Characteristics of vestibular evoked myogenic potentials in children with enlarged vestibular aqueduct.

OBJECTIVE/HYPOTHESIS: To explore the characteristics of vestibular evoked myogenic potential (VEMP) in children with enlarged vestibular aqueduct (EVA) and to determine the diagnostic value of VEMP testing for this particular inner ear structural anomaly.

STUDY

DESIGN

Retrospective cohort study in a pediatric tertiary care facility.

METHODS

A total of 25 pediatric cases (37 ears) of EVA were identified with complete records, including otologic evaluation, CT scan of the temporal bone, and audiologic assessment. Results of audiometry, tympanometry, and VEMP testing were analyzed.

RESULTS

Hearing loss was found in 97% (36/37) of the ears with EVA. Airbone gaps (conductive components) were found in all hearing losses with normal middle ear pressure and mobility. Abnormally low threshold VEMP responses were found in 92% (34/37) of the ears with EVA. VEMP responses were absent unilaterally in three EVA patients who had vestibular complaints. No clear correlation was found between the size of EVA and the audiologic findings.

CONCLUSIONS

The presence of airbone gaps in children with EVA was found without apparent middle ear pathology. Characteristics of VEMP in EVA were lower thresholds and higher amplitudes despite of the presence of airbone gaps. The abnormally low threshold VEMP responses suggested a "third" window effect in the pathologic condition of EVA. Unilateral absence of VEMP may implicate peripheral vestibular impairment. The findings from our study are helpful in clinical evaluation of young children who usually give limited and ambiguous input regarding their hearing and vestibular problems.