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The Video Head Impulse Test (vHIT) of Semicircular Canal Function - Age-Dependent Normative Values of VOR Gain in Healthy Subjects.

McGarvie LA, MacDougall HG, Halmagyi GM, Burgess AM, Weber KP, Curthoys IS - Front Neurol (2015)

Bottom Line: The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.The results are considered in relation to recent evidence about the effect of age on VOR performance.These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss.

View Article: PubMed Central - PubMed

Affiliation: Neurology Department, Institute of Clinical Neurosciences, Royal Prince Alfred Hospital , Camperdown, NSW , Australia.

ABSTRACT

Background/hypothesis: The video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus, i.e., the gain of the vestibulo-ocular reflex (VOR). However, there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to the responses of healthy subjects in their age range. In this study, we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life.

Study design: The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.

Methods: The compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS impulse prototype system. The same operator delivered every impulse to every subject.

Results: Vestibulo-ocular reflex gain decreased at high head velocities, but was largely unaffected by age into the 80- to 89-year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.

Conclusion: These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging.

No MeSH data available.


Mean and 95% confidence intervals of VOR gain as a function of age for the horizontal, anterior, and posterior canals (top, middle, and bottom panels, respectively). Ten subjects were included for each decade of age. The within-subject mean VOR gain was calculated for each of the six semicircular canals over the whole range of peak head velocities. For horizontal, anterior, and posterior canals, within-subject means were then calculated from the mean VOR gain for that canal on the left and right side of the head. These values were then used to calculate the between-subject means over all 10 subjects. As shown by the ANOVA, the gains for horizontal canals and anterior do not vary significantly with age but the average gains for the posterior canals decrease.
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Figure 6: Mean and 95% confidence intervals of VOR gain as a function of age for the horizontal, anterior, and posterior canals (top, middle, and bottom panels, respectively). Ten subjects were included for each decade of age. The within-subject mean VOR gain was calculated for each of the six semicircular canals over the whole range of peak head velocities. For horizontal, anterior, and posterior canals, within-subject means were then calculated from the mean VOR gain for that canal on the left and right side of the head. These values were then used to calculate the between-subject means over all 10 subjects. As shown by the ANOVA, the gains for horizontal canals and anterior do not vary significantly with age but the average gains for the posterior canals decrease.

Mentions: In all three ANOVAs (Table S1 in Supplementary Material), the factor velocity was significant – at every age, there was a decrease in VOR gain as head velocity increased (Figure 6). For the horizontal and anterior canals, the factor Direction was significant. For all canals, we found little decrease in VOR gain with age, at least up to the 80s, such that the factor Age was not significant for horizontal and anterior canals and Age was only weakly significant (p < 0.02) for the posterior canal. To elaborate the cause of the significant factors, Figure 6 shows the data averaged across velocity in each decade band (mean ± 95% CIs). So for the horizontal canal, the two-tailed 95% confidence intervals for VOR gain include or are very close to 1.0 even for subjects in their 70s and 80s. For the anterior and posterior canals, the average VOR gain was significantly <1 at all ages (Figure 6).


The Video Head Impulse Test (vHIT) of Semicircular Canal Function - Age-Dependent Normative Values of VOR Gain in Healthy Subjects.

McGarvie LA, MacDougall HG, Halmagyi GM, Burgess AM, Weber KP, Curthoys IS - Front Neurol (2015)

Mean and 95% confidence intervals of VOR gain as a function of age for the horizontal, anterior, and posterior canals (top, middle, and bottom panels, respectively). Ten subjects were included for each decade of age. The within-subject mean VOR gain was calculated for each of the six semicircular canals over the whole range of peak head velocities. For horizontal, anterior, and posterior canals, within-subject means were then calculated from the mean VOR gain for that canal on the left and right side of the head. These values were then used to calculate the between-subject means over all 10 subjects. As shown by the ANOVA, the gains for horizontal canals and anterior do not vary significantly with age but the average gains for the posterior canals decrease.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4495346&req=5

Figure 6: Mean and 95% confidence intervals of VOR gain as a function of age for the horizontal, anterior, and posterior canals (top, middle, and bottom panels, respectively). Ten subjects were included for each decade of age. The within-subject mean VOR gain was calculated for each of the six semicircular canals over the whole range of peak head velocities. For horizontal, anterior, and posterior canals, within-subject means were then calculated from the mean VOR gain for that canal on the left and right side of the head. These values were then used to calculate the between-subject means over all 10 subjects. As shown by the ANOVA, the gains for horizontal canals and anterior do not vary significantly with age but the average gains for the posterior canals decrease.
Mentions: In all three ANOVAs (Table S1 in Supplementary Material), the factor velocity was significant – at every age, there was a decrease in VOR gain as head velocity increased (Figure 6). For the horizontal and anterior canals, the factor Direction was significant. For all canals, we found little decrease in VOR gain with age, at least up to the 80s, such that the factor Age was not significant for horizontal and anterior canals and Age was only weakly significant (p < 0.02) for the posterior canal. To elaborate the cause of the significant factors, Figure 6 shows the data averaged across velocity in each decade band (mean ± 95% CIs). So for the horizontal canal, the two-tailed 95% confidence intervals for VOR gain include or are very close to 1.0 even for subjects in their 70s and 80s. For the anterior and posterior canals, the average VOR gain was significantly <1 at all ages (Figure 6).

Bottom Line: The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.The results are considered in relation to recent evidence about the effect of age on VOR performance.These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss.

View Article: PubMed Central - PubMed

Affiliation: Neurology Department, Institute of Clinical Neurosciences, Royal Prince Alfred Hospital , Camperdown, NSW , Australia.

ABSTRACT

Background/hypothesis: The video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus, i.e., the gain of the vestibulo-ocular reflex (VOR). However, there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to the responses of healthy subjects in their age range. In this study, we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life.

Study design: The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.

Methods: The compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS impulse prototype system. The same operator delivered every impulse to every subject.

Results: Vestibulo-ocular reflex gain decreased at high head velocities, but was largely unaffected by age into the 80- to 89-year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.

Conclusion: These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging.

No MeSH data available.