Pure alexia with intact perception of complex visual stimuli: a case study.

After a stroke involving the left occipitotemporal cortex our patient shows a word-length effect and has problems to identify letters or numbers in strings of symbols. But he is normal in identifying isolated letters and in non-verbally categorizing even complex images such as faces or natural scenes. His cortical lesion is stretching from the visual word form area (VWFA) anteriorly causing additional problems to name visual stimuli and to match acoustic stimuli with images. We conclude that our patient suffers from pure alexia without deficits to identify even complex visual stimuli. Our results directly contradict several explanations for letter-by-letter reading.

Reading on the right when there's nothing left? Probabilistic tractography reveals hemispheric asymmetry in pure alexia.

We present a patient with reading inexpertise and right hemianopia following left posterior cerebral artery (PCA) stroke. We examine the extent of disruption to reading performance and the extent of white matter tract damage relative to a patient with more limited PCA infarction and isolated right hemianopia. We show white matter disconnection of the temporal occipital fusiform cortex in our pure alexia patient. Connectivity-based laterality indices revealed right hemisphere laterality in the alexia patient; this was not associated with improved reading function. We speculate that the degree of premorbid laterality may be a critical factor affecting the extent of reading dysfunction in alexia.

To read or not to read: a neurophysiological study.

Pure alexia (PA) has been associated with visual deficits or a failure to activate the visual word form area (VWFA). We report a patient with pure alexia due to posterior cortical atrophy, in whom event-related potentials revealed a delay in the P100 component and an absent N170 compared with controls. Furthermore, there was a tendency for a larger delay in P100 latencies associated with incorrectly read words. This suggests that some cases of PA might result from deficits in visual perception, signaled by the P100 early potential which could lead to an inability to consistently activate the VWFA, marked by the absent N170.

Posterior cerebral artery stroke presenting as alexia without agraphia.

Alexia without agraphia (pure alexia) was the first of the disconnection syndromes to be described by Dejerine who reported a patient of alexia without agraphia secondary to an embolic occipital lobe infarct. We herein report a 55-year-old man who presented with alexia without agraphia with magnetic resonance imaging suggestive of left posterior cerebral artery infarct involving left occipital lobe and splenium of corpus callosum. Alexia without agraphia is a relatively uncommon clinical condition, which should always be thought in a patient presenting with difficulty in reading with normal visual acuity. Ophthalmologists should also be aware of this disconnection syndrome as many patients initially take their advice due to predominant visual complaints. Early diagnosis and treatment of this condition help in ensuring the patient and attendants about nonprogressive nature of the disease and may prevent further episodes of stroke.

Posterior cortical atrophy with prominent alexia without agraphia in a Tourette syndrome.

We report for the first time a patient with childhood-onset Tourette's syndrome (TS) who developed alexia without agraphia, acalculia, visual agnosia for objects and faces, and preserved mnesic functions in older age. Neuroimaging studies demonstrated temporo-parieto-occipital cortical atrophy and fronto-temporo-parieto-occipital hypometabolism, both more prominent on the left side. This case fulfils the diagnostic criteria of posterior cortical atrophy (PCA). The possible link between TS and PCA is discussed.

"Seeing but not identifying": pure alexia coincident with prosopagnosia in occipital arteriovenous malformation.

BACKGROUND: Pure alexia and prosopagnosia are two separate and uncommon disorders of visual recognition in neuro-ophthalmology. We report an extremely rare case of pure alexia coincident with prosopagnosia secondary to occipital arteriovenous malformation. The manifestations of these two visual recognition disorders are also described. METHODS: A 35-year-old, left-handed women had suffered from severe blurred vision when recognizing her family's faces and was unable to read or associate separate parts of a word into a whole word. Her visual field revealed slight right homonymous hemianopia. Computed tomography scans and magnetic resonance images were arranged and vertebral angiography confirmed the diagnosis of left occipital arteriovenous malformation. RESULTS: Gamma-knife stereoscopic radiotherapy was performed. Two months after the treatment, the ability to recognize faces and read improved and the visual field recovered. CONCLUSIONS: Ophthalmologists should keep in mind that usual complaints of "blurred vision" might correlate with unusual visual recognition disorders. Pure alexia and prosopagnosia have not been reported to occur together and the left-handed- dominance in our case leads to this scarce concurrence.

