Functional magnetic resonance imaging of hearing-impaired children under sedation before cochlear implantation.

OBJECTIVE

To investigate functional magnetic resonance imaging (fMRI) in pediatric cochlear implantation candidates with residual hearing who are under sedation for evaluation of auditory function.

DESIGN

During fMRI, subjects heard a random sequence of tones (250-4000 Hz) presented 10 dB above hearing thresholds. Tones were interleaved with silence in a block-periodic fMRI design with 30-second on-off intervals. Twenty-four axial sections (5 mm thick) covering most of the brain were obtained every 3 seconds for a total acquisition time of 5.5 minutes.

SETTING

Single tertiary academic medical institution.

PATIENTS: Severely to profoundly hearing-impaired children (n=10; mean age, 49.1 months). During fMRI, subjects were awake (n=2) or sedated with pentobarbital sodium if their weight was 10 kg or greater (n=4) or chloral hydrate if their weight was less than 10 kg (n=4).

MAIN OUTCOME MEASURES: Detection of brain activation by fMRI in the primary auditory cortex (A1) in hearing-impaired patients under sedation, and correlation of A1 activation with hearing levels measured after cochlear implantation.

RESULTS

In most subjects, fMRI detected significant levels of activation in the A1 region before cochlear implantation. The improvement in hearing threshold after cochlear implantation correlated strongly (linear regression coefficient, R=0.88) with the amount of activation in the A1 region detected by fMRI before cochlear implantation.

CONCLUSIONS

Functional MRI can be considered a means of assessing residual function in the A1 region in sedated hearing-impaired toddlers. With improvements in acquisition, processing, and sedation methods, fMRI may be translated into a prognostic indicator for outcome after cochlear implantation in infants.