Comparison of the Etiology and Prognosis of Fourth and Sixth Cranial Nerve Palsies (P02.261)

Abstract

Objective: We performed large, retrospective reviews comparing the etiology and prognosis of acute fourth (CN IV) and sixth (CN VI) cranial nerve palsies in the post-MRI era with more detailed analysis by age than previous studies. Background Previous studies of CN IV and CN VI palsies have variable inclusion criteria, have data collected before the common use of MRI, include other cranial nerve palsies in their analyses, have small cohorts, or report only single etiologies or limited age groups. We report the largest current cohorts of CN IV and CN VI palsies with clearly defined inclusion and outcome criteria and detailed comparison between age groups. Design/Methods: Records of CN IV palsy cases between 1995 and 2011, and CN VI palsies between 1995 and 2009 were retrospectively reviewed, and compared. Results: There were 486 recorded episodes of CN IV palsy and 541 recorded episodes of CN VI palsy (excluding congenital cases). Microvascular ischemia was the etiology in 25% of CN IV (120/486), and 49% (265/540) of CN VI. Neoplasm was the cause in 2% (8/486) of CN IV, and 9% (48/540) CN VI. Trauma was the cause in 18% (88/486) of CN IV and 8% (44/540) of CN VI. Demyelinating disease was the cause in 1% (5/486) of CN IV, and in 6% (31/540) of CN VI. 48% of all CN IV cases were undetermined compared to 14% of CN VI. Prognosis varied by etiology but not by age of onset. Complete recovery was seen in 21% of CN IV compared to 45% of CN VI. Conclusions: These post-MRI era studies show a higher incidence of microvascular than traumatic or neoplastic etiologies for both CN IV and CN VI palsies compared to pre-MRI era studies. For both CN IV and CN VI palsies, etiology depends on age, and prognosis depends on etiology. Disclosure: Dr. Atkins has nothing to disclose. Dr. Gorka has nothing to disclose. Dr. Wang has nothing to disclose. Dr. Zurevinsky has nothing to disclose.