An attempt to measure the diametric relationship between slow and quick phases of nystagmus

Abstract

Objective: To investigate whether our original method can precisely evaluate the angle between slow and quick phases of nystagmus (vector angle) and to determine whether vector angle analysis is helpful in differentiating between horizontal nystagmus and mixed nystagmus with horizontal and vertical components.

Methods: We included 20 healthy volunteers, 17 patients with horizontal nystagmus, and 15 patients with mixed nystagmus. Caloric nystagmus was recorded in healthy volunteers; positional nystagmus was recorded in each patient. We extracted the velocity of nystagmus from eye movement of each subject and analysed the vector angle.

Results: In caloric nystagmus, the vector angle approached 180 degrees as slow-phase velocity increased, suggesting that our vector angle measurement is more reliable with faster nystagmus. Importantly, in horizontal nystagmus from peripheral vestibular disease, the vector angle similarly approached 180 degrees as slow-phase velocity increased; in contrast, the vector angle in cases of mixed nystagmus from vertebrobasilar insufficiency or spinocerebellar degeneration significantly differed from the angle of caloric nystagmus.

Conclusions: Vector angle analysis using our original algorithm can precisely evaluate the diametric relationship in vestibular nystagmus; it may be helpful in diagnosis of non-peripheral vestibular disorders.

Chinese abstract

目的：探讨我们的原始方法是否能精确评估矢量角度, 判断矢量角度分析是否有助于区分水平眼球震颤和水平-垂直混合眼球震颤。

方法：我们共纳入20名健康志愿者、17名水平眼球震颤患者、15名混合性眼球震颤患者；通过目视检查筛选患者。记录了健康志愿者的热量眼球震颤；记录了每位患者的位置性眼球震颤。我们根据每个受试者的眼球运动得到眼球震颤的速度, 并分析矢量角度。

结果：在热量眼球震颤中, 随着慢相速度的增加, 向量角度接近180度, 这表明我们的向量角度测量法对于更快的眼球震颤更加可靠。重要的是, 在外周前庭疾病的水平性眼球震颤中, 随着慢相速度的增加, 矢量角度同样接近180度；相反, 椎基底动脉供血不足或脊髓小脑变性疾病的混合性眼球震颤的矢状面角度与热量眼球震颤的角度明显不同。

结论：运用我们原有的算法分析眼球震颤的慢相和快相位之间的角度（矢量角）, 可以准确评估前庭眼球震颤的直径关系；它可能有助于诊断非外周性前庭疾病。

Keywords:

• Nystagmus
• slow phase
• quick phase
• diametric relationship
• vestibular disorder
• differential diagnosis
• horizontal
• vertical
• vertebrobasilar insufficiency
• spinocerebellar degeneration

Acknowledgements

We thank Mr. Shin Kirimura (J. Morita. MFG Corporation, Kyoto, Japan) for help in building the system for eye movement analysis. We thank Dr. Chiaki Suzuki, Ms. Kyoko Shimizu (Department of Otolaryngology-Head and Neck Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan) and Dr. Makoto Miura (Department of Otolaryngology, Japanese Red Cross Wakayama Medical Center, Wakayama, Japan) for their clinical support.

Disclosure statement

The authors were supplied with the analysis application for nystagmus, but were given no financial support, from J. Morita MFG Cooperation, Kyoto, Japan.

Additional information

Funding

This work was supported by research grants from JSPS Kakenhi (26506010 to Akiko Taura).