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At least 847 records · Page 47Linked to original sources
PubMed2001

Isolated central nervous system relapse of non-seminomatous germ cell tumour of the testis. A case report and review of the literature.

Isolated central nervous system (CNS) relapse of non-seminomatous germ cell tumour (NSGCT) of the testis has been reported in only 12 patients previously. We report a patient with an isolated CNS relapse of NSGCT, following a prior systemic relapse. From a review of previous cases, isolated CNS relapse appears to be more common in patients with embryonal cell histology (alone or mixed with other elements) and occurred after a median of 8.5 months following initial presentation. Long-term survival appears possible using multi-modal treatment with whole-brain radiotherapy, surgery and/or chemotherapy. However, the optimal treatment of isolated CNS relapse remains undefined.

Adult↗
PubMed2002

Craniopharyngioma involving the infrasellar region: a case report and review of the literature.

Craniopharyngiomas are most commonly located in the intradural suprasellar region. However, ectopic craniopharyngiomas can originate in the infrasellar region. The authors present the case of an 8-year-old boy diagnosed with a large cystic craniopharyngioma involving the nasal cavities and maxillary, ethmoid and sphenoid sinuses, in addition to the sella turcica. The primary symptoms of this patient were nasal obstruction, unilateral decreased visual acuity and exophthalmos. He subsequently underwent combined radical resection of the tumor by means of an endonasal transsphenoidal approach followed by radiation therapy. During the surgery, the dura mater of the sellar floor was found to be intact. The neuroradiological and surgical findings suggested that this tumor originated in the extradural infrasellar region and invaded the sella turcica.

Child↗
PubMedDate not supplied

Ischemic optic neuropathy associated with subarachnoid hemorrhage after rupture of anterior communicating artery aneurysm.

Two clinical cases in which ischemic optic neuropathy (ION) occurred after subarachnoid hemorrhage (SAH) are reported. Hemorrhage in the proximity of the optic chiasm was confirmed in 2 cases following rupture of an anterior communicating artery aneurysm. Optic disk atrophy with excavation and permanent visual field defect (altitudinal superior hemianopia) occurred in both cases. ION seems to occur in association with the optic nerve coincidental with the hyperdensity side of SAH on head CT scan. The incidence of ION appears to be attributable to an insufficient blood supply to arteries distributed in the posterior part of the optic nerve as a result of SAH.

Aged↗
PubMedDate not supplied

Ophthalmic manifestations of multiple myeloma.

PURPOSE: To describe ophthalmic manifestations in a series of patients with multiple myeloma (MM) and review the literature. DESIGN: Retrospective case series. METHODS: Review of all cases with ophthalmic manifestations of MM seen at the Department of Ophthalmology, Royal Adelaide Hospital, between 1987 and 2002. RESULTS: Of all patients with MM who were managed at the Royal Adelaide Hospital in the study period, only 8 were referred to the Ophthalmology Department with ophthalmic manifestations. Five males and 3 females with a mean age of 61.25 years (range 42-78) who exhibited ophthalmic manifestations were studied. Six patients (75%) had known MM at the time of their ophthalmic evaluation. Four patients (50%) had neuro-ophthalmic symptoms resulting in diplopia or visual disturbances. Three patients (37.5%) presented with orbital involvement and 1 (12.5%) with hyperviscosity retinopathy. Five patients (62.5%) died within 2 months of their ophthalmic presentation. CONCLUSION: Ophthalmic manifestations of MM are uncommon and diverse. They may appear at the initial presentation of the disease or occur late in the disease process. Awareness of the possible manifestations may lead to an earlier diagnosis and have a positive influence on the disease course.

Adult↗
PubMed1992

Sphenoid sinus mucocele with recurrent visual disturbance.

We present a case of sphenoid sinus mucocele with recurrent visual disturbance on the same side. A 22-year-old female showed two episodes of visual disturbance in the left eye for 3 months, and acute retrobulbar optic neuritis was diagnosed. With corticosteroid, visual disturbance improved in 1 week. MRI and CT scans showed mucocele in the left sphenoid sinus, and left optic nerve swelling with high intensity was observed in T2-weighted MRI. No destruction of the optic canal was found. The contiguous inflammation in the optic nerve rather than compression was considered as pathogenesis.

Adult↗
PubMedDate not supplied

Migrainous cerebral infarction: a tomographic study of cerebral blood flow and oxygen extraction fraction with the oxygen-15 inhalation technique.

