Alexia with agraphia is defined as an acquired impairment affecting reading and writing ability. It can be associated with aphasia, but can also occur as an isolated entity. This impairment has classically been associated with a left angular gyrus lesion In the present study, we describe a case involving a patient who developed alexia with agraphia and other cognitive deficits after a thalamic hemorrhage. In addition, we discuss potential mechanisms of this cortical dysfunction syndrome caused by subcortical injury. We examined a patient who presented with alexia with agraphia and other cognitive deficits due to a hemorrhage in the left thalamus. Neuropsychological evaluation showed attention, executive function, arithmetic and memory impairments. In addition, language tests revealed severe alexia with agraphia in the absence of aphasia. Imaging studies disclosed an old thalamic hemorrhage involving the anterior, dorsomedial and pulvinar nuclei. Tractography revealed asymmetric thalamocortical radiations in the parietal region (left
agraphia with alexia; thalamic lesion; diaschisis phenomenon; tract disconnection.
An acquired right-sided homonymous hemianopia can result in slowed left-to-right text reading, so-called hemianopic alexia (HA). Patients with HA lack essential visual information to help guide ensuing reading fixations. We tested two hypotheses: firstly, that practice with a visual rehabilitation method that induced small-field optokinetic nystagmus (OKN) would improve reading speeds in patients with HA when compared to a sham visual rehabilitation therapy; secondly, that this therapy would preferentially affect reading saccades into the blind field.
19 patients with HA were entered into a two-armed study with two therapy blocks in each arm: one group practiced reading moving text (MT) that scrolled from right-to-left, daily for two four week blocks (group1), while the other had sham therapy (spot-the-difference) for the first block and then crossed-over to MT for the second.
Group 1 showed significant improvements in static text reading speed over both therapy blocks (18% improvement), while group 2 did not significantly improve over the first block (5% improvement) but did when they crossed-over to the MT block (23% improvement). MT therapy was associated with a direction-specific effect on saccadic amplitude for rightward but not leftward reading saccades.
OKN inducing therapy preferentially affects reading saccades in the direction of the induced (involuntary) saccadic component. This is the first study to demonstrate the effectiveness of a specific eye movement based therapy in patients with HA in the context of a therapy-controlled trial. A free web-based version of the therapy used in this study is available online to suitable patients with HA.
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.
To investigate the differences in lesion site between hemianopic alexia and pure alexia groups, as rehabilitative techniques differ between the two conditions.
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.
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.
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.
"Crossed homonymous hemianopia" and "crossed left hemispatial neglect" were observed in a woman with Marchiafava-Bignami disease. Two forms of "crossed homonymous hemianopia" were observed. Initially, Goldmann perimeter testing showed a left homonymous hemianopia with the right hand and vice versa. Later, confrontation tests showed a left homonymous hemianopia, whereas visual field testing using the Goldmann perimeter (kinetic quantitative perimeter) and the OCTOPUS (Interzeag AG, static automated perimeter) showed a right homonymous hemianopia with either hand. "Crossed left hemispatial neglect" was not seen with the left hand, but neglect of the left hemifield was seen with the right hand. CT and MRI showed a lesion occupying almost the entire corpus callosum. PET showed no significant differences between comparable areas of the left and right cerebral hemispheres. These findings indicate that both signs of interhemispheric disconnection were due to the callosal lesion. Moreover, the "crossed left hemispatial neglect" can be explained as being a consequence of the dominance of the right cerebral hemisphere for visuospatial recognition.
In contrast to the classic form of alexia without agraphia, subangular alexia results from a single lesion located deep in the white matter of the left parietal lobe. In the present report, a patient with subangular alexia and features of mixed transcortical aphasia is described. Neurolinguistic findings include: alexia without agraphia, paucity of spontaneous speech, moderate auditory comprehension difficulty, excellent repetition, echopraxia, colour agnosia, and naming disorder. Neurolinguistic tests revealed intact phonological organisation and grammatical filter." Our studies revealed a "double disconnection syndrome," the co-existence of two relatively rare neurobehavioural disorders. Furthermore, the studies reported here clearly show dissociations of language functions in both the visual and auditory modality, which demonstrates that the stages of language processing are separable.
