title: 3D analysis of benign positional nystagmus due to cupulolithiasis in posterior semicircular canal.
abstract: CONCLUSIONS
  The characteristic of both the vertical-torsional positional nystagmus with long time constant and its disappearance at the neutral head position could diagnose cupulolithiasis in posterior semicircular canal (PSCC) in the eight patients with the PSCC type of benign paroxysmal positional vertigo (P-BPPV).
  
  
  OBJECTIVE
  The aim of the study was to diagnose cupulolithiasis in patients with P-BPPV.
  
  
  METHODS
  We used three-dimensional rotation axis analysis of nystagmus of the vertical-torsional positional nystagmus in 111 patients with P-BPPV and evaluated its time constant. We then examined whether the vertical-torsional positional nystagmus with long time constant disappeared at the neutral head position where the axis of the heavy cupula of the affected PSCC is aligned with gravity.
  
  
  RESULTS
  The first parameter showed a wide variation that could be divided into two groups: one lasting more than 40 s in 8 patients and another below 20 s in 103 patients. Since the time constant of the positional nystagmus induced by cupulolithiasis was much longer than that induced by canalolithiasis, this finding suggests that cupulolithiasis in the PSCC induced the vertical-torsional positional nystagmus with a long time constant in the group of eight patients. The vertical-torsional positional nystagmus disappeared in these patients at the neutral head position, where the axis of the cupula of affected PSCC aligned with gravity.
authors.affiliation: Department of Otolaryngology, Osaka Seamen's Insurance Hospital, Osaka, Japan. imaitakao@hotmail.com
authors.forename: Takao
authors.initials: T
authors.lastname: Imai
authors.forename: Noriaki
authors.initials: N
authors.lastname: Takeda
authors.forename: Mahito
authors.initials: M
authors.lastname: Ito
authors.forename: Kazunori
authors.initials: K
authors.lastname: Sekine
authors.forename: Go
authors.initials: G
authors.lastname: Sato
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Midoh
authors.forename: Koji
authors.initials: K
authors.lastname: Nakamae
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007759:Labyrinth Diseases / Q000175:diagnosis*; D020347:Lithiasis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009760:Nystagmus, Physiologic; D055815:Young Adult