Article Text

PDF

Light cupula: the pathophysiological basis of persistent geotropic positional nystagmus
  1. Takao Imai1,
  2. Kazunori Matsuda2,
  3. Noriaki Takeda2,
  4. Atsuhiko Uno3,
  5. Tadashi Kitahara4,
  6. Arata Horii5,
  7. Suetaka Nishiike6,
  8. Hidenori Inohara1
  1. 1Department of Otorhinolaryngology—Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
  2. 2Department of Otolaryngology, University of Tokushima School of Medicine, Tokushima, Japan
  3. 3Department of Otolaryngology, Osaka General Medical Center, Osaka, Japan
  4. 4Department of Otolaryngology, Nara Medical University, Nara, Japan
  5. 5Department of Otolaryngology, Osaka National Hospital, Osaka, Japan
  6. 6Department of Otolaryngology, Osaka Rosai Hospital, Osaka, Japan
  1. Correspondence to Dr Takao Imai; timai{at}ent.med.osaka-u.ac.jp

Abstract

Objective To clarify the pathophysiological basis of persistent geotropic positional nystagmus (PGN) in patients with the horizontal canal type of benign paroxysmal positional vertigo (H-BPPV), the time constant (TC) of nystagmus and the relationship between its slow phase eye velocity (SPV) and the angle of head rotation in supine were defined.

Methods Geotropic or apogeotropic positional nystagmus was recorded by video-oculography and analysed three-dimensionally.

Results Geotropic positional nystagmuses in patients with H-BPPV were classified as transient geotropic positional nystagmus with a TC of ≤35 s or PGN with a TC of >35 s. Alternatively, the TC of persistent apogeotropic positional nystagmus (AN) in patients with H-BPPV was >35 s. The direction of the SPV of patients with PGN was opposite to that of patients with AN at each head position across the range of neutral head positions. The relationship between the SPV of patients with PGN and the angle of head rotation was linearly symmetrical against that of patients with AN with respect to a line drawn on the neutral head position.

Conclusions Since its TC was >35 s, it is suggested that PGN is induced by cupula deviation in response to gravity at each head position. It is also suggested that the direction of cupula deviation in patients with PGN is opposite to that of patients with AN across the neutral head positional range with no nystagmus where the long axis of cupula is in alignment with the axis of gravity. Since the pathophysiological basis of AN is considered a heavy cupula, it is suggested that PGN is conversely induced by a light cupula.

Statistics from Altmetric.com

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.