a. What does the CT scan show?

The can shows a hypodense area in the right posterior occipital region. The appearance is that of occipital lobe infarction.

b. What ocular signs would you expect to find?

          Lesion of the right occipital region can give rise to:

•         congruous left homonymous hemianopia with or without macular sparing
•         possible sparing of the left temporal crescent


Congruity of the field defect is a characteristic feature of lesion in the occipital lobe. It refers to the symmetry of the deficit in both eyes.

Macular sparing refers to an island of vision around the point of fixation on the side of the hemianopia. The possible mechanism is a dual supply to the macula projection of the visual cortex by both posterior cerebral or middle cerebral artery.

Sparing of the left temporal crescent can occur if the anterior part of the occipital lobe is not infarcted. This is because the anterior portion receives fibres from the most peripheral nasal retina.