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At least 613 records · Page 34Linked to original sources
PubMed1987

Posterior cerebral artery stenosis.

We analyzed the clinical features of symptomatic posterior cerebral artery (PCA) stenosis in 6 patients selected from 15 patients with angiographically documented PCA atherostenosis occurring during a 7-year period. Transient ischemic attacks (TIAs) were the major presentation in 5 patients. A homonymous visual field defect was present in 2 patients. TIA symptoms were predominantly visual or sensory, or both. The most common visual symptom was difficulty seeing to one side. One patient saw flashing lights. Sensory spells were always paresthetic, usually involving the arm and hand and occasionally the face and leg. Three patients had visual and sensory spells together. Two patients with a visual field defect had calcarine infarcts found by computed tomography. All patients were treated with warfarin. During follow-up (4 months to 4 years), no patient had a new stroke in the PCA territory, and only one continued to have TIAs. PCA atherostenosis is rarer then PCA embolic occlusion. In contrast to those with PCA embolism, our patients with PCA atherostenosis had more TIAs and fewer infarcts. The clinical features of PCA stenosis--preponderance of visual and sensory TIAs--distinguish this vascular lesion from stenosis of the middle cerebral artery.

Aged↗
PubMed1987

Irradiation of meningiomas of the intracranial anterior visual pathway.

Twenty patients with progressive visual loss caused by intracranial meningiomas involving the anterior visual pathway were treated with irradiation alone (n = 4) or with irradiation combined with tumor excision (n = 16). Improvement in visual performance occurred in 13 patients; 2 patients experienced temporary improvement; and 5 others maintained stable visual function for up to 9.5 years (mean follow-up, 4.0 years). Radiotherapy seemed to have no effect in 2 patients. One patient experienced temporary improvement, but eventually died from spread of tumor. Only one definite complication of radiotherapy occurred and was related to excessive radiation dose (greater than 7,000 cGy). Irradiation in the range of 5,000 to 5,500 cGy was effective either alone or in combination with surgical excision. Serial assessment of visual acuity and fields allowed us to demonstrate and quantify improvement in our patients following radiotherapy; in contrast, follow-up computed tomographic studies rarely demonstrated reduced tumor size.

Combined Modality Therapy↗
PubMed1992

Occipital lobe epilepsy: clinical characteristics, seizure spread patterns, and results of surgery.

Twenty-five patients with occipital lobe seizure origin were retrospectively evaluated to determine clinical seizure characteristics and electroencephalographic manifestations. Certain symptoms and signs served to identify occipital lobe origin in 22 (88%). These included elementary visual hallucinations, ictal amaurosis, eye movement sensations, early forced blinking or eyelid flutter, and visual field deficits. Eye or head deviation, or both, was observed frequently and was contralateral to the side of seizure origin in 13, but 3 patients exhibited ipsilateral deviation in some or all their seizures. After the initial signs and symptoms, clinical seizure characteristics resembled those of seizures originating elsewhere. Seizures typical of temporal lobe origin with loss of contact and various types of automatic, semipurposeful activity occurred in 11 patients. Seizures in 3 patients exhibited asymmetrical tonic or focal clonic motor patterns characteristic of frontal lobe seizures. Eleven of the 25 patients had, on two occasions, two or more distinctly different seizure types. Scalp electroencephalographic findings were seldom helpful for occipital lobe localization and were frequently misleading. Intracranial electroencephalographic recording correctly identified occipital lobe seizure origin in most, but not all, patients who had such studies. Intracranial electroencephalic recording also proved the variability in clinical seizure characteristics was related to different seizure spread patterns, medially or laterally above and below the sylvian fissure, both ipsilateral and contralateral to the occipital lobe of seizure origin. Eighteen patients had occipital lobe lesions detected with computed tomographic or magnetic resonance imaging scans or both. Resection of the lesions in 16 patients produced excellent results in 14 (88%). Five patients had temporal lobectomies, with good results in 3, but poor results in 2. Two patients with unlocalized seizures had complete section of the corpus callosum, 1 with a good result and the other with a poor result.

Adolescent↗
PubMed1997

Adult-onset subacute sclerosing panencephalitis: case reports and review of the literature.

