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Practical Neurology Mar 2024A 45-year-old woman presented with sudden complete vision loss in her left eye and retroorbital pain worsened by eye movements. A previous milder episode of vision loss...
A 45-year-old woman presented with sudden complete vision loss in her left eye and retroorbital pain worsened by eye movements. A previous milder episode of vision loss had occurred in the same eye 1 year before, with complete recovery after high-dose intravenous methylprednisolone. She had no light perception in the left eye with a swollen optic disc, but with a normal right optic disc. There were no systemic manifestations or infections. MR scan of the brain showed extensive enlargement and enhancement of the left optic nerve and optic chiasm. After excluding infections and autoimmune markers, a left optic nerve biopsy confirmed non-caseating granulomas, leading to a diagnosis of neurosarcoidosis.
Topics: Female; Humans; Middle Aged; Optic Nerve Diseases; Optic Nerve; Sarcoidosis; Central Nervous System Diseases; Neuritis; Blindness
PubMed: 37932041
DOI: 10.1136/pn-2023-003939 -
Annual Review of Neuroscience Apr 2024Seeing 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... (Review)
Review
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 on the evolution of the binocular circuit.
PubMed: 38635868
DOI: 10.1146/annurev-neuro-111020-093230 -
Journal of Neuro-ophthalmology : the... Nov 2023Over a century ago, German ophthalmologist Hermann Wilbrand reported inferonasal crossing fibers within the chiasm curve anteriorly into the contralateral optic nerve....
BACKGROUND
Over a century ago, German ophthalmologist Hermann Wilbrand reported inferonasal crossing fibers within the chiasm curve anteriorly into the contralateral optic nerve. This anatomic bend, "Wilbrand knee," is classically cited as the explanation for the "junctional scotoma," a contralateral superotemporal visual field defect associated with lesions affecting the optic nerve at its junction with the chiasm. More recent reports have called into question the existence of Wilbrand knee or suggested that it may simply be an artifact.
METHODS
Four human optic chiasms (obtained from cadaver donors with no reported premortem visual pathology) and 2 monkey chiasms were fixed and thin sectioned (40 µm), then examined using anisotropic scattering imaging, a novel technique that takes advantage of the fact that light reflects off well-defined linear structures (i.e., axonal tracts) in a predictable manner based on their orientation. Using this technique, tissue structures oriented in different directions can be distinguished at high resolution without the need for tissue staining.
RESULTS
In all 4 human optic chiasms, thin fiber tracts consistent with, but less prominent than, those Wilbrand had described were observed. No such tracts were found in the monkey chiasms.
CONCLUSIONS
Wilbrand knee exists in humans but is modest in its anterior projection. Wilbrand knee does not seem to be present in monkeys, however, which may explain conflicting reports in the literature regarding its existence.
PubMed: 37976151
DOI: 10.1097/WNO.0000000000002044 -
Journal of Medical Ultrasound 2023This article reviews the literature on different methods of prenatal ultrasound visualization of the optic chiasm (OC) and its applications. Prenatal imaging of the OC... (Review)
Review
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.
PubMed: 38025017
DOI: 10.4103/jmu.jmu_69_23 -
Brain Communications 2023Achiasmia is a rare visual pathway maldevelopment with reduced decussation of the axons in the optic chiasm. Our aim was to investigate clinical characteristics,...
Achiasmia is a rare visual pathway maldevelopment with reduced decussation of the axons in the optic chiasm. Our aim was to investigate clinical characteristics, macular, optic nerve and brain morphology in achiasmia. A prospective, cross-sectional, observational study of 12 participants with achiasmia [8 males and 4 females; 29.6 ± 18.4 years (mean ± standard deviation)] and 24 gender-, age-, ethnicity- and refraction-matched healthy controls was done. Full ophthalmology assessment, eye movement recording, a high-resolution spectral-domain optical coherence tomography of the macular and optic disc, five-channel visual-evoked responses, eye movement recordings and MRI scans of the brain and orbits were acquired. Achiasmia was confirmed in all 12 clinical participants by visual-evoked responses. Visual acuity in this group was 0.63 ± 0.19 and 0.53 ± 0.19 for the right and left eyes, respectively; most participants had mild refractive errors. All participants with achiasmia had see-saw nystagmus and no measurable stereo vision. Strabismus and abnormal head position were noted in 58% of participants. Optical coherence tomography showed optic nerve hypoplasia with associated foveal hypoplasia in four participants. In the remaining achiasmia participants, macular changes with significantly thinner paracentral inner segment ( = 0.002), wider pit ( = 0.04) and visual flattening of the ellipsoid line were found. MRI demonstrated chiasmatic aplasia in 3/12 (25%), chiasmatic hypoplasia in 7/12 (58%) and a subjectively normal chiasm in 2/12 (17%). Septo-optic dysplasia and severe bilateral optic nerve hypoplasia were found in three patients with chiasmic aplasia/hypoplasia on MRI. In this largest series of achiasmia patients to date, we found for the first time that neuronal abnormalities occur already at the retinal level. Foveal changes, optic nerve hypoplasia and the midline brain anomaly suggest that these abnormalities could be part of the same spectrum, with different manifestations of events during foetal development occurring with varying severity.
