Optic Chiasm

Magnetic resonance imaging (MRI) of the brain revealed an intensely enhancing mass lesion with calcification in the sellar and suprasellar region involving the optic chiasm and the left optic nerve.  

At the optic chiasm retinal fibers either cross the midline, or remain uncrossed. Our results therefore suggest that both the organization and development of the primate optic chiasm differ markedly from that revealed in rodents and carnivores..  

By obstructing the surgical view, an accessory MCA may increase the difficulty of exposing lesions in the vicinity of the optic chiasm..  

Purpose: To analyse retinal nerve fibre layer (RNFL) thickness in eyes with compression of the optic chiasm by a pituitary adenoma. All had bitemporal visual field depression caused by compression of the optic chiasm.  

RESULTS: A 48-year-old man had progressively deteriorating visual acuity and bitemporal hemianopia, found to be attributable to a macroadenoma encircling both carotid arteries and compressing the optic chiasm.  

We believe there is considerable uncertainty as to the optimal management of any future progression, which seems likely, and are currently considering the use of radiosurgery with careful sparing of the optic chiasm, or possibly the chemotherapeutic agent temozolomide.  

We examined the retrochiasmatic space between the superior border of the pons and posterior edge of the optic chiasm in six randomly selected adult fresh brain specimens.  

One such marker, the transcription factor Pax2, is expressed at the midbrain-hindbrain boundary and in the cerebellum, spinal cord, retina, optic stalk, and optic chiasm.  

Pituitary magnetic resonance imaging (MRI) showed an intrasellar and suprasellar mass measuring 1.9 x 1.7 x 1.7 cm, impinging on the optic chiasm.  

The authors describe an unusual case of a 56-year-old male presenting with visual loss secondary to multiple intracranial lesions, with infiltration of the optic chiasm and an incidental renal lesion.  

A wait-and-see approach may be considered in nonfunctioning macroadenomas not reaching to the optic chiasm.  

There was significantly improved dose sparing for the brain stem and ipsilateral temporal lobe with IMRT but no significant difference for the optic chiasm or pituitary gland.  

AVMs located in the cerebral hemisphere, the cerebellum, the basal ganglia, the brain stem, the corpus callosum, the optic chiasm and the lateral ventricle.  

The deficits with the immobilized eye persisted even after section of the optic chiasm, which effectively removes the direct cortical competition of the two eyes.  

A dramatic consequence of disrupting BMP signaling is a missorting of RGC axons as they exit the optic chiasm.  

Interestingly, moderate Wfs1 expression was seen in the optic nerve, particularly in astrocytes, while little Wfs1 was expressed in the optic chiasm or optic tract.  

In addition to typical AXD abnormalities, magnetic resonance imaging demonstrated a tumor-like lesion of the optic chiasm suggestive of a glioma. This patient confirms that enlargement of the optic chiasm is a rare feature of AXD, possibly linked to abnormal astrocytic proliferation..  

At the optic chiasm, retinal ganglion cell axons from each eye converge and segregate into crossed and uncrossed projections, a pattern critical for binocular vision. Here, we review recent findings on optic chiasm development, highlighting the specific transcription factors and guidance cues that implement retinal axon divergence into crossed and uncrossed pathways. Throughout this review, we compare guidance mechanisms at the optic chiasm with those in other midline models and highlight unanswered questions both for retinal axon growth and axon guidance in general..  

The navigation of retinal axons to ipsilateral and contralateral targets in the brain depends on the decision to cross or avoid the midline at the optic chiasm, a critical guidance maneuver that establishes the binocular visual pathway. Previous work has identified a specific guidance receptor, EphB1, that mediates the repulsion of uncrossed axons away from its ligand, ephrinB2, at the optic chiasm midline (Williams et al., 2003), and a transcription factor Zic2, that, like EphB1, is required for formation of the ipsilateral retinal projection (Herrera et al., 2003).  

A survey of embryos with different Pax6/PAX6 gene dosage (Pax6Sey/+, Pax6+/+, PAX77+ and PAX77+/+) showed that (1) the total number of RGC axons projected by the retina and (2) the proportions that are sorted into the ipsilateral and contralateral optic tracts at the optic chiasm vary differently with gene dosage. Before the onset of severe retinal dysplasia, Pax6 overexpression causes defects of retinal axons, preventing their normal growth and navigation through the optic chiasm..  