Subacute sclerosing panencephalitis (SSPE) is mainly thought of as a disorder of childhood and adolescence and may not be readily recognized when presenting later in life. Prior reports have suggested that adult-onset SSPE may have atypical features. We have added two cases to the existing literature on adult-onset SSPE, compared them with a more classic juvenile presentation, and extensively reviewed those reports that were published after the etiological link with the measles virus had been established. Adult-onset SSPE patients present at a mean age of 25.4 years (range 20-35 years). They have a higher proportion of either negative history of measles exposure or undocumented history by the reporting authors. Those with available history of measles exposure tend to have it either earlier (younger than 3 years old) or later (after 9 years) than the usual childhood measles infection. Where the primary infection is known, unusually long measles-to-SSPE intervals have been documented, ranging from 14 to 22 years. None of the cases followed measles vaccination. Visual symptomatology was very frequent, with 8 of the 13 cases reviewed having a purely ophthalmological presentation; only 2 patients presented with behavioral changes. Although the course of the disease was progressive and fatal in the majority, there appeared to be a higher rate of spontaneous remission as compared with childhood-onset SSPE. Myoclonus, spastic hemiparesis, bradykinesia, and rigidity were the predominant motor manifestations. Neuropathology revealed cortical and subcortical gray matter involvement preferentially of the occipital lobes, thalamus, and putamen. The importance of recognizing the spectrum of potential presentations of SSPE and providing an early diagnosis will increase as more effective treatments become available.

Adolescent↗
PubMed1994

Transient increase in the in vivo binding of the benzodiazepine antagonist [3H]flumazenil in deafferented visual areas of the adult mouse brain.

Flumazenil is an imidazobenzodiazepine, an antagonist of central benzodiazepine (BDZ) receptors. BDZ binding sites are a modulatory component located on the gamma-aminobutyric acid (GABA) receptor macromolecule. We studied the effect of monocular enucleation on [3H]flumazenil binding in deprived and intact visual areas and nonvisual areas of the adult mouse brain under in vivo conditions. [3H]flumazenil binding was examined at seven time points up to 56 days postenucleation. In some monocularly deprived mice, changes in local blood flow accompanied with the BDZ receptor response were evaluated by coinjection of [3H]flumazenil and 99mTc-HMPAO. Monocular enucleation produced a transient increase in [3H]flumazenil binding in the deprived visual cortex and superior colliculus. At 17 days postenucleation, [3H]flumazenil binding in the anterior and posterior portions of the visual cortex and the superior colliculus increased by 28%, 15% and 23%, respectively, and declined to control levels at 45 days postenucleation. The increase in [3H]flumazenil was accompanied with a decrease in blood flow. Alterations in BDZ receptors and blood flow were selective to deprived visual structures. The regional correlation between the metabolic deficit and the BDZ response provides further support that the increase in BDZ receptor binding is confined to regions of reduced neuronal activity. [11C]flumazenil is an excellent radiotracer for in vivo imaging of benzodiazepine receptors in human brain using positron emission tomography (PET). This study suggests the suitability of [11C]flumazenil for in vivo PET study of BDZ receptor response to deafferentation of visual structures in human brain.

Animals↗
PubMed1998

Cerebral processes related to visuomotor imagery and generation of simple finger movements studied with positron emission tomography.

Positron emission tomography was used to compare the functional anatomy of visual imagination and generation of movement. Subjects were asked to generate visual images of their finger movement in response to a preparatory signal. Four conditions were tested: in two, no actual movement was required; in the other two, a second signal prompted the subjects to execute the imagined movement. Which movement to imagine was either specified by the preparatory stimulus or freely selected by the subjects. Compared with a rest condition, tasks involving only imagination activated several cortical regions (inferoparietal cortex, presupplementary motor area, anterior cingulate cortex, premotor cortex, dorsolateral prefrontal cortex) contralateral to the imagined movement. Tasks involving both imagination and movement additionally increased activity in the ipsilateral cerebellum, thalamus, contralateral anteroparietal, and motor cortex and decreased activity in the inferior frontal cortex. These results support the hypothesis that distinct functional systems are involved in visuomotor imagination and generation of simple finger movements: associative parietofrontal areas are primarily related to visuomotor imagination, with inferior frontal cortex likely engaged in active motor suppression, and primary motor structures contribute mainly to movement execution.

Adult↗
PubMed1989

Corticosteroid-induced exophthalmos.

We describe twenty-one patients on sustained corticosteroid therapy who presented with exophthalmos. Each patient received a complete ophthalmologic examination and further tests were conducted to rule out other causes of exophthalmos. Our data suggest that corticosteroid-induced exophthalmos is an entity more common than has been previously recognized.

