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Biomedical subjects

S S Gebarski

Publications and source records attributed to S S Gebarski.

At least 19 recordsLinked to original sources
PubMed1992

Hippocampal formation volume, memory dysfunction, and cortisol levels in patients with Cushing's syndrome.

Patients with chronic hypercortisolemia due to Cushing's syndrome (CS) exhibit cognitive dysfunction. Because glucocorticoid excess is associated with hippocampal damage in animals, and the hippocampus participates in learning and memory, we explored the relationships between hippocampal formation (HF) volume, memory dysfunction, and cortisol levels in 12 patients with CS. After magnetic resonance imaging, HF volume was determined using digital sum of track ball traces of dentate gyrus, hippocampus proper and subiculum, correcting for total intracranial volume. For 27% of the patients, HF volume fell outside the 95% confidence intervals for normal subject volume given in the literature. In addition, there were significant and specific correlations between HF volume and scores for verbal paired associate learning, verbal recall, and verbal recall corrected for full-scale IQ (r = 0.57 to 0.70, p < 0.05). HF volume was negatively correlated with plasma cortisol levels (r = -0.73, p < 0.05). These studies suggest an association between reduced HF volume, memory dysfunction, and elevated cortisol in patients with CS.

Adolescent↗
PubMed1992

Enhancement along the normal facial nerve in the facial canal: MR imaging and anatomic correlation.

Normal facial nerves are reported to show no enhancement at magnetic resonance (MR) imaging, in contradiction to the authors' clinical experience. To investigate this inconsistency, the authors searched MR imaging files and clinical records to find patients who underwent MR imaging of the temporal bone (at 1.5 T) before and after intravenous administration of gadopentetate dimeglumine and who had bilateral clinically normal facial nerves. When the MR images of 93 patients (186 facial nerves) were analyzed subjectively, 142 nerves (76%) were visibly enhanced along at least one segment of the facial nerve within the facial canal; the nerves of 64 of the 93 patients (69%) showed right-left asymmetry in enhancement, which was inhomogeneously distributed along each nerve. The facial nerve in the cerebellopontine angle cistern and in the internal auditory canal, as well as in the visualized proximal portion of the extracranial facial nerve, showed no enhancement. Comparison with reference anatomic sections showed that this enhancement pattern corresponded exactly to the topography of the circumneural facial arteriovenous plexus and should not necessarily be considered a sign of anatomic abnormality.

Adolescent↗
PubMed1992

Radiation-induced optic neuropathy: correlation of MR imaging and radiation dosimetry.

The authors performed topographic correlation of dosimetric measurements with contrast medium-enhanced magnetic resonance (MR) imaging signal aberration in two cases of radiation optic neuropathy. The region of pathologic contrast enhancement in the optic nerve and chiasm had received 55-62 Gy, which supports the theory that the risk of injury to the optic nerve and chiasm increases steeply with radiation doses above the tolerance level of 50-55 Gy.

Female↗
PubMed1991

Nystagmus of Pelizaeus-Merzbacher disease. A magnetic search-coil study.

Magnetic search-coil oculography of three brothers with clinically diagnosed Pelizaeus-Merzbacher disease disclosed the presence of binocular elliptical pendular nystagmus in two patients in whom the waveform of the nystagmus was not obvious on inspection. This study, the first reported application of high-resolution oculography to Pelizaeus-Merzbacher disease, also demonstrated primary position upbeat nystagmus in all three patients. The importance of finding this combination of elliptical pendular and upbeat nystagmus is that it is not described in any other childhood neurodegenerative states and, in combination with supportive clinical history and magnetic resonance imaging, may be so characteristic of Pelizaeus-Merzbacher disease that a strong presumptive diagnosis can be made.

Adult↗
PubMed1991

Visual loss in tuberous sclerosis.

