Sudden-onset trochlear nerve palsy: clinical characteristics and treatment implications

PURPOSE To identify clinical characteristics, etiologies, and treatment implications of sudden-onset, acquired cases of superior oblique palsy. METHODS The medical records of patients diagnosed with trochlear nerve palsy between January 2010 and January 2018 were reviewed retrospectively to identify cases of acquired trochlear nerve palsy with a specific date of onset of acute symptoms or specific causative incident. Patients with congenital palsies or an uncertain date of onset, history of other strabismus, concomitant oculomotor or abducens nerve palsies, or history of strabismus surgery were excluded. RESULTS Of 214 patients with superior oblique palsy, 23 had sudden-onset, acquired palsies. There were 14 cases of unilateral palsy and 9 cases of bilateral palsy. Patients with unilateral palsy presented with vertical diplopia, while those with bilateral palsy complained of either torsional (4/9 patients) or vertical (5/9 patients) diplopia. The most common etiologies were severe trauma associated with traumatic brain injury, followed by central nervous system neoplasm and stroke. Fifteen patients underwent surgical intervention, 3 of whom required more than one surgery. CONCLUSIONS Patients with acute superior oblique palsy invariably complain of vertical and/or torsional diplopia. Neuroimaging should be considered in cases of acquired superior oblique palsy without a known traumatic cause. Bilateral cases of acquired superior oblique palsy are more challenging to manage surgically because of symptomatic torsional diplopia.