[17-year-old woman with headache and progressive diminishing of visual acuity].
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Adolescent↗
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Results for “Computer vision”
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Optic ataxia following unilateral stroke.
Five patients with optic ataxia together with tactile apraxia are described. They also demonstrated difficulty in finger movements under visual guidance. The CT scan showed lesions in the posterior parietal region in three and in two they were located anteriorly. It is well recognised that lesions in the posterior parietal area may cause disruption of visual guided movements. On the basis of the two cases it is postulated that the same phenomenon could occur with lesions located more anteriorly. The assumption is that optic ataxia may occur either following damage to the parieto-occipital region or to disruption of its occipitofrontal connections.
Aged↗
Simultanagnosia as the initial sign of degenerative dementia.
In a study of 10 patients with degenerative brain disease that manifested as simultanagnosia, our aims were (1) to elucidate their clinical, neuropsychologic, and radiologic findings to determine whether these patients might represent a group distinguishable from those with typical Alzheimer's disease and (2) to help clinicians recognize this entity. All patients were initially examined by ophthalmologists because of visual difficulties, and the simultanagnosia remained undiagnosed until nonophthalmologic complaints developed. Optic ataxia developed in six patients, and all patients had mildly impaired eye movements. All 10 patients could identify colors appropriately. Nine patients had language deficits (anomia, decreased auditory comprehension, alexia, and agraphia) but were fluent and had relative preservation of sentence repetition, and four performed in the normal range on a test of associative fluency. Two patients scored in the normal range on memory tests, all had preserved insight, and nine had no family history of degenerative dementia. The mean age at onset of the disorder was 60 years (range, 50 to 69). Neuroimaging disclosed prominent bilateral occipitoparietal atrophy in nine patients and generalized atrophy in one. With this unusual but consistent clinical, neuropsychologic, and anatomic profile, these patients are clinically distinguishable from those with typical Alzheimer's disease, but until a specific cause has been found, we cannot be certain that they constitute a specific biologic entity. Clinicians should consider this diagnosis in relatively young patients who have slowly progressive nonocular visual complaints.
Aged↗
PET imaging of maze processing.
Covered maze traversal models nonverbal planning, involving sequential execution of moves using learned spatial maps. To determine the neural substrate involved in maze processing, eleven adults underwent [H(2)15O]-PET while performing motor control, following the computer; visual control, choosing the wall with more dead-ends; uncovered maze, traversing fully visible mazes; covered maze, traversing mazes only locally visible. Maze processing lateralizes to the right hemisphere: uncovered maze versus controls revealed area 23 and 29 activation; covered maze versus controls activated areas 8, 10 and 19. The extrastriate region may store path information, evoked by prefrontal areas for spatial planning and navigation.
Adolescent↗
Physiologic functional imaging in "functional" visual loss.
Neuroimaging with nuclear medicine techniques permits assessment of brain function by measurement of metabolism or blood flow. Such studies complement the anatomic information derived from computed tomography (CT) or magnetic resonance imaging (MRI). We describe two patients with occipital lesions who were initially diagnosed with functional visual loss. Neither CT scan nor MRI adequately demonstrated the source of visual dysfunction; however, single proton emission tomography (SPECT) scanning in a patient with carbon monoxide poisoning and positron emission tomography (PET) scanning in a patient with post-hypoxic delayed encephalopathy were helpful in confirming the organic substrate of their visual impairment. Functional imaging techniques such as SPECT and PET should be considered in patients with suspected cortical visual loss and normal CT or MR scans.
Adult↗
How to handle the pressure or too much of a good thing.
A 28-year-old non-obese woman with pseudotumor cerebri and minimal visual loss who underwent two optic nerve sheath decompression procedures. Different diagnosis and treatment options are discussed.
Adult↗
The clinical spectrum of schwannomas presenting with visual dysfunction: a clinicopathologic study of three cases.
Schwannomas (neurilemomas) are benign tumors that arise from Schwann cells in the peripheral nervous system. The most commonly involved nerves that cause neuro-ophthalmic manifestations are cranial nerves V and VIII. In this series of three women, schwannomas presented as intraconal masses that mimicked a cavernous hemangioma, a superior orbital mass transgressing the superior orbital fissure, and an expansive frontal lobe mass with clinical symptoms and signs of increased intracranial pressure. Although all three complained of visual blurring, none of our patients presented with Vth or VIIIth cranial nerve dysfunction. Histopathologic studies demonstrated well-circumscribed, encapsulated spindle-cell lesions with classic Antoni A and B patterns. Histopathologic examination is essential to confirm the diagnosis of a schwannoma that may be otherwise clinically confusing. Direct optic nerve compression, globe indentation with induced hyperopia, or increased intracranial pressure with optic nerve compromise may be responsible for visual symptoms. A multidisciplinary approach is often required because of the size and location of schwannomas.
Adult↗
Neural network model of short-term horizontal disparity vergence dynamics.
