Interest of Audiovestibular Workup in Chiari Malformation

Objectives: Malformations in the cranio-occipital region are rare, with the Chiari malformation (CM) being the most frequent of these malformations. The aim of this study was to assess the effect on inner ear in this kind of malformation by a complete audiovestibular workup.

Material and Methods: We conducted a prospective study including 25 patients presenting with CM. This workup associated audiometry, stapedial reflex testing, tympanometry, multifrequency impedancemetry, video-nystagmography with vibratory test, vestibular-evoked myogenic potentials (VEMPs), and auditory brainstem responses (ABRs).

Results: Nineteen of the 25 patients presented with auditory troubles, with sensory-neural hearing loss of more than 15 dB. The same proportion presented with horizontal curve or hypoacusis on low frequencies. Stapedial reflexes were normal. In ABR, we observed a bilateral increase of latency of wave I in 15 cases. However, VEMPs were absent in 31% of cases. VEMP thresholds were normal. Multifrequency admittancemetry showed a positive test of conductance at 2 KHz in 75% of cases. The resonance frequency was low (mean of 812 ± 232 Hz). Videonystagmography showed central and/or peripheral abnormalities in 61.1% of patients. We observed a hyperfrequency of caloric nystagmus in 38.8% of patients. Vibratory test showed pure vertical nystagmus in only one patient.

Conclusion: These results led us to think that CM may induce abnormalities in inner ear pressure. We can suppose that abnormalities in CSF can be transmitted to the inner ear via the cochlear aqueduct.