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Journal of Clinical Neuroscience :... Feb 2018The purpose of this work is to establish a reference scale of optic nerve pathway measurements in pediatric patients according to age using MRI. Optic nerve pathway...
The purpose of this work is to establish a reference scale of optic nerve pathway measurements in pediatric patients according to age using MRI. Optic nerve pathway measurements were retrospectively analyzed using an orbits equivalent sequence on brain MRI scans of 137 pediatric patients (72 male, 65 female, average age = 7.7 years, standard deviation = 5.3). The examinations were performed on a 1.5-T or 3-T Siemens MR system using routine imaging protocols. Measurements include diameters of the orbital optic nerves (OON), prechiasmatic optic nerves (PON), optic tracts (OT), and optic chiasm (OC). Measurements were performed manually by 2 neuroradiologists, using post-processing software. Patients were stratified into five age groups for measurement analyses: (I) 0-1.49 years, (II) 1.5-2.99 years, (III) 3-5.99 years, (IV) 6-11.99 years, and (V) 12-18 years. The observed value range of OON mean diameter was 2.7 mm (Interquartile range (IQR) = 2.4-2.9), PON was 3.2 mm (IQR = 3.05-3.5), OT 2.6 mm (IQR = 2-2.9). A strong positive correlation was established between age and mean diameter of OON (r = 0.73, p < .001), PON (r = 0.59, p < .001), and OT (r = 0.72, p < .001). A significant difference in mean OON diameters was found between age groups I-II (d = 0.3, p = .01), II-III (d = 0.5, p < .001), III-IV (d = 0.5, p < .001) followed by a plateau between IV-V (d = 0.l0, p = .19). OON/OT ratio maintained a steady mean value 1 (IQR = 0.93-1.1) regardless of age (p = .7). The diameter of optic pathways was found to increase as a function of age with consistent positive correlation between nerve and tract for all ages.
Topics: Adolescent; Child; Child, Preschool; Female; Humans; Infant; Magnetic Resonance Imaging; Male; Neural Pathways; Neuroimaging; Optic Chiasm; Optic Nerve; Optic Tract; Reference Values; Retrospective Studies
PubMed: 29198418
DOI: 10.1016/j.jocn.2017.11.015 -
Magnetic Resonance Imaging Jun 2017We investigated changes in the optic tract and optic radiation in patients with multiple sclerosis (MS) by comparing unilateral and bilateral optic nerve damage assessed...
Alterations of the optic pathway between unilateral and bilateral optic nerve damage in multiple sclerosis as revealed by the combined use of advanced diffusion kurtosis imaging and visual evoked potentials.
OBJECTIVES
We investigated changes in the optic tract and optic radiation in patients with multiple sclerosis (MS) by comparing unilateral and bilateral optic nerve damage assessed based on visual evoked potentials (VEPs) using advanced diffusion MR metrics.
METHODS
In 21 MS patients, diffusion MRI was performed. Maps of fractional anisotropy, apparent diffusion coefficient (ADC), and mean kurtosis (MK) were computed. On the basis of the P100 latency in VEPs, the MS patients were divided into three groups: bilateral (n=7), unilateral (n=7), and no abnormality (n=7). Their optic tracts and optic radiations were analyzed with diffusion MRI-based fiber tracking. We also investigated the correlations between diffusion parameters and VEPs (n=21).
RESULTS
In the optic tract, the diffusion changes in each of the three groups showed step-like changes. The diffusion changes in the optic radiations of the unilateral group were similar to those in the normal VEP group. Only the bilateral group showed significantly higher ADC and lower MK relative to the other two groups (P<0.05, Steel-Dwass multiple-comparison test). A significant positive correlation between VEP latency and ADC and a significant negative correlation between VEP latency and MK were observed (P<0.01, Spearman's correction).
CONCLUSIONS
We first evaluated the relationship between VEPs and DKI and concluded that the lateral geniculate nucleus may compensate for unilateral damage in the pre-geniculate optic pathway via neural plasticity.
Topics: Adult; Anisotropy; Diffusion Magnetic Resonance Imaging; Evoked Potentials, Visual; Female; Humans; Image Processing, Computer-Assisted; Male; Middle Aged; Multiple Sclerosis; Nerve Fibers; Optic Nerve; Optic Tract; Severity of Illness Index
PubMed: 27109488
DOI: 10.1016/j.mri.2016.04.011 -
Investigative Ophthalmology & Visual... Nov 2019Regeneration of optic nerve axons after injury can be facilitated by several approaches, but misguidance at the optic chiasm is often observed. We characterized guidance...
PURPOSE
Regeneration of optic nerve axons after injury can be facilitated by several approaches, but misguidance at the optic chiasm is often observed. We characterized guidance cues in the embryonic visual system and adult optic chiasm before and after optic nerve crush (ONC) injury to better understand barriers to optic nerve regeneration in adults.
