Contraversive shift of conjugate eye deviation in hemispheric stroke indicates emerging mass effect

Conjugate eye deviation (CED) towards the ipsilateral or the contralateral side of the brain lesion can occur as a result of acute hemispheric stroke. To our knowledge, there have been no reports of CED shifting from the lesional side to the contralateral side in acute hemispheric stroke in the literature. We present four patients with right hemispheric stroke with a forced CED shift from the right to the left side during the acute stage with corresponding mass effect on the right internal capsule and right thalamus, as shown on brain imaging. Mass effect on thalamic mediated circuits and the corticopontine projection within the internal capsule probably underlies this CED shift via the dynamic balance of oculomotor control between the two hemispheres. Contraversive CED shift is a potentially useful early predictor of emerging mass effect in acute hemispheric stroke.