Aged↗
PubMed1993

A model for neural representation of binocular disparity in striate cortex: distributed representation and veto mechanism.

A model in striate cortex is proposed for a distributed neural representation of binocular disparity with a simple cell. In the model, disparity is represented by "far", "near" and "tuned inhibitory" simple cells. However, the representation will be vetoed by model cells where disparity is excessively large. The veto mechanism consists of a neural network of the model cell which received output from simple cells and which interacts with neighbors. The mechanism is necessary, the model cell responds like a simple cell, and the network is physiologically plausible in the brain. Computer simulation on the neural network model with random dot stereography indicates reasonable performance.

Computer Simulation↗
PubMed1991

Non-specific granulomas of the pituitary: report of six cases treated surgically.

Granulomatous lesions of the pituitary gland are very rare. In our department, six patients with these lesions have been operated on since 1988. The records of these patients were analysed and are reported in the following. Three of the patients were admitted because of severe and rapid development of visual disturbances caused by a suprasellar extending lesion. Endocrinological examination most often found posterior lobe insufficiency, was followed by anterior lobe dysfunction. CT and MRI demonstrated a cystic lesion with semiliquid content, where mild contrast enhancement of the walls of the tumor was observed in all cases. Surgery was performed using the transphenoidal approach. Rapid relief of visual impairment was observed in the three patients with chiasmal compression. In one patient, recurrent chiasm syndrome due to lesion regrowth required additional surgery with transcranial resection of the capsule. Unfortunately, visual impairment persisted postoperatively in one eye. Endocrinological follow-up demonstrated unchanged or even worsened pituitary functions in all cases. Our study revealed no consistent predictive preoperative finding. Therefore, we consider an indication for decompression surgery to be given in all patients with chiasmal syndrome and for diagnostic surgery for all patients with intrasellar lesions.

Adult↗
PubMed1986

Superselective intracerebral chemotherapy of malignant tumours with BCNU. Neuroradiological considerations.

Early experience shows that: Superselective intra-arterial catheterization above the ophthalmic artery minimizes the orbital complications. Catheterization in a distal branch may lead to the non-infusion of a part of the tumor territory. A much higher concentration of the drug is achieved by superselective intra-arterial infusion than by intravenous injection. Longer infusions seem more efficacious than bolus injection. Early trapping of the drug appears to be essential for therapeutic efficacy.

Blood-Brain Barrier↗
PubMed1985

Lipoma of the quadrigeminal plate cistern.

Two cases of quadrigeminal plate cistern lipoma detected by CT scan, one of which produced impairment of vertical gaze, are reported. The problems of diagnosis and therapy of intracranial lipomas are briefly discussed.

Aged↗
PubMed1990

Meso-diencephalic infarction: a not so rare form of stroke.

26 patients admitted with clinical pictures consistent with meso-diencephalic infarction were studied using computerized axial tomography, magnetic resonance imaging and angiography. All of the patients presented symptoms in two of three major categories which comprise the "top of the basilar" syndrome. Lesions in the territory of the basilar-communicating artery were demonstrated in 22 of them. The remaining patients died before adequate neuroimaging documentation was obtained. Overall prognosis appeared relatively good since 80% of the patients recovered completely or incompletely from the ictus. Meso-diencephalic infarction is a very important and not uncommon subtype of cerebrovascular disorder.

Adult↗
PubMed1995

Introduction to perceptual linearization of video display systems for medical image presentation.

The perceptual linearization of video display systems should play a significant role in medical image presentation. It maximizes the faithfulness of information transfer to the human observer; it provides a method for standardizing the appearance of images across different display devices; and it allows for calculation of the inherent contrast resolution of different display devices. This paper provides insight into the process of perceptual linearization by decomposing it into the digital driving level-to-monitor luminance relationship, the monitor luminance-to-human brightness perception relationship, and the construction of a linearization function derived from these two relationships. A discussion of previous work in these areas is given. We then compare and contrast the results of previous work with recent experiments in our laboratory and related work in vision and computer science. We conclude that (1) sufficiently good visual models exist for agreeing on a standard method of calculating the perceptual linearization function; (2) improvements in the resolution and luminance distribution of the digital-to-analog circuitry in display systems are required for medical imaging; and (3), methods for calculating a linearization remapping from a perceptual linearization function currently have significant error and should be replaced with methods that minimize perceptual error.

