Routine Vestibular Tests May Point Out Vestibular Subtype of Seasickness Only.

The vestibular system is important in the pathogenesis of seasickness. Our objective is to investigate whether routine vestibular tests detect seasickness. Included were 17 professional naval personnel (mean age of 29.76 4.73 yr) diagnosed as having seasickness and 29 healthy age- and gender-matched controls. Cervical (c) vestibular evoked myogenic potentials (VEMP) and ocular (o) VEMP and bithermal caloric tests were performed after ear, nose, and throat examination, pure tone audiometry, and magnetic resonance imaging. Severity of seasickness was evaluated based on the Graybiel scale. P1 latency, N1 latency, P1N1 amplitude, and interaural asymmetry ratios (IAR) of cVEMP and oVEMP were compared between the patients and control groups. Abnormal findings in the caloric test were noted. Presence of an abnormality in any of the three vestibular tests (cVEMP, oVEMP, or caloric test) was accepted as a positive vestibular finding. According to the Graybiel Scale, severe malaise and frank sickness were observed in 3 patients (18.7%) and 13 patients (81.3%), respectively. Graybiel scoring could not be performed in one patient due to general discomfort and bad general condition. In the caloric test, each of three patients (17.65%) showed canal paresis, an incomplete test because of severe nausea, and vomiting and hyperactive response. There were no significant differences in P1 latency, N1 latency, P1N1 amplitude, or IAR of cVEMP and oVEMP ( > 0.05). There were three patients (17.65%) and two patients (11.76%) who had abnormal IAR for cVEMP and oVEMP, respectively. Routine vestibular tests may detect some findings in only a minority of patients with seasickness.