Acute visual loss
Sherif Gonem, Ian Pavord in Diagnosis in Acute Medicine, 2017
Visual loss may be caused by pathology affecting any part of the neurological pathway comprising the eye, optic nerve, optic chiasm, optic tract, optic radiation and occipital cortex. Disruption of this pathway may result in visual field defects, reduced visual acuity or complete visual loss. The optic nerve is commonly affected by ischaemia, demyelination and drug toxicity. The optic chiasm lies adjacent to the pituitary gland, and thus pituitary and suprasellar tumours often result in bitemporal hemianopia, due to impingement on the central fibres that are crossing over at this site. The optic tract, optic radiation and occipital cortex are vulnerable to any of the pathologies that may affect the cerebral hemispheres in general, including ischaemia, haemorrhage, neoplasia and demyelination. The commonest ocular causes of acute visual loss are acute angle-closure glaucoma, retinal vascular occlusion, retinal detachment, and preretinal or vitreous haemorrhage.
Cranial Neuropathies II, III, IV, and VI
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
Strictly speaking, the optic nerve extends from the eyeball to the chiasm. Any disease that impacts the retinal ganglion cells including those of the optic chiasm and optic tract can have structural and functional effects on the optic nerves. The optic nerve head is supplied by a circular anastomosis of the posterior ciliary arteries called the circle of Zinn–Haller. These anastomoses are variable and scant, so the optic nerve head can be a watershed area. The intraorbital optic nerve travels within the cone formed by the extraocular muscles and exits the orbit through the optic canal, which is situated in the lesser wing of the sphenoid. The dura covering the optic nerve becomes invested in the periosteum of the optic canal at the annulus of Zinn at the orbital apex. Discordance between severe dyschromatopsia and mildly impaired visual acuity is a unique characteristic of optic neuropathy which can be useful in differentiating optic neuropathy from other causes of visual loss.
Hypothalamic Control Centers
Nate F. Cardarelli in The Thymus in Health and Senescence, 2019
Hypothalamic secretory dysfunction is common in patients with pineal tumors. A thymic extract was similarly evaluated with hypothalamic cells and found to decrease thymidine synthesis. In general, hypothalamic lesions in the young rat lead to a subsequent depressed humoral immune response in the mature rat. The suprachiasmatic nuclei (SCN) consist of a pair of small, generally ovoid structures in the basal hypothalamus just above the optic chiasm and connected to the pineal gland by the superior cervical ganglion and the nervi conarii. The SCN is in neural communication with a number of surrounding areas of the hypothalamus. The SCN has circadian rhythms that are synchronized with the external light-dark cycle through the eyes. Although the obvious influence of the SCN on circadian rhythm has led to considerable study of its characteristics, other areas of the hypothalamus which might also be involved in such rhythms have had much less scrutiny.
Compressive Lesions of the Optic Chiasm: Subjective Symptoms and Visual Field Diagnostic Criteria
Published in Neuro-Ophthalmology, 2018
Mikiko Takahashi, Toshiaki Goseki, Hitoshi Ishikawa, Goukon Hiroyasu, Kazunori Hirasawa, Nobuyuki Shoji
We investigated the diagnostic ability of a new criterion (simple temporal depression) for compressive lesions of the optic chiasm. The subjects were 124 eyes with compressive lesions of the optic chiasm. The controls were 84 eyes. The Humphrey (Carl Zeiss) visual field test was used for visual field testing. The simple temporal depression index was calculated as the ratio of the sums of the thresholds for one line on the nasal side and temporal side of the vertical meridian. The result of new index was 87% sensitivity and 99% specificity. This result suggested that our new criterion will assist the diagnosis in the future.
Cystic Optic Chiasm Lesion: Atypical Magnetic Resonance Imaging Findings
Published in Neuro-Ophthalmology, 2017
Sameen Haque, Kate Reid, Ross O’Neil, Christian Lueck
Intrinsic cystic lesions in the optic chiasm are an uncommon cause of bitemporal hemianopia compared with compressive lesions extrinsic to the chiasm. A 40-year-old man presented with difficulty driving. Clinical assessment revealed a bitemporal hemianopia. Magnetic resonance imaging showed an unusual cystic appearance of the chiasm. The appearance was felt to be most likely secondary to previous infective or inflammatory disease, but biopsy was not undertaken given the very significant risk of further visual loss.
Case Report: Late Sequela of a Muslinoma Involving the Optic Chiasm
Published in Neuro-Ophthalmology, 2018
Cynthia K. McClard, Claudia M. Prospero Ponce, Aroucha Vickers, Andrew G. Lee
An 84-year-old woman presented with 3 months of vertical binocular diplopia and difficulty reading at near. She had a history of bilateral ophthalmic artery aneurysm repair involving use of muslin in the 1990s. The patient then developed bitemporal hemianopsia secondary to muslin-induced inflammation (“muslinoma”) extending to the optic chiasm, which required surgical decompression. She had a persistent bitemporal hemianopsia but was stable for two decades after surgery. In 2017, the patient re-presented with double vision. Exam showed a non-paretic diplopia due to a small angle comitant right hypertropia attributed to the retinal hemi-field slide. Repeat imaging showed no new aneurysm or recurrent muslinoma. This case had originally been reported two decades ago and represents the longest duration of recurrent symptoms from muslin-related optochiasmatic arachnoiditis in the English language ophthalmic literature. Clinicians should be aware of the potential of delayed and recurrent symptoms or signs years or even decades after muslin wrapping of aneurysms.
Related Knowledge Centers
- Optic Nerve
- Prosencephalon
- Subthalamus
- Brain
- Thalamus
- Suprachiasmatic Nuclei
- Superior Colliculi