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Neuro-Ophthalmological Findings in Patients with Posterior Circulation Stroke
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Reading, language, and memory abnormalities often are found in left PCA territory infarct patients (Table 23.1). Alexia without agraphia, also referred to as pure alexia and as pure word blindness, is a syndrome found in patients with relatively large left PCA territory infarcts. Patients with pure alexia can spell words aloud and identify words spelled to them. They are able to write correctly but later cannot read back what they had written earlier. They may retain the ability to read individual letters and usually can identify numbers. Patients who have alexia without agraphia almost invariably also have a right homonymous hemianopia or hemiachromatopsia and abnormal colornaming. Some patients also have an accompanying visual agnosia characterized by difficulty naming and identifying the nature of visual objects although the same objects are recognized when presented by sound or touch or described verbally. Another common accompanying deficit is in making new memories. The causative brain lesions invariably involve the white matter undercutting the left parastriate and peristriate regions. Infarcts usually include the parieto-occipital and often the temporal artery branches of the left PCA. The splenium of the corpus callosum is usually directly damaged, or its exiting white matter fibers are undercut.
Nervous system
Published in David Sturgeon, Introduction to Anatomy and Physiology for Healthcare Students, 2018
The final lobe of the cerebrum is the temporal lobe which is separated from the frontal and parietal lobes by the lateral sulcus (Sylvian fissure). It consists of the primary auditory cortex, the auditory association area and a number of limbic system structures including the hippocampus (Figure 12.10). The primary auditory cortex receives sound information in terms of pitch, rhythm and volume from the inner ear via the auditory nerve. The auditory association area interprets and translates these noises as speech, music or other familiar/unfamiliar sounds. Memories of sounds heard in the past are also stored in the temporal lobe, and we observed earlier in the chapter that the hippocampus is closely associated with the formation and retrieval of memories. The temporal lobe also seems to play an important role in face and object recognition and speech and language processes (Wernicke’s area is situated where the temporal and parietal lobes meet). Damage to the temporal lobe can result in a condition called agnosia where individuals are unable to recognise common objects, sounds, shapes or smells. The type of agnosia is dependent on which part of temporal lobe (or elsewhere) has been affected. For example, auditory agnosia often occurs following damage to the superior temporal lobe whereas visual agnosia occurs as a result of damage to the middle-inferior temporal lobe or posterior occipital lobe.
Examination of the Nervous System
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Tim Fowler, John Scadding, Nick Losseff
Visual agnosia is the inability to recognize what is seen when the eye, optic nerve and main visual pathway to the occipital cortex are preserved. Affected patients can often describe the shape, colour or size of an object without recognizing it. Prosopagnosia is the inability to recognize a familiar face. Parieto-occipital lesions are responsible.
The neuropsychological rehabilitation of visual agnosia and Balint’s syndrome
Published in Neuropsychological Rehabilitation, 2019
Joost Heutink, Dana L. Indorf, Christina Cordes
According to Zihl (2003), visual agnosia is a difficulty or inability to identify familiar stimuli via the visual modality, although the patient possesses sufficient visual perceptual, cognitive, and verbal functioning, and is able to recognise the stimulus using other modalities. Pure visual agnosia is a relatively rare condition, with an estimated prevalence of about 1–3% (Zihl & Kennard, 2003). At least four types of visual agnosia can be differentiated: prosopagnosia (the inability to recognise familiar faces and to learn new faces); object agnosia (the inability to identify stimuli in the same class or differentiate between classes of stimuli); topographical agnosia (difficulties with geographical orientation); and letter agnosia or pure alexia (inability to recognise individual letters and their combinations; Damasio, Tranel, & Rizzo, 2000; Roberts, 1992; Zihl, 2003). However, also finer distinctions can be made and very specific agnosias can be found in the literature as well (e.g., colour agnosia; Nijboer & Heutink, 2017).
Neuro-Ophthalmic Literature Review
Published in Neuro-Ophthalmology, 2019
David Bellows, Noel Chan, John Chen, Hui-Chen Cheng, Panitha Jindahra, Rauan Kaiyrzhanov, Peter MacIntosh, Michael Vaphiades, Konrad P. Weber, Sui Wong
This paper attempts to outline the current concepts of anatomy and neurophysiology underlying selective disorders of higher visual processing, i.e. the visual agnosias, and to describe the clinical conditions themselves. Every new case of agnosia has the potential to provide greater insight into the way the brain processes vision, as reflected in the ever-increasing number of related publications in the fields of visual physiology, neuropsychology, and neuroimaging. There is currently little that can be offered by way of treatment for most cases of visual agnosia, but an increase in our understanding has the potential to change this. Owing to the limitations of space, several disorders simply could not be covered, including congenital prosopagnosia, blindsight, hemispatial neglect, various forms of specific anomia and amnesia, and the different types of alexia. Given our aging population, these disorders will become more common and are more likely to be detected if they are specifically looked for, particularly in the context of stroke and degenerative disease. If physicians are familiar with the visual agnosias then their existence in patients will be more readily detected.
Pilot Study: The Queen Square Screening Test for Visual Deficits in Dementia
Published in Neuro-Ophthalmology, 2021
Leah N Kim, Dennis Cordato, Alan McDougall, Clare Fraser
Despite increased research on the visual deficits in dementia, there is limited consensus on their specificity to the various dementia syndromes including Alzheimer’s disease (AD), Lewy body dementia (LBD), and posterior cortical atrophy (PCA). In AD, which accounts for the majority of cases, impairment of memory and executive function appear first, but visual processing may also be impaired in the early stages, manifesting as difficulties with reading, discriminating form and colour, perceiving contrast, perceiving visuospatial orientation and motion detection. This may progressively decline into visual agnosia and difficulty in developing visual strategies.5