We present a neural network model of short-term dynamics of the human horizontal vergence system (HVS) and compare its predictions qualitatively and quantitatively with a large variety of horizontal disparity vergence data. The model consists of seven functional stages, namely: (1) computation of instantaneous disparity; (2) generation of a disparity map; (3) conversion of the disparity into a velocity signal; (4) push-pull integration of velocity to generate a position signal; (5) conversion of the position signal to motoneuron/plant activity for each eye; (6) gating of velocity overdrive signal to motoneuron/plant system; and finally (7) discharge path for position cells. Closed-loop (normal binocular viewing) symmetric step and staircase disparity vergence data were collected from three subjects and model parameters were determined to quantitatively match each subject's data. The simulated closed-loop as well as open-loop (disparity clamped viewing) symmetric step, sinusoidal, pulse, staircase, square and ramp wave responses closely resemble experimental results either recorded in our laboratory or reported in the literature. Where possible, the firing pattern of the neurons in the model have been compared to actual cellular recordings reported in the literature. The model provides insights into neural correlates underlying the dynamics of vergence eye movements. It also makes novel predictions about the human vergence system.
Convergence, Ocular↗
Neural dynamics of motion processing and speed discrimination.
A neural network model of visual motion perception and speed discrimination is presented. The model shows how a distributed population code of speed tuning, that realizes a size-speed correlation, can be derived from the simplest mechanisms whereby activations of multiple spatially short-range filters of different size are transformed into speed-turned cell responses. These mechanisms use transient cell responses to moving stimuli, output thresholds that covary with filter size, and competition. These mechanisms are proposed to occur in the V1-->MT cortical processing stream. The model reproduces empirically derived speed discrimination curves and simulates data showing how visual speed perception and discrimination can be affected by stimulus contrast, duration, dot density and spatial frequency. Model motion mechanisms are analogous to mechanisms that have been used to model 3-D form and figure-ground perception. The model forms the front end of a larger motion processing system that has been used to simulate how global motion capture occurs, and how spatial attention is drawn to moving forms. It provides a computational foundation for an emerging neural theory of 3-D form and motion perception.
Form Perception↗
Human cortical areas underlying the perception of optic flow: brain imaging studies.
In summary, we have reviewed electrophysiological and brain imaging studies of motion and optic-flow processing. Single-unit studies indicate that MST (V5a) is a site of optic-flow extraction and that this information can be used to guide pursuit eye movements and to estimate heading. The EEG and MEG studies point to a localized electrical dipole in occipitotemporal cortex evoked by visual motion. We have also discussed the evidence from functional imaging studies for response specificity of the rCBF and BOLD effects in posterior cortex to visual motion and optic flow. Focal attention modulates the amplitude of the BOLD signal evoked by visual motion stimulation. Retinotopic mapping techniques have been used to locate region borders within the visual cortex. Our results indicate that striate (V1) and extrastriate areas (V2, V3/V3a) respond robustly to optic flow. However, with exception of a more pronounced response in V3/V3a to random walk, we found little evidence for response selectivity with respect to flow type and disparity in these early visual areas. In a similar fashion, the human V5/V5a complex responds well to optic flow, but these responses do not vary significantly with the type of flow field and do not seem to depend on disparity. In contrast, the kinetic occipital area (KO/V3b) responds well to optic-flow information, and it is the only area that produces more pronounced activation to the disparity in the flow fields. These initial results are promising because they suggest that the fMRI method can be sensitive to changes in stimulus parameters that define flow fields. More work will be required to explore the extent to which these responses reflect the neuronal processing of optic flow. Eye position tracking is now possible during fMRI experiments. We have demonstrated that the eye movements affect the BOLD responses in motion-sensitive areas (Kimming et al., 1999). Further experiments in our laboratory are aimed at understanding the effects of eye movements on the neuronal coding of complex optic-flow fields (Schira et al., 1999).
Animals↗
Transient enlargement of an intracranial aneurysm during pregnancy: case report.
BACKGROUND: The association of intracranial aneurysm and pregnancy is uncommon. Hemodynamic stress plays an important role in the growth of aneurysms. METHODS: The authors report the case of an enlarging cavernous carotid aneurysm in a pregnant 15-year-old young woman. RESULTS: The aneurysm was initially diagnosed prior to the patient's pregnancy by both cross-sectional imaging and cerebral angiography. Further imaging evaluation was required during pregnancy, which demonstrated significant enlargement of the aneurysm. Following delivery, the lesion decreased in size. CONCLUSIONS: We review potential factors associated with pregnancy that may increase hemodynamic stress and influence aneurysm growth. Additionally, the management of pregnancy-related intracranial aneurysms is discussed.
Adolescent↗
Computerised tomographic abnormalities in children with cerebral visual disturbance.
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Brain↗
Graves' disease presenting with bilateral acute painful proptosis, ptosis, ophthalmoplegia, and visual loss.
