title: Variable waveforms in downbeat nystagmus imply short-term gain changes.
abstract: A patient with downbeat nystagmus subsequent to ankylosing spondylitis was studied. His nystagmus was found to exhibit both increasing- and decreasing-velocity exponential slow phases as well as the linear form more often reported. Alternation between waveforms sometimes occurred on a beat-to-beat or even intrabeat basis. Possible explanations for all three waveforms are presented in terms of short-term gain changes in cerebellar compensation for leaky brainstem neural integrators. A computer model was developed and its results are discussed.
authors.affiliation: Ocular Motor Neurophysiology Laboratory, Veterans Administration Medical Center, Cleveland, OH, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Abel
authors.forename: S
authors.initials: S
authors.lastname: Traccis
authors.forename: L F
authors.initials: LF
authors.lastname: Dell'Osso
authors.forename: C F
authors.initials: CF
authors.lastname: Ansevin
mesh_terms: D001933:Brain Stem / Q000503:physiopathology; D002531:Cerebellum / Q000503:physiopathology; D003198:Computer Simulation; D005133:Eye Movements; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000209:etiology* / Q000503:physiopathology*; D013167:Spondylitis, Ankylosing / Q000150:complications*