Neuro-Ophthalmological Findings in Patients with Posterior Circulation Stroke
Vivek Lal in 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.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
Anterior disconnection syndrome may follow from lesions to the foremost portion of the corpus callosum. Such lesions are associated with infarction of the anterior cerebral artery. Patients demonstrate unilateral APRAXIA of the left hand, and cannot name or otherwise verbalize information about objects held in the left hand. Posterior disconnection syndrome is associated with lesions of the SPLENIUM portion of the corpus callosum. Tumours or infarction of the posterior cerebral artery are common aetiology. Patients may complain of visual disturbances. Functional dissociation between reading impairment (DYSLEXIA) and writing impairment (DYSGRAPHIA) may be associated with some disconnections between the cerebral hemispheres. ALEXIA without AGRAPHIA is attributable to a complex set of lesions that cause dysfunction of the left VISUAL CORTEX in conjunction with a lesion of the posterior corpus callosum which effectively isolates the right visual cortex from the (damaged) left visual cortex. Consequently, both the right and left visual cortices are isolated from the (intact) language area. The intact language areas allow written language production (WRITING) whilst the disconnection of visual stimulus input to the language areas results in failed comprehension of written language (READING). The clinical indication of this complex syndrome is demonstrated by an intact ability to copy or write spontaneously with the striking failure to read what was written.
Alexia
Alexander R. Toftness in Incredible Consequences of Brain Injury, 2023
Alexia without agraphia is usually understood as a disconnection between the part of the brain that sees the words as visual input and the part of the brain that understands the words as language. Most notably, there is a region in the middle fusiform gyrus that, when damaged, is a very good predictor of alexia (Martinaud, 2017). That middle fusiform gyrus damage is usually on the left side of the brain, but there are a few cases where damage to this area in the right hemisphere can also cause alexia (Leśniak et al., 2014).
Diagnosing and managing post-stroke aphasia
Published in Expert Review of Neurotherapeutics, 2021
Shannon M. Sheppard, Rajani Sebastian
In addition to broad language comprehension and production deficits, stroke can also cause reading and writing deficits. Alexia refers to reading deficits and agraphia refers to writing deficits. In cases of pure alexia, patients demonstrate reading impairments in the absence of any other deficits [34,35]. Pure alexia is associated with simultaneous damage to 1) left occipital cortex, which causes right homonymous hemianopsia where visual information is initially processed in the right occipital cortex, and 2) splenium of the corpus callosum, which then prevents visual information in the right hemisphere from crossing over to the left hemisphere, where language is processed [36]. Pure agraphia refers to cases where writing impairments are present in the absence of other difficulties [35]. Spelling deficits are associated with damage to left inferior parietal cortex and left occipitotemporal cortex [37].
A case of aneurysmal subarchnoid haemorrhage and superficial siderosis complicated by prospagnosia, simultagnosia and alexia without agraphia
Published in British Journal of Neurosurgery, 2023
Mohammed Fadelalla, Avinash Kanodia, Mustafa Elsheikh, John Ellis, Vivien Smith, Kismet Hossain-Ibrahim
Alexia without agraphia, also known as ‘pure alexia’, ‘word blindness’ and ‘agnostic alexia, is known to be caused by lesions to the visual word form area in the left occipital lobe.5 In our case MRI ruled out any lesions in the fusiform gyri, occipital lobes and temporal lobes. The only prominent abnormality was widespread deposition of hemosiderin over the brain surfaces especially the corpus callosum and adjacent brain surfaces.
The memory for words: Armand Trousseau on aphasia
Published in Journal of the History of the Neurosciences, 2022
The lesion causing pure alexia12Pure alexia is a disconnection syndrome in which patients cannot comprehend what is written, even if they have written it themselves. It results from a destructive lesion of the left occipital lobe that also interrupts the pathway leading from the intact right occipital lobe and the left angular gyrus at the level of the splenium of the corpus callosum. was also localized by Dejerine (1892), but Trousseau provided a concise yet full description of the syndrome of alexia without agraphia in his1865 address to the Imperial Academy of Medicine: Here is now a patient whose intelligence is trouble in a singular fashion. He no longer knows how to read. He is a merchant from Valenciennes who had a stroke13Un coup de sang. four months ago. He now speaks perfectly well and relates that following his attack he was slightly paralysed on the right and that at the time he could not speak. Little by little his speech returned, but he could no longer read. I tried in vain to have him decipher the title of a journal and I had him spell each word letter by letter, but he could not assemble the syllables. He was not, however, amblyopic, as I confirmed by having him pick up a pin on the floor. What is most implausible is that this man could write, but that he could not read what he had correctly written. I immediately invited him to sit at my desk and he quickly wrote this sentence, “I am very happy, sir, to have come to see you. I hope to leave cured.” It was absolutely impossible for him to read the sentence that he had just written. Can we find, Gentlemen, a better example to demonstrate the independence of faculties that until now have been considered to be inexorably linked, the ability of reading what we had the ability to write. (Trousseau 1865, 562)
Related Knowledge Centers
- Dyslexia
- Agraphia
- Medial Medullary Syndrome
- Eponym
- Infarction
- Posterior Cerebral Artery
- Corpus Callosum
- Visual Cortex
- Occipital Lobe
- Broca'S Area