Nystagmus duration after caloric irrigations

Abstract

Objective: To measure nystagmus duration after warm and cool caloric water irrigations, with the aim of providing preliminary evidence for the optimum interval between irrigation onsets; and to compare nystagmus durations between warm and cool irrigations, in addition to maximum slow phase velocity (SPV).

Design: Participants underwent up to four caloric irrigations during routine appointments. Nystagmus was recorded to minimal levels (within 2°/s of subject’s baseline). The nystagmus duration and maximum SPV were measured.

Study Sample: 52 vestibular assessment patients (99 ears).

Results: The mean nystagmus duration was 183.9 s (seconds) (3:04 min) from irrigation onset, and nystagmus became minimal after 264.8 s (4:25 min) in 97.5% of this sample. The population mean is within ±6.7 s of the sample mean (p = <0.001). There was no significant difference between warm and cool irrigation durations, and correlation and linear regression analysis showed duration cannot reliably be predicted by maximum SPV.

Conclusions: Mean nystagmus duration (3 min after irrigation onset) and nystagmus duration for 97.5% of patients (<4.5 min) were substantially less than the BSA recommended 7 min between irrigations. These findings provide preliminary evidence for shortening of intervals between stimulus onsets, regardless of irrigation temperature or maximum SPV, to reduce caloric testing time and improve clinical efficiency.

Keywords:

• Caloric test
• interstimulus interval
• irrigations
• nystagmus duration
• slow-phase velocity

Acknowledgement

Dr. Jamie Sergeant, Lecturer in Biostatistics School of Health Sciences, University of Manchester, UK acknowledgement for statistical advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 The data point was excluded due to a hyper-responsive maximum SPV result. Pearson’s correlation coefficient (r = .22) was significant (p = 0.007) when this value was included in analysis, with a significant slope coefficient value of 0.54 (p = 0.007) and adjusted R² value of .04.

2 Pearson’s correlation coefficient (r = .16) was not significant (p = 0.12) when the outlying data value was included in analysis.

3 Adjusted R² was .02, and slope coefficient of 0.35 was not significant (p = 0.18) when the outlying data value was included in analysis.