The Anatomy of Infarcts Causing Hemianopia and Quadrantanopia in Posterior Cerebral Artery Stroke

Introduction: Following posterior cerebral artery stroke, infarcts causing quadrantanopia are thought to be smaller than those causing homonymous hemianopia. We investigated whether these two presentations were different due to the varying involvement of the striate, extrastriate cortex, or geniculocalcarine tract.

Patients with unilateral posterior cerebral artery infarcts on magnetic resonance imaging and visual field defects, as identified by automated visual field perimetry, were included. Infarcts were manually segmented and registered to a standard brain template to facilitate comparison. Infarct volume and infarct involvement with geniculocalcarine fiber tracts were calculated in patients with hemianopia and quadrantanopia.

There were twenty-two patients: 15 patients with homonymous hemianopia (median age 68 [interquartile range, 55-76 years old]) and 7 with superior quadrantanopia (median age 40 [interquartile range, 30-56 years old]). Infarct volume significantly differed between the two groups: hemianopia 34.6 mL (interquartile range, 21.6-56.3 mL) versus superior quadrantanopia 15.5 mL (interquartile range, 7.2-24.1 mL), p = 0.026. There was significantly greater involvement of infarct with the geniculocalcarine tracts in the hemianopia group, 5.7 mL (interquartile range, 2.3-8.2 mL) than the superior quadrantanopia group, 2.0 mL (interquartile range, 1.2-2.7 mL), p = 0.042. Infarct involvement with cuneus and the calcarine cortex also significantly differed between the two groups (p ≤ 0.01).

In posterior cerebral artery infarction, sparing of the superior calcarine cortex, cuneus, and superior paraventricular geniculocalcarine tract differentiated superior quadrantanopia from homonymous hemianopia.