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To assess the sonographic visualization of the fetal optic chiasm (OC) and optic tracts (OTs), establish mid-trimester reference values, and assess the relationship between OC and OT dimensions and cavum septum pellucidum (CSP) measurements.This prospective cross-sectional study included 154 morphologically normal fetuses between 19 and 23 weeks of gestation. The diameters of the fetal OC and OTs were measured using two-dimensional transabdominal ultrasound in a transventricular axial section angled approximately 20–40° caudally. CSP length as well as anterior, middle, and posterior widths were measured by placing the cursor on the inner surfaces in the transventricular section. The average CSP width was included in the analysis.The OC and OTs were successfully visualized in 109 fetuses and included in the analysis. Visualization success in transabdominal axial sections at 19–23 weeks was 70.8 %, with high intraobserver and interobserver reproducibility. Additionally, visualization rates were higher in advanced gestational weeks and in fetuses with breech presentation (p=0.007 and p=0.017, respectively). OC and OT dimensions were positively correlated with CSP length and width, biparietal diameter (BPD), head circumference (HC), and gestational age (p<0.05, for all).The OC and OTs were successfully visualized transabdominally in axial sections with high intraobserver and interobserver reproducibility. Additionally, OC and OT dimensions were positively correlated with gestational age, as well as with BPD, HC, and CSP measurements. [ABSTRACT FROM AUTHOR]

Bitemporal hemianopia typically results from compression of the optic chiasm by sellar, suprasellar, or chiasmal lesions. Most of the cases of bitemporal hemianopia are secondary to pituitary masses. Defects in the temporal half of the visual field that mimic those that are caused by such pituitary or chiasmal lesions are known as bitemporal “pseudohemianopia” and involve orbital pathology. Tilted disc syndrome is an eye anomaly that may result in bitemporal visual field deficits similar to those that are caused by extrinsic or intrinsic mass effect on the optic chiasm. We report an incidentally found tilted disc syndrome in a patient with a history of surgically treated high myopia and the symptoms of  bilateral, gradual vision loss.

The compression of the visual pathway is associated with structural retinal changes due to retrograde neurodegeneration. It was brought into question whether visual pathway compression is also associated with retinal vascular changes as assessed by optical coherence tomography angiography (OCT-A). The objective of this review is to discuss the role of OCT-A in the evaluation of patients with tumours of the sellar, parasellar, and retrochiasmal regions. The reported OCT-A parameters were the vessel densities of radial peripapillary capillary network, macular superficial vascular plexus and/or macular deep vascular complex. Optic nerve and macular OCT-A parameters were impaired in patients versus controls. These changes were associated with altered structural OCT parameters and visual field defects. OCT-A could be considered a marker of neurodegeneration in addition to structural OCT, and it has the potential to become a visual prognostic tool in patients with visual pathway compression. [ABSTRACT FROM AUTHOR]

Introduction: Optic nerve and chiasm hemangioblastomas are rare tumors, occurring sporadically or in the context of von Hippel-Lindau (VHL) disease. They have only been portrayed in isolated case reports and small cohorts. Their natural history and therapeutic strategies are only scarcely described. To better characterize these rare tumors, we retrospectively analyzed an optic nerve and chiasm hemangioblastoma series of 12 VHL patients. By combining our own experience to a review of all known cases in literature, we intended to create treatment recommendations for optic nerve and chiasm hemangioblastomas in VHL patients. Methods: We reviewed two electronic databases in the hospitals of our senior authors, searching for VHL patients with optic nerve or chiasm hemangioblastomas. Clinical data were summarized. Tumor size and growth rate were measured on contrast enhanced MRI. Comparable data were collected by literature review of all available cases in VHL patients (Pubmed, Trip, Google and Google Scholar). Results: Of 269 VHL patients, 12 had optic nerve or chiasm hemangioblastomas. In 10 of 12 patients, tumors were diagnosed upon annual ophthalmoscopic/MRI screening. Of 8 patients who were asymptomatic at diagnosis, 7 showed absent or very slow annual progression, without developing significant vision impairment. One patient developed moderate vision impairment. Two symptomatic patients suffered from rapid tumor growth and progressive vision impairment. Both underwent late-stage surgery, resulting in incomplete resection and progressive vision impairment. One patient presented with acute vision field loss. A watchful-waiting approach was adopted because the hemangioblastoma was ineligible for vision-sparing surgery. One patient developed progressive vision impairment after watchful waiting. In the literature we found 45 patient cases with 48 hemangioblastomas. Discussion: When optic nerve and chiasm hemangioblastomas are diagnosed, we suggest annual MRI follow-up as long as patients do not develop vision impairment. If tumors grow fast, threaten the contralateral eye, or if patients develop progressive vision deficiency; surgical resection must be considered because neurological impairment is irreversible, and resection of large tumors carries a higher risk of further visual decline. [ABSTRACT FROM AUTHOR]

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]

