Abstract:
Background and Purpose: To add to the literature a case of isolated third nerve paresis involving the nerve fascicles subserving the superior rectus and the levator palpebrae muscles from brain stem infarction and presenting the characteristics of central disruption of binocular vision fusional amplitudes. Case Report: One patient with an old intracranial aneurysm and with old and recent brain stem infarcts and no other neurological manifestations, demonstrating findings characteristic of isolated paresis of the superior rectus and levator palpebrae muscles is reported. Conclusion: This dual involvement of the superior rectus and levator palpebrae muscles supports the anatomical arrangement of the ocular motor nucleus fascicles in the midbrain, clarified by experimental studies on animals and clinical data in humans and emphasizes the juxtaposition of the superior rectus and levator palpebrae fascicles and placing the levator palpebrae muscle fascicle lateral to the medial rectus fascicle in the midbrain. The comitant vertical deviation and the negative Bielschowsky head tilt test support the vertical rectus muscle involvement. The constant diplopia with only 4 prism diopters of hypotropia and with the absence of fusional amplitudes evokes disruption of central binocular fusion.