title: Incomitance of ocular rotation axes in trochlear nerve palsy.
abstract: Strabismus due to palsy of a single muscle in one eye is always incomitant, which is a consequence of Hering's law of equal innervation. We asked whether this law had similar consequences on the orientation of ocular rotation axes. Patients with unilateral trochlear nerve palsy were oscillated about the nasooccipital (= roll) axis (+/-35 degrees, 0.3 Hz), and monocularly fixed on targets on a head-fixed Hess screen. Both the covered and uncovered eyes were measured with dual search coils. The rotation axis of the covered eye (paretic or healthy) tilted more nasally from the line of sight when gaze was directed toward the side of the healthy eye. The rotation axis of the viewing eye (paretic or healthy), however, remained roughly aligned with the line of sight. We conclude that incomitance due to eye muscle palsy extends to ocular rotation axes during vestibular stimulation.
authors.affiliation: Department of Neurology, Zurich University Hospital, Zurich, Switzerland.
authors.forename: Konrad P
authors.initials: KP
authors.lastname: Weber
authors.forename: Antonella
authors.initials: A
authors.lastname: Palla
authors.forename: Klara
authors.initials: K
authors.lastname: Landau
authors.forename: Thomas
authors.initials: T
authors.lastname: Haslwanter
authors.forename: Dominik
authors.initials: D
authors.lastname: Straumann
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009886:Ophthalmoplegia / Q000503:physiopathology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012399:Rotation; D013285:Strabismus / Q000503:physiopathology*; D020432:Trochlear Nerve Diseases / Q000503:physiopathology*