4. Presbycusis, or age-related hearing loss, is the most
common cause of hearing impairment, as well as being
the most common neurodegenerative disorder. Its
incidence is highest among the over-65s, affecting
approximate 40% of this population group. Presbycusis
has a significant impact on sufferers’ quality of life. Its
diagnosis and treatment is therefore a significant public
health issue.
It involves bilateral high frequency hearing loss with
difficulty in speech discrimination and central auditory
processing of information.
INCIDENCE
5. There may be many causes for age-related hearing loss. It most often occurs because of
changes in the following areas:
Atherosclerosos
stress
Other things that affect age-related hearing loss:
Long-term exposure to loud noise (such as music or work-related noise)
Loss of hair cells (sensory receptors in the inner ear), that help you to hear
Inherited factors
Aging
Some health conditions, such as heart disease or diabetes
Side effects of some medicines, such as aspirin and certain antibiotics
WHAT CAUSES AGE-RELATED
HEARING LOSS?
6. Each person’s symptoms may vary. Some of the most common
symptoms include:
Other people’s speech sounds mumbled or slurred
Having trouble hearing high-pitched sounds
Having trouble understanding conversations, often when there is
background noise
Men's voices are easier to hear than women's
Some sounds seem very loud and annoying
A ringing sound (tinnitus) in one or both ears
SYMPTOMS
8. Schuknecht's seminal studies correlating audiogram findings in presbycusis with
histopathologic findings in human cochlea initially produced four categories of
presbycusis, which were later expanded to six:
sensory
neural
strial (metabolic)
cochlear conductive
mixed
indeterminate
TYPES
9. Sensory presbycusis was described as abrupt high‐frequency hearing loss
associated with atrophy of the basal organ of Corti.
Neural presbycusis exhibited diminished word discrimination scores and
relatively stable pure tone thresholds, with spiral ganglion cell loss.
Strial, or metabolic, presbycusis was characterized by overall diminished pure
tone thresholds in all frequencies, and associated with stria vascularis atrophy.
Cochlear conductive, or mechanical, presbycusis was described as having a
gradual down‐sloping audiogram with no obvious histologic findings, and
hypothesized to be a result of basilar membrane stiffening.
Mixed presbycusis demonstrated a combination of the previously described
audiograms and histologies, while indeterminate presbycusis (representing nearly
25% of all patients) did not demonstrate a consistent histologic appearance while
manifesting as either flat or high‐frequency loss.
10. Graph A.- Tonal audiometry of sensory
presbycusis showing how all frequencies are
affected, but particularly higher frequencies.
Graph B.- Audiometry of neural presbycusis
showing how the higher frequencies are
affected.
Graph C.Speech audiometry of the same
case as shown in Graph B in which the
marked impact on intelligibility can be
observed (normal hearing in black, reaching
100% word discrimination, presbycusis in
blue, with a maximum intelligibility of 70%).
The disproportionate effect on intelligibility
can be seen.
Graph D.- Tonal audiometry of metabolic or
strial presbycusis with all frequencies affected,
particularly higher frequencies.
Graph E.- Tonal audiometry of cochlear
conductive presbycusis, showing alteration of
the perception of higher frequencies.
11. The ethiopathogenesis of presbycusis lies in the interaction of the genome and the
environment, and is influenced by genetic factors, age-related cellular mechanisms, the
environment and associated illnesses.
A genetic predisposition to premature presbycusis exists, but despite the research done,
the genetic factors are poorly identified. Work in this field is progressing by studying
animal models. There is evidence pointing to age-related cellular mechanisms,such as
the precursor cells of the spiral ligament and vascular stria losing the ability to divide,
the death of the sense cells and auditory neurons, which are not replaced in adult
mammals, and cell stress and oxidation mechanism associated with ageing.
Insulin-like growth factor (IGF-I) plays a central role in ageing over the whole
evolutionary range and is fundamental for hearing in humans and mice. Its study is
revealing the keys to understanding the molecular basis of otic development and the
factors influencing auditory ageing. For instance, IGF-I modulates the expression of
cell cycle regulation factors such as FoxM1 and p27kip, and differentiation of stem cells
such as MEF2. IGF-I deficiency causes cell alterations in the vascular stria and loss of
auditory neurons through apoptosis.
ETHIOPATHOGENESIS
12. In terms of environmental factors, those which can have a negative
impact on the progression of presbycusis include noise exposure,
which can cause mechanical, metabolic damage or vascular changes.
Presbycusis has also been described in association with other
diseases, but it is not clear whether it is influenced by them or if
they occur in parallel, as a result of shared underlying cellular and
molecular alterations. Illnesses with a potential impact include
cardiovascular disease, diabetes mellitus, other metabolic causes
such as hyper-lipoproteinemia, obesity, vitamin deficiency, etc.
Additionally, it has been described in association with cognitive
deficit, particularly in the case of Alzheimer’s disease, and with
immune and auto-immune dysfunction.
16. Precise hearing aid fitting (vented if mild and open fitting if normal low
frequencies)
Hearing assistive devices
Lip reading classes
Possible cochlear implantation
REHABILITATION
17. reduce acoustic feedback, reduce background noise, detect
and automatically accommodate different listening environments,
control additional components such as multiple
microphones to improve spatial hearing, transpose
frequencies (shift high frequencies that a wearer may not
hear to lower frequency regions where hearing may be better.
HEARING AID
18. *Some are listening aids, while some alert or signal the user via auditory, visual, or
tactile modalities. Some may be used in combination with other hearing instruments,
e.g. telecoils which attach to HAs or CIs.
*FM systems provide a high quality speech signal because having a microphone so
close to the sound source offers a favorable signal-to-noise ratio (15–25 dB). This can
be especially helpful in situations where adults with HL are attending lectures in large
rooms or rooms with poor acoustics.
HEARING-ASSISTIVE TECHNOLOGIES
19. * Elderly adults who cannot wear conventional HAs for medical or personal
(cosmetic) reasons and whose HL is not severe enough to make them suitable
candidates for CIs, may be good candidates for active middle ear implants
(AMEIs).
*AMEIs, such as the MED-EL Vibrant
Soundbridge,
are used to treat adults with mild-to-severe
sensorineural HL (including presbycusis)
or other types of HL (mixed and conductive).
ACTIVE MIDDLE EAR IMPLANTS
20. *Electric acoustic stimulation (EAS) is the use of an HA and a CI together in one
ear.
*This combined method addresses the specific needs of patients presenting with
good low frequency hearing (a mild-to-moderate sensorineural HL in frequencies up
to 1,000 Hz) but poorer hearing in the high frequencies (sloping to 60 dB or worse
HL above 1,000 Hz).
* Many of these patients receive little or no benefit from HAs alone. The HA
component of the EAS system amplifies residual low frequency hearing while the
CI provides electrical stimulation of the high frequency regions of the cochlea.
ELECTRIC ACOUSTIC STIMULATION
22. *Many people with severe to profound HL (defined as thresholds of 80 dB or
worse) attributed to presbycusis and other factors (e.g. NIHL) reach a point where
HAs no longer provide sufficient gain or benefit.
*Cochlear implants were established to be effective for people over 60 years of
age in the 1990s, and intraoperative and postoperative complication rates were
found to be low.
*No medical contraindications, bilateral sensorineural HL, demonstrated lack of
benefit from rehabilitation with HAs, a strong desire/commitment on the part of
the candidate, and adequate support (family, caregivers, etc.) in the environment.
C.I.