Only 14 cases of spontaneous regression of low-grade gliomas in patients without neurofibromatosis have been described, and of these, the vast majority regress in association with optic chiasm gliomas.  

Macroadenomas tend to present clinically because of mass-effect on adjacent structures, such as the bitemporal hemianopsia seen with optic chiasm compression.  

We report that DSI tractography accurately shows the known anatomic fiber crossings in optic chiasm, centrum semiovale, and brainstem; fiber intersections in gray matter, including cerebellar folia and the caudate nucleus; and radial fiber architecture in cerebral cortex.  

It typically causes symptoms of pituitary dysfunction or visual change due to compression of the optic chiasm.  

Within the visual system, a loss-of-function leads to lack of choroid fissure closure (known as a coloboma), a loss of optic nerve astrocytes, and anomalous axonal pathfinding at the optic chiasm [ Favor, J., Sandulache, R., et al., 1996.  

We have investigated the role of Nogo, a protein that inhibits regenerating axons in the adult central nervous system, on axon guidance in the developing optic chiasm of mouse embryos. Nogo protein is expressed by radial glia in the midline within the optic chiasm where uncrossed axons turn, and the Nogo receptor (NgR) is expressed on retinal neurites and growth cones. In vitro coculture assays of retina and optic chiasm showed that NgR was selectively reduced on neurites and growth cones from dorsonasal retina when they contacted chiasm cells, but not on those from ventrotemporal retina. These findings provide evidence that Nogo signaling is involved in directing the growth of axons in the mouse optic chiasm and that this process relies on a differential regulation of NgR on axons from the dorsonasal and ventrotemporal retina..  

Because of the lesion's proximity to the optic chiasm and its relationship to the hypothalamic-pituitary axis, morbidity rates following treatment can be high.  

Hypertrophy of the optic nerves and optic chiasm is described in a 5-month-old boy with infantile Krabbe disease. Optic nerve and optic chiasm hypertrophy is a rarely described feature of Krabbe disease. The areas of the prechiasmatic optic nerves and optic chiasm were measured and compared with those of 26 age-matched controls. The areas of the prechiasmatic optic nerves and optic chiasm were 132% and 53% greater than normal, respectively..  

The type of radiation delivery depends on several factors, including the availability of different treatment modalities and the size of the target area (focused high dose radiation with the Gamma knife is not suitable for a large lesion close to the optic nerves or optic chiasm).  

Contrast cranial magnetic resonance imaging (MRI) showed pathologic contrast enhancement (16 of 19 cases) involving optic nerve (9), optic chiasm (1), optic radiations (1), cavernous sinus (1), leptomeninges (3), and cerebral parenchyma (3).  

Axons of retinal ganglion cells (RGCs) make a divergent choice at the optic chiasm to cross or avoid the midline in order to project to ipsilateral and contralateral targets, thereby establishing the binocular visual pathway. The zinc-finger transcription factor Zic2 and a member of the Eph family of receptor tyrosine kinases, EphB1, are both essential for proper development of the ipsilateral projection at the mammalian optic chiasm midline.  

Time measurements were recorded and dosimetry was obtained from the cornea, sphenoid sinus (near the optic chiasm), and from the operative field during acquisition of the images. Radiation doses to the cornea were 620 mrad per scan, and optic chiasm was 800 mrad/scan.  

No deviation was found in one patient with an optic chiasm lesion, which affect both retinotectal and retinogeniculostriate pathways.  

METHODS: The clinical course and magnetic resonance imaging findings of patients with VHL and hemangioblastomas affecting the anterior visual pathway from the intraorbital optic nerve to the optic chiasm are reviewed.  

This study was undertaken to test whether one of the G alpha i proteins, G alpha i3, signals in the same pathway as OA1 to regulate melanosome biogenesis and axonal growth through the optic chiasm. Furthermore, they suggest a common Oa1-G alpha i3 signaling pathway that ultimately affects axonal growth through the optic chiasm..  

Moreover, in its application for craniopharyngiomas, an understanding of tumor growth and extension with respect to the optic chiasm and infundibulum is critical to safely approach the lesion via an endonasal route..  