Seeing in three dimensions is a major property of the visual system in mammals. The circuit underlying this property begins in the retina, from which retinal ganglion cells (RGCs) extend to the same or opposite side of the brain. RGC axons decussate to form the optic chiasm, then grow to targets in the thalamus and midbrain, where they synapse with neurons that project to the visual cortex. Here we review the cellular and molecular mechanisms of RGC axonal growth cone guidance across or away from the midline via receptors to cues in the midline environment. We present new views on the specification of ipsi- and contralateral RGC subpopulations and factors implementing their organization in the optic tract and termination in subregions of their targets. Lastly, we describe the functional and behavioral aspects of binocular vision, focusing on the mouse, and discuss recent discoveries in the evolution of the binocular circuit. [ABSTRACT FROM AUTHOR]

Background: The position of the optic chiasm relative to surrounding structures is critical in planning surgical interventions for suprasellar lesions. This study explored the relationship between the angle of the optic chiasm and lamina terminalis (OC-LT) and the position of the optic chiasm. Methods: The study comprised 140 individuals who underwent midsagittal and axial MRI-T2 scans. The position of the optic chiasm was classified into three categories: sellar, prefixed, and postfixed. The OC-LT angle was measured in the midsagittal section. Results: The angle between OC-LT varied from 30 to 66 degrees with a mean of 46.6 degrees. The sellar position of the optic chiasm was predominant (85.2%), with smaller angles (30-39 degrees) significantly associated with a sellar chiasm location. Most cases with postfixed optic chiasm fell within a 40-49 degree angle range. Conclusions: The OC-LT angle variability can be linked to the position of the optic chiasm. Predominantly, smaller angles correlated with a sellar position of the optic chiasm, while larger angles were associated with a postfixed optic chiasm. This information is crucial for surgical planning in the suprasellar region. [ABSTRACT FROM AUTHOR]

Background: Optic neuritis (ON) is a common feature of inflammatory demyelinating diseases (IDDs) such as multiple sclerosis (MS), aquaporin 4-antibody neuromyelitis optica spectrum disorder (AQP4 + NMOSD) and myelin oligodendrocyte glycoprotein antibody–associated disease (MOGAD). However, the involvement of the optic chiasm (OC) in IDD has not been fully investigated. Aims: To examine OC differences in non-acute IDD patients with (ON+) and without ON (ON−) using magnetisation transfer ratio (MTR), to compare differences between MS, AQP4 + NMOSD and MOGAD and understand their associations with other neuro-ophthalmological markers. Methods: Twenty-eight relapsing-remitting multiple sclerosis (RRMS), 24 AQP4 + NMOSD, 28 MOGAD patients and 32 healthy controls (HCs) underwent clinical evaluation, MRI and optical coherence tomography (OCT) scan. Multivariable linear regression models were applied. Results: ON + IDD patients showed lower OC MTR than HCs (28.87 ± 4.58 vs 31.65 ± 4.93; p = 0.004). When compared with HCs, lower OC MTR was found in ON + AQP4 + NMOSD (28.55 ± 4.18 vs 31.65 ± 4.93; p = 0.020) and MOGAD (28.73 ± 4.99 vs 31.65 ± 4.93; p = 0.007) and in ON− AQP4 + NMOSD (28.37 ± 7.27 vs 31.65 ± 4.93; p = 0.035). ON+ RRMS had lower MTR than ON− RRMS (28.87 ± 4.58 vs 30.99 ± 4.76; p = 0.038). Lower OC MTR was associated with higher number of ON (regression coefficient (RC) = −1.15, 95% confidence interval (CI) = −1.819 to −0.490, p = 0.001), worse visual acuity (RC = −0.026, 95% CI = −0.041 to −0.011, p = 0.001) and lower peripapillary retinal nerve fibre layer (pRNFL) thickness (RC = 1.129, 95% CI = 0.199 to 2.059, p = 0.018) when considering the whole IDD group. Conclusion: OC microstructural damage indicates prior ON in IDD and is linked to reduced vision and thinner pRNFL. [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]

AIM: To evaluate the predictive value of superficial retinal capillary plexus (SRCP) and radial peripapillary capillary (RPC) for visual field recovery after optic cross decompression and compare them with peripapillary nerve fiber layer (pRNFL) and ganglion cell complex (GCC). METHODS: This prospective longitudinal observational study included patients with chiasmal compression due to sellar region mass scheduled for decompressive surgery. Generalized estimating equations were used to compare retinal vessel density and retinal layer thickness pre- and post-operatively and with healthy controls. Logistic regression models were used to assess the relationship between preoperative GCC, pRNFL, SRCP, and RPC parameters and visual field recovery after surgery. RESULTS: The study included 43 eyes of 24 patients and 48 eyes of 24 healthy controls. Preoperative RPC and SRCP vessel density and pRNFL and GCC thickness were lower than healthy controls and higher than postoperative values. The best predictive GCC and pRNFL models were based on the superior GCC [area under the curve (AUC)=0.866] and the tempo-inferior pRNFL (AUC=0.824), and the best predictive SRCP and RPC models were based on the nasal SRCP (AUC=0.718) and tempo-inferior RPC (AUC=0.825). There was no statistical difference in the predictive value of the superior GCC, tempo-inferior pRNFL, and tempo-inferior RPC (all P>0.05). CONCLUSION: Compression of the optic chiasm by tumors in the saddle area can reduce retinal thickness and blood perfusion. This reduction persists despite the recovery of the visual field after decompression surgery. GCC, pRNFL, and RPC can be used as sensitive predictors of visual field recovery after decompression surgery.

