[Intra-axial involvement of the common oculomotor nerve in mesencephalic infarctions]

Mesencephalic infarcts are rarely limited to the midbrain, and usually extend rostrally to the thalamus. This fact explains why an elective palsy of the oculomotor nerve is exceedingly uncommon in brainstem infarcts. We studied 4 cases with a unilateral infarct apparently restricted to the middle mesencephalon, with intra-axial involvement of the oculomotor nerve. In 2 cases with a fascicular lesion, there was a contralateral hemiparesis or hemi-ataxia, so that it is possible to term them Weber's syndrome and Claude's syndrome. In the 2 other cases, we suggest that a nuclear syndrome of the oculomotor nerve was present, because of bilateral involvement of the rectus superior in both cases, of the levator palpebrae in one case, and of the parasympathetic pupillary fibres in the other, although the infarct was unilateral. There are several clinical variants of the intra-axial syndrome of the oculomotor nerve which can be differentiated according to the uni or bilaterality of the oculomotor palsy, the pupillary disturbances, and the type of associated neurological dysfunction. The nuclear syndrome corresponds to an infarction of the median arterial area, which is directly supplied by the most distal part of the basilar artery. The fascicular syndromes correspond to infarction of the paramedian and intermediolateral areas supplied by the first part of the posterior cerebral artery (basilar communicating or mesencephalic artery). As the paramedian thalamic arteries also originate from the basilar communicating artery, most infarcts also involve the upper midbrain and the thalamus, producing supranuclear oculomotor disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)