title: An unusual variant of the dorsal midbrain syndrome in MS: clinical characteristics and pathophysiologic mechanisms.
abstract: Patients with MS exhibit a broad diversity of ocular motor syndromes. We describe a patient with relapsing-remitting MS who developed an unusual variation of the dorsal midbrain syndrome, characterized by monocular convergent-retraction nystagmus in the right eye, accompanied by divergent-retraction nystagmus in the fellow eye upon attempted upward gaze. Examination also revealed a skew deviation with a left hyperdeviation and severe adduction limitation in the left eye during attempted right gaze. We propose that a left INO accounted for the inability of the left eye to adduct (and result in convergent-retraction) during attempted upward saccades. We consider the pathophysiologic mechanisms responsible for our observations and review important details of the dorsal midbrain ocular motor circuitry.
authors.affiliation: Department of Neurology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA. elliot.frohman@utsouthwestern.edu
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Frohman
authors.forename: Richard B
authors.initials: RB
authors.lastname: Dewey
authors.forename: Teresa C
authors.initials: TC
authors.lastname: Frohman
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008636:Mesencephalon / Q000473:pathology* / Q000503:physiopathology*; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000473:pathology* / Q000503:physiopathology*; D009759:Nystagmus, Pathologic / Q000473:pathology / Q000503:physiopathology; D012027:Reflex, Vestibulo-Ocular