A patient with migraine who had a permanent visual field defect was studied by angiography and CT scan. He also had a tomographic study of cerebral blood flow (CBF) and oxygen extraction fraction (EO2) using the non-invasive continuous oxygen-15 (15O) inhalation technique. Angiography was normal. CT scan revealed an area of decreased density with contrast enhancement suggestive of a recent infarct in the left occipital lobe. The 15O inhalation technique showed a decrease in CBF and EO2, typical of recent infarcts, in the corresponding area, an increase in CBF with normal EO2 in the left temporal lobe, and a decrease in CBF with increased EO2 in the right occipital cortex. These findings illustrate the unusual nature and extent of the ischemic process underlying migrainous cerebral infarction.

Cerebral Angiography↗
PubMedDate not supplied

The paramedian diencephalic syndrome: a dynamic phenomenon.

The paramedian diencephalic syndrome is characterized by a clinical triad: hypersomnolent apathy, amnesic syndrome, and impaired vertical gaze. We studied 4 cases with computed tomography evidence of bilateral diencephalic infarctions. Each case began abruptly with hypersomnolent apathy followed by fluctuations from appropriate affect, full orientation, and alertness to labile mood, confabulation, and apathy. Speech varied from hypophonia to normal; handwriting varied from legible script to gross scrawl. Psychological testing revealed poor learning and recall, with low performance scores. In 3 patients the predominant abnormality was in downward gaze.

Affective Symptoms↗
PubMed1989

Clinical and radiologic features of lacunar versus nonlacunar minor stroke.

We determined the angiographic presence of extracerebral and intracerebral arterial disease in 122 patients with minor stroke within the carotid territory; we excluded patients with a recognized cardiac source of emboli. Based on clinical features and computed tomographic findings, patients were classified as having lacunar infarcts (n = 61), nonlacunar infarcts (n = 53), and infarcts of indeterminate type (n = 8). Severe carotid bifurcation disease (greater than or equal to 50% stenosis or occlusion) was significantly more common in nonlacunar than in lacunar infarcts, on both the ipsilateral (p less than 0.001) and the contralateral (p less than 0.01) sides; 79% of the patients with nonlacunar infarcts had severe carotid bifurcation and/or middle cerebral artery disease on the ipsilateral side compared with 3.3% of the patients with lacunar infarcts. Our data underscore the need for classification of patients by the underlying mechanisms in future studies of treatment of ischemic stroke.

Cerebral Angiography↗
PubMed1999

Blindsight in subjects with homonymous visual field defects.

Brain damage in the visual system can lead to apparently blind visual areas. However, more elaborate testing indicates that some visual ability may still exist for specific stimuli in the otherwise blind regions. This phenomenon is called 'blindsight' if subjects report no conscious awareness of visual stimuli but when forced to guess, nevertheless perform better than chance. It has mainly been suggested that secondary visual pathways are responsible for this phenomenon. However, no published study has clearly shown the neural mechanism responsible for blindsight. Furthermore, experimental artifacts may have been responsible for the appearance of the phenomenon in some subjects. In the present study, the visual fields of nine subjects were mapped and residual visual performance was examined in many areas using three different experimental procedures. Artifacts such as stray light or eye movements were well controlled. In addition, confidence ratings were required after each trial in the forced-choice tests. The results show that only one subject with a lesion in the optic radiation had blindsight in two discrete areas of the affected visual field. Spared optic radiation fibers of the main (primary) geniculo-striate visual pathway were most likely to account for this finding.

Adult↗
PubMed2003

Developmental constraints aid the acquisition of binocular disparity sensitivities.

This article considers the hypothesis that systems learning aspects of visual perception may benefit from the use of suitably designed developmental progressions during training. We report the results of simulations in which four models were trained to detect binocular disparities in pairs of visual images. Three of the models were developmental models in the sense that the nature of their visual input changed during the course of training. These models received a relatively impoverished visual input early in training, and the quality of this input improved as training progressed. One model used a coarse-scale-to-multiscale developmental progression, another used a fine-scale-to-multiscale progression, and the third used a random progression. The final model was nondevelopmental in the sense that the nature of its input remained the same throughout the training period. The simulation results show that the two developmental models whose progressions were organized by spatial frequency content consistently outperformed the nondevelopmental and random developmental models. We speculate that the superior performance of these two models is due to two important features of their developmental progressions: (1) these models were exposed to visual inputs at a single scale early in training, and (2) the spatial scale of their inputs progressed in an orderly fashion from one scale to a neighboring scale during training. Simulation results consistent with these speculations are presented. We conclude that suitably designed developmental sequences can be useful to systems learning to detect binocular disparities. The idea that visual development can aid visual learning is a viable hypothesis in need of study.

Learning↗
PubMed1999

Adaptive calibration of imaging array detectors.

We present two methods for nonuniformity correlation of imaging array detectors based on neural networks; both exploit image properties to supply lack of calibrations and maximize the entropy of the output. The first method uses a self-organizing net that produces a linear correction of the raw data with coefficients that adapt continuously. The second method employs a kind of contrast equalization curve to match pixel distributions. Our work originates from silicon detectors, but the treatment is general enough to be applicable to many kinds of array detectors like those used in infrared imaging or in high-energy physics.

