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Pediatric optic pathway/hypothalamic gliomas (OPHG) pose challenges in treatment due to their location and proximity to vital structures. Surgical resection plays a key role in the management of OPHG especially when the tumor exhibits mass effect and causes symptoms. However, data regarding outcomes and complications of surgical resection for OPHG remains heterogenous. The authors performed a systematic review on pediatric OPHG in four databases: PubMed, EMBASE, Cochrane Library, and Google Scholar. We included studies that reported on the visual outcomes and complications of OPHG resection. A meta-analysis was performed and reported per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 26 retrospective studies were included. Seven hundred ninety-seven pediatric patients with OPHG undergoing surgical resection were examined. A diagnosis of NF1 was confirmed in 9.7%. Gross total resection was achieved in 36.7%. Intraorbital optic pathway gliomas showed a significantly higher gross total resection rate compared to those located in the chiasmatic/hypothalamic region (75.8% vs. 9.6%). Postoperatively, visual acuity improved in 24.6%, remained unchanged in 68.2%, and worsened in 18.2%. Complications included hydrocephalus (35.4%), anterior pituitary dysfunction (19.6%), and transient diabetes insipidus (29%). Tumor progression post-resection occurred in 12.8%, through a mean follow-up of 53.5 months. Surgical resection remains an essential strategy for treating symptomatic and large pediatric OPHG and can result in favorable vision outcomes in most patients. Careful patient selection is critical. Patients should be monitored for hydrocephalus development postoperatively and followed up to assess for tumor progression and adjuvant treatment necessity. [ABSTRACT FROM AUTHOR]

Introduction: This is a unique case report in medical literature for its detailing of diagnostics of an uncommon presentation of a rapid unexplained bilateral vision loss of a 73-year-old male diabetic patient. This report highlights the crucial role of advanced molecular diagnostics in difficult neurological cases and also elucidates the difficulties involved in diagnosing optic nerve glioblastoma, an exceptionally rare and aggressive tumour. Main Concerns and Clinical Findings of the Patient: Slow and progressive loss of vision over 2 months, ultimately developing almost complete visual impairment in both eyes and a defect of right eye field of vision conclusively highlighted that the likely etiology was neuro-ophthalmic. Initially, the conditions were suspected to be an extended spectrum of diabetic eye disease complications but further deterioration was a hint towards something more substantive. Primary Diagnoses, Interventions and Outcomes: This entailed in-depth diagnosis processes that included an MRI and the analysis of cerebrospinal fluid. The important discovery was through stereotactic biopsies of the optic nerve revealing a high-grade glial neoplasm. Next generation sequencing confirmed the pathology as IDH-wildtype glioblastoma. Despite management, his vision continued to deteriorate. Hence, an aggressive clinical course was followed. Conclusion: This case highlights the important learning need in considering glioblastoma of the optic chiasm as part of the differential diagnosis of rapid vision loss, which may present as multifocal brain lesions, especially in cases of rapid loss of vision where initial workup is negative. Quite a useful lesson that can be drawn from this case relates to the diagnostic process with advanced molecular profiling, more attention given to clinical suspicion and cutting-edge diagnostic tools applied in atypical presentation of neurological conditions. [ABSTRACT FROM AUTHOR]

Background: Optimal initial exposure through an extended endoscopic endonasal approach (EEA) for suprasellar craniopharyngiomas ensures safe and unrestricted surgical access while avoiding overexposure, which may prolong the procedure and increase neurovascular adverse events. Method: Here, the authors outline the surgical nuances of a customized bony and dural opening through the transplanum/transtuberculum and transclival variants of the extended EEA to suprasellar craniopharyngiomas based on the tumor–pituitary stalk relationship. A stepwise cadaveric dissection and intraoperative photographs relevant to the approaches are also provided. Conclusion: Safe maximal resection of suprasellar craniopharyngiomas through extended EEAs can be feasibly and safely achieved by implementing of tailored ventral exposure. [ABSTRACT FROM AUTHOR]

Visual dysfunction is a prevalent symptom in patients with non-functioning pituitary macroadenoma (NFPM); the role of OCT in such patients has not been yet determined. This is a prospective longitudinal observational study over a period of 6 years, on 20 patients presenting a radiological compression of the optic chiasma without visual acuity (VA) and visual field (VF) disturbances. The primary endpoint was to evaluate the impact of NFPA on neuro-axonal loss by measuring RNFL thickness using OCT at inclusion (T0), 12 months (T1), 24 months (T2), and 36 months (T3), respectively. The secondary endpoint was to monitor the evolution of OCT over time and assess any relationship between the degree of OCT alteration and the degree of radiological and clinical optic chiasm compression syndrome. Among the 20 patients included, eight (40%) showed an altered RNFL-OCT at diagnosis, while the remaining 12 (60%) showed a normal pattern. During a mean ophthalmologic follow-up of 60 months, 4 patients (20%) presented an asymptomatic reduction of RNFL-OCT thickness although all 20 had a VA/VF stable. To our knowledge, this study represents the first attempt to longitudinally evaluate the natural history and evolution of RNFL-OCT in patients with radiologically asymptomatic chiasmatic compression syndrome. The results do not clearly demonstrate the role of the OCT as an early prognostic factor for visual dysfunction. [ABSTRACT FROM AUTHOR]

The aim of our study was to examine the variations and types of foramen of diaphragma sellae (FDS) and their relationship with nearby surgical landmarks on cadavers.Twenty adult (9 male, 11 female) formalin-fixed cadaveric heads were bilaterally used to analyze the anatomical relationships around the supradiaphragmatic region of sella turcica. Lengths and distances of nearby surgical landmarks were measured by a digital microcaliper. SPSS version 25 was used to analyze the comparison between genders and body sides. Dorsum sellae distances to tuberculum sellae and the optic chiasm(OC) were higher in males than females (p < 0.05). Type 8 infundibulum passage was the most common variation with 50%. There was no finding related to types 1–4 of infundibulum passage. Thus, the present study has indicated that the infundibulum passes mostly from the posterior half of the foramen. The shape of the foramen was irregular in 45%, circular in 20%, sagittally oval in 20%, and horizontally oval in 15% of the cases. The OC was noted normal in 60%, prefixed in 35%, and postfixed in 5% of the cases. Comprehensive anatomical knowledge about the types of the FDS and their neighboring structures is crucial for preoperative planning of sellar region diseases in terms of navigating the region when accessing the foramen. Discrimination of variations of FDS, OC, and pituitary stalk, their relationships, and differences between genders is useful to minimize potential surgical complications. [ABSTRACT FROM AUTHOR]

