SPET monitoring of auditory cortex activation by electric stimulation in apatient with auditory brainstem implant

Auditory cortex activation following multifrequency acoustic stimulation ha s been evaluated by means of single photon emission tomography (SPET) in on e patient before and after an auditory brainstem implant (ABI). No activati on could be observed after acoustic stimulation before ABI. After ABI stimu lation in the coronal and axial slices, the activation within the temporal cortex contralateral to the stimulated ear was twice (43.76%) that of norma l controls (23.94 +/- 2.74%). This marked difference was not present in oth er selected cortical auditory areas (homolateral temporal, homolateral and contralateral parietal cortices). The temporal cortex was also examined wit h six consecutive sagittal slices from 18.75 min up to 56.25 min lateral to the midline. A very strong activation (51.20%) compared with that of norma l controls (9.94 +/- 7.45%) was detected in the 25.26-mm sagittal slice of the temporal cortex contralateral to the stimulated side. The remaining sag ittal slices showed an almost normal post-stimulatory activation. As the 25 .26-mm sagittal slice corresponds to the medial part of the auditory tempor al cortex, its activation suggests that electrode stimulation is concentrat ed on the region of the cochlear nucleus in which the neurons that transduc e high frequencies are located. SPET can be considered useful, in combinati on with electric auditory-evoked potentials, to obtain information on ABI p lacement and function, effectiveness of acoustic stimulation, degree of cor tical stimulation and tonotopic spatial distribution of auditory cortex act ivation.