[Nuclear syndrome of the oculomotor nerve caused by a mesencephalic infarction confirmed by MRI].

The nuclear syndrome of the third nerve was first described in 1981. It has the very characteristic disturbance of an ophthalmoplegia with complete ipsilateral third nerve palsy associated with paresis of elevation in contralateral eye. This particularly presentation is due to the innervation of the superior rectus which comes mainly from the contralateral oculomotor nucleus. As associated signs were described contralateral cerebellar and or pyramidal syndromes, uni or bilateral parasympathetic disfunction and sometimes gaze disorders. The etiology es usually a vascular damage (ischemic most frequently) located in mesencephalon. We report on a case of a 60 years old man who developed acute nuclear ophthalmoplegia of the third right nerve accompanied with cerebellar and pyramidal syndrome and focal asterixis in left extremities. MRI showed an ischemic lesion in right paramedial mesencephalic territory with extension to the ipsilateral thalamic region. Pyramidal and cerebellar syndromes and asterixis disappeared in a few weeks, while ophthalmoplegia remained unchanged. Semiologic characteristics and anatomic basis of the nuclear oculomotor syndrome which allow to make the differential diagnosis between this syndrome and intra-axial fascicular disturbances of the third nerve (Weber, Claude and Benedikt syndromes) are discuss.