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Chapter 027. Aphasia, Memory Loss, and Other Focal Cerebral Disorders (Part 6)

Pure Alexia Without Agraphia This is the visual equivalent of pure word deafness. The lesions (usually a combination of damage to the left occipital cortex and to a posterior sector of the corpus callosum—the splenium) interrupt the flow of visual input into the language network. There is usually a right hemianopia, but the core language network remains unaffected. The patient can understand and produce spoken language, name objects in the left visual hemifield, repeat, and write. However, the patient acts as if illiterate when asked to read even the simplest sentence because the visual information from the written words (presented. | Chapter 027. Aphasia Memory Loss and Other Focal Cerebral Disorders Part 6 Pure Alexia Without Agraphia This is the visual equivalent of pure word deafness. The lesions usually a combination of damage to the left occipital cortex and to a posterior sector of the corpus callosum the splenium interrupt the flow of visual input into the language network. There is usually a right hemianopia but the core language network remains unaffected. The patient can understand and produce spoken language name objects in the left visual hemifield repeat and write. However the patient acts as if illiterate when asked to read even the simplest sentence because the visual information from the written words presented to the intact left visual hemifield cannot reach the language network. Objects in the left hemifield may be named accurately because they activate nonvisual associations in the right hemisphere which in turn can access the language network through transcallosal pathways anterior to the splenium. Patients with this syndrome may also lose the ability to name colors although they can match colors. This is known as a color anomia. The most common etiology of pure alexia is a vascular lesion in the territory of the posterior cerebral artery or an infiltrating neoplasm in the left occipital cortex that involves the optic radiations as well as the crossing fibers of the splenium. Since the posterior cerebral artery also supplies medial temporal components of the limbic system the patient with pure alexia may also experience an amnesia but this is usually transient because the limbic lesion is unilateral. Aphemia There is an acute onset of severely impaired fluency often mutism which cannot be accounted for by corticobulbar cerebellar or extrapyramidal dysfunction. Recovery is the rule and involves an intermediate stage of hoarse whispering. Writing reading and comprehension are intact so this is not a true aphasic syndrome. Partial lesions of Broca s area or subcortical lesions