A case of bilateral oculomotor nuclear palsy.

To the best of our knowledge, isolated bilateral oculomotor nuclear palsy has not yet been reported in the literature, while bilateral oculomotor nuclear palsy with more widespread rostral brainstem infarction has often been reported. We present a patient having 'top of the basilar syndrome' with midbrain infarction selectively involving the bilateral oculomotor nucleus. A 61-year-old woman with two episodes of vertebrobasilar infarction presented with sudden onset of bilateral ptosis. Examination revealed pronounced bilateral ptosis. In the primary position, fixation of either eye produced an approximately 50 prism diopter exotropia. Adduction of the right eye was restricted to the midline. There was moderately decreased adduction of the left eye, severe limitation of depression, and moderately decreased elevation of both eyes. Abduction of both eyes was normal. The pupils were equal, round, and reactive to light. Bilateral ptosis is suggestive of oculomotor nuclear palsy. On the basis of clinical findings alone, we could not establish whether the precise location of the lesion was all the subdivisions of the oculomotor nucleus except the Edinger-Westphal nucleus or the central caudal nucleus and bilateral fascicles. However, because axial MRI showed a small midbrain infarct in the oculomotor nucleus region, we concluded that she had an isolated, pupil-sparing, bilateral oculomotor nuclear palsy caused by midbrain infarct.