A new rotational test for vertical semicircular canal function.
OBJECTIVE
We developed a new rotating chair in order to assess the function of the vertical semicircular canal (VSCC) by analyzing VSCC-induced post-rotatory nystagmus (PRN).


METHODS
We examined 14 healthy subjects, wearing goggles equipped with an infrared CCD camera, and sitting on a chair which was designed to stimulate a pair of the VSCCs by tilting the head 60 degrees backward with a 45 degrees rotation to the left or right side from the sagital plane. The time constant (TC) or maximal slow phase eye velocity (MSPEV) of the vertical component of four kinds of PRN were analyzed in four corresponding rotatory conditions, and used as functional index of the corresponding VSCC.


RESULTS
The mean values of MSPEV in both anterior semicircular canal (ASCC) and posterior semicircular canal (PSCC)-induced PRN tended to be lower (P<0.10) than those induced by the lateral semicircular canal (LSCC). The result suggests that the threshold to the angular velocity in the VSCC is lower than that in the LSCC. The mean values of TC in both ASCC and PSCC-induced PRN were significantly lower (P<0.05) than those induced by the LSCC.


CONCLUSIONS
The significant reduction of TC in VSCC-induced PRN compared with LSCC-induced PRN indicates that VSCC function is less affected by velocity storage mechanisms than LSCC function. The rotational test with respect to the VSCC can be used as a tool for assessing vertical canal function.
Morita
Masahiro
M
Department of Otolaryngology, Minoo Municipal Hospital, Osaka University Medical School, 5-7-1 Kayano Minoo, Osaka 562-8562, Japan. ent@m.email.ne.jp
Imai
Takao
T
Kazunori
Sekine
S
Takeda
Noriaki
N
Koizuka
Izumi
I
Uno
Atsuhiko
A
Kitahara
Tadashi
T
Kubo
Takeshi
T
D000328:Adult; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D009760:Nystagmus, Physiologic; D012399:Rotation / Q000009:adverse effects; D012665:Semicircular Canals / Q000502:physiology*; D014717:Vertigo / Q000209:etiology; D014724:Vestibular Function Tests / Q000379:methods