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

## TL;DR

A 12-year-old boy experienced sudden vision changes resembling akinetopsia, caused by a brain abnormality in the ventral cortex, despite normal motion perception for simple stimuli.

## Contribution

This case study identifies a novel link between focal cortical dysplasia and akinetopsia-like symptoms in a child without trauma.

## Key findings

- The patient showed normal motion perception for simple stimuli but struggled with object recognition in clutter.
- MRI and PET scans revealed focal cortical dysplasia in the right lingual gyrus, correlating with the visual deficits.
- Oculomotor behavior indicated slowed saccades and impaired smooth pursuit.

## Abstract

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.