Superior Division Third Nerve Palsy as the Presenting Sign of Metastatic Breast Cancer

The third cranial nerve divides into superior and inferior branches at the level of anterior carotid sinus and superior orbital fissure. In extremely rare scenarios, metastatic lesions at this location may present with divisional third nerve involvement. We here describe an 85-year-old woman who presented with superior division third nerve palsy due to breast cancer metastasis. Our case demonstrates the rare presentation of double vision and ptosis because of superior division third nerve palsy. The differential diagnosis for this examination finding should include metastatic disease even in the absence of a known cancer diagnosis. This case also reiterates that the “rule of the pupil” should not be applied to superior division third nerve palsy.