Left Parietal Tumors Presenting with Smartphone Icon Visual Agnosia: Two Cases of a Modern Presentation of Gerstmann Syndrome.

BACKGROUND: Gerstmanns syndrome-a clinical constellation of left-right confusion, finger agnosia, agraphia, and acalculia-is frequently attributed to pathology in the dominant inferior parietal lobe or temporo-occipital region. However, these unique clinical findings are often accompanied by more subtle signs, including aphasias, neglect, and agnosias. Associative visual agnosia, in which a patient is able to accurately perceive and describe but not recognize an object or symbol, is a well-documented but infrequently observed clinical entity. CASE DESCRIPTION: Here we detail 2 unique cases of patients who presented with the inability to recognize and use smartphone application icons. Both were found to have left temporo-occipital tumors displacing the left temporo-parietooccipital cortex. CONCLUSIONS: In the era of pervasive technology, we emphasize that smartphone icon associative visual agnosias may be recognized by discerning physicians in the clinical diagnosis of dominant parietal lobe pathology.

Are unilateral right posterior cerebral lesions sufficient to cause prosopagnosia? Clinical and radiological findings in six additional patients.

Controversy has arisen regarding the neuropathological basis of prosopagnosia. Some investigators suggest that bilateral lesions are needed to cause the deficit, whereas others felt that a unilateral right posterior lesion is sufficient. Six patients with prosopagnosia with clinical and radiological evidence of unilateral right posterior lesions are presented. Our observations together with evidence from similar cases described in the literature suggest that an appropriately placed right hemispheric lesion may be sufficient to produce prosopagnosia.

Prosopagnosia: anatomic basis and behavioral mechanisms.

Critical analysis of postmortem and CT scan data indicates that prosopagnosia is associated with bilateral lesions of the central visual system. Those lesions are located in the mesial occipitotemporal region and are functionally symmetric. The prime factor in the appearance of prosopagnosia is the requirement to evoke the specific context of a given visual stimulus. The "ambiguity" of the stimulus (the frequency with which different members of a group are visually similar) is an adjuvant factor. But prosopagnosia is not specific to human faces. The phenomenon appears in relation to any visually "ambiguous" stimulus whose recognition depends on contextual memory evocation.