A case study of sudden-onset cortically mediated visual impairments in a 12-year-old

Strokes and blunt trauma can cause large changes in perception. It is rare, however, to have a sudden but persistent change to perception in the absence of trauma. Here we report a case of a 12-year-old male who reported a sudden-onset change in vision without any trauma, with akinetopsia-like symptoms: an inability to see motion. In contrast to classical cases of akinetopsia, informal testing revealed normal motion perception for simple stimuli, but difficulty in recognition of moving objects in visual clutter. Psychophysical testing confirmed normal random dot motion sensitivity and a large deficit in object recognition in clutter in moving displays, and surprisingly, in static displays. Oculomotor behavior showed both slowed saccades and difficulty in smooth pursuit. Anatomical and functional MRI showed largely intact retinotopic maps and robust responses to visual motion, including in canonical cortical motion processing areas. However, MRI imaging revealed a right lingual gyrus gray-white contrast blurring with corresponding severe focal FDG hypometabolism on PET, consistent with focal cortical dysplasia (FCD). We speculate that the abnormality in ventral cortex affects recognition in clutter, which manifests as a subjective experience of akinetopsia-like symptoms, especially in complex dynamic scenes.