1/5. Visually- and motor-based knowledge of letters: evidence from a pure alexic patient.We describe a patient, VSB, whose reading was impaired as a consequence of a left temporal-parietal lesion, whereas writing was relatively preserved. At variance with other pure alexic patients described in the literature, VSB claimed to have become unable to mentally visualise letters and words. Indeed, his performance on a series of tests tapping visual mental imagery for orthographic material was severely impaired. However, performance on the same tests was dramatically ameliorated by allowing VSB to trace each item with his finger. Visual mental imagery for non-orthographic items was comparatively spared. The pattern of dissociation shown by VSB between impaired visual mental imagery and relatively preserved motor-based knowledge for orthographic material lends support to the view that separate codes, respectively based on visual appearance and on motor engrams, may be used to access knowledge of the visual form of letters and words.- - - - - - - - - - ranking = 1keywords = visual (Clic here for more details about this article) |
2/5. Visual command hallucinations in a patient with pure alexia.Around 25% of patients with visual hallucinations secondary to eye disease report hallucinations of text. The hallucinated text conveys little if any meaning, typically consisting of individual letters, words, or nonsense letter strings (orthographic hallucinations). A patient is described with textual visual hallucinations of a very different linguistic content following bilateral occipito-temporal infarcts. The hallucinations consisted of grammatically correct, meaningful written sentences or phrases, often in the second person and with a threatening and command-like nature (syntacto-semantic visual hallucinations). A detailed phenomenological interview and visual psychophysical testing were undertaken. The patient showed a classical ventral occipito-temporal syndrome with achromatopsia, prosopagnosia, and associative visual agnosia. Of particular significance was the presence of pure alexia. illusions of colour induced by monochromatic gratings and a novel motion-direction illusion were also observed, both consistent with the residual capacities of the patient's spared visual cortex. The content of orthographic visual hallucinations matches the known specialisations of an area in the left posterior fusiform gyrus--the visual word form area (VWFA)--suggesting the two are related. The VWFA is unlikely to be responsible for the syntacto-semantic hallucinations described here as the patient had a pure alexic syndrome, a known consequence of VWFA lesions. Syntacto-semantic visual hallucinations may represent a separate category of textual hallucinations related to the cortical network implicated in the auditory hallucinations of schizophrenia.- - - - - - - - - - ranking = 1.8keywords = visual (Clic here for more details about this article) |
3/5. Alexia without agraphia following biopsy of a left thalamic tumor.Alexia without agraphia is a rare disconnection syndrome characterized by the loss of reading ability with retention of writing and verbal comprehension. We report a patient who developed alexia without agraphia after undergoing a biopsy for a malignant glioma involving the left thalamus. A 15-year-old right-handed male presented with 3 days of severe headache, and vomiting, and 1 month of blurry vision in his right visual field. magnetic resonance imaging of the brain disclosed a large exophytic mass originating in the left thalamus, with mass effect and hydrocephalus. The patient underwent biopsy of the left thalamic mass via a transcallosal approach. Postoperatively, the patient complained of inability to read or identify letters. Examination revealed alexia without agraphia. The syndrome of alexia without agraphia can be rarely caused after surgery. A transcallosal procedure through the splenium of the corpus callosum may disrupt the visual association fibers traveling from the right occipital cortex to the left angular gyrus. In our case the syndrome occurred because of a preexisting right homonymous hemianopia resulting from a left thalamic tumor.- - - - - - - - - - ranking = 0.4keywords = visual (Clic here for more details about this article) |
4/5. Transitory alexia without agraphia: a disconnection syndrome due to neurocysticercosis.We describe a 65-year-old male who presented with acute onset inability to read, without any difficulty in writing. A clinical diagnosis of alexia without agraphia was made and the patient was subjected to routine investigations including contrast MRI. MRI showed a ring-enhancing lesion in left occipital area, suggestive of neurocysticercosis supported by quantitative enzyme-linked immunosorbant assay from purified cell fraction of taenia solium cysticerci (PCF-ELISA). Patient was treated with albendazole and prednisolone for one week. The clinical manifestation as well as the radiological finding resolved after treatment.- - - - - - - - - - ranking = 0.0082766132923313keywords = contrast (Clic here for more details about this article) |
5/5. Alexia without agraphia in multiple sclerosis: case report with magnetic resonance imaging localization.The syndrome of alexia without agraphia occurs rarely in multiple sclerosis (MS). We report a patient with right homonymous hemianopsia and alexia without agraphia as his initial manifestations of relapsing-remitting MS. magnetic resonance imaging (MRI) demonstrated a hyperintense lesion in the left occipital subcortical white matter (WM) and an enhancing lesion in the splenium of the corpus callosum. The clinical presentation and MRI findings were consistent with disconnection of the functional right occipital visual cortex from structures responsible for language comprehension in the left hemisphere. The diagnosis of MS was confirmed by subsequent development of additional periventricular WM lesions.- - - - - - - - - - ranking = 0.2keywords = visual (Clic here for more details about this article) |