With the advancement of age, the deterioration of hearing ability has become inevitable. According to the patients with the age of 65 years or more, they face difficulties in hearing , even during their visits to the audiology clinics. The decline in the ability of hearing also disturbs the daily life of elderly patients and sometime causes some serious problems including inability to hear the alarms for their medications, unawareness of the door knockings and ring tone of the phones, and last but not the least, lack of ability of hearing people around them. If left untreated, this age related hearing loss (also known as Presbycusis) can cause patients to isolate themselves from their social lives, due to the problems in communication and, may leads to depression, dementia and other mental illnesses.
It has been proven that multiple factors are involved in the formation of Presbycusis, including environmental, personal and genetic factors. Apart from this, ototoxic drugs, traumatic events and rheumatologic diseases also play a crucial role in the development of Presbycusis.
Previously, Presbycusis was characterized by the low-speech-recognition scores, observed with sensorineural hearing loss that increased to high frequencies, bilaterally, but according to the audiological findings and the site of the pathology , Schuknecht divided the disease into 4 main types. Later on, 2 more types were added and they all are as follow:
1. Sensorineural Presbycusis
It occurs with the loss of support cells and feather cells, which are involved in hearing. As the number of outer hair cells are more than the inner hair cells, they destroy earlier. The region where the highest loss occurs, is the basal part of the cochlea and, as the basal part is more sensitive to high-frequency sounds, the patient's audiogram shows sensorineural hearing loss with a steep drop to high frequencies. In sensorineural presbycusis, the ability to understand speech does not deteriorate.
2. Neural Presbycusis
This type of presbycusis occurs due to the atrophy of spiral ganglia in cochlear and central hearing aids, rather than the effect of hair cells. The loss of these cells begins at an early age, and continues gradually. However, the rate of this damage is related to genetic factors. Hearing loss, in neural presbycusis, increases to high frequencies and when we distinguish the speech, we get a worse score than the one we expect based on the patient's hearing loss.
3. Metabolic Presbycusis
It is caused by a damage to the stria vascularis, which leads to the formation of endocochlear potentials. With the degeneration of these cells, endolymph production is reduced and the potential balance required for our hearing is impaired. Since this distortion is more pronounced in the middle and apical portions of the cochlea, we are confronted with a symmetrical flat-type sensorineural hearing loss that does not impair the distinction of speech.
4. Mechanical Presbycusis
Mechanical changes in the cochlea cause a significant thickening of basilar membrane, especially in the basal part. This results in a sensorineural hearing loss that does not affect the speech comprehension scores, that are falling towards high frequencies.
5. Mixed Presbycusis
Although presbycusis is examined under these four main headings, we may not always meet a table in the patients we encounter in the clinic. Damage in the different parts of the cochlea and, patients with different findings can be seen with mixed presbycusis, having more than one type of presbycusis.
6. Intermediate Presbycusis
Depending on the age, many changes occur in the inner ear’s structure. However, in this type of presbycusis, it is difficult to find which structure has been damaged, through audiological evaluation. The changes observed in the intracellular organelles, synapses, and feather cells may not yet show us an audiologic finding.
In many patients, such changes are observed in different ways, so the classification is used to better understand the disease and to examine its formation. In general, the association with such a subtype after the presbycusis is unlikely to be seen in the clinic.
Especially in elderly people, presbycusis reduces the stimuli to the central nervous system and, therefeore, it is more difficult for them to perform auditory direction, to perceive time differences of sound and, to differentiate different signals.
● John Quinlan, (2007), Beware of presbiacusis, Sixoux City Journal.
● Gates G., Mills H., (2005), Presbycusis, Volume 336, pp 1111-1120.
● Kim T., Chung J., (2013), Evaluation of age-related hearing loss, Korean Journal of Audiology
● Güneri A., (2016), Kulak Burun Boğaz Baş Boyun Cerrahisi ,Cilt 2, Ankara
Written by VUSLAT YAVUZ , an Audiology Student at Bezmialem Vakıf University Year4 –Turkey.