Objectives: To investigate whether morphological changes after surgery and delta-radiomics of the optic chiasm obtained from routine MRI could help predict postoperative visual recovery of pituitary adenoma patients. Methods: A total of 130 pituitary adenoma patients were retrospectively enrolled and divided into the recovery group (n = 87) and non-recovery group (n = 43) according to visual outcome 1 year after endoscopic endonasal transsphenoidal surgery. Morphological parameters of the optic chiasm were measured preoperatively and postoperatively, including chiasmal thickness, deformed angle, and suprasellar extension. Delta-radiomics of the optic chiasm were calculated based on features extracted from preoperative and postoperative coronal T2-weighted images, followed by machine learning modeling using least absolute shrinkage and selection operator wrapped with support vector machine through fivefold cross-validation in the development set. The delta-radiomic model was independently evaluated in the test set, and compared with the combined model that incorporated delta-radiomics, significant clinical and morphological parameters. Results: Postoperative morphological changes of the optic chiasm could not significantly be used as predictors for the visual outcome. In contrast, the delta-radiomics model represented good performances in predicting visual recovery, with an AUC of 0.821 in the development set and 0.811 in the independent test set. Moreover, the combined model that incorporated age and delta-radiomics features of the optic chiasm achieved the highest AUC of 0.841 and 0.840 in the development set and independent test set, respectively. Conclusions: Our proposed machine learning models based on delta-radiomics of the optic chiasm can be used to predict postoperative visual recovery of pituitary adenoma patients. Clinical relevance statement: Our delta-radiomics-based models from MRI enable accurate visual recovery predictions in pituitary adenoma patients who underwent endoscopic endonasal transsphenoidal surgery, facilitating better clinical decision-making and ultimately improving patient outcomes. Key Points: • Prediction of the postoperative visual outcome for pituitary adenoma patients is important but challenging. • Delta-radiomics of the optic chiasm after surgical decompression represented better prognostic performances compared with its morphological changes. • The proposed machine learning models can serve as novel approaches to predict visual recovery for pituitary adenoma patients in clinical practice. [ABSTRACT FROM AUTHOR]

An appropriate sensory experience during the early developmental period is important for brain maturation. Dark rearing during the visual critical period delays the maturation of neuronal circuits in the visual cortex. Although the formation and structural plasticity of the myelin sheaths on retinal ganglion cell axons modulate the visual function, the effects of dark rearing during the visual critical period on the structure of the retinal ganglion cell axons and their myelin sheaths are still unclear. To address this question, mice were reared in a dark box during the visual critical period and then normally reared to adulthood. We found that myelin sheaths on the retinal ganglion cell axons of dark-reared mice were thicker than those of normally reared mice in both the optic chiasm and optic nerve. Furthermore, whole-mount immunostaining with fluorescent axonal labeling and tissue clearing revealed that the myelin internodal length in dark-reared mice was shorter than that in normally reared mice in both the optic chiasm and optic nerve. These findings demonstrate that dark rearing during the visual critical period affects the morphology of myelin sheaths, shortens and thickens myelin sheaths in the visual pathway, despite the mice being reared in normal light/dark conditions after the dark rearing. [ABSTRACT FROM AUTHOR]

Background: Pituitary tumors may cause compression of the optic chiasm, resulting in decreased visual acuity. Therefore, decompression of the optic chiasm is a major goal of surgical treatment in such patients. Quantitative pupillometry has been used in various clinical settings for assessing the optic system but has not been applied in patients with pituitary tumors. This study aimed to evaluate the potential of this technique to improve treatment modalities in patients undergoing surgical resection of pituitary tumors. Method: Pupillometry using the automated NPi 200® Pupillometer was performed in seven patients who underwent surgical resection of large pituitary tumors at the University of Heidelberg in 2018. The neurological pupil index (NPi) was assessed preoperatively and postoperatively, and correlations with visual acuity and magnetic resonance imaging (MRI) findings regarding optic chiasm compression were determined. Results: All patients experienced visual disturbance due to a large pituitary tumor. The NPi was < 4.0 in all patients in at least one pupil. Intraoperative MRI demonstrated successful decompression of the optic chiasm in all cases. Postoperatively, the NPi values increased, and this increase was correlated with improved visual acuity. Conclusions: We found that quantitative pupillometry can detect optic chiasm compression in patients with pituitary tumors. Furthermore, postoperative improvement of NPi values may indicate sufficient decompression of the optic chiasm. Further studies are warranted to substantiate the granularity of this technique to gain valuable information for patients with pituitary tumors who are indicated for surgery. [ABSTRACT FROM AUTHOR]

The chiasmal and subchiasmal surfaces are of critical importance in connection with the performance of surgical procedures owing to the critical blood supply to these areas. Recently, the perforating arteries providing the blood to the optic nerves and chiasm have gained attention as they significantly affect the morbidity from surgical approaches. Intraoperative preservation of these perforating arteries is considered critical to prevent further visual loss. Thirty autopsy specimens, including the optic apparatus, were examined for their perforating arteries feeding the optic chiasm and optic nerves. The optic nerves and chiasmal surfaces were divided into four zones based on the presence and numbers of perforating arteries as anterior superior–posterior superior surfaces and anterior inferior–posterior inferior surfaces. The superior surface of the optic chiasm was supplied by the A1 segments of the bilateral anterior cerebral arteries and by the perforating arteries originating from the anterior communicating artery. On the other hand, the inferior surface of the optic chiasm was fed by the bilateral posterior communicating arteries and by the supraclinoidal segments of the bilateral carotid arteries. We demonstrated the anatomical involvement of a large number of nourishing arteries in feeding the optic apparatus related to the perforating arteries by classifying them into zones based on the surgical approaches, which has been rarely reported in the literature. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether the occurrence of chiasmal herniation coincides with visual field (VF) deterioration and to compare the course of VF defects in patients with and without radiological chiasmal herniation following treatment of pituitary adenoma. Methods: This retrospective cohort study included 48 pituitary macroadenoma patients with chiasm compression, divided into three groups: Group 1 (N = 12), downward displaced optic chiasm and deteriorated VFs; Group 2 (N = 16), downward displaced optic chiasm; Group 3 (N = 20), control-group matched for tumour size and follow-up VFs, in mean deviation (dB). VFs were compared over time and a severity index, Chiasm Herniation Scale (CHS), for herniation based on radiological parameters was designed. Results: After treatment, all groups showed improvement of VFs (Gr1: 2.97 dB p = 0.097, Gr2: 4.52 dB p = 0.001 and Gr3: 5.16 dB p = 0.000), followed by long-term gradual deterioration. The course of VFs between patients with and without herniation was not significantly different (p = 0.143), neither was there a difference in the course before and after herniation (p = 0.297). The median time till onset of herniation was 40 months (IQR 6 month-10 years) and did not significantly differ (p = 0.172) between the groups. There was no relation between VFs and the degree of herniation (p = 0.729). Conclusion: Herniation does not appear to have clinical relevance with respect to VF outcome. The newly designed CHS is the first scoring system to quantify the severity of herniation and, in the absence of alternatives, may be useful to describe MRI findings to serve future added value in larger sized outcome studies. [ABSTRACT FROM AUTHOR]