Cranial computed tomography and MRI scans revealed an intra- and suprasellar tumor of adenoma-like appearance with elevation of the optic chiasm.  

PCNSL isolated to the optic chiasm has been described only once in an immunocompetent patient.  

Imaging showed enhancing nodules in the intracranial segments of both optic nerves posterior to the optic canals and in the anterior optic tract, optic chiasm, and basal leptomeninges. Microscopic examination also showed malignant plasma cell infiltration of the leptomeninges of the cerebrum, brain stem, optic chiasm, pituitary gland, cranial bone marrow, and subarachnoid blood vessels.  

In diencephalon, moderate staining was found in all thalamic nuclei but was strong in medial habenular nucleus and the hypothalamic nuclei including suprachiasmatic nucleus, optic chiasm, arcuate nucleus and median eminence.  

Permanent ipsilaterally projecting axons approach the chiasmatic midline in rodents but are confined to lateral parts of the optic chiasm in marsupials.  

METHODS: Matrix and SAP were performed on 93 patients with neuro-ophthalmic disorders affecting the optic nerve and optic chiasm.  

Chondroitin sulfate proteoglycans elicit a selective inhibition to neurite growth from ventrotemporal (VT) but not dorsonasal (DN) retina, potentiating the bilateral routing of axons in the mouse optic chiasm.  

Median values were as follows: prescription dose, 60 Gy (range, 50-70); PTV(D95), 99% (range, 79-101%); optic nerve Dmax, 53 Gy (range, 2-54); optic chiasm Dmax, 51Gy (range, 2-55).  

The optic chiasm was expanded along the rostro-caudal axis (similar to Slit mutant mice, Plump, A.S., Erskine, L., Sabatier, C., Brose, K., Epstein, C.J., Goodman, C.S., Mason, C.A., Tessier-Lavigne, M., 2002.  

Lamina and medulla are joined by the first or outer optic chiasm (OOC). Medulla, lobula and lobula plate are connected by the second or inner optic chiasm (IOC).  

CB showed significant atrophy of the geniculo-striate system, encompassing the optic nerves, the optic chiasm, the optic radiations and the primary visual cortex (BA17).  

We have investigated the localization of Nogo, an inhibitory protein acting on regenerating axons in the adult central nervous system, in the embryonic mouse retinofugal pathway during the major period of axon growth into the optic chiasm. These expression patterns suggest an interaction of Nogo with its receptor in the mouse retinofugal pathway, which may be involved in guiding axons into the optic pathway and in governing the routing of axons in the optic chiasm..  

Modern humans have a unique configuration with relatively more anterolateral projection of the MCF pole relative to the optic chiasm and the foramen rotundum.  

Imaging suggested a pituitary macroadenoma, with spontaneous necrosis, extending into the suprasellar region, compressing the optic chiasm and invading the right cavernous sinus. An aggressive decompression of the optic chiasm was performed with complete resolution of both visual fields and third nerve palsy.  

MATERIALS AND METHODS: Automatic and manual segmentations of the eyes, optic nerves, optic chiasm, pituitary gland, brain stem and cerebellum of 11 patients on T1-weighted magnetic resonance, 3-mm thick slice images were compared using the Dice similarity coefficient (DSC).  

PURPOSE: To measure the pressure in the temporal and central aspects of the chiasm simultaneously during compression of the optic chiasm from below with an expanding simulated tumor. METHODS: Craniotomies were performed on 5 unfixed cadaveric specimens ranging in age from 49 to 89 years, and the optic chiasm was exposed. MAIN OUTCOME MEASURE: Pressure change between the temporal and nasal aspects of the optic chiasm. CONCLUSIONS: During deformation of the optic chiasm from below by a radially expanding mass analogous to a pituitary tumor, the central aspect of the optic chiasm consistently manifests a higher pressure than the temporal aspect. It is hypothesized that the peculiar geometry of the optic chiasm renders the crossing nasal fibers more prone to a deformation stress exerted from below.  

Magnetic resonance imaging demonstrated a sellar tumor mass with suprasellar extension compressing the optic chiasm, and intense gadolinium enhancement.  

The present study showed 90% of Id2-immunoreactivity in oligodendrocyte lineage cells in such brain regions as the corpus callosum, optic chiasm, the longitudinal fasciculus of pons, the medial septal nucleus, the fimbria of hippocampus, the anterior commissure, and the pyramidal tract.  

