Dynamic body tilt in internuclear ophthalmoplegia and one-and-a-half syndrome

We report five patients presenting acutely because of diplopia and lateropulsion. Four had internuclear ophthalmoplegia and the fifth, one-and-a-half syndrome. In addition, they presented with a peculiar sign, called lateropulsion, which is a slow falling down to the side in a roll plane when sitting, standing, or walking. All five patients were adults, the first three having a history of multiple vascular risk factors. Brain CT showed a mesencephalic infarct in one patient and no pathology in the rest. Brain MRI in one patient did not show any lesion in the pontomesencephalic area. Clinically, the neuro-ophthalmological constellation of these patients pointed to tegmental medial pontomesencephalic lesions, which were associated with a dynamic lateral body tilt accompanying the oculomotor signs. In all five patients, the body tilt was contralateral (contraversive) to the clinical brainstem lesion. Their recovery was good in the short term, with improvement in the body tilt and eye movements. We suggest that body tilt in the lateral (coronal) plane could be due to a graviceptive dysfunction, occurring in the medial longitudinal fasciculus or in its surrounding structures. The body tilt observed in these patients is phenomenologically identical to that observed in acute unilateral peripheral vestibulopathy.