Application of the functional Magnetic Resonance Imaging (fMRI) for the Assessment of the Primary Auditory Cortex Function in Partial Deafness Patients – A preliminary study

Auditory cortex functioning is an important factor of successful rehabilitation after cochlear implantation, particularly in partially deafened patients who have to integrate the natural acoustic hearing with the electric one. This subject has not yet been properly recognized, especially regarding the auditory cortex’ tonotopic organization in such patients. Method: Material included 20 patients referred for the Partial Deafness Treatment – Electric Complement (PDT-EC according to Skarzynski’s PDT Classification). fMRI was performed with 3T MAGNETOM TRIO scanner. Subjects were presented with chirps of two bandwidths: 50-950 Hz (middle frequency 500Hz) and 3000-5000Hz (middle frequency 4000 Hz) at 90dB (C) via MRI-compatible earphones. SPARSE paradigm was used. Results: Bilateral auditory cortex activation was observed in response to 500Hz frequency sounds. No significant activations were found in response to 4000 Hz for p<0.05 with FWE correction; some activations for lower threshold were found. Conclusions: Paradigm applied in this study gives stable and reproducible auditory cortex responses. fMRI can be considered as method of assessing residual hearing function in auditory cortex of partially deafened patients. Cortical activity in PDT-EC candidates reflects hearing levels determined before study; patients demonstrate residual cortex capacity in response to detected frequency.