Vestibular neuronitis in pilots: follow-up results and implications for flight safety

OBJECTIVES To report our experience over the past 12 years with the evaluation and follow-up of pilots with vestibular neuronitis and to discuss points relevant to flight safety and the resumption of flying duties. STUDY DESIGN A retrospective, consecutive case series.METHODS Eighteen military pilots with vestibular neuronitis were examined and followed up. A complete otoneurological workup was performed, including both physical examination and laboratory evaluation. The latter included electro-oculography (EOG) and a rotatory chair test using the smooth harmonic acceleration protocol. RESULTS The mean patient age was 35 +/- 6 years (range, 23 to 42 y), and the average follow-up period was 20.5 +/- 12.8 months (mean +/- standard deviation [SD]; (range, 11 to 48 mo). Electro-oculography caloric test on presentation documented significant unilateral hypofunction in all patients. Thirteen of the 18 patients (72%) had abnormal smooth harmonic acceleration test results. None of the pilots reported any symptoms on follow-up. However, five (28%) had positive otoneurological examination findings, and eight (44%) still had significant caloric lateralization (>25%). The average caloric hypofunction was reduced from 67.8% +/- 29.3% at onset to 40% +/- 16% (mean +/- SD, <.05, paired test). Seven of the patients (39%) had additional electro-oculography findings beyond caloric hypofunction. These included spontaneous, positional, and positioning nystagmus. Smooth harmonic acceleration disease on follow-up was documented in eight patients (44%), five of whom had canal paresis. Eleven patients (61%) demonstrated residual vestibular damage on follow-up. In 6 of these 11 cases (55%), the laboratory evaluation revealed vestibular deficits otherwise undiagnosed by the bedside test battery. CONCLUSIONS The vestibular system plays a central role in orientation awareness and is often challenged by flying conditions. The finding that approximately 60% of pilots who have had vestibular neuronitis continue to show signs of vestibular malfunction, despite apparent clinical recovery, emphasizes the need for a complete vestibular evaluation, including specific bedside testing and laboratory examinations, before flying duties can be resumed.