1993 Volume 13 Issue 4 Pages 306-312
A 64-year-old right-handed man developed right hemianopsia, disturbance of color naming, alexia without agraphia and visual agnosia following a stroke attack.
Brain CT and MRI showed infarctions in the distributions of the left posterior cerebral artery, involving the splenium of the collupus callosum and the stem of the left temporal lobe.
The patient experienced difficulty naming familiar objects or their pictures and could not describe how to use them. However, he was able to distinguish one picture from another and to copy those pictures. Also, as soon as an appeal was made to his understanding through another sense such as auditory or tactile, he could recognize and name the object correctly. These features of his visual disturbance were consistent with associative visual agnosia as proposed by Lissauer.
The mechanism of the patient's visual agnosia might be explained on the basis of the disconnection theory advocated by Geschwind. But we cannot exclude the possible effects of lesions in the right posterior lobe which are too small to be visible on CT or MRI, and so more cases like this are needed in order to recognize the mechanism of visual agnosia definitively.
The present case may provide evidence that associative visual agnosia can develop on unilateral lesions of the left hemisphere with callosal lesions.
