SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Optic chiasm

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Meningiomas of the midline anterior skull base (ASB) typically grow around the optic chiasm. These tumors can displace or adhere to the optic apparatus, resulting in visual abnormalities. For this reason, in most studies of surgically resected meningiomas, only surgical and visual outcomes have been evaluated. However, in this study, we assessed overall clinical outcomes and the effects of different surgical approaches on outcomes. Clinical data for 126 patients who were treated surgically for midline ASB meningiomas between 1994 and 2009 were collected and reviewed retrospectively. The mean follow-up duration was 39months (range: 0.5-146months). Most procedures were performed via a pterional approach and did not require an aggressive skull base approach. Clinical outcomes were evaluated using our own criteria, and potential predictive factors for visual and clinical outcomes were tested statistically. The tumor control rate was 83% (105/126). Immediate postoperative visual status and optic canal involvement were correlated with visual outcome. Of the patients who ultimately had improved visual status, only six were originally categorized as having severe visual impairment (all were only able to count fingers). In terms of clinical outcome, 41 patients were classified as “excellent”, 32 as “good”, 29 as “fair”, and 20 as “poor”. A symptom duration of less than six months, less severe preoperative visual symptoms of the affected eye, and the extent of resection were all correlated with improved clinical outcome. Involvement of the optic canal, adherence of the tumor to the optic nerve, and major arterial encasement by the tumor were associated with poor clinical outcome. We recommend that in patients with unilateral severe visual impairment, the focus should be on improving visual function in the contralateral eye. Preoperative and postoperative evaluation of several variables allows for the prediction of clinical and visual outcomes.

Concepts: Nervous system, Visual system, Ophthalmology, Resection, Visual impairment, Optic nerve, Optic chiasm

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This brief article looks back on some of the work and interactions I had with Ray Guillery when I started my academic career in Oxford. I review some of the anatomical work we did using a comparative approach to study the development of the visual pathway, and particularly the optic chiasm. I think many of the questions we tried to address many years ago, are still relevant, and still poorly understood. This article is protected by copyright. All rights reserved.

Concepts: Retina, Photoreceptor cell, Visual perception, Visual system, Optic nerve, Optic chiasm

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Despite advances in endoscopic techniques, retrochiasmatic craniopharyngiomas are difficult to remove completely, because the low-lying optic chiasm often provides an obstacle to endoscopic endonasal approach. This study aimed to identify the endoscopic surgical outcomes of the retrochiasmatic CP and resolve the issues related to the low-lying optic chiasm.

Concepts: Optic nerve, Optic chiasm, Chi

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OBJECTIVE Tumor-related edema of the optic tract (EOT) corresponds to a preferential posterior distribution of peritumoral edema along the white matter tract of the visual system. To date, the consequences of EOT have never been evaluated specifically in the pediatric population. In this study, the authors attempted to identify clinical and radiological features associated with the development of EOT and the specific influence of this edema on visual function. METHODS A retrospective review was performed of data collected from patients younger than 18 years who underwent surgery for a tumor in the sellar region at the authors' institution between January 2005 and January 2016. Data were collected on patient characteristics, ophthalmological evaluations, and neuroimaging findings. To evaluate and compare visual function impairment, ophthalmological data were converted to a global visual function score, which took into account visual acuity, visual field evaluations, and laterality deficiencies. The visual acuity score was defined according to the International Classification of Diseases, 10th Revision. Visual field deficiencies were converted to a score of 0-2. Two opposing groups were then distinguished according to the presence or absence of EOT. Visual acuity, visual field results, and global scores were compared between groups before and after treatment. RESULTS Twenty-six patients were included in the study: 17 patients with craniopharyngioma, 3 patients with pilocytic astrocytoma, 2 patients with ganglioglioma, 2 patients with germ cell tumor, 1 patient with macroprolactinoma, and 1 patient with Rathke’s cleft cyst. There were 11 children in the group with edema and 15 children in the group without edema. None of the following criteria were statistically different between the 2 groups: age, sex, clinical symptoms at presentation (endocrine deficiency or intracranial hypertension signs), incidence of hydrocephalus, compression of the optic tracts and mass effect on the optic chiasm, tumor size and localization, presence of intratumoral cysts, treatment, type of tumor, or recurrence. The median global visual function and visual acuity scores were not significantly different between the groups either at presentation or at final evaluation. The visual field score was lower (i.e., more deficiency) in the group with edema than in the group without edema (p < 0.05); 89% of the patients with edema had severe or mild visual field impairment versus only 40% of the patients without edema. At the final examination after treatment, the visual field scores were not different between the 2 groups. Although not significant, the number of patients with optic disc pallor was greater in the group without edema both at diagnosis and at final examination. CONCLUSIONS This study confirms that EOT in the context of sellar region tumor in children is not necessarily associated with a less-favorable visual prognosis.

Concepts: Visual perception, Visual system, Ophthalmology, Germ cell tumor, Optic nerve, Optic chiasm, Rathke's pouch, Optic tract

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The aim of this study was to characterize brain and orbital MRI features of patients with Leber hereditary optic neuropathy (LHON), with particular attention to the optic nerves and chiasm.