Alexia without agraphia.

Alexia without agraphia (also called pure alexia or word blindness) was the first of the disconnection syndromes (syndromes caused by disconnection of the right from the left cerebral hemisphere through interruption of the communication pathways between them) to be described. Déjerine in 1892 reported a patient who developed this syndrome after an infarct of the left occipital lobe and splenium of the corpus callosum. We describe a patient who developed alexia without agraphia due to an embolic left occipital lobe infarct extending to the posterior commissure and splenium of the corpus callosum.

Seeing is not believing.

An 84-year-old woman with a history of dry age-related macular degeneration presented with an acute inability to read, but intact writing ability (pure alexia or alexia without agraphia). She denied any difficulty speaking, paresthesias, or hemiparesis. Her visual acuity was 20/20 in each eye. Macular examination, optical coherence tomography, and fluorescein angiography demonstrated the previously diagnosed macular drusen and geographic atrophy of the retinal pigment epithelium consistent with the dry form of age-related macular degeneration both eyes. Automated perimetry revealed a right homonymous hemianopsia. Neuroimaging confirmed a left occipital ischemic infarction with involvement of the splenium of the corpus callosum producing the classic disconnection syndrome of alexia without agraphia.

Pure alexia as a disconnection syndrome: new diffusion imaging evidence for an old concept.

Functional neuroimaging and studies of brain-damaged patients made it possible to delineate the main components of the cerebral system for word reading. However, the anatomical connections subtending the flow of information within this network are still poorly defined. Here we study the connectivity of the Visual Word Form Area (VWFA), a pivotal component of the reading network achieving the invariant identification of letter strings, and reproducibly located in the left lateral occipitotemporal sulcus. Diffusion images and functional imaging data were gathered in a patient who developed pure alexia following a small surgical lesion in the vicinity of his VWFA. We had a unique opportunity to compare images obtained before, early after, and late after surgery. Analysis of diffusion images with white matter tractography and voxel-based morphometry showed that the VWFA was mainly linked to the occipital cortex through the inferior longitudinal fasciculus (ILF), and to perisylvian language areas (supramarginal gyrus) through the arcuate fasciculus. After surgery, we observed the progressive and selective degeneration of the ILF, while the VWFA was anatomically intact. This allowed us to establish the critical causal role of this fiber tract in normal reading, and to show that its disruption is one pathophysiological mechanism of pure alexia, thus clarifying a long-standing debate on the role of disconnection in neurocognitive disorders.

Alexia with and without agraphia: an assessment of two classical syndromes.

BACKGROUND: Current cognitive models propose that multiple processes are involved in reading and writing. OBJECTIVE: Our goal was to use linguistic analyses to clarify the cognitive dysfunction behind two classic alexic syndromes. METHODS: We report four experiments on two patients, one with alexia without agraphia following occipitotemporal lesions, and one with alexia with agraphia from a left angular gyral lesion. RESULTS: The patient with occipital lesions had trouble discriminating real letters from foils and his reading varied with word-length but not with linguistic variables such as part of speech, word frequency or imageability. He read pseudo-words and words with regular spelling better, indicating preserved use of grapheme-to-phoneme pronunciation rules. His writing showed errors that reflected reliance on 'phoneme-to-grapheme' spelling rules. In contrast, the patient with a left angular gyral lesion showed better recognition of letters, words and their meanings. His reading was better for words with high imageability but displayed semantic errors and an inability to use 'grapheme-to-phoneme' rules, features consistent with deep dyslexia. His agraphia showed impaired access to both an internal lexicon and 'phoneme-to-grapheme' rules. CONCLUSION: Some cases of pure alexia may be a perceptual word-form agnosia, with loss of internal representations of letters and words, while the angular gyral syndrome of alexia with agraphia is a linguistic deep dyslexia. The presence or absence of agraphia does not always distinguish between the two; rather, writing can mirror the reading deficits, being more obvious and profound in the case of an angular gyral syndrome.