Analog-Digital Conversion↗
PubMed1985

Effect of chronic bromocriptine administration on tumor size in patients with "nonsecreting" pituitary adenomas.

The effect of chronic bromocriptine administration (7.5-20 mg/day for 1-32 months) on the size of "nonsecreting" pituitary adenomas (NPA) was studied in 20 patients. Brain computed tomography showed a marked reduction of the adenoma in one patient after 1 month of treatment (7.5 mg/day); further scans taken 2 and 15 months later, under the same bromocriptine dose, did not show any other variations in the tumoral mass. In the remaining 19 patients, no changes in tumor size were documented by CT during the treatment. Four patients had a worsening of visual fields during bromocriptine administration and they were referred for neurosurgery. In conclusion, bromocriptine was ineffective in reducing tumor size in all but one patient with NPA and, in some cases, it did not prevent tumor growth as is suggested by the worsening of visual fields. Thus, bromocriptine treatment, at least at the doses capable of shrinking macroprolactinomas, seems to be of limited value in patients with NPA.

Adenoma↗
PubMed1997

The role of posterior parietal cortex in visually guided reaching movements in humans.

Positron emission tomography (PET) was used to identify the brain areas involved in visually guided reaching by measuring regional cerebral blood flow (rCBF) in six normal volunteers while they were fixating centrally and reaching with the left or right arm to targets presented in either the right or the left visual field. The PET images were registered with magnetic resonance images from each subject so that increases in rCBF could be localized with anatomical precision in individual subjects. Increased neural activity was examined in relation to the hand used to reach, irrespective of field of reach (hand effect), and the effects of target field of reach, irrespective of hand used (field effect). A separate analysis on intersubject, averaged PET data was also performed. A comparison of the results of the two analyses showed close correspondence in the areas of activation that were identified. We did not find a strict segregation of regions associated exclusively with either hand or field. Overall, significant rCBF increases in the hand and field conditions occurred bilaterally in the supplementary motor area, premotor cortex, cuneus, lingual gyrus, superior temporal cortex, insular cortex, thalamus, and putamen. Primary motor cortex, postcentral gyrus, and the superior parietal lobule (intraparietal sulcus) showed predominantly a contralateral hand effect, whereas the inferior parietal lobule showed this effect for the left hand only. Greater contralateral responses for the right hand were observed in the secondary motor areas. Only the anterior and posterior cingulate cortices exhibited strong ipsilateral hand effects. Field of reach was more commonly associated with bilateral patterns of activation in the areas with contralateral or ipsilateral hand effects. These results suggest that the visual and motor components of reaching may have a different functional organization and that many brain regions represent both limb of reach and field of reach. However, since posterior parietal cortex is connected with all of these regions, we suggest that it plays a crucial role in the integration of limb and field coordinates.

Adult↗
PubMed2003

Tactile feedback contributes to consistency of finger movements during typing.

Touch typing movements are typically too brief to use on-line feedback. Yet, previous studies have shown that blocking tactile feedback of the fingertip of typists leads to an increase in typing errors. To determine the contribution of tactile information to rapid fine motor skills, we analyzed kinematics of the right index finger during typing with and without tactile feedback. Twelve expert touch typists copy-typed sentences on a computer keyboard without vision of their hands or the computer screen. Following control trials, their right index fingertip was anesthetized, and sentences were typed again. The movements of the finger were recorded with an instrumented glove and electromagnetic position sensor. During anesthesia, typing errors of that finger increased sevenfold. While the inter-keypress timing and average kinematics were unaffected, there was an increase in variability of all measures. Regression analysis showed that endpoint variability was largely accounted for by start location variability. The results suggest that tactile cues provide information about the start location of the finger, which is necessary to perform typing movements accurately.

Adult↗
PubMed2004

Osteosarcoma of the ethmoid sinus.

A rare case of chondroblastic osteosarcoma arising from the ethmoid sinus is reported. The patient, a 34-year-old woman, presented with diminished visual acuity of the left eye. CT and MR imaging showed a heterogeneous left-sided nasoethmoidal mass destroying the medial orbital wall. Biopsy revealed a chondroblastic osteosarcoma containing malignant chondroid elements and calcified malignant osteoid. Treatment consisted of craniofacial resection followed by radiotherapy and chemotherapy with symptomatic improvement. We briefly discuss ethmoidal osteosarcomas.

Adult↗