Anatomical correlate of positive spontaneous visual phenomena: a voxelwise lesion study.

OBJECTIVES

Visual phenomena such as phosphenes, photopsias, or complex visual hallucinations occur in patients with lesions affecting the occipital, parietal, or temporal lobe. Whether these phenomena are provoked by lesions in specific anatomical regions is still uncertain. To determine which brain regions might be involved in such visual phenomena, we used new brain imaging and lesion analysis tools that allow a direct comparison with control patients.

METHODS

Visual phenomena were investigated in a total of 23 patients with acute infarctions along the visual pathways (6 patients with left-sided and 17 patients with right-sided lesions).

RESULTS

Ten of these 23 patients (43%) reported positive spontaneous visual phenomena (PSVP). Nine of the 10 patients (90%) with PSVP reported phosphenes; only 3 of the 10 (30%) reported photopsias. Statistical voxelwise lesion-behavior mapping revealed that the areas specifically related to PSVP are V1, V2, and the optic radiation.

CONCLUSIONS

Disinhibition of earlier visual areas after lesions of the visual cortex and its afferent fibers seems to be the crucial mechanism in the genesis of visual phenomena in acute stroke patients.