Agraphia for kanji resulting from a left posterior middle temporal gyrus lesion.

OBJECTIVE: To clarify whether agraphia or alexia occurs in lesions of the left posterior middle temporal gyrus. METHODS: We assessed the reading and writing abilities of two patients with this lesion using kanji (Japanese morphograms) and kana (Japanese syllabograms). RESULTS: Patient 1 first presented with pure alexia more impaired for kana after an infarction in the left middle and inferior occipital gyri and right basal occipital cortex, and after a second infarction in the left posterior middle temporal gyrus adjoining the first lesion he showed alexia with agraphia for kanji and worsened alexia for kana; kanji alexia recovered over the following six to 10 months. Patient 2 presented with alexia with agraphia for kanji following a hemorrhage in the left posterior middle and inferior temporal gyri, which resolved to agraphia for kanji at two months after onset. Kana nonword reading was also slightly impaired, but became normal by six months post-onset. In both patients, kanji agraphia was mostly due to impaired character recall. CONCLUSION: The present patients demonstrate that damage to the left posterior middle temporal gyrus alone can cause agraphia for kanji. If the adjacent mid fusiform/inferior temporal gyri (Area 37) are spared, the kanji alexia is transient.

Examination of the split fovea theory in a case of pure left hemialexia.

To address the extent to which the visual foveal representation is split, we examine the case of a patient, M.B., suffering from a left mesial occipital lesion and presenting a pure left hemialexia and a right hemianopia with a spared area of the macula. Reading performance on tachistoscopically presented four-letter words and pseudowords in the spared area of the right visual field was significantly better than reading performance in the intact left visual field. Reading performance in the spared area of the right visual field was also significantly better than reading performance of stimuli centred on the fovea. Moreover, a length effect was found only in the left half of pseudowords centred on the fovea, but not in the right half (up to five letters). These differences in reading efficiency between the left and right halves of the foveal region militates in favour of the split fovea theory and cannot be explained by the bilateral projection theory.

Qualitatively different forms of pure alexia.

In this study we investigated two patients with pure alexia, F.C. and L.D.S., in order to make inferences about how processes and levels involved in the early stage of visual word recognition are organized and how they can be selectively damaged. Moreover, we investigated whether pure alexia can be caused by different functional deficits. F.C. and L.D.S. were presented with tasks of letter processing and tasks of orthographic integration. There was a clear double dissociation between the pattern of performance of F.C. and L.D.S. F.C. was able to process single letters rapidly and accurately, but was unable to group together the letters that he had correctly identified. By contrast, L.D.S. was slower and more impaired at letter identification, but she could use letter groups to assist reading. Thus, two different forms of pure alexia emerged: F.C. has a higher level deficit in integrating letters, whereas L.D.S. has a lower level deficit in letter processing. The results support the assumption of a functional organization of the reading process that involves a series of orthographic units (i.e., single letters, sublexical letter groups, and the lexical unit), which can be selectively damaged. Finally, our data present difficulties for models of pure alexia that assume all patients to have a low-level processing deficit.

Large acute cerebral hemorrhage presenting with pure alexia.

Alexia (the acquired inability to read) is an uncommon presenting complaint in the emergency department (ED). It is usually associated with a lesion in the brain located within the dominant hemisphere near the parieto-occipital junction, with some involvement of the splenium of the corpus callosum. Our review of the literature revealed multiple distinct causes for the finding of alexia, and a majority of the cases uncovered also involved agraphia (the acquired inability to write) and frequently visual field defects. We present the case of an otherwise healthy 35-year-old white man who arrived at our ED with the chief complaint of having difficulty reading. He was, however, able to write, and he exhibited no defects in his visual fields on gross testing in our ED. The patient was found to have a large, acute, intraparenchymal hemorrhage in the right posterior/inferior parietal cortex, very near the occipital lobe. We present this case, followed by a brief discussion, to heighten awareness of the complaint of alexia with or without agraphia as a possible presenting symptom of intracranial hemorrhage, or ischemic cerebrovascular accident.

