Evaluation of Brain Activation (NeuroSPECT) by Uni- and Bilateral Auditory Stimulation in Patients with Conductive Hearing Loss and Bilateral Bone Conduction Devices

Abstract

Ab s t r Ac t Background: This prospective study evaluated sound localization and brain responses to monaural and binaural stimulation via bone conduction devices in 3 individuals with bilateral conductive hearing loss (1 acquired and 2 congenital). Aims and objectives: To determine the (1) Cortical areas that are activated with pure tones. (2) Potential benefits of bilateral devices. Materials and methods: A new audiological test is described (real-life lateralization test) and applied. NeuroSPECT studies were done using pure tones delivered via bone conduction devices (Baha Attract) stimulating monaurally and binaurally. The tests were performed 2–4 months after the placement of the second device. Results: The use of unilateral devices as well as bilateral devices under our testing conditions did not improve sound localization. There was improvement in lateralization with bilateral devices. In the three subjects, cortical activation with binaural auditory stimulation with the Baha Attract occurred in the same auditory areas compared with monaural stimulation. However, while in the individual with acquired loss, the degree of activation was less intense in binaural compared to monaural stimulation; in the congenital cases, binaural stimulation resulted in summation of stimuli. Conclusion: In congenital bilateral conductive hearing losses that have not been stimulated early, there are central auditory areas that are deprived. Even if these are only two cases, this is suggestive of the importance of bilateral early auditory stimulation in cases of congenital conductive hearing losses and supportive of the use of bilateral rather than unilateral devices.