IntroductionOptic nerve and chiasm hemangioblastomas are rare tumors, occurring sporadically or in the context of von Hippel-Lindau (VHL) disease. They have only been portrayed in isolated case reports and small cohorts. Their natural history and therapeutic strategies are only scarcely described. To better characterize these rare tumors, we retrospectively analyzed an optic nerve and chiasm hemangioblastoma series of 12 VHL patients. By combining our own experience to a review of all known cases in literature, we intended to create treatment recommendations for optic nerve and chiasm hemangioblastomas in VHL patients.MethodsWe reviewed two electronic databases in the hospitals of our senior authors, searching for VHL patients with optic nerve or chiasm hemangioblastomas. Clinical data were summarized. Tumor size and growth rate were measured on contrast enhanced MRI. Comparable data were collected by literature review of all available cases in VHL patients (Pubmed, Trip, Google and Google Scholar).ResultsOf 269 VHL patients, 12 had optic nerve or chiasm hemangioblastomas. In 10 of 12 patients, tumors were diagnosed upon annual ophthalmoscopic/MRI screening. Of 8 patients who were asymptomatic at diagnosis, 7 showed absent or very slow annual progression, without developing significant vision impairment. One patient developed moderate vision impairment. Two symptomatic patients suffered from rapid tumor growth and progressive vision impairment. Both underwent late-stage surgery, resulting in incomplete resection and progressive vision impairment. One patient presented with acute vision field loss. A watchful-waiting approach was adopted because the hemangioblastoma was ineligible for vision-sparing surgery. One patient developed progressive vision impairment after watchful waiting. In the literature we found 45 patient cases with 48 hemangioblastomas.DiscussionWhen optic nerve and chiasm hemangioblastomas are diagnosed, we suggest annual MRI follow-up as long as patients do not develop vision impairment. If tumors grow fast, threaten the contralateral eye, or if patients develop progressive vision deficiency; surgical resection must be considered because neurological impairment is irreversible, and resection of large tumors carries a higher risk of further visual decline.

Background: The position of the optic chiasm relative to surrounding structures is critical in planning surgical interventions for suprasellar lesions. This study explored the relationship between the angle of the optic chiasm and lamina terminalis (OC-LT) and the position of the optic chiasm. Methods: The study comprised 140 individuals who underwent midsagittal and axial MRI-T2 scans. The position of the optic chiasm was classified into three categories: sellar, prefixed, and postfixed. The OC-LT angle was measured in the midsagittal section. Results: The angle between OC-LT varied from 30 to 66 degrees with a mean of 46.6 degrees. The sellar position of the optic chiasm was predominant (85.2%), with smaller angles (30-39 degrees) significantly associated with a sellar chiasm location. Most cases with postfixed optic chiasm fell within a 40-49 degree angle range. Conclusions: The OC-LT angle variability can be linked to the position of the optic chiasm. Predominantly, smaller angles correlated with a sellar position of the optic chiasm, while larger angles were associated with a postfixed optic chiasm. This information is crucial for surgical planning in the suprasellar region.

Simple Summary: Short-headed dogs exhibit shallow orbits and forward-facing eyes, while their medium- and long-headed counterparts have deep orbits with relatively laterally oriented eyes; these traits are classified by skull index (SI) value. In this study, we employed landmark-based morphometric analysis based on computed tomography scan data of 50 adult dogs to investigate the correlation between the SI and optic chiasm, and orbital shape. We found a consistent placement of the optic chiasm at the anterior neurocranial margin across all breeds. However, short-headed breeds exhibit a wider angle between the bilateral optic canals, and the anterior margin of the zygomatic bone-forming orbit was wider in the anterior direction compared to medium- and long-headed breeds. Breed-specific orbital differences were determined by the zygomatic bone, which connects the face to the neurocranium. The orbital margin of the zygomatic bone projects outward and forward, correlating with the degree of facial shortening. Taken together, our findings suggest that the zygomatic bone influences breed-specific orbital formation, especially in cases of facial shortening. This study's CT scan-based morphometric analysis of 50 adult dogs explored the relationship between skull shape variations (determined by the skull index, SI), optic chiasm, optic canals, and orbital shape. Dogs were classified as brachycephalic (SI ≥ 59), mesocephalic (SI ≥ 51 but <59), and dolichocephalic (SI < 51). No significant age or weight differences were observed. Skull lengths (brachycephalic: 11.39 ± 1.76 cm, mesocephalic: 15.00 ± 2.96 cm, dolichocephalic: 17.96 ± 3.44 cm) and facial lengths (brachycephalic: 3.63 ± 1.00 cm, mesocephalic: 6.46 ± 1.55 cm, dolichocephalic: 8.23 ± 1.03 cm) varied significantly, with shorter orbital depths (brachycephalic: 2.58 ± 0.42 cm, mesocephalic: 3.19 ± 0.65 cm, dolichocephalic: 3.61 ± 0.77 cm) in brachycephalic dogs. The optic chiasm-to-inion horizontal length ratio to cranial horizontal length positively correlated with the SI (r = 0.883, p < 0.001), while the ratio to neurocranial length showed no SI correlation (range: 55.5–75.0). Brachycephalic breeds had a significantly wider optic canal angle (93.74 ± 16.00°), along with broader lacrimal-zygomatic and zygomatic frontal process angles. These findings highlight the zygomatic bone's role in influencing breed-specific orbital variations by connecting the face to the neurocranium, projecting the orbital rim outward and forward with facial shortening. [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]

