How does age influence the results of vestibular exams?
Age can influence the outcome of vestibular exams in diverse ways, depending on the test considered.
In the saccade test, saccade latencies usually increase with age, however accuracy or peak velocities are not significant. Notice that increased latencies may be related to poor visual acuity, as patients cannot wear corrective glasses during VNG. A considerable number of drugs can interfere with saccade parameters.
In the pursuit test, the gain decreases with age, especially if stimulus has a high frequency. In older individuals, nystagmus in the optokinetic test decreases for higher-velocity stimuli. Again, effects of poor vision and drugs must be considered in the interpretation of results.
In gaze stabilization tests, end-point nystagmus usually becomes evident closer to the midline gaze positions and is more common in the elderly. In the same way, square-wave jerk nystagmus during visual fixation appears very often in the elderly and can be considered normal; therefore, patient age is crucial when determining its clinical significance.
In caloric tests, bilateral weakness is quite common in older patients. Although decreased caloric reactivity may represent an age-related reduction of vestibular function, it could be a false-positive finding related to poor thermic gradient transfer from the external auditory canal to the lateral semicircular canal.
In rotary chair testing, reduced VOR gain and VOR phase lead are common in older asymptomatic individuals, especially during low frequencies stimulation. These findings indicate that vestibular function and velocity storage mechanism in the vestibular nuclei are declining.
In vHIT, some precaution is needed regarding neck stiffness to avoid neck injuries. The results of vHIT appear to be independent of normal aging, as only the posterior semicircular canal demonstrates a slight decrease in gain with increasing age. The increasing frequency of corrective saccades after and during the VHIT with higher age could be caused by different mechanisms: contamination by nystagmus, a deficient VOR, fixation instability, adaptation effects caused by optic corrections, and inability to suppress saccades to novel stimuli.
In cVEMP and oVEMP, parameters are influenced by age. VEMP amplitudes decline while VEMP thresholds increase with age. Age-related changes in VEMP latencies are controversial. In the elderly, it is necessary to emphasize the reduced ability to maintain high levels of muscle contraction, particularly for cVEMP, due to the loss of age-related muscle tone or use of muscle relaxants. This condition can modify VEMP amplitude and threshold, and it must be considered when interpreting results.
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The Effects of Aging on Clinical Vestibular Evaluations. Maxime Maheu, Marie-Soleil Houde, Simon P Landry, François Champoux. Front Neurol. 2015 Sep 22:6:205. doi: 10.3389/fneur.2015.00205. eCollection 2015. PMID: 26441824 PMCID: PMC4585272 DOI: 10.3389/fneur.2015.00205
Dizziness in the elderly. Michael S. Harris, Kamran Barin, Edward E Dodson in Dizziness and Vertigo Across the Lifespan. A. Tucker Gleason, Bradley W. Kesser. 2019 Elsevier Inc. ISBN 978-0-323-55136-6. doi: 10.1016/C2016-0-05415-3