This study performed ocular vestibular-evoked myogenic potential (oVEMP) test via Fpz bone vibration (termed Fpz-oVEMP) and Fz bone vibration (termed Fz-oVEMP) using a minishaker. The aim of this study was to evaluate the resonance effect of the frontal sinus on the oVEMP recordings, so as to establish an optimal clinical protocol for eliciting oVEMPs by bone vibration.
Thirty healthy volunteers (15 children and 15 adults) and 15 adults with frontal sinusitis were enrolled in this study. All subjects underwent oVEMP test via Fpz and Fz bone vibration stimuli, and volume of the frontal sinus was measured by CT scan.
Because healthy adults (3.20 ± 1.08 mL) had significantly larger frontal sinus volume than healthy children (2.04±1.87 mL), the former (100%) showed higher response rates of Fpz-oVEMP than the latter (30%), but not Fz-oVEMP. When the frontal sinus volume is >1.91 mL (approximately at the age of 14 years), Fpz-oVEMP displayed larger reflex amplitude than Fz-oVEMP did. In contrast, Fpz-oVEMP (30%) displayed lower response rate than Fz-oVEMP (73%) in patients with frontal sinusitis.
Both developmental (frontal sinus volume) and pathological (frontal sinus inflammation) factors may affect the oVEMP responses via altering resonance function. For the developmental factor, frontal sinus volume >1.91 mL may initiate the resonance effect on oVEMPs, as evidenced by higher response rate with larger reflex amplitude of Fpz-oVEMP than Fz-oVEMP. For the pathological factor, frontal sinusitis may hamper the resonance effect on oVEMPs, as shown by the lower response rate of Fpz-oVEMP than Fz-oVEMP. Hence, oVEMP test may be performed via Fpz bone vibration first in healthy adults, while via Fz bone vibration first in children aged under 14 years or subjects with frontal sinusitis.