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Biomedical subjects

R G Peyster

Publications and source records attributed to R G Peyster.

At least 19 recordsLinked to original sources
PubMed2000

The potential for vigabatrin-induced intramyelinic edema in humans.

PURPOSE: Vigabatrin (Sabril, Hoechst Marion Roussel) is an antiepilepsy drug (AED) presently marketed in 64 countries for the treatment of partial and secondarily generalized seizures. Vigabatrin (VGB) is marketed in a subset of these countries for the treatment of infantile spasms. Clinical experience in humans has shown that VGB provides effective seizure control with a wide margin of safety. However, animal toxicity studies raised concern when prolonged administration of VGB was shown to induce intramyelinic edema (IME) in some laboratory animal species. METHODS: Animal and human data were reviewed with respect to the potential for VGB-induced IME. Surveillance of patients receiving VGB in clinical trials or by prescription has been conducted for >15 years to identify patients developing clinical abnormalities that might be IME related. RESULTS: The histologic lesions of VGB-induced IME in animals are reliably reproduced and correlate with changes in multimodality evoked potentials (EPs) and magnetic resonance imaging (MRI). Numerous studies of the effects of VGB on EP and MRI in epilepsy patients have demonstrated no clear-cut IME-related changes in these modalities. Additionally, autopsy and surgical brain samples from VGB-treated patients have been scrutinized for potential IME histopathology. In an estimated 350,000 patient-years of VGB exposure (approximately 175,000 patients exposed for 2 years at an average dose of 2 g/day), no definite case of VGB-induced IME has been identified. CONCLUSIONS: Comprehensive review of a variety of sources of data failed to identify any definite case of IME in humans treated with VGB.

Animals↗
PubMed1995

Use of ex vivo magnetic resonance imaging to detect onset of vigabatrin-induced intramyelinic edema in canine brain.

Vigabatrin (VGB) causes intramyelinic edema (microvacuolation) in brain of dogs and rodent, which has encouraged development of noninvasive methods to monitor for this effect during clinical trials. We report the qualitative ex vivo magnetic resonance imaging (MRI) changes observed in a neuropathology study in dogs to detect time of onset and regression of VGB-induced intramyelinic edema. Beagles were randomly assigned to 18 groups of 6 dogs per group and administered vigabatrin orally (p.o.) at a dose of 300 mg/kg/day (2 males, 2 females) or placebo (1 male, 1 female). Animals were killed and examined at weekly intervals during the 12 weeks of treatment and at 1, 2, 4, 8, 12, and 16 weeks after discontinuation of drug treatment. Myelin microvacuolation in thalamus, hypothalamus, and fornix were noted histologically after 4-5 weeks of treatment. Increases in MRI T2 intensity were observed in hypothalamus after 4 weeks and in thalamus and columns of the fornix after 7 weeks. Both MRI T2 intensity and microvacuolation continued to increase during 12-week VGB treatment. When VGB treatment was discontinued after 12 weeks, both MRI T2 intensity and microvacuolation began to decrease. Sixteen weeks after VGB discontinuation, histopathology had returned to normal and MRI examination demonstrated a marked trend toward reversal of the increased T2 signal intensity. MRI thus has potential as a noninvasive surveillance technique in certain experimental and clinical conditions associated with intramyelinic edema.

Animals↗
PubMed1991

Abnormal corpus callosum: a sensitive and specific indicator of multiple sclerosis.

The authors investigated whether identification of corpus callosal (CC) involvement might increase the specificity of magnetic resonance (MR) imaging in differentiating multiple sclerosis (MS) from other periventricular white matter diseases (PWDs). They prospectively evaluated 42 patients with MS and 127 control patients with other PWDs. Ninety-three percent of the MS patients demonstrated confluent and/or focal lesions involving the callosal-septal interface (CSI). These lesions characteristically involved the inferior aspect of the callosum and radiated from the ventricular surface into the overlying callosum. CSI lesions were optimally demonstrated on sagittal long repetition time (TR)/short echo time (TE) images and frequently (45% of cases) went undetected on axial images. Only 2.4% of the control patients had lesions of the CC. The authors conclude that midsagittal long TR/short TE images are highly sensitive and specific for MS and that callosal involvement in MS is more common than previously reported.

Adult↗
PubMed1988

Intraocular tumors: evaluation with MR imaging.

