Conjugate eye deviation: side, site, and size of the hemispheric lesion.

Conjugate eye deviation (CED) is a well-known sign that occurs rather frequently in stroke patients. To study the lateralizing and localizing value of this sign, we investigated prospectively 78 consecutive patients presenting with CED due to a hemispheric lesion. CED occurred more frequently after right-sided hemispheral damage (64%). The lesions in the right hemisphere were located predominantly in the subcortical (fronto-) parietal region and the internal capsule; the lesions in the left hemisphere were larger, covering the entire fronto-temporo-parietal area. In the majority of patients there was no direct involvement of the frontal eye fields on either side. The results indicate that a lesion at different sites within the circuit between the inferior parietal lobule and frontal eye fields, and their projections to the superior colliculus or paramedian pontine reticular formation, can be responsible for CED. The right-left asymmetry is probably related to cerebral asymmetry for directed spatial attention.