PurposeDosimetric and clinical predictors of radiation-induced optic nerve/chiasm neuropathy (RION) after single-fraction stereotactic radiosurgery (SRS) or hypofractionated (2-5 fractions) radiosurgery (fSRS) were analyzed from pooled data that were extracted from published reports (PubMed indexed from 1990 to June 2015). This study was undertaken as part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, investigating normal tissue complication probability (NTCP) after hypofractionated radiation.Methods and materialsEligible studies described dose delivered to optic nerve/chiasm and provided crude or actuarial toxicity risks, with visual endpoints (ie, loss of visual acuity, alterations in visual fields, and/or blindness/complete vision loss). Studies of patients with optic nerve sheath tumors, optic nerve gliomas, or ocular/uveal melanoma were excluded to obviate direct tumor effects on visual outcomes, as were studies not specifying causes of vision loss (ie, tumor progression vs RION).ResultsThirty-four studies (1578 patients) were analyzed. Histologies included pituitary adenoma, cavernous sinus meningioma, craniopharyngioma, and malignant skull base tumors. Prior resection (76% of patients) did not correlate with RION risk (P = .66). Prior irradiation (6% of patients) was associated with a crude 10-fold increased RION risk versus no prior radiation therapy. In patients with no prior radiation therapy receiving SRS/fSRS in 1-5 fractions, optic apparatus maximum point doses resulting in

Introduction: In intensity-modulated radiation therapy (IMRT) techniques, although the dose conformity increases, the out-of-field doses would not decrease. This study aimed to assess the dose error calculated by the treatment planning system (TPS) in the out-of-field regions using the dynamic IMRT (D-IMRT) method in nasopharyngeal cancer (NPC) patients. Methods: The out-of-field doses were measured for the chiasm and parotid organs using the D-IMRT technique (6 MV energy) with Monaco TPS. Computed tomography (CT) images of 10 NPC patients (54–77 years, mean: 61.6 ± 12.2 years) were considered and countered using 7-field and 11-field methods. The OCTAVIUS 4D phantom was utilized for dose assessment. Results: According to the OCTAVIUS measurements, the Monaco TPS dose errors ranged from −58.8 to 105.5%. The average dose error for optic chiasm and parotid organs was −25% and 8.5%, respectively, with several cases falling within tolerance (±5%). Conclusion: There were considerable dose calculation errors by Monaco TPS for organs located in out-of-field regions (optic chiasm and parotid) during IMRT for NPC patients. Therefore, accurate dose estimation in the out-of-field regions should be considered in clinical practices.

Spike conduction velocity characteristically differs between myelinated and unmyelinated axons. Here we test whether spikes of myelinated and unmyelinated paths differ in other respects by measuring rat retinal ganglion cell (RGC) spike duration in the intraretinal, unmyelinated nerve fiber layer and the extraretinal, myelinated optic nerve and optic chiasm. We find that rapid spike firing and illumination broaden spikes in intraretinal axons but not in extraretinal axons. RGC axons thus initiate spikes intraretinally and normalize spike duration extraretinally. Additionally, we analyze spikes that were recorded in a previous study of rhesus macaque retinogeniculate transmission and find that rapid spike firing does not broaden spikes in optic tract. The spike normalization we find reduces the number of spike properties that can change during RGC light responses. However, this is not because identical spikes fire in all axons. Instead, our recordings show that different subtypes of RGC generate axonal spikes of different durations and that the differences resemble spike duration increases that alter neurotransmitter release from other neurons. Moreover, previous studies have shown that RGC spikes of shorter duration can fire at higher maximum frequencies. These properties should facilitate signal transfer by different mechanisms at RGC synapses onto subcortical target neurons.

Spike conduction velocity characteristically differs between myelinated and unmyelinated axons. Here we test whether spikes of myelinated and unmyelinated paths differ in other respects by measuring rat retinal ganglion cell (RGC) spike duration in the intraretinal, unmyelinated nerve fiber layer and the extraretinal, myelinated optic nerve and optic chiasm. We find that rapid spike firing and illumination broaden spikes in intraretinal axons but not in extraretinal axons. RGC axons thus initiate spikes intraretinally and normalize spike duration extraretinally. Additionally, we analyze spikes that were recorded in a previous study of rhesus macaque retinogeniculate transmission and find that rapid spike firing does not broaden spikes in optic tract. The spike normalization we find reduces the number of spike properties that can change during RGC light responses. However, this is not because identical spikes fire in all axons. Instead, our recordings show that different subtypes of RGC generate axonal spikes of different durations and that the differences resemble spike duration increases that alter neurotransmitter release from other neurons. Moreover, previous studies have shown that RGC spikes of shorter duration can fire at higher maximum frequencies. These properties should facilitate signal transfer by different mechanisms at RGC synapses onto subcortical target neurons.