Objectives: We aimed to evaluate optic chiasm (OC) measures as potential imaging marker for anterior optic pathway damage assessment in the context of neuromyelitis optica spectrum disorders (NMOSD).Materials and Method: This cross-sectional study included 39 patients exclusively with aquaporin 4-IgG seropositive NMOSD of which 25 patients had a history of optic neuritis (NMOSD-ON) and 37 age- and sex-matched healthy controls (HC). OC heights, width, and area were measured using standard 3D T1-weighted MRI. Sensitivity of these measures to detect neurodegeneration in the anterior optic pathway was assessed in receiver operating characteristics analyses. Correlation coefficients were used to assess associations with structural measures of the anterior optic pathway (optic nerve dimensions, retinal ganglion cell loss) and clinical measures (visual function and disease duration).Results: OC heights and area were significantly smaller in NMOSD-ON compared to HC (NMOSD-ON vs. HC p < 0.0001). An OC area smaller than 22.5 mm2 yielded a sensitivity of 0.92 and a specificity of 0.92 in separating chiasms of NMOSD-ON from HC. OC area correlated well with structural and clinical measures in NMOSD-ON: optic nerve diameter (r = 0.4, p = 0.047), peripapillary retinal nerve fiber layer thickness (r = 0.59, p = 0.003), global visual acuity (r = - 0.57, p = 0.013), and diseases duration (r = - 0.5, p = 0.012).Conclusion: Our results suggest that OC measures are promising and easily accessible imaging markers for the assessment of anterior optic pathway damage.Key Points: • Optic chiasm dimensions were smaller in neuromyelitis optica spectrum disorder patients compared to healthy controls. • Optic chiasm dimensions are associated with retinal measures and visual dysfunction. • The optic chiasm might be used as an easily accessible imaging marker of neurodegeneration in the anterior optic pathway with potential functional relevance. [ABSTRACT FROM AUTHOR]

Background: Meningioma arising from locations in the vicinity of the optic nerve or chiasm may affect the visual function and sometimes the presentation of such tumors. Decompression of the optic nerve or chiasm can give a chance for the visual function to recover. Methods: Thirty patients who had visual function affection and underwent meningioma excision are followed up for a period of 1 year with regular follow of their visual function periodically. Results: In this study, females were more prevalent than males, 24 out of 30, age ranged from 24 to 72 years at the time of surgery, half the patients (15) presented with visual deterioration, the other patients presented with headache, seizure, proptosis, or accidentally discovered. Twenty-two patients improved concerning their visual function over time, 6 patients had a stationary course, and 2 patients deteriorated postoperatively. Conclusion: Follow-up of patients after surgical excision of meningioma compressing the anterior optic pathway showed gradual improvement in vision in follow-up period up to 1 year, although the improvement in visual function showed a surge in early postoperative period, with continuous less steep improvement afterwards till the end of the observation period. Surgical excision of meningiomas compressing the anterior visual pathway gives chance for recovery of visual function, more in younger patients, patients with a shorter period of visual deterioration, and patients with mild affection of the preoperative visual status. No statistically significant influence of tumor site, size, degree of excision, and surgical approach on the postoperative visual outcome in this series. [ABSTRACT FROM AUTHOR]

In patients with pituitary adenomas (PA) who are unable to undergo complete surgical resection, radiation therapy (RT), specifically stereotactic radiosurgery (SRS), results in excellent local control. However, the utility of radiosurgery may be limited by the proximity of the lesion to the optic chiasm (OC). We evaluate the efficacy of debulking surgery in increasing the PA-OC separation to convert patients into SRS candidates. From 2007 to 2015, 31 patients with PA < 2 mm from the OC underwent debulking surgery followed by RT within 2 years of resection. Coronal and sagittal T1-pre- and post-contrast sequences were used to determine PA-OC separation. Time interval between postoperative and pre-radiotherapy MRI scans and type of radiation therapy were analyzed. Functional tumor status, tumor characteristics [cavernous sinus (CS) or suprasellar (SS) involvement, chiasm/nerve encasement (NE)], and presence of ≥ 2 of these characteristics (multiple factors, MF) was also noted. Surgery converted 9 of 31 patients (29%) to SRS candidates. Median time from surgery to pre-RT planning MRI was 8 months (range 2-20). Of the 31 patients initially ineligible for SRS, 6 became eligible immediately after surgery, and another 3 were deemed eligible on follow-up. Mean PA-OC separation was 0.3 mm preoperative, 1.4 mm postoperative, and 2.1 mm at time of SRS (p = 0.002). Preoperative SS, NE, and MF involvement predicted pre-RT separation < 2 mm. Debulking surgery of unresectable pituitary tumors is a successful strategy for converting select radiosurgery-ineligible patients to radiosurgery candidates. Absence of preoperative SS, NE, and MF predicts for successful conversion. [ABSTRACT FROM AUTHOR]

Purpose: The optic chiasm is an essential structure located at the skull base that stirred over time the curiosity of anatomists, who became more and more interested in its structure and function. Through centuries, the optic chiasm was viewed as a vessel crossing, a way of transporting tears secreted by the brain to the eye, integrating images, or responsible for coordinated eye movements. The paper aims to overview the history of understanding the optic chiasm from the beginnings of antiquity to the twentieth century. Methods: We reviewed the literature and studied all the historical sources on optic chiasm and eyes in the works of ancient, medieval, Renaissance authors, and the seventeenth to nineteenth century works. Results: The optic chiasm is a structure that fascinated ancient anatomists and made them develop various theories on its function. In terms of function, the optic chiasm had a history based more on speculation, the seventeenth century bringing its first understanding and reaching the peak in the nineteenth century with the understanding of the anatomical structure of the chiasm and its role in the visual process. Conclusion: The history of the optic chiasm is a fascinating time travel displaying the conceptual transformations that have been made in anatomy and medicine by our forerunners. [ABSTRACT FROM AUTHOR]

Introduction: 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. Methods: In this study, we report a case of a 29-year-old female with bitemporal hemianopia due to a cystic intrasellar tumor. The patient underwent surgical decompression of the lesion, which was found to be an intrachiasmatic abscess. Results: The histologic findings were consistent with IgG4 hypophysitis. Conclusion: This rare clinical presentation suggests that in case of a disproportionate degree of visual impairment in relation to the size of the lesion, suspicion should lead to an intrachiasmatic lesion. [ABSTRACT FROM AUTHOR]

