Age-Related Changes in Vestibular Evoked Myogenic Potentials

Vestibular evoked myogenic potentials: past, present and future

Since the first description of sound-evoked short-latency myogenic reflexes recorded from neck muscles, vestibular evoked myogenic potentials (VEMPs) have become an important part of the neuro-otological test battery. VEMPs provide a means of assessing otolith function: stimulation of the vestibular system with air-conducted sound activates predominantly saccular afferents, while bone-conducted vibration activates a combination of saccular and utricular afferents. The conventional method for recording the VEMP involves measuring electromyographic (EMG) activity from surface electrodes placed over the tonically-activated sternocleidomastoid (SCM) muscles. The "cervical VEMP" (cVEMP) is thus a manifestation of the vestibulo-collic reflex. However, recent research has shown that VEMPs can also be recorded from the extraocular muscles using surface electrodes placed near the eyes. These "ocular VEMPs" (oVEMPs) are a manifestation of the vestibulo-ocular reflex. Here we describe the historical development and neurophysiological properties of the cVEMP and oVEMP and provide recommendations for recording both reflexes. While the cVEMP has documented diagnostic utility in many disorders affecting vestibular function, relatively little is known as yet about the clinical value of the oVEMP. We therefore outline the known cVEMP and oVEMP characteristics in common central and peripheral disorders encountered in neuro-otology clinics.

Loss of otolith function with age is associated with increased postural sway measures

Loss of balance and increased fall risk is a common problem associated with aging. Changes in vestibular function occur with aging but the contribution of reduced vestibular otolith function to fall risk remains unknown. We examined a population of 151 healthy individuals (aged 21-93) for both balance (sway measures) and ocular counter-rolling (OCR) function. We assessed balance function with eyes open and closed on a firm surface, eyes open and closed on a foam surface and OCR during +/-20 degree roll tilt at 0.005 Hz. Subjects demonstrated a significant age-related reduction in OCR and increase in postural sway. The effect of age on OCR was greater in females than males. The reduction in OCR was strongly correlated with the mediolateral measures of sway with eyes closed. This correlation was also present in the elderly group alone, suggesting that aging alone does not account for this effect. OCR decreased linearly with age and at a greater rate in females than males. This loss of vestibular otolith-ocular function is associated with increased mediolateral measures of sway which have been shown to be related to increased risk of falls. These data suggest a role for loss of otolith function in contributing to fall risk in the elderly. Further prospective, longitudinal studies are necessary to confirm these findings.

The diagnostic value of vestibular-evoked myogenic potential in patients with vestibular schwannoma

OBJECTIVE

This study examined the diagnostic value of the vestibular-evoked myogenic potential (VEMP) in comparison with the caloric test in patients with vestibular schwannoma (VS).

METHODS

Data were retrospectively collected from 803 consecutive patients who visited our vertigo clinic and underwent vestibular tests. Amongst them, 78 patients were diagnosed as having untreated unilateral VS. VEMP was performed using click and short-tone burst stimulation. The caloric test was performed using ice water. The sensitivity and specificity of each test were evaluated.

RESULTS

Of the 78 patients with VS, 63 had abnormal VEMPs as well as abnormal caloric responses. Of the 725 patients without VS, 382 had normal VEMPs and 416 had normal caloric responses. The sensitivity and specificity of VEMP were 80.8% (95% CI: 72.0-89.5%) and 52.7% (95% CI: 49.1-56.3%), respectively; those of the caloric test were 80.8% (95% CI: 72.0-89.5%) and 57.4% (95% CI: 53.8-61.0%), respectively.

CONCLUSIONS

The sensitivity and specificity of VEMP and the caloric test showed no significant differences.

SIGNIFICANCE

In patients with VS, although the specificity of VEMP was not very high, its sensitivity was high and comparable to that of the caloric test.

[Vertigo and falls in the elderly. Part 1: epidemiology, pathophysiology, vestibular diagnostics and risk of falling]

Disorders of the equilibrium function in the elderly will increase in the coming years due to demographic changes in Germany. In addition to a reduction in the quality of life of affected patients, the risk of suffering from a fall increases with age. At the morphological level age-specific changes of the peripheral vestibular structures, somatosensory pathways and vision can be found, such as degenerative alterations, reduced number of cells and receptors and an accumulation of lipofuscin. Disorders of the equilibrium function in old age are individual-specific, complex procedures which develop from age-related physiological, degenerative alterations in the components of the sensomotor system which maintain equilibrium and can come into being together with vestibular and non-vestibular accompanying diseases as well as psychological factors.

Vestibular-evoked myogenic potentials

PURPOSE OF REVIEW

This article reviews the literature on vestibular-evoked myogenic potential testing, a short latency electromyogram evoked by high acoustic stimuli and recorded via surface electrodes over the sternocleidomastoid muscle. Applications and refinements of this technique are described for different pathologies and in adults and children.

RECENT FINDINGS

Various techniques for electrode placement have been described to elicit a vestibular-evoked myogenic potential response, which has been clinically investigated in normal individuals, under pathological conditions, and in adult and pediatric patients. As vestibular-evoked myogenic potential amplitude is linearly related to the level of background activity of the sternocleidomstoid muscle, maintaining steady contraction of the muscle can be challenging in some patients.

SUMMARY

Vestibular-evoked myogenic potential testing may provide additional information about the vestibular system and allow site of lesion testing (e.g. saccule and inferior vestibular nerve) in patients of all ages. Its role has yet to be defined in the diagnosis and treatment of common vestibular disorders, including Meniere's disease, vestibular neuronitis, labyrinthitis, and other diseases. Further research is needed to support its clinical usefulness in patients with balance disorders, to optimize patient selection, and to establish its cost effectiveness.