A hallmark of visuospatial neglect syndrome is that patients with lesions to right parietal cortex misbisect horizontal lines far rightward of veridical center. Neurologically normal subjects misbisect lines with a systematic leftward bias (pseudoneglect). Both phenomena, as well as neuroimaging studies, disclose a predominant right hemisphere control of spatial attention. Numerous studies of patients with schizophrenia have implicated global deficits of either right or left hemisphere function, as well as compromised integrity of the corpus callosum.
To better understand the functional implications of schizophrenia we utilized a forced-choice tachistoscopic line bisection task to probe the status of right hemisphere control of spatial attention, and compared left- versus right-hand unimanual responses to index the degree of callosal transfer of visuospatial information in both patient and control groups.
In contrast to the significant leftward bisection errors of control subjects, patients exhibit no significant leftward error. Whereas control subjects evince a significant correlation between left- and right-hand bisection errors, patients lack a significant intermanual correlation.
The lack of significant leftward bisection error of patients implies a deficit of right hemisphere function. The lack of a significant correlation between left- and right-hand bisection errors in patients implies a loss of callosal integrity.
Line Bisection; Pseudoneglect; Visuospatial Attention; Corpus Callosum; Schizophrenia; Magnocellular
Letter recognition is the foundation of the human reading system. Despite this, it tends to receive little attention in computational modelling of single word reading. Here we present a model that can be trained to recognise letters in various spatial transformations. When presented with degraded stimuli the model makes letter confusion errors that correlate with human confusability data. Analyses of the internal representations of the model suggest that a small set of learned visual feature detectors support the recognition of both upper case and lower case letters in various fonts and transformations. We postulated that a damaged version of the model might be expected to act in a similar manner to patients suffering from pure alexia. Summed error score generated from the model was found to be a very good predictor of the reading times of pure alexic patients, outperforming simple word length, and accounting for 47% of the variance. These findings are consistent with a hypothesis suggesting that impaired visual processing is a key to understanding the strong word-length effects found in pure alexic patients.
► We develop a connectionist letter recognition model which provides the link between visual input and letter recognition. ► The model can deal with the invariance problem and generalise to previously unseen letters. ► The model can extract key features for letter recognition. ► We demonstrate the model can simulate confusability effects in normal readers and predict PA patients' RTs. ► Impaired visual processing is a key to understanding the strong word-length effects found in PA patients.
Letter recognition; Letter confusability; Pure alexia; Computational modelling
A 59-year-old, right-handed, college-educated male examined after stroke presented spelling alexia with relative sparing of writing. He was not aphasic. A striking feature of the alexia was preserved recognition of letters printed in view by the clinician. He was able to read words through letter-by-letter oral spelling when letters were presented in this dynamic fashion. We describe this as a dynamic form of spelling alexia. Head CT scan showed a large left hemisphere posterior lesion infringing on the corpus callosum, and a right hemisphere opercular lesion. We suggest that sparing of the right parietal-occipital cortex may contribute to the remarkable sparing of dynamic letter reading.
A patient presented with agraphia and acalculia associated with a left frontal (F1, F2) infarction. He made mainly phonological but also lexical errors in writing (syllabograms), but his ability to write kanji (morphograms) was relatively preserved. Although he could add and subtract numbers, he could neither multiply nor divide them because of a difficulty in retrieving the multiplication tables and calculation procedures. Positron emission tomography showed decreased cerebral blood flow and metabolism limited to the infarct site. These findings suggest that agraphia and acalculia may occur associated with a left prefrontal lesion, and that the retrieval of arithmetic processes is modality specific.
A 25-year-old woman was diagnosed to have tubercular meningitis (TBM) with a right parietal infarct. She responded well to four-drug anti-tubercular treatment (ATT), systemic steroids and pyridoxine. Steroids were tapered off in one and a half months; she was put on two-drug ATT after two months. Six months after initial diagnosis she presented with sudden, bilateral visual loss. Vision was 3/200 with afferent pupillary defect and un-recordable field in the right eye; vision was 20/60 in the left eye, pupillary reaction was sluggish and the field showed a temporal hemianopia. On reintroduction of systemic corticosteroids vision improved (20/120 in right eye and 20/30 in left eye) within three days; the field defects improved sequentially to a left homonymous hemianopia, then a left homonymous inferior quadrantonopia. A diagnosis of TBM, on treatment, with bilateral optic neuritis, and right optic radiation involvement was made. Since the patient had been off ethambutol for four months, the optic neuritis and optic radiation lesion were attributed to a paradoxical reaction to tubercular allergen, corroborated by prompt recovery in response to corticosteroids. This is the first report of optic radiation involvement in a paradoxical reaction in neuro-tuberculosis in a young adult.
