title: Atypical periodic alternating nystagmus responding to high-dose intravenous immunoglobulins: a case report.
abstract: Acquired periodic alternating nystagmus (PAN) is a rare but well-defined syndrome that consists of a horizontal nystagmus that cyclically reverses its direction. PAN can be caused by degenerative, neoplastic, or toxic diseases of the cerebellum and, in a few cases, by subacute cerebellar ataxia of immune origin.
  
  
  
  A 44-year-old man came to our attention because of rapidly progressive gait instability and blurred vision. Clinical examination showed PAN and a mild pancerebellar syndrome. Eye movement recordings disclosed a short cycle PAN with significant slow-phase velocity only in darkness. Under the effect of a γ-aminobutyric acid type B (GABAB) agonist, PAN was not modified. Right after treatment with intravenous immunoglobulin (IVIg) was started, PAN was essentially eliminated. Three months after last dose of IVIg, this nystagmus reappeared.
  
  
  
  IVIg resolved PAN in this patient. This finding may point to an autoimmune mechanism underlying this patient's nystagmus. This case suggests that the usefulness of IVIg at treating PAN might be worth a consideration in similar clinical settings.
authors.affiliation: Department of Neurology, Hospital Universitari i Politècnic La Fe, 106 Fernando Abril Martorell Ave, 46026, Valencia, Spain.
authors.forename: Herminia
authors.initials: H
authors.lastname: Argente-Escrig
authors.affiliation: Department of Neurology, Hospital Universitari i Politècnic La Fe, 106 Fernando Abril Martorell Ave, 46026, Valencia, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Bataller
authors.affiliation: Department of Otolaryngology, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Claudio
authors.initials: C
authors.lastname: Krstulovic Roa
authors.affiliation: Department of Otolaryngology, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Vanesa
authors.initials: V
authors.lastname: Pérez Guillén
authors.affiliation: Department of Otolaryngology, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Herminio
authors.initials: H
authors.lastname: Perez Garrigues
authors.affiliation: Department of Neurology, Hospital Universitari i Politècnic La Fe, 106 Fernando Abril Martorell Ave, 46026, Valencia, Spain. casanova.bonaventura@gmail.com.
authors.forename: Bonaventura
authors.initials: B
authors.lastname: Casanova Estruch
mesh_terms: D000328:Adult; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use*; D008297:Male; D009759:Nystagmus, Pathologic / Q000188:drug therapy*
chemical_list: D016756:Immunoglobulins, Intravenous
keywords: Ataxia; Autoimmune disease; Cerebellum; Gait disorders; Nystagmus; Oscillopsia