Correct! In order to answer this question correctly, you had to know three things: 1) that horizontal saccades are generated in the cerebral hemispheres and that they move the eyes toward the opposite side; 2) that the patient is displaying a dissociation between loss of volitional leftward horizontal saccades and preservation of the leftward vestibulo-ocular reflex (“supranuclear ophthalmoplegia”); and 3) that the vestibulo-ocular reflex pathway is confined motorically to the brainstem.

Acute right hemisphere lesions (usually infarcts or hemorrhages)--especially if they involve the parietal lobe or its efferent pathway--often produce ipsilateral gaze deviation and a supranuclear gaze disturbance, as described here. These phenomena are probably manifestations of “hemispatial neglect.” In fact, other aspects of hemispatial neglect are usually present, including extinction to double simultaneous stimulation in the visual, auditory, and tactile domains. The presence of multimodal--visual, auditory, and tactile--extinction favors neglect over a topographic disorder of vision such as a homonymous hemianopia. Patients with hemispatial neglect consistently ignore stimuli in one hemifield and bisect a line segment more toward the side of the lesion. When the lesion is severe, neglect will extend to lack of awareness of contralateral limbs (“anosognosia”). Fortunately, the manifestations of neglect gradually lessen with time, but may never completely disappear. This patient had a right parietal infarct.