Further debulking of unresectable lesions may also prove beneficial in delaying symptom recurrence and facilitating radiotherapy, where distance between the tumor and optic chiasm is an important predictor of visual outcome.  

The tumor location defines prognosis in OPGs; optic nerve gliomas (ONG) have the lowest rate of complications and death, and optic chiasm and retrochiasmal gliomas the highest.  

Magnetic resonance imaging scans demonstrated extensive enhancement of the coil ball, surrounding brain parenchyma, and optic chiasm, with perianeurysmal edema.  

For the head and neck case, identical target coverage was achieved, while a comparable sparing of the brain stem, optic chiasm, and optic nerves was observed.  

The process may extend to the optic chiasm and tracts, cerebellar peduncle, subcortical resion, neighboring white matter, and rarely, cortical gray matter.  

A case in point is the belladonna mutation, where an axonal misrouting effect at the optic chiasm leads to a reversed OKR with a number of interesting properties..  

In animals with binocular vision, retinal fibers either project across the midline or they remain on the same side of the ventral diencephalon, forming an X-shaped commissure known as the optic chiasm. The correct formation of the optic chiasm during development is essential to establish a fully functional visual system. Visual dysfunction associated with axonal misrouting at the optic chiasm has been described in albino individuals and in patients with non-decussating retinal-fugal fiber syndrome. Although little is known about the causes of retinal misrouting in these conditions, the molecular mechanisms responsible for the formation of the optic chiasm are beginning to be elucidated in vertebrates. This review focuses on our current knowledge of how the optic chiasm forms, which will hopefully help us to better understand these congenital anomalies..  

Stereotactic radiotherapy is useful for larger meningiomas (> 3-3.5 cm) and those closely approximating critical structures, such as the optic chiasm and brainstem.  

Magnetic resonance imaging of the brain revealed an enhancing pituitary mass with hemorrhage extending to the optic chiasm, consistent with pituitary apoplexy.  

The optic chiasm with its complex fiber micro-structure is a challenge for diffusion tensor models and tractography methods. Likewise, it is an ideal candidate for evaluation of diffusion tensor imaging tractography approaches in resolving inter-regional connectivity because the macroscopic connectivity of the optic chiasm is well known. Here, high-resolution (156 microm in-plane) diffusion tensor imaging of the human optic chiasm was performed ex vivo at ultra-high field (9.4 T). Despite the complex microstructure of the fiber paths through the optic chiasm, all known connections could be tracked by a line propagation algorithm.  

Fifteen months after initial diagnosis, considerable enlargement of the lesion was noted, extending mainly superiorly and indenting the optic chiasm.  

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. 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 implies that optic chiasm formation in rodents and ferrets is not common to placental mammals in general..  

STS-evoked potentials (EPs) were recorded from the optic chiasma.  

PURPOSE: To apply and to evaluate the newly developed advanced fast marching algorithm (aFM) in vivo by reconstructing the human visual pathway, which is characterized by areas of extensive fiber crossing and branching, i.e., the optic chiasm and the lateral geniculate nucleus (LGN). Due to the proximity to bony structures and air-filled spaces of the optic chiasm, a high sensitivity encoding (SENSE) reduction factor was applied to reduce image distortions in this area. CONCLUSION: The present work shows that the advanced aFM, which is especially designed for overcoming tracking limitations within areas of extensive fiber crossing, handles the fiber crossing and branching within the optic chiasm and the LGN correctly, thus allowing the reconstruction of the entire human visual fiber pathway, from the intraorbital segment of the optic nerves to the visual cortex..  

They present with clinical features of hyperprolactinaemia (galactorrhoea, gonadal dysfunction), and more rarely with large tumours, headache and visual field loss due to optic chiasm compression.  

Perturbations of interaction of hyaluronan (HA) with its receptor CD44 cause multiple errors in axon routing at the mouse optic chiasm. These findings support a direct role of HA, acting probably through CD44, on axon decussation during early phase of chiasm development, but argue against a direct function of HA on the turning of uncrossed axons in the mouse optic chiasm..  

Retinal ganglion cells (RGCs) extend axons that exit the eye, cross the midline at the optic chiasm, and synapse on target cells in the optic tectum. Also, we show that sema3Aa and sema3E are present near or at the optic chiasm.  

