Newer Developments in Geriatrics

**113**

**Chapter 7**

Loss

**Abstract**

**1. Introduction**

Genetics and Acquired Hearing

Hearing loss (HL) is a worldwide disease with substantial economic costs for the public health. Around 466 million people have disabling hearing loss and the WHO estimated that by 2050 over 900 million people will suffer hearing loss. Several factors including infections, noise-exposure, ototoxic medications or genetic disorders could cause hearing impairment. Hearing devices such as cochlear implants and aids are the current therapies. Although the prevalence of hearing loss is very high, alternative treatments as pharmaceutical agents are currently insufficient. Within the past years, increased knowledge on hearing loss etiology and physiopathology opened new opportunities for future research towards hearing loss treatment. Here we aim to review current bibliography on

**Keywords:** hearing loss, genetics, syndromic, non-syndromic, age-related

The World Health Organization (WHO) defines hearing loss (HL) as the inability to perceive the sounds with different grades of impairment, from slight to

Sound waves move from outer (or external) to middle and then to the inner ear, three anatomically distinct structures of the ear which transmit the sound to a signal into the brain. The sound waves travel down the cannel of the outer and middle ear until hitting the tympanic membrane. Vibrations from the middle ear create movement of the fluid in the inner ear. This movement of the fluid is transmitted through the tectorial membrane to the hair cells in the organ of Corti, then the stimulus is transmitted by electric signals up to the auditory nerve to the brain. The brain interprets the electrical signals as sound. **Figure 1** shows the different

Depending on the compartment affected, hearing loss could be classified as *conductive* or *sensorineural*. Conductive hearing loss is when the outer and middle ear are affected, and it results in the inability to transmit sound waves to the inner ear [3]. On the other hand, impairments in the inner ear are known as sensorineural [4]. Conductive hearing loss could be treated by medication, surgery cochlear implants or hearing aids, meanwhile sensorineural is mostly irreversible because of the complexity of the structure, the limited regeneration and access to the sensory

*Moza Al-Kowari and Meritxell Espino-Guarch*

genetics factors involved in hearing loss.

profound including deafness [1].

structures in the cochlea [5].

compartment of the ear as described above.
