AUDITORY-CORTEX ACTIVATION IN DEAF SUBJECTS DURING COCHLEAR ELECTRICAL-STIMULATION - EVALUATION BY FUNCTIONAL MAGNETIC-RESONANCE-IMAGING

RATIONALE AND OBJECTIVES. The authors detect activation in the auditor y cortex during cochlear electrical stimulation in deaf patients using functional magnetic resonance (MR) imaging. METHODS. Stimulating elec trode was inserted gently under local anesthesia close to the round wi ndow membrane of the cochlea in seven cochlear implant candidates. The se patients suffered from postlingual-acquired deafness. Four patients were stimulated above the electrical perception threshold and three b elow the electrical discomfort threshold. Functional scans (fast low-a ngle shot 91 mseconds/60 mseconds) were acquired in an oblique axial p lane running parallel to the sylvian fissure. Pour consecutive series of six images were obtained in 6 minutes. The acquisition time of each image was 15 seconds. RESULTS. During electrical cochlear stimulation below the discomfort threshold, the three patients described ''audito ry'' sensations with activation of the superior temporal regions. In t wo patients with electrical stimulation of the left ear, the maximum s ignal intensity increased by 8.42% in the right auditory cortex and 5. 69% in the left. In one patient with a right electrical stimulation on ly the left cortex was activated. Electrical cochlear stimulation abov e the perception threshold induces no significant activation in the au ditory cortex. CONCLUSION. Functioning MR imaging can detect activatio n in the auditory cortex during cochlear electrical stimulation in dea f patients using a conventional 1.5-tesla system in a routine hospital environment. Further studies are needed to investigate its usefulness in clinical practice.