This article reviews the literature on different methods of prenatal ultrasound visualization of the optic chiasm (OC) and its applications. Prenatal imaging of the OC is feasible from 19 to 37 weeks of gestation. Evaluation of the OC has been shown crucial in differentiating isolated agenesis of the septum pellucidum from septo-optic dysplasia. Multiple methods can be applied for imaging of the OC, including three-dimensional and two-dimensional ultrasounds in different views, as well as color Doppler. According to the literature, both transabdominal and transvaginal routes produce equally acceptable images. OC visualization might be challenging but can be achieved by developing a standard scanning protocol and raising awareness.

This article reviews the literature on different methods of prenatal ultrasound visualization of the optic chiasm (OC) and its applications. Prenatal imaging of the OC is feasible from 19 to 37 weeks of gestation. Evaluation of the OC has been shown crucial in differentiating isolated agenesis of the septum pellucidum from septo-optic dysplasia. Multiple methods can be applied for imaging of the OC, including three-dimensional and two-dimensional ultrasounds in different views, as well as color Doppler. According to the literature, both transabdominal and transvaginal routes produce equally acceptable images. OC visualization might be challenging but can be achieved by developing a standard scanning protocol and raising awareness. [ABSTRACT FROM AUTHOR]

Introduction: Diabetic neuropathy and diabetic eye disease are well known complications of type 1 diabetes. We hypothesized that chronic hyperglycemia also damages the optic tract, which can be measured using routine magnetic resonance imaging. Our aim was to compare morphological differences in the optic tract between individuals with type 1 diabetes and healthy control subjects. Associations between optic tract atrophy and metabolic measures, cerebrovascular and microvascular diabetic complications were further studied among individuals with type 1 diabetes. Methods: We included 188 subjects with type 1 diabetes and 30 healthy controls, all recruited as part of the Finnish Diabetic Nephropathy Study. All participants underwent a clinical examination, biochemical work-up, and brain magnetic resonance imaging (MRI). Two different raters manually measured the optic tract. Results: The coronal area of the optic chiasm was smaller among those with type 1 diabetes compared to non-diabetic controls (median area 24.7 [21.0-28.5] vs 30.0 [26.7-33.3] mm2, p<0.001). In participants with type 1 diabetes, a smaller chiasmatic area was associated with duration of diabetes, glycated hemoglobin, and body mass index. Diabetic eye disease, kidney disease, neuropathy and the presence of cerebral microbleeds (CMBs) in brain MRI were associated with smaller chiasmatic size (p<0.05 for all). Conclusion: Individuals with type 1 diabetes had smaller optic chiasms than healthy controls, suggesting that diabetic neurodegenerative changes extend to the optic nerve tract. This hypothesis was further supported by the association of smaller chiasm with chronic hyperglycemia, duration of diabetes, diabetic microvascular complications, as well as and CMBs in individuals with type 1 diabetes. [ABSTRACT FROM AUTHOR]

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(1) Background: The normal A1 segment of the anterior cerebral artery (ACA) has a supraoptic course. The proximal infraoptic course of an A1 segment leaving the internal carotid artery (ICA) near the origin of the ophthalmic artery is a rare possibility. This study aimed to determine the prevalence and detailed anatomy of infraoptic A1 segments. (2) Methods: We retrospectively studied 145 computed tomography angiograms from 92 male and 53 female cases, with ages varying from 61 to 78 y.o. (3) Results: In 21/145 cases, infraoptic or infrachiasmatic horizontal-medial courses of A1 segments that emerged distally from the ICA were found. Distal infraoptic A1 segments were bilateral in 16/145 cases and unilateral in 3/145 cases. Infrachiasmatic A1 segments were found bilaterally in 2/145 male cases. All the infraoptic/infrachiasmatic A1 segments left long ICAs with low bifurcations. In 7/34 sides with distal infraoptic or infrachiasmatic A1 segments, supracarotid courses were present. In one female, the right A1 segment had an anterior supraclinoid, supracarotid and infraoptic course. In two female cases with a bilateral distal infraoptic A1, the segment was almost contacting the respective posterior cerebral artery. (4) Conclusions: In cases with dolicho(ectatic) ICAs, the A1 segments could have infraoptic and supracarotid courses the neurosurgeons should be aware of.

