title: Upbeat nystagmus from a demyelinating lesion in the caudal pons.
abstract: A 51-year-old man developed positional vertigo, ataxia, dysgeusia, diplopia, and oscillopsia. Eye movement examination and video-oculographic recording disclosed primary position upbeat nystagmus (PPUN) and a right internuclear ophthalmoplegia. Brain MRI showed a small focal lesion in the right dorsal tegmentum of the caudal pons with signal characteristics consistent with a primary demyelinating central nervous system disease. PPUN has not been described previously with a lesion in such a location. Clinicoanatomic correlation in this patient suggests that a lesion of the superior vestibular nucleus and its efferent crossing ventral tegmental tract could be responsible for the PPUN. This case report contributes to a better understanding of the role of this pathway in humans.
authors.affiliation: Neuro-Ophthalmology Unit, Hôpital Neurologique, Hospices Civils de Lyon, 59 Bd Pinel, 69 677, Bron, France. caroline.tilikete@lyon.inserm.fr
authors.forename: Caroline
authors.initials: C
authors.lastname: Tilikete
authors.forename: Dan
authors.initials: D
authors.lastname: Milea
authors.forename: Charles
authors.initials: C
authors.lastname: Pierrot-Deseilligny