Ocular torsion and tilt of subjective visual vertical are sensitive brainstem signs

Abstract

Deviations of the position of the eye in the roll plane, ocular torsion (OT), and the subjective visual vertical (SVV) were systematically studied in 111 patients with acute vascular brainstem lesions. Of the 111 patients, 104 (94%) showed a direction-specific pathological tilt of the static SVV in our series. Seventy-one (83%) of 86 patients exhibited pathological static OT of one (47%) or both (36%) eyes. OT and SVV tilts are therefore sensitive signs in acute unilateral brainstem disorders. Measurements of SVV and OT may prove to be useful components of the neuro-ophthalmological evaluation. With respect to the directions of pathological tilt, SVV and OT are generally in the same direction. Based on neuroimaging, we conclude that all unilateral brainstem lesions caudal to the upper pons cause ipsiversive OT of one or both eyes, with concurrent ipsiversive tilts of SVV adjustments; all lesions rostral to this pontine level cause contraversive tilts of OT and SVV. Evidence is presented that pathological tilts of OT and SVV are secondary to a dysfunction of the tonic bilateral vestibular inputs that stabilize the eyes and head in normal upright position in the roll plane and dominate our perception of verticality.