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

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Abstract
Deviations of the position of the ey in the roll plance, ocular trosion (OT), and the subjective visual vertical (SVV) wre systematically studied in 111 patients with acure vascular brainstem lesions. Of the 111 partents, 104 (94%) showed a direction-specific pathological tilt of the static SVV in our series, Sevenry-one (83%) of 86 partients exhibited pathological static OT of one (47%) or both (36%) eyes. OT and SVV tilts are therefore sensitive signs in acture unilateral brainstem disorders. Measurements of SVV and OT may prove to be useful components of the neuroophthalmological evaluation. With respect to the directions of pathological tilt, SVV an OT are generally in the same direction. Based on neuroimaging, we conclude that all unilateral brainstem lesion 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 tills of OT and SVV. Evidence is presented that pathological tilts of OT and SVV are secondary to a dysfunction of the tonic bilateral vestibular imputs that stabilize the eyes and head in normal upright position in the roll plance and dominate our perception of verticality.