Calibration↗
PubMed1999

Learning to design synergetic computers with an extended symmetric diffusion network.

This article proposes an extended symmetric diffusion network that is applied to the design of synergetic computers. The state of a synergetic computer is translated to that of order parameters whose dynamics is described by a stochastic differential equation. The order parameter converges to the Boltzmann distribution, under some condition on the drift term, derived by the Fokker-Planck equation. The network can learn the dynamics of the order parameters from a nonlinear potential. This property is necessary to design the coefficient values of the synergetic computer. We propose a searching function for the image processing executed by the synergetic computer. It is shown that the image processing with the searching function is superior to the usual image-associative function of synergetic computation. The proposed network can be related, as a special case, to the discrete-state Boltzmann machine by some transformation. Finally, the extended symmetric diffusion network is applied to the estimation problem of an entire density function, as well as the proposed searching function for the image processing.

Artificial Intelligence↗
PubMed2000

Learning in brains and machines.

The problem of learning is arguably at the very core of the problem of intelligence, both biological and artificial. In this paper we sketch some of our work over the last ten years in the area of supervised learning, focusing on three interlinked directions of research: theory, engineering applications (that is, making intelligent software) and neuroscience (that is, understanding the brain's mechanisms of learning).

Brain↗
PubMed1994

A network model for generating differential symmetry axes of shapes via receptive fields.

Some symmetries (e.g. bilateral, rotational, translational) only describe quite specialized shapes, but differential symmetry axes (e.g. Blum, J. Theoret. Biol. 38, 205-287, 1973; Brady and Asada, Int. J. Robotics Res. 3, 36-61, 1984) describe more general shapes. Such axes are of interest in part because they form the 'backbone' of generalized cylinder and other shape representations used in shape recognition (e.g. Marr, Vision, W. H. Freeman and Co., NY, 1982; Biederman, Psychol. Rev. 94, 115-147, 1987). However, despite the popularity of these representations as psychological models, algorithms from machine vision for computing them have strong limitations as psychological models. This paper presents two versions of a network model, one of which is more plausible as a psychological model because it derives symmetry axes from the activations of idealized visual receptive fields.

Form Perception↗
PubMed1996

Preferential metabolic involvement of visual cortical areas in a subtype of Alzheimer's disease: clinical implications.

OBJECTIVE: A subgroup of patients with Alzheimer's disease present with visual disturbances at onset. This study investigated whether specific cortical networks associated with visual processes are preferentially affected in this subgroup and determined the clinical implications of such abnormalities. METHOD: Regional cerebral glucose metabolic rates were assessed with positron emission tomography and [18F]2-fluoro-2-deoxy-D-glucose, and general intellectual functions, memory, and visual skills were measured with cognitive tests in patients with probable Alzheimer's disease-10 with and 22 without prominent visual symptoms-and in 25 healthy comparison subjects. RESULTS: Both patient groups showed reduced glucose metabolism in parietal regions and in middle and superior temporal regions in comparison with the healthy subjects. The Alzheimer's disease patients without visual symptoms also showed reductions in inferior temporal, frontal, and limbic structures, as is typical of Alzheimer's disease. In contrast, the patients with visual symptoms had larger metabolic deficits than the patients without visual symptoms in the parietal and occipital cortices (including the primary visual cortex), with a relative sparing of inferior temporal, frontal, and limbic regions. Consistently, the patients with visual symptoms had significantly greater visuospatial deficits and less severe memory impairments than the patients without visual symptoms. CONCLUSIONS: Alzheimer's disease patients with visuospatial deficits who are studied while alive have a distinctive regional distribution of cerebral metabolic impairment that is related to specific cognitive deficits and that distinguishes them from patients with typical Alzheimer's disease. These findings imply that regional variations in brain dysfunction can occur in Alzheimer's disease, with differential involvement of cortical systems resulting in distinctive clinical subgroups.

Aged↗
PubMed1997

Simultaneous multiple brain hemorrhage associated with migraine--a case report.

A fifty-five-year-old woman with a history of migraine suddenly developed an occipital headache and visual disturbance after a typical migrainous attack. On admission, she had a left homonymous hemianopsia, and computed tomography of the brain demonstrated intracranial hematomas in the occipital subcortices bilaterally. Cerebral arteriography revealed diffuse vasospasm of the intracranial arteries attributed to the migraine. The cystatin C concentration in the cerebrospinal fluid was low, which suggested the existence of cerebral amyloid angiopathy. According to the clinical course and angiographic findings, it is suggested that the vasospasm associated with migraine played an important role in developing multiple brain hemorrhage in this patient.

Cerebral Amyloid Angiopathy↗