METHODS
Radial glial (RC2/BLBP/Slit1), developmental (Pax2) and extracellular markers (CSPG: H2B/CS-56) were assessed in C57BL/6J mice by immunohistochemistry. RC2, BLBP, Slit1, and CSPG are known inhibitory guidance cues while Pax2 is a permissive guidance cue.
RESULTS
At embryonic day 15.5 (E.15.5), RC2 and BLBP were identified superior to, and extending through, the optic chiasm. The optic chiasm was BLBP-ve in adult uninjured mice but BLBP+ve in adult mice 10 days after ONC injury. The reverse was true for RC2. Both BLBP and RC2 were absent in adult mice 6 weeks post-ONC. Slit1 was present in the optic chiasm midline and optic tracts in embryonic samples but was absent in uninjured adult tissue. Slit1 was observed superior to and at the midline of the optic chiasm 10 days post-ONC but absent 6 weeks after injury. Pax2 was expressed at the junction between the optic nerve and optic chiasm in embryonic brain tissue. In embryonic sections, CS-56 was observed at the junction between the optic chiasm and optic tract, and immediately superior to the optic chiasm. Both 2H6 and CS-56 staining was absent in uninjured and ONC-injured adult brains.
CONCLUSION
Differences in guidance cue expression during development, in adulthood and after injury may contribute to misguidance of regenerating RGC axons in the adult optic chiasm.
Topics: Animals; Axon Guidance; Biomarkers; Brain; Cues; Fatty Acid-Binding Protein 7; Female; Gene Expression Regulation, Developmental; Immunohistochemistry; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Nerve Crush; Nerve Tissue Proteins; Optic Chiasm; Optic Nerve Injuries; PAX2 Transcription Factor; Pregnancy; Retinal Ganglion Cells
PubMed: 31731293
DOI: 10.1167/iovs.19-26732 -
Radiologia 2008Tractography of cerebral white matter fibers based on diffusion tensor imaging (DTI) is a recent magnetic resonance technique that enables the visualization of the... (Review)
Review
Tractography of cerebral white matter fibers based on diffusion tensor imaging (DTI) is a recent magnetic resonance technique that enables the visualization of the anatomy and integrity of white matter tracts. This article aims to provide two- and three-dimensional representations of the main white matter tracts in the brain from high spatial resolution DTI data and to explain the physical basis of the technique, its main clinical applications, and how we use it. We provide examples of the use of DTI in the study of the corpus callosum, the anterior white commissure, the corticospinal tract, the limbic system, the long association fibers, the cerebellar peduncles, and the optic tract.
Topics: Adult; Brain; Diffusion Magnetic Resonance Imaging; Female; Humans; Male
PubMed: 18367058
DOI: 10.1016/s0033-8338(08)71944-1 -
Annual International Conference of the... Jul 2020Glaucoma is a neurodegenerative disease of the visual system and is the leading cause of irreversible blindness worldwide. To date, its pathophysiological mechanisms...
Glaucoma is a neurodegenerative disease of the visual system and is the leading cause of irreversible blindness worldwide. To date, its pathophysiological mechanisms remain unclear. This study evaluated the feasibility of advanced diffusion magnetic resonance imaging techniques for examining the microstructural environment of the visual pathway in glaucoma. While conventional diffusion tensor imaging (DTI) showed lower fractional anisotropy and higher directional diffusivities in the optic tracts of glaucoma patients than healthy controls, diffusion kurtosis imaging (DKI) and the extended white matter tract integrity (WMTI) model indicated lower radial kurtosis, higher axial and radial diffusivities in the extra-axonal space, lower axonal water fraction, and lower tortuosity in the same regions in glaucoma patients. These findings suggest glial involvements apart from compromised axonal integrity in glaucoma. In addition, DKI and WMTI but not DTI parameters significantly correlated with clinical ophthalmic measures via optical coherence tomography and visual field perimetry testing. Taken together, DKI and WMTI provided sensitive and comprehensive imaging biomarkers for quantifying glaucomatous damage in the white matter tract across clinical severity complementary to DTI.
Topics: Diffusion Tensor Imaging; Glaucoma; Humans; Neurodegenerative Diseases; Optic Tract; White Matter
PubMed: 33018335
DOI: 10.1109/EMBC44109.2020.9176192 -
Acta Biomaterialia Aug 2019Investigation of neurodegeneration in glaucoma, a leading cause of irreversible blindness worldwide, has been obfuscated by the lack of an efficient model that provides...