Of 11 patients with tuberous sclerosis complex (TSC) treated from 1980 to 1990 for obstructive hydrocephalus secondary to subependymal giant-cell astrocytoma, four had adequate documentation to determine visual outcome. Despite surgical relief of elevated intracranial pressure in all cases, two patients sustained further visual loss. In one patient, visual loss was arrested, and in one patient, it was prevented. Although hydrocephalus is uncommon in TSC, its effects on the optic nerves are serious and eventually irreversible. Because TSC patients may not be able to express early symptoms of increased intracranial pressure, periodic ophthalmologic examination and brain imaging may be advisable when a subependymal lesion has been identified.

Adolescent↗
PubMed1990

The Marinesco-Sjögren syndrome examined by computed tomography, magnetic resonance, and 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography.

The Marinesco-Sjögren syndrome is an autosomal recessive degenerative disorder characterized by congenital cataracts, cerebellar ataxia, spasticity, mental deficiency, and skeletal abnormalities. We studied two adult siblings with Marinesco-Sjögren syndrome using anatomic and metabolic brain imaging techniques to characterize the pattern and nature of abnormalities in the brain. Computed tomographic and magnetic resonance imaging showed diffuse brain atrophy of mild to moderate degree, involving primarily the white matter of the cerebrum, cerebellum, brain stem, and cervical spinal cord. The pattern of atrophy resembled that seen in diffuse leukoencephalopathies. Measurements of local cerebral glucose metabolic rates with positron emission tomography revealed no statistically significant differences from normal control subjects in most regions, but metabolic rate was decreased in the thalamus in one patient. The findings support a diffuse white matter disorder in Marinesco-Sjögren syndrome.

Adult↗
PubMed1990

Intra-arterial bromodeoxyuridine radiosensitization of malignant gliomas.

In the 1950's it was first observed that mammalian cells exposed to the halogenated deoxyuridines were more sensitive to ultraviolet light and radiation than untreated cells. This prompted early clinical trials with bromodeoxyuridine (BUdR) which showed mixed results. More recently, several Phase I studies, while establishing the feasibility of continuous intravenous (IV) infusion of BUdR, have reported significant dose limiting skin and bone marrow toxicities and have questioned the optimal method of BUdR delivery. To exploit the high mitotic activity of malignant gliomas relative to surrounding normal brain tissue, we have developed a permanently implantable infusion pump system for safe, continuous intraarterial (IA) internal carotid BUdR delivery. Since July 1985, 23 patients with malignant brain tumors (18 grade 4, 5 grade 3) have been treated in a Phase I clinical trial using IA BUdR (400-600 mg/m2/day X 8 1/2 weeks) and focal external beam radiotherapy (59.4 Gy at 1.8 Gy/day in 6 1/2 weeks). Following initial biopsy/surgery the infusion pump system was implanted; BUdR infusion began 2 weeks prior to and continued throughout the 6 1/2 week course of radiotherapy. There have been no vascular complications. Side-effects in all patients have included varying degrees of anorexia, fatigue, ipsilateral forehead dermatitis, blepharitis, and conjunctivitis. Myelosuppression requiring dose reduction occurred in one patient. An overall Kaplan-Meier estimated median survival of 20 months has been achieved. As in larger controlled series, histologic grade and age are prognostically significant. We have shown in a Phase I study that IA BUdR radiosensitization is safe, tolerable, may lead to improved survival, and appears to be an efficacious primary treatment of malignant gliomas.

Adult↗
PubMed1990

Three-dimensional x-ray computed tomography of the temporal bone as an aid to surgical planning.

Three-dimensional x-ray computed tomography (3DCT) has been useful in planning surgical procedures involving craniofacial reconstruction, the pelvis, hip, spine, knee and shoulder. The clinical use of 3DCT in temporal bone surgery has not been evaluated. We used 3DCT to assess temporal bone anatomy in 9 patients. These cases evaluated two encephaloceles, two postinflammatory dehiscences, two temporal bone fractures, one glomus jugulare tumor, one acoustic neuroma, and one meningioma. We found 3DCT useful in these temporal bone applications as a supplement to standard two-dimensional CT scanning (2DCT). While 3DCT provided a better preoperative understanding of the underlying anatomy, no treatment was modified solely on the basis of the information derived from the 3-D presentation of data. We conclude that, although 3DCT images have some qualitative advantages over 2DCT techniques, their value in further defining temporal bone morphology must be evaluated against the cost entailed by their use.

