Conjugate gaze paresis in stroke patients with unilateral damage. An unexpected instance of hemispheric asymmetry.

Conjugate gaze paresis was investigated in 436 patients who had suffered a severe stroke and were consecutively hospitalized for unilateral hemispheric damage. Gaze paresis was found in 120 and was associated with a high mortality, severe neurological impairment, and was more frequent in women. However, conjugate gaze paresis was also dependent on the side and locus of the lesion. It was more frequent, severe, and long-lasting in patients with right-sided brain damage. Moreover, it was preponderantly associated with post-Rolandic lesions in patients with right-sided brain damage and with involvement of the entire territory of distribution of the Sylvian artery in those with left-sided brain damage. This suggests that oculomotor centers have an asymmetrical organization in the two hemispheres, diffuse on the left and focalized on the right. It also explains why visual neglect occurs more frequently following right-sided brain damage.