Clinical outcomes and aetiology of fourth cranial nerve palsy with acute vertical diplopia in adults

BACKGROUND: We investigated the clinical outcomes of fourth cranial nerve (CN4) palsy with acute vertical diplopia in adults. METHODS: A total of 80 patients with acute CN4 palsy who underwent at least 3 months of follow-up were included in this study. We retrospectively investigated the aetiology, rate of recovery, and factors associated with recovery between March 2016 and January 2019. RESULTS: The average age of patients with CN4 palsy was about 60 years, and the duration of recovery was 1.5 months: 48 (60.0%) patients had a vascular aetiology and 17 (21.3%) patients had a trauma history. Brain lesions were found in four (5.0%) patients and decompensated cause accounted for four (5.0%) cases. Among the total of 80 patients, 13 (16.3%) failed to completely recover. Non-isolated CN4 palsy with other cranial nerve palsies were recorded in seven cases. The comparison between recovery and non-recovery groups showed that initial deviation angle, aetiology, fundus extorsion, and head tilt status were significantly different factors. CONCLUSION: The recovery rate of acute CN4 palsy was about 80% and duration of recovery was 1.5 months. However, the varying rates and duration of recovery was presented according to aetiology thus we should consider the prognosis by aetiology.