Etiology and Outcomes of Acquired Pediatric Sixth Nerve Palsies

Background: Acquired sixth nerve (CN6) palsies in children may be benign or associated with an underlying neurologic condition. In children who presented with isolated (no associated neurologic or ophthalmic symptoms or signs) CN6 palsies, the rate of newly diagnosed neurologic disorders (such as tumors) is unclear. Moreover, the factors associated with spontaneous resolution and amblyopia in children with acquired CN6 palsies are unknown.

Methods: We retrospectively reviewed the charts of all children younger than 18 years diagnosed with CN6 palsy at our institution from 2010 to 2020. We recorded ophthalmologic and neurologic history and examination findings, neuroimaging results, etiology of CN6 palsy, and outcomes including spontaneous resolution and amblyopia. We assessed etiologies of isolated and nonisolated CN6 palsies as well as frequency and factors associated with spontaneous resolution and amblyopia (in children ≤7 years).

Results: One hundred seventy-two children met inclusion criteria. Twenty CN6 palsies (12%) were isolated at presentation. Most isolated cases were presumed postviral or postvaccination (50%) or idiopathic (30%), but 2 cases (10%) were associated with newly diagnosed tumors. Spontaneous resolution occurred in 59% of CN6 palsies at a median of 12.3 weeks and was associated with older age (P = 0.03) and nontumor etiology (P = 0.006). Amblyopia developed in 18% of children at risk, exclusively in those with anisometropia, pre-existing strabismus, or younger than 12 months.

Conclusions: Our findings and chart reviews suggest that approximately 10% of isolated acquired pediatric CN6 palsies are associated with a newly diagnosed brain tumor. This risk must be discussed with parents when considering immediate vs delayed neuroimaging. In addition, infants and children ≤7 years with secondary amblyogenic risk factors (anisometropia or pre-existing strabismus) require close follow-up to monitor and treat amblyopia.