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Stroke
Published in Henry J. Woodford, Essential Geriatrics, 2022
The middle cerebral artery (MCA) supplies the majority of the parietal and temporal lobes. Any motor deficit is usually more severe in the arm than the leg. Due to the large representation of the hand in the motor cortex, it is possible to have a localised infarct that affects solely hand function. There will usually be associated cortical deficits, such as sensory inattention or aphasia. Visual function may be affected with either homonymous hemianopia or an upper or lower quadrantanopia (due to involvement of all or part of the optic radiation).
Impact of Retinal Stimulation on Neuromodulation
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
The signal content in the optic radiations depends on the originating location of the visual signal. Signals from superior space (at or above eye level) travel through the bottom portions of each retina and head through temporal lobes, while targets below eye level send signals through the superior retina and interact with the parietal lobes. Meyer’s loop in the temporal lobe was originally thought to be an anterior looping of optic radiation fibers (Jeelani et al. 2010). However, in 2015, scientists determined that Meyer’s loop is a conglomeration of many sensory signals (Goga and Ture 2015) (Figure 22.4).
Optic radiations
Published in Fiona Rowe, Visual Fields via the Visual Pathway, 2016
The optic radiations pass through a large area of the posterior cranial cavity including the temporal and parietal lobes before reaching their termination in the occipital lobe. They are therefore susceptible to a number of different types of pathological lesions including space-occupying lesions and cerebro vascular disorders.
Visual Acuity in Glaucomatous Eyes Correlates Better with Visual Field Parameters than with OCT Parameters
Published in Current Eye Research, 2021
Yukihisa Suzuki, Motohiro Kiyosawa
We observed significant correlation between visual acuity and GCC thickness of macula in glaucomatous groups. Information sent by the retinal ganglion cells (RGCs) is received in the sensory retina, which is then sent to the lateral geniculate nucleus (LGN) through the optic nerve. The information is finally sent to the visual cortex through the optic radiation (OR). Previous studies observed alterations not only in the RGCs but also in the LGN20 and OR21,22 in glaucoma patients. There is no report examining the mechanism by which decrease of visual acuity occurs in glaucoma patients. In previous studies, a decrease in GCC thickness was reported in glaucoma patients,23,24 and it was reported that GCC was thinner in advanced glaucoma.8 Kim et al.8 also observed a significant correlation between visual acuity and GCC thickness in glaucomatous eyes. The reduction of RGCs would cause a decrease in the amount of visual information that is transmitted to the visual cortex.
Impact of Amblyopia on the Central Nervous System
Published in Journal of Binocular Vision and Ocular Motility, 2020
Nathaniel P. Miller, Breanna Aldred, Melanie A. Schmitt, Bas Rokers
There are also notable changes to white-matter structure in the optic radiations, the major visual pathways connecting LGN to the primary visual cortex (V1). In general, structural integrity of the optic radiations appears to be reduced compared to those of control subjects, as revealed by changes in mean diffusivity (MD) and fractional anisotropy (FA). Allen et al. reported significantly increased MD in the optic radiations (averaged across both hemispheres) of amblyopes compared to controls.62,80 Other studies have noted bilateral FA reductions in the optic radiations compared to controls.81,82 Duan, et al. reported increased MD in the optic radiation; however, their results were hemisphere-specific, with significant increases in the left optic radiation, but not in the right optic radiation.83 Li, et al. reported decreased FA in the optic radiation, however their effects were restricted to the right, rather than the left optic radiation.84
Contemporary surgical management of drug-resistant focal epilepsy
Published in Expert Review of Neurotherapeutics, 2020
Jasmina R. Milovanović, Slobodan M. Janković, Dragan Milovanović, Dejana Ružić Zečević, Marko Folić, Marina Kostić, Goran Ranković, Srđan Stefanović
A patient with epilepsy who is candidate for surgical treatment should be subjected to additional diagnostics aimed to determine precise location of the epileptogenic zone and to evaluate risk of postoperative neurological deficit [3]. At first noninvasive methods are used to locate the epileptogenic zone (magnetic resonance imaging (MRI), high-resolution electroencephalography (HR-EEG), magnetoencephalography (MEG), positron emission tomography (PET) and single-photon emission computed tomography (SPECT)), and if unsuccessful, intracranial EEG monitoring with stereo-electroencephalography (S-EEG) is undertaken. By means of functional magnetic resonance imaging (FMRI) and the Wada test a dominant brain hemisphere in regard to the speech is determined, and a risk of postoperative memory impairment is estimated. Finally, tractographies of the optic radiations and pyramidal tract are made to estimate risks of visual fields defects and motor deficits. If the epileptogenic zone was precisely located and estimated risks are much lower than expected benefits, the patient may proceed with surgery [3].