Anti-tubercular treatment; optic neuritis; optic radiation; paradoxical reaction; tubercular meningitis
Objective: To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia.
Methods: The patient, a 48 year old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera.
Results: The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields.
Conclusions: The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET.
Functional magnetic resonance imaging (fMRI) was used to compare brain activation from Japanese readers reading hiragana (syllabic) and kanji (logographic) sentences, and English as a second language (L2). Kanji showed more activation than hiragana in right-hemisphere occipito-temporal lobe areas associated with visuospatial processing; hiragana, in turn, showed more activation than kanji in areas of the brain associated with phonological processing. L1 results underscore the difference in visuospatial and phonological processing demands between the systems. Reading in English as compared to either of the Japanese systems showed more activation in inferior frontal gyrus, medial frontal gyrus, and angular gyrus. The additional activation in English in these areas may have been associated with an increased cognitive demand for phonological processing and verbal working memory. More generally, L2 results suggest more effortful reading comprehension processes. The study contributes to the understanding of differential brain responses to different writing systems and to reading comprehension in a second language.
The Japanese language represents numbers in kana digit words (a syllabic notation), kanji numbers and Arabic numbers (logographic notations). Kanji and Arabic numbers have previously shown similar patterns of numerical processing, and because of their shared logographic properties may exhibit similar brain areas of numerical representation. Kana digit words require a larger phonetic component, and therefore may show different areas of numerical representation as compared to kanji or Arabic numbers. The present study investigated behavioral reaction times and brain activation with fMRI during the numerical processing of kana digit words, kanji numbers and Arabic numbers. No differences in behavioral reaction time were found between kanji and Arabic numbers. In contrast, kana digit words produced a longer reaction time as compared to the other two notations. The imaging data showed that kana activated the posterior cingulate cortex when compared to kanji and Arabic numbers. It is suggested that this posterior cingulate activation reflects an additional attentional demand in this script which may be related to the infrequent use of kana digit words, or may reflect an extra step of phonological mediation in converting the visual word form to the verbal word form. Overall, the data suggest that number reading is processed differently in these three notations.
number processing; Japanese kana and kanji; symbolic notation; fMRI
Neurologically normal observers misperceive the midpoint of horizontal lines as systematically leftward of veridical center, a phenomenon known as pseudoneglect. Pseudoneglect is attributed to a tonic asymmetry of visuospatial attention favoring left hemispace. Whereas visuospatial attention is biased toward left hemispace, some evidence suggests that audiospatial attention may possess a right hemispatial bias. If spatial attention is supramodal, then the leftward bias observed in visual line bisection should also be expressed in auditory bisection tasks. If spatial attention is modality specific then bisection errors in visual and auditory spatial judgments are potentially dissociable. Subjects performed a bisection task for spatial intervals defined by auditory stimuli, as well as a tachistoscopic visual line bisection task. Subjects showed a significant leftward bias in the visual line bisection task and a significant rightward bias in the auditory interval bisection task. Performance across both tasks was, however, significantly positively correlated. These results imply the existence of both modality specific and supramodal attentional mechanisms where visuospatial attention has a prepotent leftward vector and audiospatial attention has a prepotent rightward vector of attention. In addition, the biases of both visuospatial and audiospatial attention are correlated.
Line Bisection; Pseudoneglect; Visuospatial Attention; Audiospatial Attention
Of 500 left brain-damaged patients with educational level above elementary school investigated with a standard quantitative battery for dissociation between oral and written expression, speech was found to be selectively impaired in seven (three with "pure anarthria," two with anarthria in the context of Broca's aphasia, and two with fluent aphasia with remarkable sparing of writing), and writing in another seven (two with "pure" agraphia, two with "agraphia with mild alexia," and three with "agraphia with mild fluent aphasia.") The nature of three conditions (pure anarthria, fluent aphasia with sparing of writing, and pure agraphia) is discussed, with evidence of a selective association between pure agraphia and lesions of the upper left parietal lobule.
Reading and writing disturbances are common accompaniments of aphasia following brain damage. However, impaired writing in the absence of apparent primary linguistic disturbances is infrequently reported in the literature.
