Post-stroke Chinese pure alexia: linguistic features and neuropsychological profiles.

PURPOSE: Very few cases of Chinese pure alexia have been reported to date. We aim to summarize the linguistic features and neuropsychological profiles of Chinese pure alexia through a case series study. METHODS: 11 consecutive patients with post-stroke Chinese pure alexia and 11 healthy controls were included. The Aphasia Battery of Chinese (ABC) and 68-Chinese character oral reading test (68-character test) were used to evaluate the reading and writing ability. Reading errors were classified based on the performance of 68-character test. Neuropsychological profiles were evaluated with corresponding scales. The possible correlation between the reading ability and the writing ability or neuropsychological performance was analyzed. RESULTS: The patients had a correct rate of 43.7 ± 23.2% in the 68-character test, significantly lower (P < 0.001) than that of controls. Shape-similar error was the most common type of reading error (101/209, 48.3%). The ABC total writing score rate of the patients ranged from 68.9% to 98.7% (median, 90.5%), significantly lower (P < 0.001) than that of the controls. The patients also showed worse performance in MMSE, auditory verbal learning test, Boston naming test, intersecting pentagons copying and clock-drawing test (all P < 0.05). In the patient group, the correct rate of 68-character test was significantly correlated with the ABC total writing score rate (P = 0.008), the score rate of Boston naming test (P = 0.017), and the clock-drawing test score (P = 0.010). CONCLUSION: Shape-similar errors may be a characteristic of Chinese pure alexia. The correlation between visuospatial dysfunction and pure alexia might explain the frequent occurrence of shape-similar errors in Chinese pure alexia.

A case of aneurysmal subarchnoid haemorrhage and superficial siderosis complicated by prospagnosia, simultagnosia and alexia without agraphia.

A 42-year-old lady presented with acute aneurysmal subarachnoid haemorrhage and developed difficulty recognising faces (prosopagnosia), inability to process visual information in busy environments (simultagnosia) and difficulty to read (alexia). She was subsequently found to have superficial siderosis on MRI.

Right hemi-alexia.

While pure alexia was long considered a disconnection syndrome, it may also be a selective visual word agnosia due to damage to the visual word form area. Disconnection is still the likely explanation of hemi-alexias, though, particularly when splenial lesions damage inter-hemispheric projections and cause left hemi-alexia. An intra-hemispheric disconnection causing right hemi-alexia is theoretically possible but seems very rare, with only a single report that has been challenged on the grounds of inadequate perimetry. We describe the case of PH, who had a severe reading deficit in her right hemifield. Detailed perimetry showed only a small relative hemi-scotoma along the horizontal meridian, while word reading was impaired over a much larger expanse of her right hemifield, in which object recognition was spared. Reading, lexical decisions, and perceptual discrimination of words were impaired in the right hemifield, and this extended to letters and numbers, with a trend to an effect on the perception of an unfamiliar script, namely Korean. On magnetic resonance imaging she had a large left lateral occipital meningioma with vasogenic edema of occipital white matter tracts. Functional magnetic resonance imaging showed that the visual word form area was located just anterior to the mass. Her perceptual abnormalities resolved after resection of the tumor. We conclude that right hemi-alexia exists and is most likely due to intra-hemispheric disconnection of occipital input to the visual word form area.

White matter disconnectivity fingerprints causally linked to dissociated forms of alexia.

For over 150 years, the study of patients with acquired alexia has fueled research aimed at disentangling the neural system critical for reading. An unreached goal, however, relates to the determination of the fiber pathways that root the different visual and linguistic processes needed for accurate word reading. In a unique series of neurosurgical patients with a tumor close to the visual word form area, we combine direct electrostimulation and population-based streamline tractography to map the disconnectivity fingerprints characterizing dissociated forms of alexia. Comprehensive analyses of disconnectivity matrices establish similarities and dissimilarities in the disconnection patterns associated with pure, phonological and lexical-semantic alexia. While disconnections of the inferior longitudinal and posterior arcuate fasciculi are common to all alexia subtypes, disconnections of the long arcuate and vertical occipital fasciculi are specific to phonological and pure alexia, respectively. These findings provide a strong anatomical background for cognitive and neurocomputational models of reading.

Transcranial direct current stimulation with multiple oral re-reading therapy for pure alexia without agraphia: a case report.

Pure alexia without agraphia is characterized by impaired reading due to damage to the occipitotemporal cortex with preserved writing skills. In this case report, we investigate the effect of multiple oral re-reading (MOR) therapy adjunct with transcranial direct current stimulation (tDCS) in improving reading recovery of a 64-year-old patient with pure alexia without agraphia following a stroke. His MRI revealed an area of infarct with microhemorrhages at the left occipitotemporal region. The patient was blinded to each therapy and underwent seven consecutive sessions of sham tDCS followed by seven consecutive sessions of real tDCS, coupled with 1-hour MOR therapy during each session. Western Aphasia Battery (WAB) was performed at baseline, before sham and real-tDCS, and 6 weeks after completing tDCS therapy. The patient showed improvement using both sham and real-tDCS with better reading comprehension, average reading time, and word per minute after real-tDCS. This study suggests that MOR, coupled with tDCS therapy may accelerate the reading recovery in patients with pure alexia.

Whole-object effects in visual word processing: Parallels with and differences from face recognition.

