalis bacteremia in children, 14 (63%) of which occurred in patients who had no identified underlying condition. Eight (36%) cases were seen in children who were immunocompromised. Nine (40%) patients presented with either purpura, petechia, or a maculopapular rash. M. catarrhalis is well known as a respiratory pathogen, but it has not been recognized as a common cause of unsuspected bacteremia in children.

Anti-Bacterial Agents↗
PubMed1994

Selective incorporation of 111In-labeled PHOTOFRIN by glioma tissue in vivo.

The use of PHOTOFRIN for photodynamic therapy of human gliomas has been studied by i.v. administration and laser photosensitization. Defining the uptake of PHOTOFRIN in the patient's tumor in comparison with the surrounding normal brain tissue is highly desirable for patient selection and study of in vivo kinetics. We utilized a non-invasive approach to the detection of PHOTOFRIN uptake in brain tumors with 111In-oxine radiolabeled PHOTOFRIN and external imaging and quantitation using a gamma camera. Biodistribution of 111In-labeled PHOTOFRIN in 13 organs was determined in four dogs and 15 mice with gliomas. 99mTc-DTPA was used as a control for nonspecific uptake. The greatest concentration of 111In-PHOTOFRIN in the brain tumor occurred at 24 hours post i.v. administration. The brain tumor PHOTOFRIN uptake was seven times greater than that of normal brain. The decreased blood background at 72 hours made this the optimum time for imaging. Specific tumor tissue uptake of 111In-PHOTOFRIN occurred, well beyond that resulting from blood-brain-barrier (BBB) breakdown.

Animals↗
PubMed1993

The role of photodynamic therapy in posterior fossa brain tumors. A preclinical study in a canine glioma model.

Photodynamic therapy was studied in dogs with and without posterior fossa glioblastomas. This mode of therapy consisted of intravenous administration of Photofrin-II at doses ranging from 0.75 to 4 mg/kg 24 hours prior to laser light irradiation in the posterior fossa. Tissue levels of Photofrin-II were four times greater in the tumor than in the surrounding normal brain. Irradiation was performed using 1 hour of 500 mW laser light at a wavelength of 630 nm delivered through a fiberoptic catheter directly into the tumor bed via a burr hole. All animals receiving a high dose (4 or 2 mg/kg) of Photofrin-II developed serious brain-stem neurotoxicity resulting in death or significant residual neurological deficits. A lower dose (0.75 mg/kg) of Photofrin-II produced tumor kill without significant permanent brain-stem toxicity in either the control animals or the animals with cerebellar brain tumors receiving photodynamic therapy.

Animals↗
PubMed1992

Increased sacroiliac joint uptake after lumbar fusion and/or laminectomy.

Of 753 adult patients undergoing SPECT and planar bone scintigraphy for the evaluation of low back pain, 43 (6%) showed either unilateral or bilateral increased sacroiliac joint (SIJ) uptake. Five of the 58 abnormal joints were only identified with SPECT (9%), whereas 20 of the 58 abnormal joints were much more convincingly demonstrated by SPECT (34%). Fifteen of the 43 patients with increased SIJ uptake had undergone prior lumbar laminectomy and/or spinal fusion. Such spinal surgery can increase impact loading on the SIJ, leading to mechanical overload and sacroiliitis. Degenerative joint disease, trauma, or other benign pathology accounted for the remaining patients with increased SIJ uptake. The authors conclude that for patients with a history of lumbar spinal fusion and/or laminectomy, increased SIJ uptake usually is caused by altered spinal mechanics rather than malignancy or infection.

Adult↗
PubMed1991

Optic chiasm glioma associated with inappropriate secretion of antidiuretic hormone, cerebral ischemia, nonobstructive hydrocephalus and chronic ascites following ventriculoperitoneal shunting.

An optic chiasm glioma may cause loss of vision, endocrine disturbances, hydrocephalus and cerebral ischemia due to its proximity to the pituitary, hypothalamus, III ventricle and internal carotids. A 3-month-old infant with optic chiasm glioma developed hypopituitarism and inappropriate secretion of antidiuretic hormone with plasma hypo-osmolality. The cerebrospinal fluid (CSF) protein concentration was markedly elevated. The impairment of fluid absorption via arachnoid villi and peritoneum by the high protein content, and reversed osmotic gradient between protein-rich CSF and hypo-osmolar plasma may have contributed to both nonobstructive hydrocephalus and recurrent ascites following ventriculoperitoneal shunting. Cerebral ischemia from carotid compression may have led to cerebral atrophy.

Ascites↗
PubMed1990

Trigeminal nerve neurofibroma: case report.

A case of left trigeminal nerve neurofibroma is presented. The location of the lesion required a multidisciplinary surgical effort for total excision. A vertical ramus osteotomy allowed access to the infratemporal space and base of skull. The frequency and clinical features of trigeminal nerve tumors are discussed.

Bone Plates↗
PubMed1989

Gradient recalled echo MR imaging of superior sagittal sinus occlusion.

