**Abstract**

Approximately one-third of persons over 65 years are affected by disabling hearing loss. It is estimated that the number of people with disabling hearing loss will grow to 630 million by 2030 and maybe over 900 million by 2050. Deafness has significant consequences on many aspects of an individual's life, including their socioeconomic status, mental and physical well-being, educational and employment opportunities. When congenital or early in the developmental years, deafness results in a delay or loss of language acquisition. Deafness can result from damage or disease anywhere along the auditory pathway. Hearing prosthetic devices help restore hearing and the use of these devices depends on the degree and type of hearing loss. This chapter will give a brief account of the currently available prosthetic hearing solutions.

**Keywords:** auditory brainstem implant, auditory midbrain implant, bone conduction implant, cochlear implant, hearing aid, middle ear implant

## **1. Introduction: the neurosensory problem**

The global burden of disabling hearing impairment is estimated at 466 million people (6.1% of the world's population) where 432 million (93%) of these are adults (242 million males, 190 million females) and 34 million (7%) children. It is estimated that the number of people with deafness will grow to 630 million by 2030 and maybe over 900 million by 2050 [1].

Hearing impairment has a significant bearing on many aspects of an individual's life, including their socioeconomic status, mental well-being, education and employment opportunities. Older people with moderate or more severe hearing loss were more likely to feel depressed and suffer with poor mental health [2]. The deaf child cannot listen to her or his mother and focus on an activity simultaneously since both inputs must be processed visually. In addition, the deaf child is unaware of sounds of the outside environment, and thus, is centered on self and own activities. This has consequences on the child's development of language, social skills and cognition [3].

Hearing impairment results from damage or disease anywhere along the auditory pathway. Surgical restoration of hearing involves procedures that range from ossicular reconstruction to implantation of devices which serve to assist the functioning of the auditory pathway. The prosthetic devices currently being used for restoration of hearing are classified based on their mode of action in **Figure 1**.