Investigation of neurodegeneration in glaucoma, a leading cause of irreversible blindness worldwide, has been obfuscated by the lack of an efficient model that provides chronic, mild to moderate elevation of intraocular pressure (IOP) with preservation of optical media clarity for long term, in vivo interrogation of the structural and functional integrity of the retinal ganglion cells (RGCs). Here, we designed and formulated an injectable hydrogel based on in situ cross-linking of hyaluronic acid functionalized with vinyl sulfone (HA-VS) and thiol groups (HA-SH). Intracameral injection of HA-VS and HA-SH in C57BL/6J mice exhibited mild to moderate elevation of IOP with daily mean IOP ranged between 14 ± 3 and 24 ± 3 mmHg, which led to progressive, regional loss of RGCs evaluated with in vivo, time-lapse confocal scanning laser ophthalmoscopy; a reduction in fractional anisotropy in the optic nerve and the optic tract projected from the eye with increased IOP in diffusion tensor magnetic resonance imaging; a decrease in positive scotopic threshold response in electroretinography; and a decline in visual acuity measured with an optokinetic virtual reality system. The proportion of RGC loss was positively associated with the age of the animals, and the levels and the duration of IOP elevation. The new glaucoma model recapitulates key characteristics of human glaucoma which is pertinent to the development and pre-clinical testing of neuroprotective and neuroregenerative therapies. STATEMENT OF SIGNIFICANCE: A new model to study chronic neurodegeneration in glaucoma has been developed via intracameral injection of a specifically designed hyaluronic acid functionalized with vinyl sulfone and thiol groups for cross-linking. Intracameral injection of the chemically cross-linked hydrogel generates mild to moderate IOP elevation, resulting in progressive degeneration of the retinal ganglion cells, optic nerve, and optic tract, and a decline in visual function. The model recapitulates the key features of neurodegeneration in human glaucoma, which will facilitate and expedite the development of neuroprotective and neuroregenerative therapies.
Topics: Age Factors; Animals; Cross-Linking Reagents; Disease Models, Animal; Elasticity; Electroretinography; Glaucoma; Hyaluronic Acid; Hydrogels; Injections; Injections, Intraocular; Intraocular Pressure; Kinetics; Magnetic Resonance Imaging; Mice, Inbred C57BL; Neurodegenerative Diseases; Optic Nerve; Retinal Ganglion Cells; Sulfhydryl Compounds; Sulfones; Viscosity
PubMed: 31176841
DOI: 10.1016/j.actbio.2019.06.005 -
Frontiers in Integrative Neuroscience 2014Vision is a complex function, which is achieved by movements of the eyes to properly foveate targets at any location in 3D space and to continuously refresh neural... (Review)
Review
Vision is a complex function, which is achieved by movements of the eyes to properly foveate targets at any location in 3D space and to continuously refresh neural information in the different visual pathways. The visual system involves five main routes originating in the retinas but varying in their destination within the brain: the occipital cortex, but also the superior colliculus (SC), the pretectum, the supra-chiasmatic nucleus, the nucleus of the optic tract and terminal dorsal, medial and lateral nuclei. Visual pathway architecture obeys systematization in sagittal and transversal planes so that visual information from left/right and upper/lower hemi-retinas, corresponding respectively to right/left and lower/upper visual fields, is processed ipsilaterally and ipsialtitudinally to hemi-retinas in left/right hemispheres and upper/lower fibers. Organic neurovisual deficits may occur at any level of this circuitry from the optic nerve to subcortical and cortical destinations, resulting in low or high-level visual deficits. In this didactic review article, we provide a panorama of the neural bases of eye movements and visual systems, and of related neurovisual deficits. Additionally, we briefly review the different schools of rehabilitation of organic neurovisual deficits, and show that whatever the emphasis is put on action or perception, benefits may be observed at both motor and perceptual levels. Given the extent of its neural bases in the brain, vision in its motor and perceptual aspects is also a useful tool to assess and modulate central nervous system (CNS) in general.
PubMed: 25538575
DOI: 10.3389/fnint.2014.00089 -
The Journal of Comparative Neurology Mar 2010The dorsal lateral geniculate nucleus (dLGN) of the mouse has emerged as a model system in the study of thalamic circuit development. However, there is still a lack of...
