title: Neutral position of persistent direction-changing positional nystagmus.
abstract: The aim of this study was to measure the neutral position of direction-changing apogeotropic positional nystagmus (heavy cupula of the horizontal semicircular canal) and persistent direction-changing geotropic positional nystagmus (light cupula of the horizontal semicircular canal). We conducted a prospective case series study on 31 patients with heavy cupula (12 males, 19 females; mean age, 64.3 years) and 33 patients with light cupula (10 males, 23 females; mean age, 60.9 years). We measured the angle of the neutral position in patients with heavy cupula (θ 1) and that in patients with light cupula (θ 2) using a large protractor. The mean value and standard deviation of θ 1 was 31.6 ± 22.4°, minimum value was 5°, and maximum value was 89°. The mean value and standard deviation of θ 2 was 44.4 ± 20.5°, minimum value was 5°, and maximum value was 85°. θ 2 was significantly greater than θ 1 (p < 0.05). The neutral position varies widely. Some patients exhibit a great angle (more than 40°); therefore, examiners should make patients adopt a completely lateral position in the supine head roll test and should confirm the direction of nystagmus in order to avoid mistaking positional nystagmus for spontaneous nystagmus.
authors.affiliation: Ichijo Ear, Nose and Throat Clinic, 3-2-1, Ekimae, Hirosaki, 036-8002, Japan. hiro3387@mvj.biglobe.ne.jp.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ichijo
mesh_terms: D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000175:diagnosis / Q000503:physiopathology*; D009760:Nystagmus, Physiologic / Q000502:physiology*; D011446:Prospective Studies; D012665:Semicircular Canals / Q000503:physiopathology*; D016683:Supine Position / Q000502:physiology*; D014724:Vestibular Function Tests
keywords: Buoyancy; Heavy cupula; Horizontal semicircular canal; Light cupula; Supine head roll test