MRI revealed agenesis of the pituitary stalk, hypoplasia of the optic chiasm and periventricular nodular heterotopia.  

OBJECTIVES: Analysis of form and function relationships with tumour-mediated dislocations and deformations of the optic chiasm.  

They can also be classified depending on the location from the optic chiasm and the third ventricle.  

The number of non-neuronal elements of the optic nerve remained virtually unchanged immediately behind the eye-ball and in the middle part of the nerve, whereas it increased significantly close to the optic chiasm (3040+/-433 versus 3888+/-403).  

The optic canal was subsequently removed en bloc, beginning at the annulus of Zinn and extending to the optic chiasm.  

Immunoreactivity for GH is also traced through the optic nerve head, at the back of the eye, into the optic nerve, through the optic chiasm, into the optic tract and into the stratum opticum and the retinorecipient layer of the optic tectum, where the RGC axons synapse.  

Albinism is associated with a misrouting of fibers at the optic chiasm where the majority of fibers cross to the contralateral side. Growing axons from retinal ganglion cells therefore arrive later than usual at the optic chiasm and are misrouted contralaterally. This atypical decussation leads to morphological changes of the optic chiasm including a reduced chiasm width with larger angles between optic nerves and tracts which can be shown by magnetic resonance imaging..  

Normal-tissue dose constraints were 50-54 Gy for the optic chiasm and nerves, and 55-60 Gy for the brainstem. With IMRT, the percent volume of optic chiasm receiving more than 45 Gy was also reduced by 30.40% (p = 0.047). Intensity-modulated radiation therapy improved target coverage and reduced radiation dose to the brain, brainstem, and optic chiasm.  

Perturbation of the transmembrane glycoprotein, CD44, has been shown to cause multiple errors in axon routing in the mouse optic chiasm.  

The mean dosages to the optic chiasm and brainstem were 0.159 and 0.040 Gy (median, 0.163 and 0.031 Gy) per fraction.  

CONCLUSION: Antero-posterior distortion of the skull following such a deceleration injury can cause laceration and thrombosis of the pre-chiasmal and pial arteries supplying the optic chiasm.  

Magnetic resonance imaging revealed diffuse enlargement of the pituitary gland, which encroached on but did not compress the optic chiasm. Once physiologic doses of glucocorticoids were instituted, however, follow-up magnetic resonance imaging showed substantial progression of the diffuse pituitary enlargement and mild compression of the optic chiasm.  

MRI showed a large pituitary mass compressing the optic chiasm and infiltrating the cavernous sinus.  

MRI scan revealed multiple enhancing lesions involving the optic chiasm, left optic tract, right lateral geniculate body, and right optic radiation in the temporal lobe.  

CD44 has been shown to be involved in midline crossing and the generation of ipsilateral projections in the mouse optic chiasm.  

It is associated with neoplastic lesions of the hypothalamic-optic chiasmatic region.  

METHODS: The subarachnoid portions of the CN3s were imaged with a 1.5-T MRI scanner and conventional head coils, acquiring heavily T(2)-weighted oblique axial planes 1-mm thick and parallel to the optic chiasm.  

Neuroimaging demonstrated damage to the optic chiasm. Although rare, head trauma may cause a bitemporal hemianopia secondary to optic chiasmal injury..  

Here it was found that endocannabinoids inhibited GABAergic inhibitory postsynaptic currents in POMC neurons only in intact sagittal brain slices, but not coronal, horizontal, or sagittal slices that were truncated rostrally at the level of the optic chiasm.  

Repeat MRI revealed a recurrent cystic craniopharyngioma, now measuring approximately three centimeters with subfrontal and parasellar extension and compression of the optic chiasm.  

We report a 48-year-old woman with a glioblastoma multiforme arising from the optic chiasm. There have only been four other reports of glioblastoma multiforme arising from the optic chiasm as distinct from secondary involvement of the chiasm, in the last 40 years..  

CONCLUSIONS: Apparently the retinal pattern of nerve fibres remains intact even when approaching the optic chiasm.  

Herein an unusual case of LCH involving the optic chiasm is presented.  

The cases presented are rare examples of congenital nystagmus associated with isolated absence of the optic chiasm.  

