Homonymous Sectoranopia: Asymptomatic Presentation of a Lateral Geniculate Nucleus Lesion

Abstract

This is a rare presentation of brain tumour in the region of the lateral geniculate nucleus (LGN) presenting as a homonymous horizontal sectoranopia (HHS). The case highlights that subtle field defects can be asymptomatic and only detected by formal perimetry. Although homonymous sectoranopia is a rare form of visual field defect, it should be recognised as a potential manifestation of potentially significant intracranial pathology.

In vivo Probabilistic Structural Atlas of the Inferior and Superior Colliculi, Medial and Lateral Geniculate Nuclei and Superior Olivary Complex in Humans Based on 7 Tesla MRI

“…Brainstem nuclei such as the inferior colliculus (IC), superior colliculus (SC) and the superior olivary complex (SOC), as well as thalamic nuclei such as the medial geniculate nucleus (MG) and lateral geniculate nucleus (LG) modulate auditory/auditory-motor (IC, SOC and MG) and visual/oculo-motor (SC and LG) functions. These nuclei are also involved in the pathogenesis of disorders such as auditory agnosia, pure-word deafness, eye-movement and visual-field deficits, hallucinations in Parkinson’s disease, and glaucoma (Joswig et al, 2015; Pasu et al, 2015; Wang et al, 2015; Biotti et al, 2016; Lee et al, 2016). Nevertheless, a stereotaxic probabilistic structural atlas of these nuclei in living humans does not exist.…”

Cytoarchitectonic Maps of the Human Metathalamus in 3D Space

“…2 This way, the maps may provide a reference to localize findings from neuroimaging and serve as seed regions for functional connectivity and diffusion weighted imaging analyses. In this regard, they can be used to study brain disorders and functional impairments, including the LGB’s involvement in visual field and eye movement deficits ( Dai et al, 2011 ; Pasu et al, 2015 ; Usrey and Alitto, 2015 ; Wang et al, 2015 ), multiple sclerosis ( Sepulcre et al, 2009 ; Hickman et al, 2014 ; Papadopoulou et al, 2019 ), Parkinson’s disease ( Lee et al, 2016 ), psychiatric disorders ( Mai et al, 1993 ; Selemon and Begovic, 2007 ; Dorph-Petersen et al, 2009 ), as well as the MGB’s involvement in tinnitus ( Llinas et al, 2002 ; Rauschecker et al, 2010 ; Leaver et al, 2011 ; Ridder et al, 2015 ; Caspary and Llano, 2017 ; Berlot et al, 2020 ), and both structures’ involvement in Leber’s hereditary optic neuropathy ( Jonak et al, 2020 ). In tinnitus patients, the maps have the potential to aid future neurosurgical planning for deep-brain stimulation ( Smit et al, 2016 ; van Zwieten et al, 2021 ).…”

Homonymous Horizontal Sectoranopia Caused by an Occipital Lobe Infarct

“…Homonymous horizontal sectoranopia is an unusual visual field defect, accounting for only 0.3% of all homonymous field defects. 1 Classically, an homonymous sectoranopia results from an infarct to the LGN in the distribution of the lateral posterior choroidal artery. Although ischaemic infarction is the most common cause of LGN damage leading to homonymous horizontal sectoranopia, other causes include trauma, infection, malignancy, malformations, and central pontine myelinolysis.…”

“…Although ischaemic infarction is the most common cause of LGN damage leading to homonymous horizontal sectoranopia, other causes include trauma, infection, malignancy, malformations, and central pontine myelinolysis. [1][2][3][4][5] Although less common, there have been a few cases of apparent homonymous sectoranopia resulting from lesions in the optic radiations and the temporooccipital and parieto-occipital lobes. 2,3,6,7 Holmes et al were the first to report homonymous horizontal sectoranopia caused by damage to the optic radiations in 1931.…”

“…Homonymous horizontal sectoranopia is a wedgeshaped defect in the visual field that surrounds the horizontal meridian and typically results from an insult to the lateral geniculate nucleus (LGN). 1 Ultimately, an understanding of the blood supply to the retrochiasmal visual pathway is important in localising a lesion causing a distinctive visual field defect. The LGN is structurally arranged into six neuronal layers that are retinotopically organised.…”