Tonic ocular tilt reaction simulating a superior oblique palsy - Diagnostic confusion with the 3-step test

Background: The tonic ocular tilt reaction (OTR) consists of vertical diver gence of the eyes (skew deviation), bilateral conjugate ocular torsion, and paradoxical head tilt. The head and superior pole of both eyes are rotated toward the hypotropic eye. Objective: To describe ocular motility and torsion findings in 5 patients w ith OTRs that mimicked superior oblique palsies (SOPs). Results: In 5 patients, results of the 3-step test suggested an SOP (bilate ral in 1 patient); however, no patient had the expected excyclotorsion of t he hypertropic eye. Two patients had conjugate ocular torsion (intorsion of the hypertropic eye and extorsion of the hypotropic eye), and 2 patients h ad only intorsion of the hypertropic eye. All had other neurologic features consistent with more widespread brainstem disease. Conclusions: Vertical ocular deviations that 3-step to an SOP are not alway s caused by fourth nerve weakness. When a patient with an apparent fourth n erve palsy has ocular torsion that is inconsistent with an SOP, OTR should be suspected, especially if vestibular system or posterior fossa dysfunctio n coexists. The rules for the 3-step test for an SOP may be fulfilled by da maging the otolithic projections corresponding to projections of the contra lateral anterior semicircular canal. Because results of the Bielschowsky he ad tilt test may be positive in patients with the OTR, the feature distingu ishing OTR from an SOP is the direction of torsion. We advocate use of a fo urth step-evaluation of ocular torsion-in addition to the standard 3 steps.