Homonymous hemianopia (HH) results from damage to visual pathways posterior to the optic chiasm.  

The optic chiasm also can be easily identified superiorly.  

AIM: To study a possible relationship between dimensions of the optic chiasm and extent of visual field impairment in patients with pituitary adenoma.  

Retinal ganglion cell axons exit the eye, enter the optic stalk, cross the ventral midline at the optic chiasm, and terminate in the optic tectum of the zebrafish.  

All three patients responded rapidly to cabergoline (CAB) by shrinkage of the tumor and release of the optic chiasm compression.  

CONCLUSION: Shh executes a transient but important function in axon decussation in the early stage of mouse optic chiasm development and signals axon turning in the later stage..  

The case is reported of a 55-year-old man with diffuse malignant lymphoma type B associated with transient optic chiasm infiltration and visual disturbances but with persistent hypopituitarism, hyperprolactinaemia and diabetes insipidus. Repeated MR and CT scans showed optic chiasm infiltration, which disappeared in the course of the chemotherapy but then recurred, changed its appearance and finally disappeared again.  

Achiasmia is a rarely diagnosed visual pathway maldevelopment where all or the majority of nasal retinal fibres fail to decussate at the optic chiasm. The aim was to study VEP asymmetry to flash stimulation in two children with maldevelopment of the optic chiasm in comparison to control children.  

1.38, p < 0.001), and enabled dose reductions of normal tissues, including brainstem (D(mean) by 19.8% and D(max) by 10.7%), optic chiasm (D(mean) by 25.3% and D(max) by 22.6%), right optic nerve (D(mean) by 37.3% and D(max) by 28.5%), and left optic nerve (D(mean) by 40.6% and D(max) by 36.7%), p < or = 0.01.  

Treatment plans were designed to provide a dose of 70 Gy to 95% or more of the gross tumor volume (GTV) and 60 Gy to 95% or more of the clinical tumor volume (CTV) while sparing neighboring critical structures including the optic chiasm, optic nerves, eyes, and brainstem.  

A magnetic resonance imaging (MRI) scan revealed pituitary enlargement with compression of the anterior optic chiasm. RESULTS: At 16 weeks after delivery, visual acuity was 1.5 in both eyes with normal visual field, and an MRI scan revealed a normal-sized pituitary without compression of the optic chiasm.  

RESULTS: Optic nerve regeneration was observed in P5 3M mice all the way to optic chiasm in P18 3M mice, only local sprouting regeneration was observed.  

Magnetic resonance imaging (MRI) of the brain showed symmetrical enlargement of the pituitary gland and stalk due to the presence of a mass lesion extending toward the optic chiasm.  

An enhanced CT scan of the head revealed a large suprasellar mass impinging on the optic chiasm and hypothalamus.  

We report a 14-year-old boy with cavernous malformation of the optic chiasm.  

In the distal nerve, loss of axonal staining progressed to the optic chiasm by 7 days and remained undetectable at 2 weeks.  

Hemianopia respecting the vertical meridian generally results from a disturbance in the optic chiasm or the postchiasmal visual pathway. Although visual field defects respecting the vertical meridian, and without any evidence of distinct disease, are uncommon, neurologists and neuro-ophthalmologists should consider the differential diagnosis if MRI is negative for distinct lesions in the optic chiasm or the postchiasmal visual pathway..  

Neurological examination revealed enlargement of bilateral central scotoma and blurred vision, and brain MRI showed masses in the optic chiasma and right hypothalamus on Ti-weighted image with contrast enhancement. Although primary central nervous system lymphoma (PCNSL) developing from the optic chiasma and hypothalamus is rare, PCNSL should be considered in patients with multiple lesions in the optic chiasma and hypothalamus..  

In patients treated with focal SRT, the median doses to the tumour, optic chiasm and brainstem were 41.92, 0.25 and 0.07 Gy, respectively, and to the ipsilateral optic nerve, globe and lens were 9.98, 19.11 and 3.74 Gy, respectively.  

A left frontotemporal craniotomy was done with subtotal resection of the tumor because it was strongly adhered to the optic chiasm.  

A large fraction of homozygous zebrafish mutant belladonna (bel) larvae display a reversed optokinetic response (OKR) that correlates with failure of the retinal ganglion cells to cross the midline and form the optic chiasm.  

