Chapters authored
Cisplatin Ototoxicity in Children
Cisplatin is a highly effective chemotherapy medicine used in the treatment of many childhood cancers. Like all medications, cisplatin has many side effects and as always the treatment of cancer in children is a balance between the risks of the medications used and their potential benefits. While many side effects of cisplatin chemotherapy are reversible, one major side effect is permanent and irreversible hearing loss (ototoxicity) in both ears which may worsen with time. The severity of cisplatin-related ototoxicity is associated with age and the cumulative dose received: the younger the child and the higher the total dose, the more severe the hearing loss may be. The spectrum of hearing loss varies from mild to moderate high tone hearing loss, to profound loss across the hearing range and permanent deafness. In addition to hearing loss, some children, especially adolescents, also experience tinnitus and vertigo. Cisplatin ototoxicity is one of most important of the many long-term effects experienced by children who are cured of their cancer. The burden of this toxicity may be compounded by other long-term health issues that emerge with time. This chapter will focus on cisplatin-induced hearing loss, its mechanisms, its health impact on the young person and ways to mitigate or reduce the severity of ototoxicity. This chapter has been written by a multi-disciplinary team including paediatric oncologists, audiologists, a psychologist, a health scientist and a parent of a child growing up with high frequency hearing loss.
Part of the book: Hearing Loss
Short-Latency Evoked Potentials of the Human Auditory System
Auditory Brainstem Responses (ABR) are short-latency electric potentials from the auditory nervous system that can be evoked by presenting transient acoustic stimuli to the ear. Sources of the ABR are the auditory nerve and brainstem auditory nuclei. Clinical application of ABRs includes identification of the site of lesion in retrocochlear hearing loss, establishing functional integrity of the auditory nerve, and objective audiometry. Recording of ABR requires a measurement setup with a high-quality amplifier with adequate filtering and low skin-electrode impedance to reduce non-physiological interference. Furthermore, signal averaging and artifact rejection are essential tools for obtaining a good signal-to-noise ratio. Comparing latencies for different peaks at different stimulus intensities allows the determination of hearing threshold, location of the site of lesion, and establishment of neural integrity. Audiological assessment of infants who are referred after failing hearing screening relies on accurate estimation of hearing thresholds. Frequency-specific ABR using tone-burst stimuli is a clinically feasible method for this. Appropriate correction factors should be applied to estimate the hearing threshold from the ABR threshold. Whenever possible, obtained thresholds should be confirmed with behavioral testing. The Binaural Interaction Component of the ABR provides important information regarding binaural processing in the brainstem.
Part of the book: Auditory System