Sixty-seven ocular tumors were studied with magnetic resonance (MR) imaging and computed tomography (CT). These tumors included primary uveal melanoma (n = 55), circumscribed choroidal hemangioma (n = 3), diffuse choroidal hemangioma (n = 1), retinal capillary hemangioma (n = 1), medulloepithelioma (n = 1), choroidal nevus (n = 1), retinoblastoma (n = 1), and choroidal metastases (n = 4). MR imaging demonstrated all these lesions, while CT demonstrated 88%. Associated retinal detachment was more easily distinguished from the neoplasms with MR imaging. Extrascleral extension of melanoma and hemorrhagic cystic necrosis within the melanoma were clearly demonstrated with MR imaging, but not with CT. Ninety-three percent of melanomas were markedly hyperintense, compared with the intensity of the vitreous body, on T1-weighted images and hypointense on T2-weighted images. All metastatic lesions were isointense on T1-weighted images and hypointense on T2-weighted images. The circumscribed choroidal hemangiomas were hyperintense on T1-weighted images and isointense on T2-weighted images. MR imaging is superior to CT in detection of intraocular tumors and may be more specific in diagnosis.

Choroid Neoplasms↗
PubMed1987

Orbital metastasis from a carcinoid tumor. Computed tomography, magnetic resonance imaging, and electron microscopic findings.

An otherwise asymptomatic 63-year-old woman with a history of a carcinoid tumor of the ileum and a cutaneous melanoma of the shoulder developed unilateral proptosis. Orbital ultrasonography, computed tomography, and magnetic resonance imaging revealed a large, well-circumscribed orbital mass involving the superior rectus muscle. The surgically excised tumor was studied by light microscopy, histochemistry, and transmission electron microscopy. These studies confirmed the diagnosis of carcinoid tumor. The clinical and pathologic features of this rare type of orbital metastasis are discussed.

Carcinoid Tumor↗
PubMed1987

Computed tomography of posterior uveal melanomas.

Computed tomographic (CT) scans were obtained from 48 patients with posterior uveal melanoma. The CT measurements of maximal and minimal basal diameters and thickness of each tumor were compared with the assessments of these tumor dimensions obtained by ophthalmoscopic estimation (basal diameters only) and standardized A-scan ultrasonography (thickness only) and with the gross pathologic measurements of these tumors. The correlation between measurements of tumor thickness by CT scanning, standardized A-scan ultrasonography, and gross pathologic analysis was substantially better than that between the CT, ophthalmoscopic, and gross pathologic measurements of tumor basal diameters. Computed tomographic scanning appears to be a good method for determining the in vivo size of choroidal and ciliary body melanomas.

Adult↗
PubMed1987

Isolation of the right subclavian artery with subclavian steal in a child with Klippel-Feil anomaly: an example of the subclavian artery supply disruption sequence.

We studied a patient with Klippel-Feil anomaly and subclavian steal due to isolation of the right subclavian artery. Other anomalies included hypoplasia of the right clavicle and right vertebral artery, low bifurcation of the left common carotid artery and left choanal atresia. The patient was mentally retarded with corticospinal, cerebellar, and brain stem signs. The entire brain and cervical spinal cord were small; there was no central nervous system malformation, hydrocephalus, or bony impingement on neural structures. Embryologic vascular disorders have been found to be responsible for various congenital systemic and neurologic anomalies such as intestinal atresia and hydranencephaly. Subclavian artery supply disruption sequence has been hypothesized to result in Klippel-Feil, Poland, and Möbius anomalies. In this case the vertebral and facial abnormalities may well be related to anomalous subclavian and carotid supply. An embryonic vascular "steal" has been thought to cause the sirenomelia anomaly. We postulate that the subclavian steal, during the embryonic period, may have been responsible for the small size of this patient's cerebral hemispheres, brain stem, cerebellum, and cervical spinal cord.

Adolescent↗
PubMed1986

CT of the normal pituitary gland.

Retrospective evaluation of the pituitary gland on coronal post-contrast CT scan in 251 patients demonstrated that the pituitary gland is somewhat larger in females than in males. In males, glands measuring greater than 7.7 mm should be considered abnormal; in females, a statistically significant decline of gland height occurs with increasing age, the upper limit of normal for female gland height decreasing from 9.2 cm for a 20-year-old to 6.0 cm for a 90-year-old. Focal low densities greater than 3 mm are rare in males and probably should be considered abnormal.

Adolescent↗
PubMed1986

Exophthalmos caused by excessive fat: CT volumetric analysis and differential diagnosis.