Transient visual obscurations (TVOs) represent brief ischaemic events of the optic nerve. These most commonly occur in the setting of raised intracranial pressure or more localised aetiologies within the orbit that result in decreased perfusion pressure. Transient vision loss has rarely been associated with pituitary tumours or optic chiasm compression, but details are lacking. We describe classic TVOs that completely resolved following resection of a pituitary macroadenoma causing chiasmal compression with a relatively normal eye examination. Clinicians should consider neuro-imaging in patients with TVOs and a normal evaluation. [ABSTRACT FROM AUTHOR]

Objectives We investigated the optic nerve (ON) and chiasm (OC) in magnetic resonance (MR) in diabetic patients by comparing them with hemoglobin A1c (HbA1c) levels. Methods In this retrospective study, cranial MRIs of 42 adults (19 males and 23 females) with diabetes mellitus (DM) (group1) and 40 healthy controls (19 males and 21 females) (group 2) were included. In both groups, bilateral ON widths and OC area, width, and height were measured. In the DM group, HbA1c values were also obtained at the time of MRI or within the same month. Results In the DM group, the mean of the HbA1c values was 8.31 ± 2.51%. There were no significant differences between ON diameter; and OC area, width and height of the DM and control groups (p > 0.05). In each of the DM and control groups, ON diameter was not different between the right and left sides (p > 0.05). In DM groups, correlation tests showed that there were positive correlations between right and left ON diameters, OC area and OC width, and OC height (p < 0.05). In males, ON diameters were higher than those in females bilaterally (p < 0.05). In patients with higher HbA1c values, OC width was smaller (p < 0.05). Conclusion A significant correlation of OC width and HbA1c levels suggests that uncontrolled DM causes ON atrophy. Our study represents a thorough assessment of OC measures using standard brain MRI to evaluate optic degeneration in DM patients and shows that the OC width measurement is suitable and reliable. This simple method can be obtained from clinically available scans. [ABSTRACT FROM AUTHOR]

Craniopharyngiomas remain surgically challenging because of the strong adhesion to vital neurovascular structures. We propose a system for the selection of surgical approaches based on the optic recess (OR) displacement pattern to facilitate surgical planning and obtain optimum visual and endocrinologic outcomes. Craniopharyngiomas were divided into 3 types based on the OR displacement pattern: superior, anterior, and involvement types. Selected surgical approaches and patient outcome were retrospectively reviewed according to these classifications. Visual and endocrinologic outcomes were compared among the groups. This study included 26 patients with primary craniopharyngiomas who underwent surgery at our institution, classified into 11 anterior, 11 superior, and 4 involvement types. The extended endoscopic endonasal approach provided excellent exposure inferodorsal aspect of the chiasm for manipulation of the dissection plane in the anterior and superior types with midline location. A unilateral subfrontal approach was required for tumor of the superior type with lateral extension. An interhemispheric translamina terminalis approach could provide safe dissection under direct vision of strong adhesion at the superior aspect of the chiasm in the involvement type. Visual and endocrinologic outcomes were better in the involvement type compared with the superior and anterior types. Visual outcome was significantly correlated with preoperative visual function. Craniopharyngiomas with the involvement type are indicated for the translamina terminalis approach to achieve the best visual and endocrinologic outcome. Our classification of the OR displacement pattern is useful to select the optimal surgical approach for craniopharyngiomas more accurately and concisely, especially in cases with third ventricular extension. [ABSTRACT FROM AUTHOR]

We describe gross and histopathological features of multiple ocular and neuro-ophthalmic abnormalities in a fox squirrel (Sciurus niger). Ophthalmic findings included severe bilateral microphthalmos, with the right eye more affected than the left. Histopathology confirmed severe microphthalmia, aphakia, disorganized retinal tissue and small optic nerves, as well as agenesis of the optic chiasm and optic tract. This combination of neuro-ophthalmic abnormalities has not been previously described in wild animals. [ABSTRACT FROM AUTHOR]

• Friedrich Bonhoeffer and his team discovered Roger Sperry's molecular labels. • He was pioneer in developing powerful in vitro assays for axon guidance. • He showed these labels were graded, membrane bound cues in retina and targets. • Throughout the 80′s-90′s, his lab was an epicenter of scientific innovation. • The fixed tissue DiI labeling method was discovered in his lab. The main focus of research for which Friedrich Bonhoeffer's work is known in the Neuroscience community was pioneer experiments on how axonal projections could organize into "maps", what mechanisms are involved in axon guidance and involve gradients of guiding molecules, and isolation of the first such molecules, e.g. RAGS (ephrin A5) and RGM (repulsive guidance molecule). Other papers have described in detail these contributions as well as Friedrich Bonhoeffer's personality. In the mid-eighties, I made a 2-year stay in his lab and initiated a line of research on development of binocular connections in Mammals, particularly the guidance of retinal fibers to one or the other side of the brain. In this paper I recall these circumstances as they pertain to Neuroscience as it stood at the time, and explain as best as I can how his lab was a conducive setting for the discoveries made there and how Friedrich Bonhoeffer acted for me as a scientist and a tutor. [ABSTRACT FROM AUTHOR]