Background: One of the main drawbacks in the surgery of large craniopharyngiomas is the presence of a prefixed optic chiasm. Our main objective in this study is to compare the predictive value of the optic nerve length and optic chiasm location on large craniopharyngiomas' extent of resection. Method: We retrospectively studied 21 consecutive patients with large craniopharyngiomas who underwent tumor resection through the trans-eyebrow supraorbital approach. Clinical and radiological findings on preoperative MRI were recorded, including the optic chiasm location classified as prefixed, postfixed or normal. We registered the optic nerve length measured intraoperatively prior to tumor removal and confirmed the measurements on preoperative MRI. Using a linear regression model, we calculated a prediction formula of the percentage of the extent of resection as a function of optic nerve length. Results: On preoperative MRI, 15 patients were considered to have an optic chiasm in a normal location, 3 cases had a prefixed chiasm, and the remaining 3 had a postfixed chiasm. In the group with normal optic chiasm location, a wide range of percentage of extent of resection was observed (75-100%). The percentage of extent of resection of large craniopharyngiomas was observed to be dependent on the optic nerve length in a linear regression model ( p < 0.0001). According to this model in the normal optic chiasm location group, we obtained an 87% resection in 9-mm optic nerve length patients, a 90.5% resection in 10-mm optic nerve length patients and 100% resection in 11-mm optic nerve length patients. Conclusions: Optic chiasm location provides useful information to predict the percentage of resection in both prefixed and postfixed chiasm patients but not in the normal optic chiasm location group. Optic nerve length was proven to provide a more accurate way to predict the percentage of resection than the optic chiasm location in the normal optic chiasm location group. [ABSTRACT FROM AUTHOR]

Optic pathway glioma (OPG) encompasses a spectrum of findings ranging from lesions confined to the optic nerve only, lesions affecting the optic chiasm and hypothalamus, and lesions with diffuse involvement of a large part of the optic pathway and neighboring structures. The majority of pediatric low-grade astrocytomas in the optic/chiasmatic region are typical pilocytic astrocytoma. The rest of them (10 %) may be other gliomas such as fibrillary pilomyxoid astrocytoma (grade 2 WHO). The postsurgical local recurrence rate of 55 to 76 % has been reported in some histological subtypes such as pilomyxoid astrocytoma (grade 2). Performing a prechiasmatic transection might offer a new surgical option to avoid further tumor growth toward the chiasm in the optic nerve glioma with predominantly orbital manifestations. In this retrospective study, four patients (three children, two without neurofibromatosis type 1 (NF1), and one with NF1 and one adult without NF1) with optic nerve glioma without involvement of the chiasm but blindness, disfiguring proptosis, and pain of the affected eye were included. The surgical approach was performed as a combined approach from pterional extradural and intradural. Without any exceptions, vision of the contralateral eye could be preserved and did not show any deterioration after surgery or during the follow-up time between 17 and 106 months. Furthermore, in all patients, gross total tumor resection could be achieved. During follow-up observation in all patients, no further tumor progress or recurrences could be observed. None of the patients were treated postoperatively by radiotherapy or chemotherapy. Prechiasmatic transection of the optic nerve in optic nerve glioma without affecting the chiasm might offer a surgical treatment option to control tumor growth and to preserve vision of the contralateral eye. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this study was to measure the angle ( Interneural angle, INA) between intracranial segments of optic nerves (ISON), and to look for any relation between it and the relative anteroposterior location (RAPL) of the optic chiasm (OC)-viz. prefixed, normofixed and postfixed. Methods: The sample comprised of 100 autopsy specimens from South Indian population. INA was measured using software-aided processing of digital photographs. Length of the ISON was measured on each side using Vernier calipers. RAPL of the OC was noted during dissection. These were analysed with statistical methods. Results: RAPL of OC was found to be prefixed in 24 %, normofixed in 65 % and postfixed in 11 %. The INA had an overall mean of 69.9° (SD 9.29°). ANOVA confirmed statistically significant difference in INA among different groups; the corresponding mean value for the group was as follows: 79.61° (prefixed), 68.10° (normofixed) and 59.48° (postfixed). ROC curve was plotted for the use of various 'cut off' values of INA to 'diagnose' prefixed OC; an INA ≥71.4° was seen to diagnostically correlate with prefixed OC with 83.3 % sensitivity and 75 % specificity. Conclusions: The INA is wider when OC is prefixed, intermediate when normofixed and narrowed when postfixed. This observation throws light on the possibility of using INA as a marker of RAPL of OC. As INA can be measured in axial MRI sections, it can be used in differentiation of the cases with prefixed OC from others during pre-operative work up for pituitary surgeries and to identify individuals 'at risk' during subfrontal approach for pituitary lesions. [ABSTRACT FROM AUTHOR]

Background and purpose: Sparing of the organs at risk is one of the primary end-points of radiotherapy. The effects of organ-at-risk delineation on the dosimetric parameters can be critical and can influence treatment planning and outcomes. The aim of our study was to provide anatomical boundaries for the identification and delineation of the following critical organs at risk in the head and neck district: brachial plexus, cochlea, pharyngeal constrictor muscles and optic chiasm. Patients and methods: One patient was initially selected to elaborate our atlas. This patient was subjected to a planning computed tomography of the brain and head and neck district; axial images of 3-mm thickness at 3-mm intervals were obtained. In the same set-up a magnetic resonance imaging study was also performed. The obtained images were fused based on anatomical landmarks and used by a radiation oncologist, supported by a neuroradiologist, to provide anatomo-radiological limits for the identification of the brachial plexus, cochlea, pharyngeal constrictor muscles and optic chiasm. These limits were further verified on three consecutive patients. Results: A computed tomography-based atlas was developed with definition of cranial, caudal, medial, lateral, anterior and posterior limits for each organ considered. Conclusions: This study allows improvement of definitions of anatomic boundaries for the brachial plexus, cochlea, pharyngeal constrictor muscles and optic chiasm. Our multidisciplinary experience led to the production of an institutional reference tool that could represent a useful aid for radiation oncologists in clinical practice. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the clinical significance of optic chiasmal edema (OCE) observed in hydrocephalus. Materials and methods: Twenty patients with obstructive hydrocephalus and eight patients with communicating hydrocephalus were recruited. We classified both groups into OCE-positive and negative subgroups on three-dimensional T2-weighted images. In the obstructive hydrocephalus group, the pre- and postoperative periventricular hyperintensity (PVH) grade, Evans index, and third ventricle diameter were compared between the subgroups. The visual disturbances were reviewed in the medical records. Results: Eleven obstructive hydrocephalus patients (55 %) had OCE, while none of communicating hydrocephalus patients did. OCE was improved in all patients postoperatively. Preoperative PVH grade was significantly higher in the OCE-positive subgroup ( p < 0.01). There were no statistically significant differences in the other indices. Visual disturbances were observed in two OCE-negative patients alone. Conclusion: OCE is a reversible finding frequently observed in obstructive hydrocephalus and may not be associated with visual disturbances. [ABSTRACT FROM AUTHOR]

