Etiology of Isolated Third, Fourth, and Sixth Cranial Nerve Palsies with a Cancer History

Purpose: To investigate the causes of isolated ocular motor nerve palsy in patients with a history of cancer. Methods: The charts of 30 patients with cancer diagnosed with isolated acquired third, fourth, and sixth cranial nerve palsies from March 2013 to December 2021 were retrospectively reviewed. Sex, age of onset, underlying disease and causes of cranial nerve palsy were analyzed. Results: Sixth cranial nerve palsy (n = 18, 60.0%) was the most common. Brain metastasis (n = 13, 43.3%) was the most common etiology, followed by microvascular causes (n = 11, 36.7%), radiation-induced neuropathy (n = 2, 6.7%), and undetermined (n = 4, 13.3%). Among the 13 patients with palsies due to brain metastasis, only one (7.7%) had been in complete remission for more than 1 year. Of the remaining 17 patients with other causes, seven (41.2%) had been in complete remission of a previously diagnosed cancer for more than 1 year. Conclusions: In patients with a history of cancer, cranial nerve palsy due to brain metastasis was the most common cause, and it was more likely if the primary cancer had not been in remission for more than 1 year. Brain magnetic resonance imaging should be performed as soon as possible to confirm brain metastasis and a differential diagnosis including various other causes is also important.