The cochlea is a snail-like structure located in the inner ear. It contains canals that transmit pressure and the organ of Corti, which is the sensitive part that detects pressure impulses. These impulses travel along the auditory nerve and are absorbed as electrical impulses from the cochlea. The semicircular canals balance the body and detect acceleration in three perpendicular planes, which helps you maintain your balance.

Auditory hair cells are a vital part of the ear’s ability to detect sound easily. They have microscopic hair-like projections that consist of channels or pores that open after the hair-like projections are subjected to mechanical force. The channels then release small molecules in a chemical reaction that directly tells the brain that sound has been detected.

Three fluid sections of the cochlea are the following: perilymph fluid in canals, endolymph cochlear duct fluid, and the organ of Corti, which detects pressure.

Common Causes of Hearing Impairments:

Age is a general cause of acquired hearing impairments. According to Loh & Elango (2005), Age-correlated morphologic changes in the human cochlea focus on the deterioration of the Stria Vascularis (SV) and the Spiral Ganglion (SG).” In the study by Ramadan & Schuknecht (1989), “Stria Vascularis (SV) and the Spiral Ganglion (SG) showed a tendency for progressive degeneration to grow with age.” It has been statistically shown that the difference between aging and Stria Vascularis (SV) becomes atrophied only in the apical and basal cochlear turns, as stated by Ohlemiller & Gagnon (2004). There is a relation between Stria Vascularis or Spiral Ganglion, which becomes atrophied, and audiometric findings noted. The most prominent anatomic characteristic of the aged human cochlea is Stria Vascularis (Suzuki et al., 2006).

In the study by Zagolski (2006), it was found that the inevitable deterioration in hearing ability that occurs with age, known as presbycusis, is a multifactorial process that can vary in severity from mild to substantial. When presbycusis becomes unmanageable, it can reach a moderate or greater degree that affects communication and quality of life, leading to depression and dementia in patients suffering from it. These psychological effects can be reversible, and restoration of good health is possible through comprehensive rehabilitation. However, this type of rehabilitation is often underused due to social attitudes that do not value hearing and can even cause spots in hearing aids. Remedying presbycusis is an important factor in geriatric medicine and includes education for better communication, the use of hearing aids, assistive listening devices, and cochlear implants to prevent severe hearing loss. According to Shehata-Dieler, Volter, Hildmann, Hildmann, & Helms (2007), the main focus of physicians is to screen and refer their elderly patients for effective assessment and remediation. Sometimes, hearing aids are not beneficial to users, and the best treatment of choice is cochlear implantation, which has shown excellent results even in octogenarians (Gates & Mills, 2005).

According to Ulualp, Wright, Pawlowski, and Roland (2004), they used human temporal bones to expound the result of aging on the auditory system. They had respondents of 68 individuals from ninety-six ears, from infancy to 84 years old, serving as normal ears.” None of these cases had medical or pathological proof of exact ear disease. “Pathological ears” from 58 persons, which consist of 89 ears, exhibited slowly progressive hearing loss, which had no specific recognized cause of the loss. According to the learning of Ravnal, Kossowski, and Job (2006), these two age phenomena are found to manipulate the human ear. The first is physiological and has been called “auditory senility.” This involves dissimilar parts of the auditory mechanism and is liable for the rise in auditory threshold for the elevated frequencies, commonly seen in elderly people. The second phenomenon is pathological, termed as “auditory decay,” pertaining to the system of the ear, resulting from dissimilar types of clinical performance, according to the structural layer involved. The situation of these two aging phenomena that affect the individual ear explains the cause why auditory acuity is related to old age. It is according to Belal (1975).

Hearing Disability in All Age Groups

Hearing disability can occur in all age groups. Children can acquire hearing loss genetically or due to infections during the developmental stage of the fetus. This includes congenital syndromes such as Down Syndrome or Trisomy 21, as well as familial deafness inherited from a parent. Infections during pregnancy, such as German measles (rubella) or cytomegalovirus, can also increase the risk of hearing loss. Superficial hearing loss can lead to difficulties in speech development and learning.

In adults, the most common causes of hearing loss are progressive bilateral hearing loss or senile deafness, as well as noise exposure. Old hearing” affects men more than women and is often linked to noise exposure in industrial or military settings. The mechanism of hearing is complicated. Sound waves enter the ear canal and move freely in the eardrum, or tympanic membrane. The eardrum is connected to the hearing organ, or cochlea, by small bones called ossicles. The cochlea, also known as the oval window, moves in response to the eardrum’s movements, stimulating tiny hair cells that line the cochlea. These hair cells transmit nerve impulses to the brain, which detects the sound.

Conductive hearing loss can be caused by cerumen, or earwax, impaction. This can occur when cleaning the ears with cotton swabs, which can push earwax back into the canal and cause impaction. Children are notorious for introducing foreign objects into their ears, which can cause damage to the inner ear and should be removed immediately. Disruption or dislocation of the bones in the inner ear can also cause hearing loss and requires immediate operation. Common colds and other upper respiratory tract infections can cause hearing impairment, including infections in the inner ear. The Eustachian tube drains the inner ear back into the throat. Cholesteatoma is a buildup of skin cells that surround the ear bones and prevent movement, leading to complications of chronic middle ear infections. Otosclerosis is a slowly progressive hearing loss that is more common in women than men and is caused by changes in bone and surgery. Inflexibility of the eardrum can also cause conductive hearing loss, often caused by scarring left by matured ear infections, a series of holes in the eardrum, or injury to the ear.

Reference:

Belal, A., Jr. (1975). Presbycusis: physiological or pathological. J Laryngol Otol, 89(10), 1011-1025.

Gates, G. A., and Mills, J. H. (2005). Presbycusis. Lancet, 366(9491), 1111-1120.

Loh, K. Y., and Elango, S. (2005) studied hearing impairment in the elderly in the Medical Journal of Malaysia. The article is found in volume 60, issue 4, pages 526-529, with a quiz on page 530.

Ohlemiller, K. K., and Gagnon, P. M. (2004). Apical-to-basal gradients in age-related cochlear degeneration and their relationship to primary” loss of cochlear neurons. J Comp Neurol, 479(1), 103-116.

Ramadan, H. H., and Schuknecht, H. F. (1989). Is there a conductive type of presbycusis? Otolaryngol Head Neck Surg, 100(1), 30-34.

Raynal, M., Kossowski, M., and Job, A. (2006). Hearing in Military Pilots: One-Time Audiometry in Pilots of Fighters, Transports, and Helicopters.” Aviat Space Environ Med, 77(1), 57-61.

Shehata-Dieler, W., Volter, C., Hildmann, A., Hildmann, H., and Helms, J. (2007). Clinical and audiological findings in children with auditory neuropathy.” Laryngorhinootologie, 86(1), 15-21.

Suzuki, T., Nomoto, Y., Nakagawa, T., Kuwahata, N., Ogawa, H., Suzuki, Y., et al. (2006). Age-dependent degeneration of the stria vascularis in human cochleae. Laryngoscope, 116(10), 1846-1850.

Ulualp, S. O., Wright, C. G., Pawlowski, K., & Roland, P. S. (2004). Cochlear degeneration in Leigh disease: histopathologic features. Laryngoscope, 114(12), 2239-2242.

Zagolski, O. (2006). Management of tinnitus in patients with presbycusis. Int Tinnitus J, 12(2), 175-178.

Anatomy and Physiology of the Aging Cochlea