Background: In this article, we report on the technique of placing fat in between a sellar or parasellar neoplasm and the optic chiasm to possibly protect the optic chiasm from sequelae of radiation. Methods: A review was performed on three patients, each of whom had planned subtotal resection with fat placed near their optic chiasm to facilitate future radiosurgery. Results: Follow-up on our three patients varied from 6 months to 3 years post-stereotactic radiosurgery. The fat remained stable and in place. The tumors either remained stable or reduced in size. No infections, postoperative marker dependent neurological complications or unusual symptoms were encountered. Conclusions: Placement of fat between a parasellar neoplasm and the optic chiasm appears to be a safe approach to help define the tumor chiasm space, helping to facilitate radiosurgery. Future experience is warranted to determine the efficacy of this technique. [ABSTRACT FROM AUTHOR]

Purpose: This study was conducted to characterize topographic variations of the optic chiasm (OC) and the pituitary stalk (PS) in situ based on MR images. Methods: Normal T2-weighted midsagittal MR images were obtained in 157 children and 323 adults. The height of OC (PC) and the inclination angle of PS (PS-AP angle) were measured in each case. All chiasms were classified into prefixed, normal and postfixed types, and low, medium and high types, respectively. All stalks were performed classification (prefixed, centered and postfixed PS) and grading (Grade 1-3 according to the relationship between PS and the dorsum sellae), respectively. Results: PC averaged 4.33 ± 1.59 mm. Adults had a greater PC ( P = 0.023) than children. There were 80 (16.7 %) prefixed, 354 (73.8 %) normal and 46 (9.6 %) postfixed chiasms, and 112 (23.3 %), 295 (61.5 %) and 73 (15.2 %) cases with low, medium and high OC, respectively. High OC was more frequent in adults than in children ( P = 0.001). The mean PS-AP angle of the whole group was 59.47 ± 8.62º. Children had a greater PS-AP angle than adults ( P = 0.012). Adults had a greater percentage of postfixed ( P = 0.000) and grade 3 ( P = 0.000) PS than children, whereas centered ( P = 0.002) and grade 1 ( P = 0.001) PS were more prevalent in children than in adults. Conclusions: The classifications of OC and PS based on MR images reflect the topographic variations of their real position in vivo. It would be helpful to identify and characterize the anomalies involving OC and PS and understand the anatomical and physiological influence in pathological situations. [ABSTRACT FROM AUTHOR]

Chiasmal dysfunction produces a characteristic clinical picture, regardless of the mechanism. In most cases a compressive lesion is the cause. In occasional cases, however, no such extrinsic mass is found and other possible etiologies must be explored. In some of these cases, the pathologic process is identifiable with appropriate neuroimaging. For example, inflammation, infiltrative tumors, and radiation necrosis produce intrinsic chiasmal enhancement. Chiasmal ischemia may require specialized magnetic resonance (MR) sequences for diagnosis. Chiasmal hemorrhage, trauma and chiasmal herniation typically produce distinctive changes on noncontrasted imaging. In cases of metabolic insult, either toxic or hereditary, radiographic changes are typically absent. In each of these, the correct diagnosis can usually be made with a combination of clinical and radiographic features. [ABSTRACT FROM AUTHOR]

In this study we explored possible applications of the da Vinci system in approaching the skull base at optic chiasm level on two cryopreserved cadavers, using an entirely transoral robotic technique (TORS). We used a standard 12 mm endoscopy and 8 mm terminals. Bone drilling was performed manually. The da Vinci system is equipped with very good illumination and 3D viewing, thus providing excellent vision and great maneuverability even in the less accessible areas of the skull. Our experience demonstrates that an entirely transoral skull base robotic approach to this complex anatomical region has many advantages as compared to traditional techniques. [ABSTRACT FROM AUTHOR]

Background: The relationship between the optic apparatus and the skull base is important during approaches near the sella turcica. One relationship that dictates which approach is taken is whether the optic chiasm is prefixed or postfixed or in a 'normal' location, (centered over the diaphragma sella). The relationship between the position of the chiasm and the angulation of the pituitary stalk has not been investigated. Methods: Forty adult cadavers without intracranial pathology were dissected and parasagitally hemisected lateral to the sella turcica. The angulations between the pre- and postfixed and normal chiasm and the pituitary stalk were evaluated under magnification. Additionally, 50 MRIs performed among patients evaluating headache were analyzed for these relationships. Results: For cadavers, the chiasm was prefixed in 7.5 % ( n = 3), normal in 85 % ( n = 34), and postfixed in 7.5 % ( n = 3). On imaging, the chiasm was prefixed in 4 % ( n = 2), normal in 88 % ( n = 44), and postfixed in 8 % ( n = 4). For all, the relation between the type of chiasm and the pituitary stalk was more often ( p < 0.05) 90° or greater for prefixed chiasmata and acute angles for normal or postfixed chiasmata. Conclusions: These data may assist skull base surgeons when approaching pathology near the optic chiasm and pituitary stalk. [ABSTRACT FROM AUTHOR]

Immunohistochemical studies addressed the distribution of α-tubulin microtubules in rat forebrain structures. Non-uniform staining was seen with the reaction for α-tubulin. High immunoreactivity was detected in the cingulate and piriform cortex, olfactory bulbs, and the optic chiasma. The weakest immunohistochemical reactions were seen in the corpus striatum, the superficial layers of the septum, the cingulum, and structures around the third ventricle. Immunoreactivity in neurons was clearly apparent at the periphery of the perikaryon and in the apical dendrite. It is suggested that the intensity of the immunohistochemical reaction for α-tubulin may reflect the functional state of neurons. [ABSTRACT FROM AUTHOR]

Masses beneath the chiasm usually cause superiorly denser field defects. This report showed two very rare field defects related with infrachiasmal compression, monocular inferotemporal quadrantanopia in Case 1 and monocular temporal and inferonasal field defect in Case 2. We presume that these very rare visual field defects might be caused by a compression between the mass and the anterior cerebral artery. The detailed anatomic relations of the compressed optic chiasm between the mass and the anterior cerebral artery are best revealed on a coronal T2-weighted image with a section thickness of 3 mm or less, and a routine brain MRI with a larger section thickness may not reveal such findings. Therefore, appropriate resolutions and a meticulous review of MR imaging may provide the clues to the etiology of these visual defects. In conclusion, the clinician should be aware that such unusual visual field defects could also be caused by a compression between the mass and anterior cerebral arteries. [ABSTRACT FROM AUTHOR]

