Hearing Loss
Introduction
Hearing loss is a common chronic impairment, particularly for older adults.
- It can range from a mild loss, in which a person misses certain high-pitched sounds to a total loss of hearing.
- It is associated with depression, social isolation, poor self-esteem, cognitive decline and functional disability.
Pure tone audiometry is the reference standard for screening for hearing loss, but a simple whispered voice test is also highly sensitive and specific.
Classification
It may be classified into 3 types.
- Sensorineural
- Involving the inner ear, cochlea or the auditory nerve
- Usually permanent
- Conductive
- Involving any cause that in some way limits the amount of external sound from gaining access to the inner ear.
- Examples include cerumen impaction and middle ear fluid
- Medical treatment or surgery can usually restore conductive hearing loss.
- Mixed loss
- A combination of conductive and sensorineural hearing loss.
Causes
Congenital - The external auditory canal (EAC) develops from the 8th to 28th week of gestation; problems can occur anytime during this developmental phase.
Presbycusis - Age-related hearing loss is a common cause of hearing loss worldwide. The hallmark of presbycusis is the progressive, symmetric loss of high-frequency over many years in an older adult.
Noise exposure - Constant exposure to loud noises can cause high-frequency sensorineural hearing loss.
Infection - Infection may lead of blockage of the EAC due to the accumulation of debris, oedema or inflammation.
Penetrating Trauma
Ototoxic substances - Aminoglycosides, chemotherapeutic agents (e.g. cisplatin, fluorouracil, bleomycin and nitrogen mustard), heavy metals (e.g. lead, mercury, cadmium, arsenic)
Tumour - relatively rare
Sudden Sensorineural Hearing Loss in Adults
Sudden sensorineural hearing loss (SSNHL) is characterized by an acute sensorineural hearing loss, nearly always unilateral (<5% of cases reported to be bilateral), that occurs within a 72-hour period.
- Often defined as hearing loss of ≥30 decibels over 3 sequential frequencies in standard pure-tone audiogram over <72 hours.
Most cases are idiopathic, and the prognosis for hearing recovery depends largely upon the severity of the hearing loss.
Many patients with idiopathic SSNHL, however, may only notice a sensation of a blocked ear or aural fullness at first, without recognizing that they have lost hearing.- Because a blocked ear is a common occurrence and may be attributed to a number of less concerning conditions (e.g., cerumen impaction, serous otitis media), patients may not seek immediate attention.
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