Materials and Methods:
A 67-year-old right-handed subject underwent neurological, neuroradiological, and linguistic investigations following development of a minimal right upper limb weakness.
The patient had polycythemia and the neurological investigation revealed right upper limb paresis. The neuroradiological investigation revealed hypodense areas involving the gray-white matter of the left postero-parietal and frontal lobe, left caudate and lentiform nuclei, and the anterior limb of the internal capsule, suggesting an infarct. The linguistic investigation revealed a mild anomic aphasia with apraxic agraphia. This mild anomic aphasia resulted primarily from the relatively poor scores on the verbal fluency tests.
The marked writing impairment, even with the left hand, points to disturbances in written output – apraxic agraphia – in the presence of near-normal spoken output. This finding should raise suspicion about hidden apraxic agraphia in subjects with posterior aphasias.
Apraxic agraphia; aphasia; pure motor agraphia
Alexia is usually seen after ischaemic insults to the dominant
parietal lobe. A patient is described with a particular alexia to
reading Hebrew (right to left), whereas no alexia was noted when
reading in English. This deficit evolved after a hypertensive right
occipitoparietal intracerebral haemorrhage, and resolved gradually over
the ensuing year as the haematoma was resorbed. The deficit suggests
the existence of a separate, language associated, neuronal network
within the right hemisphere important to different language reading modes.
A 67-year-old left-handed woman with a diagnosis of pseudodementia was being treated for depression with little benefit. Neuropsychological evaluations revealed features of angular gyrus syndrome, namely, agraphia, alexia, Gerstmann's syndrome and behavioural manifestations such as depression, poor memory, frustration and irritability. A computed tomographic scan showed a right occipito-temporal infarction, which had occurred 18 months earlier. The patient demonstrated aspects of language dysfunction associated with the syndrome and showed reversed lateralization of cerebral functions. Recognizing and distinguishing between angular gyrus syndrome and depression is important because the appropriate therapies differ. The use of the term pseudodementia can be misleading.
depressive disorder; dementia; dementia, multi-infarct; Gerstmann syndrome; language disorders
Damage to left perisylvian cortex often results in impaired phonological processing abilities with written language profiles consistent with phonological alexia and phonological agraphia. The purpose of this article was to examine a behavioral treatment sequence for such individuals intended to strengthen phonological processing and links between phonology and orthography, as well as train a means to maximize use of residual orthographic and phonological knowledge for spelling.
Two women with persistent impairments of written language and phonological processing following damage to left perisylvian cortical regions participated in this study. Both exhibited characteristic features of phonological alexia and agraphia in that reading and spelling performance for real words was better preserved than nonwords (lexicality effect). A 2-stage treatment protocol was administered to strengthen sublexical skills (phonological treatment) and to train interactive use of lexical and sublexical information to maximize spelling performance (interactive treatment).
Both participants improved phonological processing abilities and reading/spelling via the sublexical route. They also improved spelling of real words and were able to detect and correct most residual errors using an electronic spelling aid. Conclusions: Behavioral treatment served to strengthen phonological skills supporting reading and spelling, and provided a functional compensatory strategy to overcome residual weaknesses.
aphasia; dyslexia; dysgraphia; rehabilitation; stroke
A 59-year-old Caucasian woman presented with an acute onset of alexia, noticed whilst driving. She described how while she could read car number plates, she had lost the ability to read and understand words on roadside advertisements and car window stickers.
Neurological examination was unremarkable apart from the inability to read full words or sentences. Imaging of the brain, initially computed tomography, followed by magnetic resonance venography, confirmed a diagnosis of sigmoid sinus thrombosis with associated venous infarction. The patient's past medical history revealed that she had suffered an ischemic stroke and following investigation for this, had undergone a nephrectomy for renal cell carcinoma. This was complicated by postoperative deep venous thrombosis. She had a persistent polycythaemia that was managed with venesection, and recently she had been diagnosed with Behçet's disease. Prior to this presentation, she had recently stopped her prophylactic antiplatelet medication as she was due to undergo a total knee replacement for osteoarthritis. She was managed with weight-adjusted, low molecular weight heparin followed by oral anticoagulation, and made a good recovery from her symptoms.
This case illustrates a classical neurological syndrome, highlights the importance of cerebral venous and sinus thrombosis as a cause of stroke, and the importance of remaining vigilant to a person's changing risk of venous thrombosis with evolving comorbidity.