Pituitary adenomas can expand upward through the foramen diaphragma sellae (FDS), compress the visual pathways on the suprasellar region, and cause diverse visual defects. However, the relationship between the FDS and the visual pathway has not been thoroughly clarified. This study was thus performed to determine the topographic relationship between these two structures. One hundred heads of adult cadavers were examined in this study. The FDS was classified into five types (Ia, Ib, Ic, II, and III) according to its location relative to the four parts of suprasellar region of the visual pathways. The midpoint of the optic chiasm (OC) was located on the midline passing through the crista galli in 70% of cases, but to the left and right sides of the midline in 9 and 21% of cases, respectively. The FDS was completely covered by OC in 30% of the cases, but it was partly seen superiorly in 70%. The pituitary infundibulum passed mainly through the center middle or posterior middle part of nine partitions of the FDS. The horizontal and vertical diameters of the foramen were 7.9 ± 2.0 and 7.6 ± 1.9 mm, respectively. The length of the optic nerve was 9.7 ± 1.9 mm on the left side and 9.5 ± 1.9 mm on the right side. The angle between the optic nerve and the midline was 34.5° ± 5.7° on the left side and 36.0° ± 6.3° on the right side. The results of this study are expected to further the current knowledge of the topographic anatomy on suprasellar structures. [ABSTRACT FROM AUTHOR]

This study described a 23-year experience in the treatment of children with pilocytic astrocytomas (piloA) with the aim of identifying putative clinical, histopathological, and/or immunohistochemical features that could be related to the outcome of these patients. Clinical data of 31 patients under 18 years of age with piloA were obtained from 1984 to 2006. The mean age at the time of surgery was 7.8 ± 4.2 years (1 to 17 years), and the mean follow-up was 5.7 ± 5.4 years (1 to 20 years). The most common site of tumor formation was the cerebellum (17), followed by brainstem (4), optic chiasmatic hypothalamic region (4), cerebral hemisphere (3), cervical spinal cord (2), and optic nerve (1). Gross total resection (GTR) was achieved in 23 (74.1%), mainly in those with tumors located in the cerebellum and cerebral hemispheres ( P = 0.02). The global mortality rate was 6.4%. Nine patients were reoperated. Rosenthal fibers, eosinophilic granular bodies, microvascular proliferation, and lymphocytic infiltration were observed in most cases. The mean Ki-67LI was 4.4 ± 4.5%. In all cases, Gal-3 expression in tumor cells was observed with variable staining pattern. Aside from GTR, no other clinical, histopathological, or immunohistochemical features were found to be related to the prognosis. We postulate that strict follow-up is recommended if piloA is associated with high mitotic activity/Ki67-LI, or if GTR cannot be achieved at surgery. Tumor recurrence or progression of the residual lesion should be strictly observed. In some aspects, childhood piloA remains an enigmatic tumor. [ABSTRACT FROM AUTHOR]

Perturbations of optic flow can induce changes in walking speed since subjects modulate their speed with respect to the speed perceived from optic flow. The purpose of this study was to examine the effects of optic flow on steady-state as well as on non steady-state locomotion, i.e. on spontaneous overground walk-to-run transitions (WRT) during which subjects were able to accelerate in their preferred way. In this experiment, while subjects moved along a specially constructed hallway, a series of stripes projected on the side walls and ceiling were made to move backward (against the locomotion direction) at an absolute speed of −2 m s−1 (condition B), or to move forward at an absolute speed of +2 m s−1 (condition F), or to remain stationary (condition C). While condition B and condition F entailed a decrease and an increase in preferred walking speed, respectively, the spatiotemporal characteristics of the spontaneous walking acceleration prior to reaching WRT were not influenced by modified visual information. However, backward moving stripes induced a smaller speed increase when making the actual transition to running. As such, running speeds after making the WRT were lower in condition B. These results indicate that the walking acceleration prior to reaching the WRT is more robust against visual perturbations compared to walking at preferred walking speed. This could be due to a higher contribution from spinal control during the walking acceleration phase. However, the finding that subjects started to run at a lower running speed when experiencing an approaching optic flow faster than locomotion speed shows that the actual realization of the WRT is not totally independent of external cues. [ABSTRACT FROM AUTHOR]

Solitary fibrous tumor (SFT) is rarely located in the central nervous system, and sella turcica involvement was reported in only two patients. We report the case of a 28-year-old man with a SFT of the sella turcica mimicking a pituitary nonfunctioning macroadenoma. He presented with optic nerve compression caused by a heterogeneous tumor located in the sellar and suprasellar area. At surgery, the tumor was hard and infiltrated the sellar diaphragm, so that resection resulted in a cerebrospinal fluid fistula. His postoperative course was also complicated by complete central diabetes insipidus, hypopituitarism, and two episodes of meningitis. After surgical resection, the diagnosis of SFT was reached on the basis of histological and immunohistochemical studies. He was discharged after 49 days. Ten months after surgery, he was clinically well, and magnetic resonance images showed no evidence of residual or recurrent tumor. SFT should be considered in the differential diagnosis of sellar and parasellar tumors. [ABSTRACT FROM AUTHOR]

At the optic chiasm axons make a key binary decision either to cross the chiasmal midline to innervate the contralateral optic tract or to remain uncrossed and innervate the ipsilateral optic tract. In rodents, midline interactions between axons from the two eyes are critical for normal chiasm development. When one eye is removed early in development the hemispheric projections from the remaining eye are disrupted, increasing the crossed projection at the expense of the uncrossed. This is similar to the abnormal decussation pattern seen in albinos. The decussation pattern in marsupials, however, is markedly different. Early eye removal in the marsupial has no impact on projections from the remaining eye. These differences are related to the location of the uncrossed projection through the chiasm. In rodents, axons that will form the uncrossed projection approach the chiasmal midline, while in marsupials they remain segregated laterally through the chiasm. Histological analysis of the optic chiasm in man provides anatomical evidence to suggest that, unlike in rodents, uncrossed axons are confined laterally from the optic nerve through to the optic tract and do not mix in each hemi-chiasm. This is a pattern similar to that found in marsupials. Electrophysiological evidence in human anophthalmics shows that the failure of one eye to develop in man has no impact on the hemispheric projections from the remaining eye. This strongly suggests that the mechanisms regulating chiasmal development in man differ from those in rodents, but may be similar to marsupials. This implies that optic chiasm formation in rodents and ferrets is not common to placental mammals in general.Eye (2007) 21, 1264–1270. doi:10.1038/sj.eye.6702839 [ABSTRACT FROM AUTHOR]

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Aim. To study a possible relationship between dimensions of the optic chiasm and extent of visual field impairment in patients with pituitary adenoma. Methods. Pre-operative magnetic resonance (MR) scans and Goldmann perimetry charts of patients having undergone resection of a pituitary adenoma were retrieved. Area of the chiasm ( A chiasm), central height of the chiasm ( H chiasm), and perpendicular height of tumour ( H tumour) were measured on coronal images using standard software. Visual fields were quantified by subdividing the central 30 degrees of vision into 72 subunits each bounded by 15 degree meridians and 10 degree isoptres. Results. Nineteen patients were included in this study. There was a strong statistically significant linear correlation between H chiasm and bitemporal (Pearson’s coefficient r = −0.69, p = 0.001), binocular ( r = −0.63, p = 0.004) and binasal ( r = −0.52, p = 0.01) central field loss. A similar relationship was observed between H tumour and bitemporal ( r = 0.55, p = 0.015) and binocular ( r = 0.46, p = 0.05) central field loss. Conclusion. Height of the chiasm and height of the tumour can be used to predict extent of central visual impairment. [ABSTRACT FROM AUTHOR]