The dorsal lateral geniculate nucleus (dLGN) of the mouse has emerged as a model system in the study of thalamic circuit development. However, there is still a lack of information regarding how and when various types of retinal and nonretinal synapses develop. We examined the synaptic organization of the developing mouse dLGN in the common pigmented C57/BL6 strain, by recording the synaptic responses evoked by electrical stimulation of optic tract axons, and by investigating the ultrastructure of identified synapses. At early postnatal ages (
optic tract evoked responses were primarily excitatory. The full complement of inhibitory responses did not emerge until after eye opening (>P14), when optic tract stimulation routinely evoked an excitatory postsynaptic potential/inhibitory postsynaptic potential (EPSP/IPSP) sequence, with the latter having both a GABA(A) and GABA(B) component. Electrophysiological and ultrastructural observations were consistent. At P7, many synapses were present, but synaptic profiles lacked the ultrastructural features characteristic of the adult dLGN, and little gamma-aminobutyric acid (GABA) could be detected by using immunocytochemical techniques. In contrast, by P14, GABA staining was robust, mature synaptic profiles of retinal and nonretinal origin were easily distinguished, and the size and proportion of synaptic contacts were similar to those of the adult. The emergence of nonretinal synapses coincides with pruning of retinogeniculate connections, and the transition of retinal activity from spontaneous to visually driven. These results indicate that the synaptic architecture of the mouse dLGN is similar to that of other higher mammals, and thus provides further support for its use as a model system for visual system development. Topics: Animals; Animals, Newborn; Cell Differentiation; Electric Stimulation; Excitatory Postsynaptic Potentials; Geniculate Bodies; Inhibitory Postsynaptic Potentials; Mice; Mice, Inbred C57BL; Microscopy, Immunoelectron; Neural Inhibition; Neuronal Plasticity; Organ Culture Techniques; Photic Stimulation; Presynaptic Terminals; Receptors, GABA-A; Receptors, GABA-B; Retinal Ganglion Cells; Synapses; Visual Pathways; gamma-Aminobutyric Acid
PubMed: 20034053
DOI: 10.1002/cne.22223 -
International Journal of Molecular... Apr 2021Decussation of axonal tracts is an important hallmark of vertebrate neuroanatomy resulting in one brain hemisphere controlling the contralateral side of the body and...
Decussation of axonal tracts is an important hallmark of vertebrate neuroanatomy resulting in one brain hemisphere controlling the contralateral side of the body and also computing the sensory information originating from that respective side. Here, we show that BMP interferes with optic chiasm formation and RGC pathfinding in zebrafish. Experimental induction of BMP4 at 15 hpf results in a complete ipsilateral projection of RGC axons and failure of commissural connections of the forebrain, in part as the result of an interaction with shh signaling, transcriptional regulation of midline guidance cues and an affected optic stalk morphogenesis. Experimental induction of BMP4 at 24 hpf, resulting in only a mild repression of forebrain shh ligand expression but in a broad expression of pax2a in the diencephalon, does not per se prevent RGC axons from crossing the midline. It nevertheless shows severe pathologies of RGC projections e.g., the fasciculation of RGC axons with the ipsilateral optic tract resulting in the innervation of one tectum by two eyes or the projection of RGC axons in the direction of the contralateral eye.
Topics: Animals; Axons; Bone Morphogenetic Proteins; Optic Chiasm; Optic Nerve; Retina; Retinal Ganglion Cells; Visual Pathways; Zebrafish; Zebrafish Proteins
PubMed: 33925390
DOI: 10.3390/ijms22094560 -
BMC Ophthalmology Mar 2022RNFL thickness measured by optical coherence tomography (OCT) and visual pathway measured by diffusion tensor imaging (DTI) can be used to predict visual field recovery,...
A pilot study of combined optical coherence tomography and diffusion tensor imaging method for evaluating microstructural change in the visual pathway of pituitary adenoma patients.
BACKGROUND
RNFL thickness measured by optical coherence tomography (OCT) and visual pathway measured by diffusion tensor imaging (DTI) can be used to predict visual field recovery, respectively. However, the relationship between RNFL thickness and visual pathway injury in patients with pituitary adenoma (PA) remains unclear. This study aims to evaluate the combining DTI and OCT methods in observing the microstructural change in the visual pathway in patients with PA.
METHODS
Twenty-nine patients who were diagnosed with PA were included in the study group, and 29 healthy subjects were included as the control group. OCT detected the thickness of circumpapillary retinal nerve fiber layer (CP-RNFL) and ganglion cell layer (GCL). DTI measured the values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Correlation between CP-RNFL and GCL thickness and FA and ADC values was analyzed in the study group.
RESULTS
Compared with the control group, the FA values of the bilateral optic nerve, chiasma, bilateral optic tract, and left optic radiation in the study group were reduced, and the ADC values of the bilateral optic nerve and optic chiasma were increased. Correlation analysis showed that the FA value of the optic chiasma was positively correlated with the average thickness of RNFL, the CP-RNFL thickness in the nasal and temporal retinal quadrants in both eyes, as well as the thickness of macular ring GCL in the nasal, supra, and inferior quadrants. The FA values of the optic nerve, optic chiasma, optic tract, and optic radiation were positively correlated with CP-RNFL thickness in the nasal and temporal quadrants.
CONCLUSION
Combined DTI and OCT can provide a comprehensive understanding of the microscopic changes in the structure and function of the whole visual pathway in patients with PA.
Topics: Diffusion Tensor Imaging; Humans; Pilot Projects; Pituitary Neoplasms; Tomography, Optical Coherence; Visual Pathways
PubMed: 35279128
DOI: 10.1186/s12886-022-02320-2