Chapter 1 14 with their peers. Eye glass mounted options have specific limitation due to the weight of the processor. This is even more pronounced in patients with microtia, many of whom may not have sufficient external pinna to hold their eyeglasses level with the additional weight. Furthermore, microtia is often asymmetrical and pinna position may be lower making the use of eye glasses very unsightly and impractical [14,15]. With the headband options, migration of the sound processor away from an optimal position over the mastoid bone reduces its efficacy [16]. It can also increase artifact production by movement over the patient’s own hair, clothing, head dresses or hats. This often leads to the position of the processor being far from the mastoid process and therefore the cochlea. This becomes more pronounced for those children requiring eye glasses or those with variations in skull shape and contour. When compared to the unaided condition, both soundfield thresholds and speech reception thresholds are improved with the application of a softband and sound arc, with no significant difference being demonstrated between the two [17,18]. An adhesive bone conduction system was designed as an alternative to these. It is comprised of two components - a novel sound processor and an adhesive adaptor. The sound processor attaches to the adhesive adaptor via a preformed snap coupler in the centre of the adhesive pad. The adhesive pad is placed onto the hairless post auricular skin, directly over the mastoid bone and is replaced every 3-5 days to maintain adequate adhesion to the skin. This adhesive adaptor is designed to prevent sound processor migration and removes the requirement for an unsightly and tight-fitting headband. To date, reports of outcomes with the adhesive hearing system in adults and children demonstrated high levels of user satisfaction with improvement in pure tone threshold (functional gain of 23 dbHL and speech recognition of 23 dB SPL [1922]. However, there is significant variation in the longevity of the adhesive pad and a narrow fitting range of <25dB BC PTA. Historically novel devices such as ‘Sound bite hearing system,’ have been trialed but with limited success. The soundbite processor is mounted on a dental splint where sound is conducted through the maxilla and indirectly to the mastoid bone. At this time these bone conduction solutions are not widely offered for hearing rehabilitation, although have been repurposed and applied in the military setting in the United States of American.
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