The anterior optic pathways are rarely affected by vascular malformations. In a meticulous literature review, 42 published cases of patients with vascular malformations within optic nerves, chiasma and/or optic tract were found, 30 of them being diagnosed as cavernous haemangiomas. All of them suffered from visual disturbances; in 38.1% previous symptoms had occurred. Surgical treatment resulted in major improvement in most patients. We include a further patient with a cavernous haemangioma of the optic chiasma and left optic tract who presented with an acute defect of the right visual field and severe retro-orbital pain. We succeeded in total excision of the malformation via a neuronavigationally guided approach. In the postoperative course, vision of our patient improved immediately and was found to be completely normal three months after the surgical intervention. Considering our patient and the published cases in the literature, we are of the opinion that microsurgical excision is a safe and efficient treatment for these rare pathologies. [ABSTRACT FROM AUTHOR]

We have determined whether chondroitin sulphate (CS) glycosaminoglycans are sufficient to direct a selective inhibition of neurite growth from ventral temporal (VT) but not from dorsal nasal (DN) retina in mouse embryos; this may underlie the formation of axon divergence in the optic chiasm. Explants from the retinal region of embryonic day-14 mouse were grown on a laminin–polylysine substrate near to a circular spot coated with CS. In control cultures, in which no CS was added to the spot, both VT and DN retinal neurites grew extensively into the coated territory. When presented with spots coated with 10 mg/ml CS, neurite growth from the VT retina into the CS territory was dramatically reduced but that from the DN retina was not significantly affected. The selective inhibition to VT neurites was completely abolished by treatment with chondroitinase ABC, indicating a specific contribution of CS glycosaminoglycan in this regionally specific behaviour. This differential behaviour was not observed in explants presented with a lower or higher concentration of CS or in explants grown on substrate coated with a different laminin concentration. Thus, a critical ratio of CS to laminin seems to be essential to induce this differential behaviour in retinal neurites towards contact with CS. Furthermore, this behavior was not observed in explants cultured directly on a CS-rich substrate, suggesting that contact with growth-promoting molecules is necessary for the selective responses of retinal neurites during subsequent contact with CS. We concluded that CS glycosaminoglycan is sufficient to drive selective inhibition of VT but not DN neurites and that, together with a critical combination of growth-promoting factors, it may control the axon divergence process at the mouse optic chiasm. [ABSTRACT FROM AUTHOR]

Five cases of pilomyxoid astrocytoma (PmA) characterized by a monophasic pattern with a myxoid background were selected for a clinicopathological study from 23 cases previously diagnosed as pilocytic astrocytoma (PA). All PmA patients were either infants or young children (mean age 2.1 years), and all tumors were located in the optic chiasm/hypothalamus region. All cases received chemotherapy, which reduced tumor size, and the location of the tumor became confined to the optic chiasm. In two cases, tumor recurrence occurred 3 and 7 years after chemotherapy. Histology of the recurrent tumors showed the biphasic pattern of classical PA. Hence, we conclude that PmA might be an infantile form of PA and speculate that a subset of PmA in the optic pathway/hypothalamus originates from the optic chiasm, possibly derived from radial glia existing in the embryonic optic chiasm. [ABSTRACT FROM AUTHOR]

The suprachiasmatic nucleus (SCN) of the hypothalamus is a dominant circadian pacemaker in the mammalian brain controlling the rest-activity cycle and a series of physiological and endocrine functions to provide a foundation for the successful elaboration of adaptive sleep and waking behavior. The SCN is anatomically and functionally organized into two subdivisions: (1) a core that lies adjacent to the optic chiasm, comprises predominantly neurons producing vasoactive intestinal polypeptide (VIP) or gastrin-releasing peptide (GRP) colocalized with GABA and receives dense visual and midbrain raphe afferents, and (2) a shell that surrounds the core, contains a large population of arginine vasopressin (AVP)-producing neurons in its dorsomedial portion, and a smaller population of calretinin (CAR)-producing neurons dorsally and laterally, colocalized with GABA, and receives input from non-visual cortical and subcortical regions. In this paper, we present a detailed quantitative analysis of the organization of the SCN core and shell in the rat and place this in the context of the functional significance of the subdivisions in the circadian control of regulatory systems. [ABSTRACT FROM AUTHOR]

Summary Objective. Location of anterior optic pathways in sellar and parasellar tumours was preoperatively evaluated, by use of heavily T2 weighted MR images. Methods. Heavily T2 and conventional T1 weighted images were studied in 20 patients with sellar and parasellar tumours who underwent craniotomy. Pathology revealed pituitary adenoma in 5 patients, craniopharyngioma in 8 and parasellar meningioma in 7. Maximum sizes ranged from 15 mm to 58 mm. Sequence parameters of TR/TE for heavily T2 weighted and T1 weighted images were 5800/220 msec and 600/20 msec, respectively, and slice thickness was 3 mm for both. Results. The anterior optic pathway was detected in 95% on heavily T2 weighted images and 50% on T1 weighted images. All preoperative heavily T2 weighted images were compatible with operative findings. The optic chiasms were most commonly supero-posterior in pituitary adenomas, anterior (prefixed) in craniopharyngiomas and posterior in meningiomas. The optic nerves were commonly located superior or lateral to the tumours. However, parasellar meningiomas, off the midline, revealed the optic nerves in various locations, depending on the tumour origin. In such tumours, heavily T2 weighted images provided surgical information on the width of the working space through prechiasmal and/or optico-carotid spaces in the pterional approach. Spatial relation of the tumours to the lamina terminalis, anterior commissure and anterior communicating artery complex was clearly shown in craniopharyngioma patients, who underwent the anterior interhemispheric approach. Conclusion. Heavily T2 weighted MR images are useful in determining the location of optic pathways and surgical approach and in individual prediction of the anatomy for even large sellar and parasellar tumours. [ABSTRACT FROM AUTHOR]