Concepts: Nervous system, Ophthalmology, Optic nerve, Leber's hereditary optic neuropathy, Optic chiasm

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The purpose of this work is to establish a reference scale of optic nerve pathway measurements in pediatric patients according to age using MRI. Optic nerve pathway measurements were retrospectively analyzed using an orbits equivalent sequence on brain MRI scans of 137 pediatric patients (72 male, 65 female, average age = 7.7 years, standard deviation  = 5.3). The examinations were performed on a 1.5-T or 3-T Siemens MR system using routine imaging protocols. Measurements include diameters of the orbital optic nerves (OON), prechiasmatic optic nerves (PON), optic tracts (OT), and optic chiasm (OC). Measurements were performed manually by 2 neuroradiologists, using post-processing software. Patients were stratified into five age groups for measurement analyses: (I) 0-1.49 years, (II) 1.5-2.99 years, (III) 3-5.99 years, (IV) 6-11.99 years, and (V) 12-18 years. The observed value range of OON mean diameter was 2.7 mm (Interquartile range (IQR) = 2.4-2.9), PON was 3.2 mm (IQR  =  3.05-3.5), OT 2.6 mm (IQR = 2-2.9). A strong positive correlation was established between age and mean diameter of OON (r = 0.73, p < .001), PON (r = 0.59, p < .001), and OT (r = 0.72, p < .001). A significant difference in mean OON diameters was found between age groups I-II (d = 0.3, p = .01), II-III (d = 0.5, p < .001), III-IV (d = 0.5, p < .001) followed by a plateau between IV-V (d = 0.l0, p = .19). OON/OT ratio maintained a steady mean value 1 (IQR = 0.93-1.1) regardless of age (p = .7). The diameter of optic pathways was found to increase as a function of age with consistent positive correlation between nerve and tract for all ages.

Concepts: Median, Magnetic resonance imaging, Multiple sclerosis, Visual system, Cranial nerves, Optic nerve, Optic chiasm, Optic tract

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Although there have been many studies of the arterial cerebral blood supply, only seven have described the optic chiasm (OC) blood supply and their results are contradictory. The aim of this study was to analyze the extrinsic and intrinsic OC blood supply on cadaveric specimens using dissections and microcomputer tomography (Micro-CT).

Concepts: Blood, Heart, Blood vessel, Artery, Cultural studies, Intrinsic and extrinsic properties, Optic nerve, Optic chiasm

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A multiphase, approximate biological effective dose (BEDA) equation was introduced because most treatment planning systems (TPS) are incapable of calculating the true BED (BEDT). This work investigates the accuracy and precision of the multiphase BEDA relative to the BEDT in clinical cases. Ten patients with head and neck cancer and 10 patients with prostate cancer were studied using their treatment plans from Pinnacle(3) 9.2 (Philips Medical, Fitchburg, WI). The organs at risk (OARs) that were studied are the normal brain, left and right optic nerves, optic chiasm, spinal cord, brainstem, bladder, and rectum. BEDA and BEDT distributions were calculated using MATLAB 2010b (MathWorks, Natick, MA) and analyzed on a voxel basis for percent error, percent error volume histograms (PEVHs), Pearson correlation coefficient, and Bland-Altman analysis. The maximum BED values that were calculated using the BEDA and BEDT methods were also analyzed. BEDA was found to always underestimate BEDT. The accuracy and precision of BEDA distributions varied between the organs: for optic chiasm and brainstem, 50% of the patients had an overall BEDA percent error of <1%; for left and right optic nerves, rectum, and bladder, 60% to 70% of the patients had an overall BEDA percent error of <1%; and for normal brain and spinal cord, 80% of the patients had an overall BEDA percent error of <1%. BEDA distributions had maximum errors ranging from 2% to 11%, with the 11% error occurring for bladder. BEDA produced much more accurate maximum BED values with adjacent organs such as normal brain, bladder, and rectum. This study has shown that BEDA can calculate BED distributions with acceptable accuracy under certain circumstances. However, its consistency and accuracy strongly depend on the dose distributions of the different treatment phases. One should be cautious when using BEDA.

Concepts: Spearman's rank correlation coefficient, Correlation and dependence, Normal distribution, Pearson product-moment correlation coefficient, Accuracy and precision, Karl Pearson, Optic nerve, Optic chiasm

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Autoimmune hypophysitis is a rare disease of the pituitary, which may affect vision by inflammation and compression of the optic chiasm. However, intrachiasmatic abscess formation has not been previously reported.

Concepts: Optic nerve, Optic chiasm

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Cavernoma of the optic chiasm is a rare disease, and the most common clinical presentation is chiasmal apoplexy. Almost all the cases reported in the literature were treated surgically with craniotomy.

Concepts: Medicine, Epidemiology, Report, Ophthalmology, Case, Optic nerve, Optic chiasm, Chiasmal syndrome