title: Primary position upbeat nystagmus.
abstract: Primary position upbeat nystagmus is a rare clinical finding. We report a patient with clinically isolated syndrome suggestive of multiple sclerosis who presented with primary position upbeat nystagmus. MRI revealed a demyelinating lesion in the lower medulla, which affected the nucleus intercalatus; this type of lesion inhibits the flocculovestibular inhibitory pathway, thereby causing upbeat nystagmus. Nystagmus still persisted after pulsed corticosteroid therapy. This could be due to a loss of central adaptation of the vestibulo-ocular system in our patient, because of more diffuse brainstem damage, shown on vestibular-evoked myogenic potentials as delayed latencies on both sternocleidomastoid muscles and a conduction block for the left extraocular muscles.
authors: Department of Neurology, Zagreb School of Medicine and University Hospital Center, Referral Center for Demyelinating Diseases of the Central Nervous System, Kišpatićeva 12, Zagreb HR-10000, Croatia.
authors: Ivan
authors: I
authors: Adamec
authors: Tereza
authors: T
authors: Gabelić
authors: Magdalena
authors: M
authors: Krbot
authors: David
authors: D
authors: Ozretić
authors: Iva
authors: I
authors: Milivojević
authors: Mario
authors: M
authors: Habek
mesh_terms: D003711:Demyelinating Diseases / Q000150:complications / Q000175:diagnosis / Q000473:pathology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008526:Medulla Oblongata / Q000473:pathology* / Q000503:physiopathology; D009759:Nystagmus, Pathologic / Q000175:diagnosis / Q000209:etiology*; D014724:Vestibular Function Tests / Q000379:methods; D055815:Young Adult