Equilibrium Research
Online ISSN : 1882-577X
Print ISSN : 0385-5716
ISSN-L : 0385-5716
原著
良性発作性頭位めまい症における眼振消失・再出現のメカニズム
―新しい概念 “クリスタ結石症”―
城守 美帆大塚 康司許斐 氏元鈴木 衞
著者情報
ジャーナル フリー

2017 年 76 巻 4 号 p. 277-285

詳細
抄録

 [Introduction] Nystagmus associated with benign paroxysmal positional vertigo (BPPV) canalolithiasis gradually decreases with repeated positional change (fatigability). In other examples, the nystagmus disappears suddenly with positional change and appears again, the mechanism behind which would appear to be different from fatigability. We suspect this phenomenon is being induced by otoconia attached to and detached from the base of the crista. We have arbitrarily called this “cristolithiasis.” The validity of this theory was investigated.

 [Method] The bullfrog labyrinth was used as a model. The membranous labyrinth was cut at the crus commune to create a tiny opening. A small piece of otoconia, removed from the sacculus of the other ear, was introduced through this opening into the canal lumen. Experiment 1: The position of the preparation was changed so that the otoconia move back and forth within canal to canal and canal to ampulla. We observed the movement of the otoconia for maximum up to ten times. The rates of otoconia attachment to the canal wall and the crista were investigated. Experiment 2: The model of the otoconia attached to the cupula (cupulolithiasis) or the crista (cristolithiasis) was used. These models were given two kinds of stimuli, a. gravity and b. vibration. Experiment 2a (Gravity): The labyrinth preparation was placed so that the cupula-to-crista axis was in the horizontal plane with the canal side in downward position for 30 minutes. The rates of the otoconia detachment from the crista or the cupula were investigated. Experiment 2b (Vibration): Mechanical vibration was applied to the bony labyrinthine capsule of these models using a surgical drill. The time required for otoconial detachment was measured.

 [Result] Experiment 1: No otoconial mass was attached to the canal wall in 6 labyrinth preparations. The otoconial mass was attached to the crista in 5 out of 6 (83.3%). The otoconia were attached more easily to the crista than the canal wall. Experiment 2a (Gravity): In cupulolithiasis models, the otoconial mass was detached within 30 minutes in 2 out of 10 (20%) labyrinth preparations. In cristolithiasis models, the otoconial mass was detached within 30 minutes in 11 out of 14 (78.6%), which was significantly higher than in the cupulolithiasis models (p=0.015). Experiment 2b (Vibration): In the cupulolithiasis models (n=14), the average detachment time was 140.3 seconds. In the cristolithiasis models (n=11), the average detachment time was 25.5 seconds, which was significantly shorter than in the cupulolithiasis models (p=0.0010). The otoconia associated with cristolithiasis were detached more easily than in the case of cupulolithiasis.

 [Discussion] The inner wall of the semicircular canal is covered by cells with a smooth surface. In canalolithiasis, the otoconia move along the canal smoothly. On the other hand, the basal portion of the wall near the crista has transitional cells, planum semilunatum, and dark cells. The epithelia have microvilli and secretory activity to which the otoconia easily become attached. The attachment is weaker than in cupulolithiasis. It is assumed that this attachment and detachment of the otoconia near the crista lead to disappearance and return of the nystagmus.

著者関連情報
© 2017 一般社団法人 日本めまい平衡医学会
前の記事 次の記事
feedback
Top