The Visual Word Form Area remains in the dominant hemisphere for language in late-onset left occipital lobe epilepsies: A postsurgery analysis of two cases.
Automatic recognition of words from letter strings is a critical processing step in reading that is lateralized to the left-hemisphere middle fusiform gyrus in the so-called Visual Word Form Area (VWFA). Surgical lesions in this location can lead to irreversible alexia. Very early left hemispheric lesions can lead to transfer of the VWFA to the nondominant hemisphere, but it is currently unknown if this capability is preserved in epilepsies developing after reading acquisition. In this study, we aimed to determine the lateralization of the VWFA in late-onset left inferior occipital lobe epilepsies and also the effect of surgical disconnection from the adjacent secondary visual areas. Two patients with focal epilepsies with onset near the VWFA underwent to surgery for epilepsy, with sparing of this area. Neuropsychology evaluations were performed before and after surgery, as well as quantitative evaluation of the speed of word reading. Comparison of the surgical localization of the lesion, with the BOLD activation associated with the contrast of words-strings, was performed, as well as a study of the associated main white fiber pathways using diffusion-weighted imaging. Neither of the patients developed alexia after surgery (similar word reading speed before and after surgery) despite the fact that the inferior occipital surgical lesions reached the neighborhood (less than 1cm) of the VWFA. Surgeries partly disconnected the VWFA from left secondary visual areas, suggesting that pathways connecting to the posterior visual ventral stream were severely affected but did not induce alexia. The anterior and superior limits of the resection suggest that the critical connection between the VWFA and the Wernicke's Angular Gyrus cortex was not affected, which is supported by the detection of this tract with probabilistic tractography. Left occipital lobe epilepsies developing after reading acquisition did not produce atypical localizations of the VWFA, even with foci in the close neighborhood. Surgery for occipital lobe epilepsy should take this into consideration, as well as the fact that disconnection from the left secondary visual areas may not produce alexia.
Faculty of Psychology and Education Sciences - University of Coimbra, Coimbra, Portugal. Electronic address: r.lopes@clix.pt.
Ricardo
R
Lopes
Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências, Universidade de Lisboa, Portugal.
Rita Gouveia
RG
Nunes
Faculty of Psychology and Education Sciences - University of Coimbra, Coimbra, Portugal.
Mário Rodrigues
MR
Simões
Department of Physics - Faculty of Sciences and Technologies, New University of Lisbon, Caparica, Portugal; Ressonância Magnética - Caselas, Lisboa, Portugal.
Mário Forjaz
MF
Secca
Department of Neurophysiology, Centro Hospitalar Psiquiátrico de Lisboa, Lisbon, Portugal.
Alberto
A
Leal
D000293:Adolescent; D017668:Age of Onset; D038524:Diffusion Magnetic Resonance Imaging; D004292:Dominance, Cerebral / Q000502:physiology*; D004411:Dyslexia, Acquired / Q000517:prevention & control*; D004828:Epilepsies, Partial / Q000601:surgery*; D006801:Humans; D007802:Language; D008297:Male; D019635:Neurosurgical Procedures / Q000592:standards*; D011183:Postoperative Complications / Q000517:prevention & control*; D013702:Temporal Lobe / Q000601:surgery*
Alexia; Epilepsy Surgery; Neuropsychology; Pediatric; Surgery; Visual Word Form Area