[Display omitted] • We summarize landmark discoveries resulting in today's concept of axon guidance. • We list key assays that have contributed to the discovery of axon guidance molecules. • We outline the importance of using many different model organism for axon guidance studies. • Live imaging studies are pivotal in better understanding axon guidance mechanisms. The molecular mechanisms of neural circuit formation have been of interest to Santiago Ramón y Cajal and thousands of neuroscientists sharing his passion for neural circuits ever since. Cajal was a brilliant observer and taught us about the connections and the morphology of neurons in the adult and developing nervous system. Clearly, we will not learn about molecular mechanisms by just looking at brain sections or cells in culture. Technically, we had to come a long way to today's possibilities that allow us to perturb target gene expression and watch the consequences of our manipulations on navigating axons in situ. In this review, we summarize landmark steps towards modern live-imaging approaches used to study the molecular basis of axon guidance. [ABSTRACT FROM AUTHOR]

In this article, we present a case of diffuse follicular variant papillary thyroid carcinoma with pituitary metastasis, which is a rare cause of pituitary metastasis. The follicular variant of papillary thyroid carcinoma is an uncommon variant of papillary carcinoma. A 74-year-old male was presented with weakness, fatigue, and a decreased appetite. The patient was diagnosed with secondary adrenal and thyroid insufficiencies. Imaging revealed a pituitary mass with suprasellar extension, right cavernous sinus invasion, and optic chiasm compression. Thyroid ultrasonography revealed a nodule with a maximum size of 7.2cm in the right lobe. Cytological examination via fine-needle aspiration suggested papillary thyroid cancer. Total thyroidectomy with central and right lateral neck dissection confirmed the diagnosis of diffuse follicular variant of papillary thyroid carcinoma. Owing to visual field defects, the patient underwent transsphenoidal surgery. Histological and immunohistochemical evaluations confirmed pituitary metastasis from the papillary thyroid cancer. Radioactive iodine treatment and gamma knife radiotherapy of the pituitary gland were performed. The initiation of sorafenib treatment was deemed appropriate during the follow-up. A significant decrease in the thyroglobulin levels was observed after sorafenib treatment. Pituitary metastasis should be considered in patients diagnosed with hypopituitarism and pituitary lesions at initial evaluation. The presence of visual field defects may be an indication for neurosurgical intervention and guide both diagnosis and treatment. The management of papillary thyroid cancer and the role of treatment modalities in prognosis depend on the biological behavior of the tumor. Early diagnosis and multidisciplinary management are crucial for the treatment of these patients. [ABSTRACT FROM AUTHOR]

Objective: Pituitary tumours that compress the optic chiasm are associated with long-term alterations in sleep-wake rhythm. This may result from damage to intrinsically photosensitive retinal ganglion cells (ipRGCs) projecting from the retina to the hypothalamic suprachiasmatic nucleus via the optic chiasm to ensure photoentrainment (i.e. synchronisation to the 24-h solar cycle through light). To test this hypothesis, we compared the post-illumination pupil response (PIPR), a direct indicator of ipRGC function, between hypopituitarism patients with and without a history of optic chiasm compression. Design: Observational study, comparing two predefined groups. Methods: We studied 49 patients with adequately substituted hypopituitarism: 25 patients with previous optic chiasm compression causing visual disturbances (CC+ group) and 24 patients without (CC- group). The PIPR was assessed by chromatic pupillometry and expressed as the relative change between baseline and post-blue-light stimulus pupil diameter. Objective and subjective sleep parameters were obtained using polysomnography, actigraphy, and questionnaires. Results: Post-blue-light stimulus pupillary constriction was less sustained in CC+ patients compared with CC- patients, resulting in a significantly smaller extended PIPR (mean difference: 8.1%, 95% CI: 2.2-13.9%, P = 0.008, Cohen's d = 0.78). Sleep-wake timing was consistently later in CC+ patients, without differences in sleep duration, efficiency, or other rest-activity rhythm features. Subjective sleep did not differ between groups. Conclusion: Previous optic chiasm compression due to a pituitary tumour in patients with hypopituitarism is associated with an attenuated PIPR and delayed sleep timing. Together, these data suggest that ipRGC function and consequently photoentrainment of the central biological clock is impaired in patients with a history of optic chiasm compression. [ABSTRACT FROM AUTHOR]

Slit-Robo signaling regulates midline crossing of commissural axons in different systems. In zebrafish, all retinofugal axons cross at the optic chiasm to innervate the contralateral tectum. Here, the mutant for the Robo2 receptor presents severe axon guidance defects, which were not completely reproduced in a Slit2 ligand null mutant. Since slit3 is also expressed around this area at the stage of axon crossing, we decided to analyze the possibility that it collaborates with Slit2 in this process. We found that the disruption of slit3 expression by sgRNA-Cas9 injection caused similar, albeit slightly milder, defects than those of the slit2 mutant, while the same treatment in the slit2−/−mz background caused much more severe defects, comparable to those observed in robo2 mutants. Tracking analysis of in vivo time-lapse experiments indicated differential but complementary functions of these secreted factors in the correction of axon turn errors around the optic chiasm. Interestingly, RT-qPCR analysis showed a mild increase in slit2 expression in slit3-deficient embryos, but not the opposite. Our observations support the previously proposed "repulsive channel" model for Slit-Robo action at the optic chiasm, with both Slits acting in different manners, most probably relating to their different spatial expression patterns. [ABSTRACT FROM AUTHOR]