The patterns of cell death and of macrophages were investigated in the forebrain and eyes of the tree shrew Tupaia belangeri during five phases of optic cup formation. Seventeen embryos were studied. Three- dimensional reconstructions were made from one embryo of each phase. In phase 1 (V-shaped optic evagination) a midline band of cell death passes through the closing anterior neuroporus. From phases 2 (optic vesicle) to 5 (far-advanced invagination) the midline band of cell death extends in the dorsal wall of the forebrain to its rostral pole and, further, into its ventral wall. At the approximate future position of the optic chiasm this ventral pycnotic area, predicted but so far unidentified by others, is connected to a previously described second band of cell death passing through the optic anlagen. Recently, evidence has been presented that chicken embryos develop holoprosencephaly and cyclopia when ventral forebrain structures are lost secondary to experimentally induced apoptosis. Our findings in Tupaia suggest that, in cases of spontaneous malformations of this kind, such an atypical pycnotic area in the ventral telencephalon might result from the defective regulation of cell death processes during optic cup formation. In the forebrain and eyes of Tupaia, the occurrence of bands of cell death precedes the appearance of the earliest intraepithelial macrophages. From phase 3 (onset of invagination) onwards almost all of them are concentrated along the band of cell death. [ABSTRACT FROM AUTHOR]

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Two parallel visual systems, the magnocellular (M) and parvocellular (P) pathways, originate from different types of retinal ganglion cells, and are known to be segregated in different portions of the pregeniculate visual pathways. Their relative contribution to two main cortical streams, dorsal and ventral, is still under discussion, but it is reasonable to suppose that selective damage to the M or P subcortical system might interfere with specific aspects of processing within one or the other cortical system. Using two different apparent-motion tasks, we compared the performance of patients affected by compression of the ventral part of the pregeniculate visual pathways with that of normal controls. In the first task, observers detected small displacements of a low-contrast vertical bar, while in the second task they estimated the visible persistence of moving dots. In the first task, patients were impaired with parafoveal displays, especially in the temporal portion of the visual field. In the second task, patients showed reduced suppression of visible persistence at long, but not at short, exposure durations. Three considerations support the hypothesis that these results represent a selective impairment of the M system. First, M axons are more likely to suffer from compression, particularly in the case of a mass growing from below since they are known to occupy a ventral subpial position in the optic chiasm and tract. Second, the performance of patients with a ventral compression is consistent with the characteristics of the response properties of P ganglion cells, which have previously been shown to exhibit elevated and unmodulated thresholds for displacement detection in the macaque monkey. Third, such patients are less sensitive to the inhibitory signals that suppress visible persistence, which probably originate in the M system. [ABSTRACT FROM AUTHOR]

Abstract. We analyze the dynamic properties of a neural network model for on-off spiking neurons recorded in the first optic chiasm of the fly visual system. The model consists of two parallel pathways and three sequential processing stages. The first stage models photoreceptors. At the second stage, the signal is segregated into on- and off-pathways. These pathways are proposed to correspond to two populations of amacrine cells. At the third stage, the on- and off-pathways converge to on-off' neurons. Furthermore, according to the model, on-off neurons interact via recurrent connections. This stage is proposed to correspond to lamina L4 neurons. In response to luminance increments and decrements, the model exhibits a three-component response and suggests pathways for each of the components. When stimulated by a train of pulses, the model exhibits fast adaptation for frequencies higher than about 5 Hz. Furthermore, adaptation to on- and off-pulses occurs independently. When the frequency of stimulation is reduced, the unit recovers rapidly from its adapted state. The temporal modulation transfer function has its peak around 7 Hz. The phase characteristics show a phase lead for low temporal frequencies changing to a phase lag for high frequencies. These model predictions are compared with data from Jansonius and van Hateren (1991). [ABSTRACT FROM AUTHOR]

Pax genes are expressed in specific patterns in the nervous system during development and in the adult. Recent findings suggest a link between the expression of Pax-2 and axonal guidance. Mice with a targeted deletion of Pax-2 are an excellent tool for studying axonal pathfinding at the molecular level, especially with respect to the optic chiasm. The date reviewed here suggest that Pax-2 regulates the expression of surface molecules involved in contact attraction and that the mutual regulation of the expression of Pax-2 and the Sonic hedgehog gene is of importance in the formation of the chiasm region. [ABSTRACT FROM AUTHOR]

The effect of transsphenoidal hypophysectomy is presented in 60 patients with visual impairment due to a pituitary adenoma, derived from a total series of 194 patients. The preoperative visual acuity and visual fields were compared with those one year after operation. The visual field loss was estimated using a semi-quantitative method. Seventy-two eyes had diminished visual acuity, and this improved in 45 eyes (63%). Visual field loss was present in 102 eyes and this improved in 71 eyes (70%). Improvement of either visual acuity and/or visual field was found in 84 eyes (78%). In 16 patients (27%) vision became normal after operation. Improvement of the visual acuity was usually accompanied by an improvement in the visual fields. [ABSTRACT FROM AUTHOR]

Intra-ocular deposition of horseradish peroxidase was used to visualize optic tract projections in normal and congenitally monophthalmic catfish and Xenopus. In neither species was evidence for an increased ipsilateral visual component found in congenitally one-eyed specimens. This indicates that competition between axons from both eyes is not an important mechanism for fiber distribution in the chiasm during ontogeny. Furthermore, it suggests that enhanced ipsilateral components, previously noted in unilaterally enucleated fish and anurans, are caused by debris of degenerated axons. [ABSTRACT FROM AUTHOR]

We studied the role of the transcallosal pathway in stereopsis by measuring binocular and monocular depth perception in two cats that had undergone section of the optic chiasm at the age of 21 d. To ensure that the surgery did not impair vision to the extent that depth perception could not be evaluated, visual acuity and visual fields were also measured. In both of the chiasm-sectioned animals the visual fields were reduced and the visual acuity was substantially lower than in normal cats, with a maximum of about 2 cyc deg. Binocular depth thresholds of the chiasm-sectioned cats were worse than those of the normal cat but were better than their own monocular thresholds. These results suggest that the chiasm-sectioned animals were still able to use binocular cues to judge depth and indicate that the indirect pathway through the corpus callosum is sufficient to mediate binocular depth perception. [ABSTRACT FROM AUTHOR]

We present three cases of suprasellar cavernous haemangioma with characteristic high-field MRI features. Clinical, CT and MRI data were retrospectively analysed. The patients had progressive neurological, endocrinological and visual complaints. In the three cases CT revealed a high-density suprasellar mass. In all cases the combination of a reticulated core of mized signal intensity with a surrounding rim of decreased signal on T1- and T2-weighted MRI scans suggested the presence of a cavernous haemangioma. Two patients underwent surgical biopsy after their first MRI examination. Cavernous haemangiomas located in the suprasellar area may show typical MRI features. [ABSTRACT FROM AUTHOR]

Visual disturbance in hydrocephalus is typically due to raised intracranial pressure. We describe a patient who presented with marked loss of peripheral visual fields, but without features suggestive of raised intracranial pressure. MR scan showed an enlarged third ventricle and a downward displacement of the optic chiasm, Chiari II malformation. These radiological changes and the visual field deficits reversed after endoscopic third ventriculostomy and foramen magnum decompression. These observations support the view that the treatment of the hydrocephalus in such patients can help to reverse the change in the position of the optic chiasm and the visual field deficits. [ABSTRACT FROM AUTHOR]