Adult↗
PubMed1990

MR imaging of the brain in five members of a family with Pelizaeus-Merzbacher disease.

MR imaging was performed in five members of a family afflicted with Pelizaeus-Merzbacher disease. The individuals imaged included a male proband, his mother, and three maternal uncles. Clinically affected members showed generalized white matter signal aberration consistent with dys- and demyelination, basal ganglia, and thalamic signal aberration suggestive of pathologic iron storage and diffuse brain atrophy. These findings are similar to those seen in other leukodystrophies. The proband's mother was normal by neurologic examination but showed a suspicious but not definitely abnormal similar pattern of basal ganglionic and white matter signal aberration. In our limited patient sample, MR appears to be able to: (1) demonstrate a pattern of imaging abnormalities characteristic of Pelizaeus-Merzbacher disease (we do not know if this pattern is specific); (2) potentially detect the obligate carrier state; and (3) detect the facultative carrier state.

Adult↗
PubMed1989

Visual outcome in cystic craniopharyngiomas treated with intracavitary phosphorus-32.

Seven patients with cystic craniopharyngiomas were treated with stereotactic instillation of radioactive phosphorus-32 (32P). Five patients had been previously treated with various combinations of surgery and external beam irradiation, whereas two had the 32P instillation at a primary therapy. Visual acuity improved in 13 eyes and remained stable in 1. Visual fields normalized in three patients, improved in two, and remained stable in two. Two patients received single treatments with 32P, whereas five required multiple instillations for recurrent cyst expansion.

Adolescent↗
PubMed1989

Optic tract injury after anterior temporal lobectomy.

Three patients had complete homonymous hemianopia with clinical and neuroimaging characteristics of ipsilateral optic tract infarction after anterior temporal lobectomy for seizure control. This injury presumably resulted from irritative vasospasm of the anterior choroidal artery. The features of this pure optic tract syndrome should be distinguished from the more common compressive optic tract syndrome which generally also impairs ipsilateral optic nerve function.

Adult↗
PubMed1989

Idiopathic intracranial hypertension (pseudotumor cerebri): MR imaging.

Magnetic resonance (MR) imaging was performed on six patients with idiopathic intracranial hypertension (IIH). The patients were all women with a mean age of 27 years (range, 17-41 years). Six healthy women volunteers with a mean age of 33 years (range, 25-46 years) were studied for comparison. All six patients had elevated opening pressures at lumbar puncture. MR imaging demonstrated a partially empty sella in two patients, and one patient had signal aberration in the dural venous sinuses suggestive of slow flow. There were no white matter signal abnormalities, even in the periependymal space. Volumetric pixel analysis revealed significantly larger subarachnoid space volumes in patients than in control subjects, without a significant difference in ventricular volumes. No other intracranial abnormalities were found in any IIH patient or control subject. The results suggest that, in IIH, (a) although the subarachnoid spaces are enlarged, the wide range of normal values would limit the clinical use of these measurements and (b) the role of MR imaging, as with CT, is primarily in the exclusion of other diseases with clinical presentations similar to that of IIH.

Adolescent↗
PubMed1989

Intraoperative sonography in low-grade gliomas.

A retrospective study of intraoperative sonography and preoperative head computed tomography (CT) in 15 patients with low-grade brain gliomas was undertaken to determine whether areas of increased echogenicity without shadowing corresponded with areas of pathologic CT enhancement. Glioma echogenicity was considered increased if greater than or equal to adjacent sulcal echogenicity. Of the 15 lesions, 7 of 8 with pathologic CT enhancement showed areas of increased echogenicity without shadowing. Areas of increased echogenicity topographically correlated with areas of pathologic CT enhancement. One of eight lesions with pathologic enhancement had no areas of increased echogenicity; however, the enhancement in this lesion was minimal. Six of seven patients without pathologic CT enhancement had areas of echogenicity always less than sulcal echogenicity. Our results suggest that, in low-grade gliomas, regions of enhancement usually correspond to areas of increased echogenicity without shadowing. These findings differ from those found with high-grade gliomas.

