Purpose:
Early studies of retinotopic mapping onto the primary visualcortex relied on correlating visual field plots against autopsyfindings, or surface reference points in cases of survivorsfrom shrapnel wounds. Modifications have come with the use ofmodern imaging techniques. Study of new cases provides confirmatorydata.
Methods:
We present the case of a 19-year-old woman who collapsed withloss of consciousness. On recovery, she was left with a bilateralhomonymous hemianopia with vertical meridian sparing (Figure1).
Results:
Magnetic resonance imaging revealed bilateral occipital infarctswith sparing of the calcarine lips on the right and an asymptomaticleft cerebellar hemisphere infarct (Figure 2). A patent foramenovale with a right-to-left shunt was found on transoesophagealechocardiography.
Conclusions:
Bilateral homonymous hemianopia is often asymmetrical. The usualsite of sparing is of macular vision. Sparing of the calcarinelips is unusual because they are supplied by terminal branchesof the calcarine artery. There has been one other report ofa unilateral homonymous quadrantinopia with vertical meridiansparing. This is the first report of this phenomenon in a caseof bilateral homonymous hemianopia and confirms the calcarinelips as the site of the vertical meridian.Figure1: Goldmannperimetry.Figure 2: (a) Axial and (b) coronal T2-weighted magneticresonance imaging showing bilateral infarcts (black arrows)with sparing of the calcarine lips on the right (white arrow)and a left cerebellar hemisphere infarct (arrowhead).
Keywords: visual fields • visual cortex • ischemia