MRI Inquiry into the Anatomic Aspects of Alexia Without Agraphia

We reviewed brain MRI imaging in patients with alexia without agraphia (AWA) to better classify the pathophysiology of AWA as a disconnection syndrome or as a word form agnosia. AWA is primarily thought of as a disconnection syndrome in which a left occipital lobe lesion affects the callosal fibers of the splenium and disrupts access between the right striate cortex and the language regions for reading (Geschwind N 1965). Disconnection may also occur in unusual lesion combinations. Other authors have suggested that AWA may be word form agnosia from left fusiform gyrus damage (Warrington and Shallice 1980; Beversdorf et al 1997). The only systematic study of the neuro-anatomy of these lesions in a larger series of 16 patients with AWA was CT based (Damasio 1983).

Poster 269 MRI Inquiry into the Anatomic Aspects of Alexia Without Agraphia Jeremy Shapiro 1, Aseem Sharma 2, Jonathan Trobe 2, Michael Lee 3, Ryan Walsh 4, Sangeeta Khanna 2 University of Michigan Medical School, 2 University of Michigan, 3 University of Minnesota Department of Ophthalmology & Visual Neurosciences, 4 Medical College of Wisconsin 1 Introduction: We reviewed brain MRI imaging in patients with alexia without agraphia (AWA) to better classify the pathophysiology of AWA as a disconnection syndrome or as a word form agnosia. AWA is primarily thought of as a disconnection syndrome in which a left occipital lobe lesion affects the callosal fibers of the splenium and disrupts access between the right striate cortex and the language regions for reading (Geschwind N 1965). Disconnection may also occur in unusual lesion combinations. Other authors have suggested that AWA may be word form agnosia from left fusiform gyrus damage (Warrington and Shallice 1980; Beversdorf et al 1997). The only systematic study of the neuro-anatomy of these lesions in a larger series of 16 patients with AWA was CT based (Damasio 1983). Methods: We performed a MRI study of 26 patients, 13 with right hemianopsia with AWA and 13 with right hemianopsia but without AWA. All patients were evaluated in neuro-ophthalmologic clinic at our institution and had brain MRI imaging available since the onset of the problem. MRIs were evaluated in a masked fashion by one neuroradiologist looking for changes in the occipital cortex, splenium, forceps major, and fusiform gyrus. Results: Of controls, 8 were female, average age was 64.4(34-84), and the etiology of all lesions was posterior cerebral artery (PCA) stroke. Of AWA cases, 5 were female, average age was 63.8(47-83) and lesion etiology was stroke in 11 cases and glioblastoma in 2 cases. 100% of AWA patients showed lesions in either splenium, left forceps major, or left fusiform gyrus with 69% showing lesions in both left fusiform gyrus and splenium/left forceps major. No controls showed lesions in these areas. Conclusions: Lesion combinations in these areas supports the word form agnosia hypothesis rather than the disconnection syndrome hypothesis alone. We plan on expanding our cohort with additional institutional collaboration. References: 1) Geschwind N. Disconnexion syndromes in animals and man. Brain 1965; 88: 17-294. 2) Beversdorf DQ, Ratcliffe NR, Rhodes CH, Reeves AG. Pure alexia: clinical-pathologic evidence for a lateralized visual language association cortex. Clin Neuropathol. 1997 Nov-Dec;16(6):328-31. PMID: 9401800. 3) Damasio AR, Damasio H. The anatomic basis of pure alexia. Neurology. 1983 Dec;33(12):1573-83. doi: 10.1212/wnl.33.12.1573. PMID: 6685830. 4) Warrington EK, Shallice T. Word-form dyslexia. Brain. 1980 Mar;103(1):99-112. doi: 10.1093/brain/103.1.99. PMID: 6244876 Keywords: Higher visual functions, Neuroimaging, Stroke, Visual fields Financial Disclosures: The authors had no disclosures. Grant Support: None. Contact Information: Dr. Sangeeta Khanna, [e-mail] 2023 Annual Meeting Syllabus | 457