Two middle-aged women presented with bilateral acute painful proptosis, ptosis, ophthalmoplegia, and visual loss. In both an initial diagnosis of orbital cellulitis was made, but they did not respond to systemic antibiotics. Orbital computerised tomographic (CT) scans were thus done within 36 h of admission and they showed grossly enlarged extraocular muscles in each case suggestive of dysthyroid eye disease. Clinical examination was otherwise normal. When high doses of systemic steroids were substituted for the antibiotics the physical signs resolved rapidly, accompanied by a dramatic reduction in the size of extraocular muscles on CT scanning. One patient subsequently became clinically hypothyroid, while the other showed clinical and biochemical evidence of thyroid overactivity. These case-reports suggest that patients with bilateral acute painful proptosis should have an early CT scan to exclude atypical dysthyroid disease. Delay in giving systemic steroids may allow the development of unnecessary visual loss due to optic nerve damage.
Acute Disease↗
[Imaging of neuro-ophthalmological emergencies].
MRI often is mandatory in the diagnostic work-up of visual loss, visual field alterations and oculomotor problems. It is performed emergently in patients with painful diplopia associated to mydriasis, to exclude aneurysm, or in patients with painful Horner syndrome to exclude dissection of the internal carotid artery. CT scan in emergency remains useful in case of acute lateral hemianopsia or acute post traumatic visual loss. Progressive neuro-ophthalmological symptoms may require imaging examination in a short delay to define the therapeutic strategy: monocular transient blindness (dissection or carotid stenosis), progressive visual loss (optic nerve compression), bitemporal hemianopsia (optic chiasm lesion), painful visual loss (optic neuritis). A very precise clinical indication is helpful for the choice of imaging protocol and to improve its diagnosis value.
Acute Disease↗
Neuro-ophthalmic findings in the visual variant of Alzheimer's disease.
PURPOSE: To describe the clinical features of a visual variant Alzheimer's disease, a disorder that might be seen by the ophthalmologist with visual symptoms and signs. DESIGN: Retrospective case series. PARTICIPANTS: Eight patients with Alzheimer's disease presenting with predominantly visual complaints. METHODS: A retrospective review of patients at a tertiary care academic center seen by the authors from 1999 to 2001 with Alzheimer's disease and predominantly visual complaints. RESULTS: Eight patients with the visual variant of Alzheimer's disease were reviewed. All had seen eye care providers before referral to the neuro-ophthalmology clinic for visual complaints but without a diagnosis. Four patients had homonymous visual field loss, and two had presumed cortical visual impairment. Neuroimaging showed either normal brain (1 patient) or atrophy of the parietal or occipital areas but no structural lesions (7 patients). Fluoro-18-deoxyglucose positron emission tomography scans were performed in five of the cases, and all showed hypoperfusion in the parietooccipital areas. Neuropsychologic testing revealed visuospatial deficits in all 5 patients tested. CONCLUSIONS: Visual symptoms might be the presenting (or rarely only) manifestation of Alzheimer's disease. Clinicians should be aware of the visual variant of Alzheimer's disease. Neuropsychological testing and magnetic resonance imaging (MRI) provide supporting evidence for the diagnosis. Positron emission tomography scans might be helpful in selected cases, especially those with a normal MRI.
Aged↗
Orbital emphysema as an ophthalmologic emergency.
Orbital emphysema is generally a benign, self-limited condition. However, if a fracture produces a ball-valve effect allowing air to enter but not to leave the orbit, and if the orbital septum remains intact, then extremely high intraorbital pressure and visual loss is possible. Two cases are described of visual loss from orbital emphysema, in a 33-year-old man and a 28-year-old man, which were successfully treated by a lateral canthotomy and cantholysis.
Adult↗
Management of limited rhino-orbital mucormycosis without exenteration.
Eight cases of rhino-orbital mucormycosis managed successfully without exenteration were reviewed. The favorable outcome was attributable to early diagnosis and management of focal areas of fungus infection. Treatment included: correction of diabetic ketoacidosis or other concomitant metabolic derangement; wide local excision and debridement of all involved and devitalized oral, nasal, sinus, and orbital tissue, while establishing adequate sinus and orbital drainage; daily irrigation and packing of the involved orbital and paranasal areas with amphotericin B; and intravenous amphotericin B. This represents the largest reported series of rhino-orbital mucormycosis survivors without mutilating surgery and with unaltered visual acuity.
Adult↗
Invasive sinonasal polyps causing ophthalmoplegia, exophthalmos, and visual field loss.
In a 20-year-old man with a history of sinonasal polyps, bilateral ophthalmoplegia, exophthalmos, and optic nerve dysfunction developed. Radiologic imaging showed a polypoid mass filling the nose and sinuses, eroding into the pituitary fossa, basal cisterns, and orbits, and compressing the cavernous sinuses. Six months after bilateral maxillary, ethmoid, and sphenoid exploration, ocular motility returned to normal, but there remained mild generalized visual field loss in the right eye. The pathologic specimen showed polypoid respiratory mucosa with acute and chronic inflammation as well as eosinophiles.
Adult↗