PubMed: 37680693
DOI: 10.1093/braincomms/fcad219 -
Annales D'endocrinologie Aug 2023Thyrotropic adenomas (TSH-PitNET) are the rarest pituitary tumours. Most TSH-PitNETs are secreting adenoma, with a biological picture of inappropriate TSH secretion... (Review)
Review
Thyrotropic adenomas (TSH-PitNET) are the rarest pituitary tumours. Most TSH-PitNETs are secreting adenoma, with a biological picture of inappropriate TSH secretion (moderately elevated TSH, elevated FT3 and FT4). Patients present most often clinical hyperthyroidism, but with more moderate symptoms than in peripheral hyperthyroidism. Biological diagnosis is not always easy. The main differential diagnoses are interfering antibody assay interactions, dysalbuminemia and thyroid hormone resistance syndrome. Misdiagnosis is common. However, the diagnosis is easier when macroadenomas are involved (80% of cases), with symptoms of optic chiasm compression, headache and signs of hypopituitarism. Treatment is initially based on surgery. In case of failure, somatostatin analogues are very effective in controlling tumor volume and secretion, although there is a risk of thyroid insufficiency, which is usually transient.
Topics: Humans; Thyrotropin; Pituitary Neoplasms; Adenoma; Antineoplastic Agents; Hyperthyroidism
PubMed: 36716819
DOI: 10.1016/j.ando.2023.01.004 -
The Canadian Journal of Neurological... Jul 2023Optic nerve hypoplasia (ONH) and septo-optic-pituitary dysplasia (SOD) are common causes of congenital visual impairment. Our primary aim was to investigate the...
BACKGROUND
Optic nerve hypoplasia (ONH) and septo-optic-pituitary dysplasia (SOD) are common causes of congenital visual impairment. Our primary aim was to investigate the prevalence of abnormal neuroimaging features in patients with these disorders in Manitoba, Canada, and compare them with published reports.
METHODS
A retrospective neuroimaging review was performed in patients resident in Manitoba with ONH/SOD.
RESULTS
There were 128 patients ( = 70) with ONH/SOD who had neuroimaging. Their mean age (SD) at the end of the study was 13.2 (7.5) years. Males were significantly more likely to have bilateral ONH and a small optic chiasm size, while females were more likely to have a left ONH and a small left optic chiasm size on neuroimaging ( = 0.049). ONH and small optic chiasm size were seen in most patients on neuroimaging. Absent septum pellucidum was noted in 40%, small pituitary gland size in 28%, neuronal migration disorders (NMD) in 20% (>1 type and bilateral in 13 cases), corpus callosum abnormalities were present in 9%, while olfactory bulbs-tracts and olfactory sulci were absent in 8.6% of cases. Unilateral ONH was not significantly associated with other structural brain abnormalities, while NMD were significantly associated with other midline brain abnormalities including a symmetrically small optic chiasm size.
CONCLUSION
The prevalence of structural neuroimaging abnormalities in our cohort with ONH/SOD was generally in the same range reported in other studies with corpus callosum abnormalities being relatively less common in our study. Bilateral NMD were relatively common among patients with NMD. The association between sex and ONH laterality requires further study.
PubMed: 37492885
DOI: 10.1017/cjn.2023.263 -
The Canadian Journal of Neurological... Jan 2024Optic nerve hypoplasia (ONH) and septo-optic-pituitary dysplasia (SOD) are neurodevelopmental disorders associated with congenital visual impairment. Our aim was to...
BACKGROUND
Optic nerve hypoplasia (ONH) and septo-optic-pituitary dysplasia (SOD) are neurodevelopmental disorders associated with congenital visual impairment. Our aim was to investigate associations between several ophthalmic and neuroimaging features in patients with ONH/SOD.
METHODS
A retrospective chart and neuroimaging review was performed in patients with ONH/SOD. Ophthalmic signs (e.g., monocular best-corrected visual acuity [BCVA], nystagmus, and strabismus) and neuroimaging data were extracted and their associations were investigated.
RESULTS
There were 128 patients (70 males) with ONH/SOD who had neuroimaging. Their mean age at the end of the study was 13.2 (: 7.5) years. Ophthalmic data were available on 102 patients (58 males). BCVA varied from normal to no light perception. There were statistically significant associations between: (A) Reduced optic nerve or chiasm size on neuroimaging and more severely impaired BCVA and (B) laterality of the reduced optic nerve or chiasm size on neuroimaging and laterality of: (1) The eye with reduced BCVA, (2) small optic disc size, and (3) RAPD, if present ( ≤ 0.0002 each). The presence of symmetrically small optic nerves on MRI was significantly more common in patients with nystagmus than when nystagmus was absent ( = 96, 75% vs. 38.6%, < 0.0001). The presence of neuronal migration disorders, their type and laterality were not associated with BCVA and laterality of the reduced BCVA.
CONCLUSION
The functional and structural associations in ONH are consistent with the impaired visual function that results from the hypoplastic anterior visual pathways. However, these associations were not perfectly concordant making prediction of adult BCVA challenging in these patients.
PubMed: 38178708
DOI: 10.1017/cjn.2024.2