With T1-weighted gradient recalled echo (GRE) MR images and flow compensation, we studied the superior sagittal sinus in 3 normal volunteers and 3 patients with sinus occlusion. In these images, sites of patency of the superior sagittal sinus were identified due to the high signal intensity of the normal sinus. Tumor invading the sinus was nearly isointense with cerebral gray matter. T1-weighted GRE imaging proves to be an effective technique to evaluate sinus blood flow.

Cerebrovascular Circulation↗
PubMed1989

MR imaging of facial nerve enhancement in Bell palsy or after temporal bone surgery.

The authors evaluated magnetic resonance (MR) images obtained with intravenously administered gadolinium in ten patients who had facial paralysis and no facial nerve tumor. In patients with either Bell palsy (four patients) or facial paralysis after temporal bone surgery (six patients), intratemporal facial nerve enhancement was seen. Facial nerve enhancement on MR images proved to be a nonspecific finding.

Facial Nerve↗
PubMed1989

Gadolinium-enhanced magnetic resonance imaging in temporal bone lesions.

A 2-year experience with an enhancement agent in magnetic resonance imaging (MRI) is examined through case presentations. Characteristics of the agent Gadolinium DTPA/Dimeglumin are reviewed. Radiographic capabilities in enhanced versus unenhanced MRI are compared. Temporal bone lesions, including acoustic neuromas and facial nerve neuromas, are presented. Recent experience with facial nerve enhancement in Bell's palsy is also presented. Greater accuracy in defining small temporal bone lesions and increased delineation of facial nerve involvement appear to be significant benefits with enhanced MRI.

Adult↗
PubMed1987

MR detection of tumor in the internal auditory canal.

The MR appearance of 15 tumors within or near the internal auditory canal was analyzed in detail and compared with the subsequent surgical observations. In most cases, nonenhanced MR showed the precise extent of the intracanalicular and extracanalicular tumor despite minor variations in appearance. In a case of facial nerve neurinoma, the extent to which the tumor invaded the canal was underestimated by MR. Gadolinium-DTPA enhancement is expected to eliminate uncertainties in MR imaging of the internal auditory canal.

Cerebellar Neoplasms↗
PubMed1986

Arachnoid cyst of the collicular cistern.

Arachnoid cysts of the collicular cistern are rare. Two patients with this lesion are reported in whom the extent and location of the cyst were shown by computed tomography. The clinical and radiographic features of this lesion are summarized.

Adolescent↗
PubMed1986

Cerebral toxoplasmosis in an immunocompromised host. A precise and rapid diagnosis by electron microscopy.

In immunocompromised patients with cerebral toxoplasmosis, the tachyzoite forms rather than cystic and bradyzoite forms of the protozoon are commonly seen. These tachyzoites are minute, scattered among cellular debris, sometimes lodged inside macrophages and neutrophils, and difficult to visualize by light microscopy, even with special stains. Immunodiagnostic tests may be falsely negative due to inability of the host to produce appropriate antibodies. Isolation of the organism is dangerous because Toxoplasma gondii is highly infective. In this situation, transmission electron microscopy (EM) may be a diagnostic tool of choice. It demonstrates the fine definitive features of the protozoon and can be expedited to give results in five hours. Further evaluation of EM for diagnosing possible toxoplasmosis in immunocompromised patients is indicated.

Adolescent↗
PubMed1986

BSS Plus: a potential irrigating solution for neurosurgery.

BSS Plus is a pH-stable balanced salt solution similar to glutathione bicarbonate Ringer's solution. Extensively used in ophthalmology, it is of potential value in neurosurgery. In comparative tests of its effectiveness, 28 cats underwent bilateral irrigation of the surface of the cerebral cortex with normal saline on one side and BSS Plus on the other. After 2 hours, a marked decrease was seen in the surface pH of the hemisphere irrigated with normal saline but not of the hemisphere treated with BSS Plus. Blood-brain barrier changes (measured with Evans blue dye techniques) were more evident following saline irrigation. Somatosensory evoked potentials and cerebral blood flow were not significantly altered. Conventional light microscopy using three standard stains did not reveal a significant difference. Transmission electron microscopy studies were performed in 14 animals and scanning electron microscopy in six. In five animals both transmission and scanning electron microscopy studies were conducted after irrigation with both agents without a cottonoid cover and with immediate harvest of superficial layers from the living brain and immersion-fixation in glutaraldehyde. Tissue preservation was superior on the BSS Plus side in all studies. This agent may represent an improved irrigation solution for neurosurgery, but further studies are required.

Animals↗
PubMed1985

Painful spondylolysis or spondylolisthesis studied by radiography and single-photon emission computed tomography.

Planar bone scintigraphy (PBS) and single-photon emission computed tomography (SPECT) were compared in 19 adults with radiographic evidence of spondylolysis and/or spondylolisthesis. SPECT was more sensitive than PBS when used to identify symptomatic patients and sites of "painful" defects in the pars interarticularis. In addition, SPECT allowed more accurate localization than PBS. In 6 patients, spondylolysis or spondylolisthesis was unrelated to low back pain, and SPECT images of the posterior neural arch were normal. The authors conclude that when spondylolysis or spondylolisthesis is the cause of low back pain, pars defects are frequently heralded by increased scintigraphic activity which is best detected and localized by SPECT.

Adolescent↗