Visual words and faces differ in their structural properties, but both are objects of high expertise. Holistic processing is said to characterize expert face recognition, but the extent to which whole-word processes contribute to word recognition is unclear, particularly as word recognition is thought to proceed by a component-based process. We review the evidence for experimental effects in word recognition that parallel those used to support holistic face processing, namely inversion effects, the part-whole task, and composite effects, as well as the status of whole-word processing in pure alexia and developmental dyslexia, contrasts between familiar and unfamiliar languages, and the differences between handwriting and typeset font. The observations support some parallels in whole-object influences between face and visual word recognition, but do not necessarily imply similar expert mechanisms. It remains to be determined whether and how the relative balance between part-based and whole-object processing differs for visual words and faces.

Complementary deficits in perceptual classification in pure alexia and acquired prosopagnosia - New insights from two classic cases.

Pure alexia and prosopagnosia traditionally have been seen as prime examples of dissociated, category-specific agnosias affecting reading and face recognition, respectively. More recent accounts have moved towards domain-independent explanations that postulate potential cross-links between different types of visual agnosia. According to one proposal, abnormal crowding, i.e. the impairment of recognition when features of adjacent objects are positioned too closely to each other, might provide a unified account for the perceptual deficits experienced by an agnosic patient. An alternative approach is based on the notion of complementary visual subsystems favouring the processing of abstract categories and specific exemplars, respectively. To test predictions of these two approaches with regard to pure alexia and prosopagnosia, we present previously unpublished data on digit recognition and visual crowding from two in the neuropsychological literature extensively studied patients, KD and MT (e.g., Campbell et al., 1986; Landis and Regard, 1988; Rentschler et al., 1994). Patient MT, diagnosed with pure alexia, showed pronounced abnormal foveal crowding, whereas KD, diagnosed with prosopagnosia, did not. These results form a distinct double dissociation with the performance of the two patients in other perceptual classification tasks involving Gabor micropatterns and textures, as well as Glass patterns, which revealed a significantly greater impairment in KD relative to MT. Based on an analysis of the specific task demands we argue that prosopagnosia and pure alexia may involve complementary deficits in instantiation and abstraction, respectively, during perceptual classification, beyond any category specificity. Such an explanation appears in line with previous distinctions between a predominantly left-hemispheric, abstract-category and a predominantly right-hemispheric, specific-exemplar subsystem underlying object recognition.

Can the right hemisphere read? A behavioral and disconnectome study on implicit reading in a patient with pure alexia.

Patients with pure alexia have major difficulties in reading aloud. However, they often perform above chance level in reading tasks that do not require overt articulation of the target word - like lexical decision or semantic judgment - a phenomenon usually known as "implicit reading." There is no agreement in the literature on whether implicit reading should be attributed to relative sparing of some left hemisphere (LH) reading centers or rather to signs of compensatory endeavors by the right hemisphere (RH). We report the case of an 81-year-old patient (AA) with pure alexia due to a lesion involving the left occipital lobe and the temporal infero-mesial areas, as well as the posterior callosal pathways. Although AA's reading was severely impaired and proceeded letter by letter, she showed an above-chance-level performance for frequent concrete words in a tachistoscopic lexical decision task. A structural disconnectome analysis revealed that AA's lesion not only affected the left occipital cortex and the splenium: it also disconnected white-matter tracts meant to connect the visual word-form system to decision-related frontal areas within the LH. We suggest that the RH, rather than the LH, may be responsible for patient AA's implicit reading.

Examining the function of the visual word form area with stereo EEG electrical stimulation: A case report of pure alexia.

Functional imaging studies have implicated an area in the left lateral fusiform gyrus, known as the visual word form area (VWFA), in pre-lexical orthographic processing. There are very few studies that have examined the functional specificity of this area in patients with discrete lesions limited to this region. Here we describe a rare opportunity to examine the functional specificity of the VWFA in a patient with stereo EEG (sEEG) electrodes implanted for localization of seizures prior to epilepsy surgery. sEEG offers the opportunity to create a transient and highly localized electrophysiological lesion to examine brain behavior correlates during functional mapping. In this case, word reading and writing as well as a variety of non-orthographic language functions (e.g., picture and face naming, auditory naming, and non-word repetition), were tested during electrical stimulation at a series of different electrode contact sites in the ventral temporal region. Pure alexia resulted from stimulation of the lateral fusiform gyrus at coordinates nearly identical to those published for the VWFA in the functional imaging literature.

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: A Combined First-Person Account and Neuropsychological Investigation.

Pure alexia is an acquired reading disorder where patients' ability to read words and text is severely impaired, while their writing is left unaffected. Patients with pure alexia typically recover some reading ability over time, although most never regain their premorbid reading skills. A few studies have reported some behavioral and imaging correlates of such remission; however, little is known about the patients' experience of their reading impairment. This paper contains a first-person account of pure alexia, describing the first author's (K.H.) experience of his remission from severe reading problems immediately following a posterior cerebral artery stroke to the mild pure alexia characterizing his reading ability today. To provide a context for this account, we also present neuropsychological and reading data obtained from K.H. at several time points during his recovery.

Alexia without Agraphia-report of Five Cases and Review of Literature.

Alexia without agraphia (also called pure alexia or word blindness) was the first of the disconnection syndromes to be described. It results from the loss of visual input to the language area without involvement of the language area. The most common cause is occlusion of the left posterior cerebral artery with involvement of left occipital cortex and the splenium of corpus callosum. However, it can also be caused by any lesion affecting the splenium of corpus callosum disrupting the white matter tracts from the left visual cortex to the angular gyrus. We hereby describe five cases of alexia without agraphia, of which three are due to involvement of the left occipital cortex and splenium, and two are due to involvement of the splenium of corpus callosum alone.