Differential reorganization of fusiform gyrus in two types of alexia after stroke.

Lesions affecting the left fusiform gyrus (FG) commonly result in dyslexia and recovery largely depends on efficient reorganization of the reading network. We performed a follow-up fMRI study to elucidate the reorganization patterns of the FG according to the recovery of reading ability in two patients (MH with pure alexia and KM with alexia with agraphia) after stroke involving the left FG. Initially, MH was an effortful letter-by-letter (LBL) reader, and she improved to become a proficient LBL reader. The initial fMRI results showed scattered activation on occipital and ventral temporal cortex during reading, which was localized to right FG in the follow-up study. KM's severe alexia with agraphia did not improve, even after 6 months had passed since the onset of the alexia. The initial and follow-up fMRI results showed no significant activation in the bilateral FG or central higher language areas during word reading. Our results suggest that the reorganization of the FG is different according to the type of alexia and the amount of clinical recovery in each patient. Also, the successful reorganization of the visual component of reading in the right FG is responsible for the recovery of LBL reading in pure alexia.

Structural anatomy of pure and hemianopic alexia.

BACKGROUND: The two most common types of acquired reading disorder resulting from damage to the territory of the dominant posterior cerebral artery are hemianopic and pure alexia. Patients with pronounced hemianopic alexia have a right homonymous hemianopia that encroaches into central or parafoveal vision; they read individual words well, but generate inefficient reading saccades when reading along a line of text. Patients with pure alexia also often have a hemianopia but are more disabled, making frequent errors on individual words; they have sustained damage to a brain region that supports efficient word identification. OBJECTIVE: To investigate the differences in lesion site between hemianopic alexia and pure alexia groups, as rehabilitative techniques differ between the two conditions. METHODS: High-resolution magnetic resonance images were obtained from seven patients with hemianopic alexia and from six patients with pure alexia caused by a left occipital stroke. The boundary of each lesion was defined and lesion volumes were then transformed into a standard stereotactic space so that regional comparisons could be made. RESULTS: The two patient groups did not differ in terms of damage to the medial left occipital lobe, but those with pure alexia had additional lateral damage to the posterior fusiform gyrus and adjacent tissue. CONCLUSIONS: Clinicians will be able to predict the type of reading disorder patients with left occipital lesions have from simple tests of reading speed and the distribution of damage to the left occipital lobe on brain imaging. This information will aid management decisions, including recommendations for reading rehabilitation.

Fusiform type alexia: pure alexia for words in contrast to posterior occipital type pure alexia for letters.

OBJECTIVE: To clarify the behavioral differences between patients with pure alexia from different lesions. METHODS: Two patients with pure alexia caused by damage to the fusiform or posterior occipital gyri were given reading and writing tests including kanji (Japanese morphograms) and kana (Japanese phonetic writing). RESULTS: Patient 1 (pure alexia from a fusiform gyrus lesion) had difficulty reading both kanji and kana, with kanji reading more impaired, and imageability and visual complexity effects (imageable or less complex words/characters were read better than nonimageable or more complex words/characters), whereas patient 2 (pure alexia from a posterior occipital gyri lesion) showed selective impairment of kana reading. CONCLUSION: Pure alexia for kanji (and kana; fusiform type) is characterized by impairments of both whole-word reading, as represented in kanji reading, and letter identification, and is different from pure alexia for kana (posterior occipital type) in which letter identification is primarily impaired. Thus, fusiform type pure alexia should be designated pure alexia for words, whereas posterior occipital type pure alexia should be designated pure alexia for letters.