Evaluation of bone-conducted oVEMPs using frontal medial and mastoid stimulations

Aims: To determine the optimal stimulation intensity for frontal stimulation with a modified slit lamp holder and to compare the reliability and symmetry of bone-conducted ocular vestibular evoked myogenic potentials (oVEMPs) using two stimulation sites: frontal medial and mastoid.

Methods: This observational study included 33 healthy volunteers (15 women, 18 men; mean age 24.5years) at the University Hospital of Lausanne. Participants underwent otoneurological assessments, and those with normal results were included. Bone-conducted oVEMPs were recorded using a Brüel and Kjaer mini-shaker type 4810. A modified slit lamp holder was used for frontal stimulation to ensure consistent application pressure, freeing the examiner's hands. Mastoid stimulation was performed manually.

Results: The best reproducibility of oVEMP recordings was observed at 70dB nHL. Frontal stimulation demonstrated lower dispersion of data and lower asymmetry ratios of latencies (up to 7%) and amplitudes (up to 50%) compared to mastoid stimulation (up to 40% for latencies). Single stimulations at both frontal and mastoid sites were sufficient to obtain reliable measurements of both utricles.

Conclusion: Frontal stimulation at 70dB nHL using a modified slit lamp holder is recommended for bone-conducted oVEMP recordings due to its superior reproducibility, comfort, and reliability. This study establishes a new standard for optimal stimulation intensity and supports the use of frontal stimulation in clinical practice.