Objective: To validate the correlation between visual impairment (VI) and suprasellar extension (SSE) in pituitary macroadenomas and to identify patients at heightened risk of preoperative visual deficits by analyzing anatomical distortion of optic nerve and optic chiasm (OC) using preoperative magnetic resonance imaging., Methods: Ninety-seven patients with pituitary macroadenomas and SSE, treated between January 2015 and April 2022, were analyzed. Associations between VI, demographic data, SSE, and optic pathway deformation were assessed. SSE cutoff points for predicting VI were determined using receiver operating characteristic curves, with univariate and multivariate logistic regression identifying potential risk factors., Results: Of the 97 patients, 47 had confirmed VI. Independent predictors of VI included visual symptoms lasting >1 month, sagittal SSE >10.35 mm, and vertical OC width >5.6 mm. Additional risk factors were older age, nonfunctioning pituitary adenoma, coronal SSE, dumbbell-shaped tumors, large and giant adenomas, reduced optic nerve diameter, increased horizontal OC width, and thinned OC thickness., Conclusions: Tumor morphology and optic pathway distortion predict preoperative VI in patients with pituitary macroadenomas. These findings support the development of a viable approach for assessing VI risk in clinical practice, aiding in decisions regarding optimal surgical timing., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

(1) Background: The normal A1 segment of the anterior cerebral artery (ACA) has a supraoptic course. The proximal infraoptic course of an A1 segment leaving the internal carotid artery (ICA) near the origin of the ophthalmic artery is a rare possibility. This study aimed to determine the prevalence and detailed anatomy of infraoptic A1 segments. (2) Methods: We retrospectively studied 145 computed tomography angiograms from 92 male and 53 female cases, with ages varying from 61 to 78 y.o. (3) Results: In 21/145 cases, infraoptic or infrachiasmatic horizontal-medial courses of A1 segments that emerged distally from the ICA were found. Distal infraoptic A1 segments were bilateral in 16/145 cases and unilateral in 3/145 cases. Infrachiasmatic A1 segments were found bilaterally in 2/145 male cases. All the infraoptic/infrachiasmatic A1 segments left long ICAs with low bifurcations. In 7/34 sides with distal infraoptic or infrachiasmatic A1 segments, supracarotid courses were present. In one female, the right A1 segment had an anterior supraclinoid, supracarotid and infraoptic course. In two female cases with a bilateral distal infraoptic A1, the segment was almost contacting the respective posterior cerebral artery. (4) Conclusions: In cases with dolicho(ectatic) ICAs, the A1 segments could have infraoptic and supracarotid courses the neurosurgeons should be aware of. [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]

The purpose of this study was to examine if the use of a bolus helmet when treating the head with intensity modulated proton therapy (IMPT) will maintain organs at risk (OAR) sparing while improving the clinical target volume (CTV) coverage. A bolus helmet is a device that aims to improve on the traditionally used range shifter in proton therapy by improving dose distribution characteristics. Ten patients were retrospectively selected who had 2 separate treatment planning scans performed, a scan with the bolus helmet and a second scan without. Plans were created using both scans. Dose to organs at risk (OAR) including the left optic nerve, right optic nerve, optic chiasm, and normal brain minus CTV (brain-CTV), as well as CTV coverage were compared between the 2 plans. The use of the bolus helmet displayed lower mean OAR doses as well as higher CTV coverage, suggesting that use of the bolus helmet provides benefit when treating the head with IMPT. [ABSTRACT FROM AUTHOR]

Because of their proximity to the visual structures, tuberculum sellae meningiomas are frequently revealed by ophthalmologic impairment. The goal of surgery is gross total resection and improvement of visual function. The purpose of the present study was to identify the predictors of favorable visual outcomes after surgery of tuberculum sellae meningioma. We retrospectively collected tuberculum sellae meningiomas treated at 2 neurosurgical centers from 2010 to 2020. We collected the clinical, imaging and surgical data and analyzed their effects on the visual outcome. A favorable visual outcome was defined as an increase in visual acuity of ≥0.2 point and/or an increase of >25% of the visual field or complete recovery. A total of 50 patients were included. At 4 months after surgery, 30 patients (60%) had experienced visual improvement. The predictors of a favorable visual outcome were a symptom duration of <6 months, preoperative visual acuity >0.5, a smaller tumor size, and tumor with T2-weighted/fluid attenuated inversion recovery hypersignal on magnetic resonance imaging. During surgery, a soft tumor and a clear brain–tumor interface were associated with favorable visual outcomes. Preoperative optic coherence tomography measurements of the retinal nerve fiber layer thickness >80 μM and ganglion cell complex thickness >70 μM were also associated with a better ophthalmologic outcome. In tuberculum sellae meningiomas, rapid surgical treatment must be performed to optimize vision improvement. A hyperintense lesion on T2-weighted/fluid attenuated inversion recovery magnetic resonance imaging and minor vision impairment at the initial ophthalmologic presentation might give hope for a favorable outcome. Performing optic coherence tomography measurements before surgery could clarify patients' expectations regarding their recovery. [ABSTRACT FROM AUTHOR]