Astrocytoma↗
PubMed1988

Cerebellar and brainstem hypometabolism in olivopontocerebellar atrophy detected with positron emission tomography.

We studied local cerebral metabolic rates for glucose (1CMRglc) with 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET) in 30 patients with olivopontocerebellar atrophy (OPCA) and 30 age-matched control subjects without neurological disease. The diagnosis of OPCA was based on the history and physical findings and on the exclusion of other causes of cerebellar ataxia by means of laboratory investigations. Computed tomographic scans revealed some degree of atrophy of the cerebellum in most patients with OPCA, and many also had atrophy of the brainstem. PET studies in these patients revealed significant hypometabolism in the cerebellar hemispheres, cerebellar vermis, and brainstem in comparison with the normal control subjects. A significant relationship was found between the degree of atrophy and the level of 1CMRglc in the cerebellum and brainstem. Nevertheless, several patients had minimal atrophy and substantially reduced 1CMRglc, suggesting that atrophy does not fully account for the finding of hypometabolism. 1CMRglc was within normal limits for the thalamus and cerebral cortex. The data suggest that PET/1CMRglc may be useful as a diagnostic test in patients with the adult onset of cerebellar ataxia.

Adult↗
PubMed1988

Motor dysfunction in olivopontocerebellar atrophy is related to cerebral metabolic rate studied with positron emission tomography.

We compared the severity of motor dysfunction with local cerebral metabolic rates for glucose (lCMRGlc) and the degree of tissue atrophy in 30 patients with olivopontocerebellar atrophy (OPCA). We devised a scale to quantitate the degree of ataxia in the neurological examinations. lCMRGlc was measured with 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET). Tissue atrophy was assessed by visual rating of computed tomographic scans. PET studies revealed marked hypometabolism in the cerebellar vermis, cerebellar hemispheres, and brainstem of OPCA patients compared with 30 control subjects. A significant correlation was found between severity of motor impairment and lCMRGlc within the cerebellar vermis, both cerebellar hemispheres, and the brainstem. A significant but weaker relationship was noted between the degree of tissue atrophy in these regions and clinical severity. Partial correlation analysis revealed that motor dysfunction in OPCA correlated more strongly with lCMRGlc than with the amount of tissue atrophy. These results suggest that the clinical manifestations of OPCA are more closely related to the metabolic state of the tissue than to the structural changes in the cerebellum.

Adult↗
PubMed1988

Intra-arterial 5-bromo-2-deoxyuridine (BUdR) radiosensitization with external beam radiation in rhesus monkeys: toxicity study.

A primate toxicity study was performed to test the hypothesis that BUdR does not increase the likelihood of unilateral or bilateral central nervous system damage secondary to radiation therapy. BUdR, a halogenated pyrimidine analog is incorporated into DNA of dividing cells and sensitizes them to radiation. It is best given unilaterally, intra-arterially by continuous infusion because of its regional advantage (Rd) estimated to be between 11 and 16. Six rhesus monkeys were implanted with a Model 400 Infusaid pump perfusing the right internal carotid artery. Three of the six monkeys received intra-arterial (IA) BUdR infusion plus whole brain external beam radiation (6,000 R over 6 weeks) and three received radiation alone. The two BUdR treated animals completing radiation developed symmetric bilateral high signal aberrations on MRI in the frontal, parietal, and occipital centrum semiovale and corona radiata at nine months. At autopsy, confluent microinfarcts were found to correspond topographically to the MRI abnormalities. In the radiation alone group, two animals had normal MRI and autopsy while the third animal had bilateral MRI high signal aberrations develop sequentially with corresponding microinfarcts at autopsy. These changes were greater in severity than those seen in the BUdR treated animals. We support previous evidence that there is differential intraspecies sensitivity to radiation. We find that BUdR produces no unilateral potentiation of radiation toxicity.

Animals↗