Patients most often present with findings associated with ventricular outflow obstruction causing hydrocephalus, optic chiasm compression resulting in visual dysfunction or hypothalamic/pituitary compression leading to endocrinopathy.  

Patients with pituitary adenomas may present with endocrine dysfunction or neuro-ophthalmic pathology, resulting from compression of surrounding structures, most notably the optic chiasm. The specific visual field defect usually results from the anatomic compression of the tumor upon the optic chiasm.  

It lies in close proximity to numerous vital structures, including the optic chiasm, sphenoid sinus, cavernous sinus and hypothalamus.  

The primary visual pathway in albino mammals is characterized by an increased decussation of retinal ganglion cell axons at the optic chiasm and an enhanced contralateral projection to the dorsal lateral geniculate nucleus.  

RESULTS: Magnetic resonance imaging (MRI) of the brain confirmed the presence of a 2.6-cm lesion within the sella turcica extending above the sella and compressing the optic chiasm.  

Monocular temporal visual field loss from organic lesions is quite rare but has been reported in conjunction with compressive lesions at the optic nerve-optic chiasm junction.  

RESULTS: IMRI images were obtained in all cases and were of sufficiently high quality to indicate adequate decompression of the optic chiasm and the removal of all suprasellar tumor.  

We report a case presenting with septal agenesis and normal optic chiasm and pituitary function in a fetus at 19 weeks of gestation..  

The staining pattern for the PLP/DM20 and MBP overlapped during the lizard ontogeny and was first observed at E39 in cell bodies and fibers located in the temporal optic nerve, optic chiasm, middle optic tract, and in the stratum album centrale of the optic tectum (OT).  

The pathological process developing in the paracellar area in the presence of primary empty sella syndrome inevitably involves the optic chiasm and optic nerves closely anatomically connected with hypothalamic nuclei and pituitary infundibulum.  

We report a case of clinically mute median fore brain tumor with meningeal origin and optic chiasm compression.  

Thirty-five tumors were < or = 1 mm from the optic chiasm/nerve.  

Measurements before and after resection of the ACP included the length of C6 segment of the ICA on its lateral aspect; C6 segment length on its medial aspect; and medial length of the optic nerve from the optic chiasm to falciform ligament (before ACP resection) then to the annulus of Zinn (after ACP resection).  

A magnetic resonance imaging (MRI) scan subsequently confirmed absence of the optic chiasm.  

An intrasellar heterogenous mass lesion compressing the optic chiasm was resected subtotally via an endonasal transsphenoidal approach.  

The optic chiasm is one of the most popular models for studying axon guidance. We suggest that mouse models of the organization and development of the optic chiasm are not common to placental mammals in general..  

At the age of three cafĂ© au lait spots on the skin and an incranial tumour situated near the optic chiasm--qualified as inoperable--were discovered.  

Retinal ganglion cell (RGC) axons from each eye execute a series of maneuvers as they converge on the ventral surface of the brain at the optic chiasm for sorting into the optic tracts. We suggest that (1) Hs2st and Hs6st1 are each deployed to generate distinct patterns of heparan sulfation on RGCs and at the optic chiasm and (2) this differential sulfation directs retinal axons through the chiasm, at least in part by modulating the response of the navigating growth cone to Slit proteins..  

CONCLUSION: Diffuse destruction of the complete pituitary gland including the infundibulum has to be considered in lymphocytic and granulomatous hypophysitis, whereas in xanthomatous, a circumscribed anterior pituitary lesion leading to compression of the pituitary gland without alteration of the pituitary stalk and optic chiasm can be assumed..  

A 4-step approach was designed to dissect the internal carotid artery and its proximal branches, the optic nerve, the optic chiasm, and the pituitary stalk.  

For large and/or invasive tumours where the prospect of surgical cure is remote, first-line therapy is somatostatin analogue treatment with debulking surgery having an adjunctive role to achieve tight control or to alleviate compression of the optic chiasm.  

Patients with thickened sphenoid sinus mucosa had larger tumors that compressed the optic chiasm or cavernous sinus, and these individuals also had a higher rate of cranial nerve deficits at presentation than those without mucosal thickening (73% compared with 0%).  

Brain MRI revealed a hyperintense lesion in the optic chiasm on T2-weighted imaging.  

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