CT has proven to be excellent in identifying orbital pathology responsible for proptosis. Occasionally, no discrete mass or extraocular muscle enlargement to explain the exophthalmos is found, only an appearance suggestive of an abnormal increase in orbital fat volume. Fifteen patients were studied with proptosis apparently resulting from increased orbital fat. Clinical follow-up revealed that four of them had Graves orbitopathy, unilateral in one; two had Cushing disease/syndrome; and nine were obese without endocrinopathy. The orbital volume and percentage orbital fat volume were measured by CT software analysis in these patients and in a control group of 16 patients without proptosis. Measurements of proptosis and thickness of the scalp fat pad at the inion level were also performed. Significantly greater values for orbital fat volume, percentage fat volume, and proptosis were found in the proptosis group compared with the control group. There was excellent correlation between proptosis and percentage fat volume, supporting the contention that increased orbital fat is responsible for the proptosis. The thickness of the scalp fat pad at the inion level was significantly greater in obese and Cushing patients than in control subjects, but the thickness was not significantly greater in Graves patients than in controls. Proptosis and inion fat were well correlated (r = 0.74) in the control and obese patients, which suggests a relation between general body fat and orbital fat volume.

Adipose Tissue↗
PubMed1985

Computed tomography of lumbosacral conjoined nerve root anomalies. Potential cause of false-positive reading for herniated nucleus pulposus.

Conjoined origin anomalies of lumbosacral nerve roots, if incorrectly interpreted, could be misdiagnosed as disc herniations on computed tomography (CT). Several characteristic CT features of these anomalies are presented that should distinguish them from herniated discs. A conjoined root anomaly was found in approximately 2% of the 8,000 lumbosacral CT scans.

Adult↗
PubMed1985

Massive juvenile ossifying fibroma of maxillary sinus with orbital involvement.

A 14-year-old black girl had painless, progressive proptosis and upward displacement of the left eye for approximately six months. Computed tomography showed a massive tumour involving the maxillary sinus with extension into the sphenoid sinus, ethmoid sinus, and orbit. The mass was excised surgically and proved histopathologically to be a juvenile ossifying fibroma. The clinical and histopathological features of this uncommon orbital tumour are discussed and its place in the spectrum of fibro-osseous tumours of the orbital region is considered.

Adolescent↗
PubMed1985

Choroidal melanoma: comparison of CT, fundoscopy, and US.

Computed tomography (CT) was compared with fundoscopy and ultrasound (US) in 62 patients with primary choroidal melanoma. All lesions were detected with CT and fundoscopy and all but one with US. Of five cases of extrascleral extension, four were identified with CT and fundoscopy and two with US. CT best depicted the extent of retrobulbar tumor. Tumor thickness was best evaluated with CT, with good correlation between CT and US. Tumor enhancement was noted in all 51 patients who had both noncontrast and contrast CT. Because of its higher density, tumor could be distinguished from retinal detachment on CT scans in most cases.

Adult↗
PubMed1984

Computed tomography and aging: results in a normal elderly population.

CT studies on 212 normal elderly individuals were analyzed for ventricular enlargement and cortical atrophy. Results show a positive correlation between ventricular enlargement and age with greater degrees of ventricular enlargement and cortical atrophy in men as compared to women. While some degree of atrophy is common in normal elderly individuals it is mild, minimal, or noexistent in 86%.

Age Factors↗
PubMed1984

An unusual late complication of orbital floor fracture repair.

Three patients developed unilateral proptosis 13, 16, and 20 years after repair of blow-out fracture with orbital floor Teflon implants. In one patient trauma preceded the onset of proptosis. In all three cases, the cause of the proptosis was probably hemorrhage of the capillaries in a fibrous capsule that surrounded the implant and that was evident on orbital CT scan. In two cases on CT scan, a retrobulbar cyst-like structure surrounded the implant, which was confirmed on ultrasonography. In the third case, an irregular soft-tissue density surrounded the implant. Histologically, a fibrous capsule surrounded the implant in all three cases, and in one case, the inner lining of the fibrous capsule was respiratory epithelium. The contents of the cyst-like structure, in two cases, were fresh blood and disintegrating red blood cells and blood products. In the third case, no cyst-like structure or "cyst" contents were identified; however, fibrous tissue containing hemosiderin-laden macrophages suggested the presence of an organized hemorrhage. The patients' proptosis resolved almost completely after surgical removal of the implant, decompression of the "cyst," and partial removal of the "cyst" wall in two cases. The same result followed removal of the implant and part of the fibrous capsule in the third case.

Adult↗