From the Research
The normal range for slow phase velocity (SPV) in caloric testing is typically between 10 to 50 degrees per second. During a caloric test, when warm (44°C) or cold (30°C) water or air is introduced into the ear canal, it creates a temperature gradient in the semicircular canals, particularly the horizontal canal. This temperature change causes movement of the endolymph fluid, which stimulates hair cells and generates nystagmus (involuntary eye movements). The SPV measures how quickly the eyes drift during the slow component of this nystagmus. Values below 10 degrees per second may indicate canal paresis or vestibular hypofunction, while asymmetry between ears greater than 20-25% is considered abnormal.
Key Points to Consider
- The caloric test is an important component of videonystagmography (VNG) or electronystagmography (ENG) assessments used to evaluate vestibular function in patients with dizziness, vertigo, or balance disorders.
- Clinicians should consider that normal values can vary slightly between laboratories due to differences in equipment and protocols.
- A study published in 2018 1 found that air caloric test can be used instead of water caloric test in clinic, and if the patient has no contraindications, air caloric test can be used as a priority.
- Another study published in 2018 2 found that subjective sensations other than spinning and rotating are reported 20-25% of the time and these tend to be associated with lower peak SPV.
Recommendations
- Use the normal range of 10 to 50 degrees per second for SPV in caloric testing.
- Consider using air caloric test as a priority if the patient has no contraindications.
- Be aware that subjective sensations other than spinning and rotating can be associated with lower peak SPV.
- Consider the study published in 2021 3 which found that tasking of any kind resulted in significantly larger peak SPV responses when compared to the no tasking condition for rotary chair testing, but no significant difference was noted when comparing the conditions with tasking to the no tasking condition for caloric testing.