Sensorineural Hearing Loss

2 Otology

3. Tympanomastoidectomy with canal wall down (CWD): indicated for large cholesteatomas, cholesteatomas with significant preoperative

2.5 Hearing Loss

2.5.2 Sensorineural Hearing Loss

Ototoxicity

Exposure to a variety of medications may induce permanent hearing loss (Table 2.9). This hearing loss is typically first noted in the highest frequencies, and then progresses to lower pitches. Common agents include aminoglycoside antibiotics, vinca alkaloids, and platinum-based chemotherapeu- tic agents. Careful monitoring of audiograms during therapy allow for early identification of hearing loss. Prolonged use of high dose loop diuretics (e.g., furosemide) may also lead to hearing loss. Of note, many ototoxic drugs are also nephrotoxic, therefore renal function studies should be obtained as well.

Hearing Loss Present at Birth

See Fig. 2.11 for a classification overview of hearing loss at birth. About 50% of cases are nonhereditary, i.e., due to prematurity, sepsis, or TORCHES infections (toxoplasmosis, rubella, cytomegalovirus, herpes simplex en- cephalitis, and otosyphillis). Of the 50% that are congenital hereditary cases, these may be syndromic (one third of cases) or nonsyndromic (two thirds Table 2.9 Common Ototoxic Drugs

Aminoglycoside antibiotics Platinum-based chemotherapy (especially cisplatin)

Loop diuretics

Vinca alkaloids (especially vincristine) Quinine

Salicylates

Fig. 2.11 Hearing loss present at birth: a classification overview.

of cases); see Table 2.10. Of the nonsyndromic cases, ⬃80% are autosomal recessive.

Hearing loss may be present at birth due to congenital defects in either the structure or the physiology of the inner ear. Cochlear malformations (e.g., Mondini malformation) may be associated with various syndromes.

Many cases of nonsyndromic congenital hearing loss have been attributed to chromosomal defects in the hair cell protein connexin 26 (Cx 26). Most congenital cases are now discovered early due to universal newborn screen- ing programs. However, certain types, e.g., enlarged vestibular aqueduct syndrome, may not manifest until later in life.

Metabolic

Symmetric bilateral rapidly progressive hearing loss may be caused by a variety of systemic diseases, including autoimmune disease.

Other

Cochlear otosclerosis, primary autoimmune inner ear disease, barotrauma, perilymph fistula, migraine, vertebrobasilar occlusion, and a variety of autoimmune disorders may all be associated with SNHL.

Differential Diagnosis for Asymmetric Hearing Loss Tumors

Neoplasms of the CPA and/or internal auditory canal, such as vestibular schwannomas and meningiomas may cause unilateral hearing loss, and are the primary pathologies the must be ruled out when encountering significant asymmetric hearing loss. Metastatic disease and endolymphatic sac tumors must also be considered. Diseases of the temporal bone such as fibrous dysplasia and Paget disease can cause hearing loss through destruc- tion of the otic capsule.

Ménière Disease

Active Ménière disease typically causes a fluctuating low-frequency hearing loss. As the disease progresses, higher frequencies are effected and can progress to severe levels.

Table 2.10 Hereditary Syndromic Hearing Loss

Autosomal Dominant Autosomal Recessive Sex-Linked Treacher-Collins

Goldenhar Waardenberg Branchio-oto-renal Stickler

Usher Pendred

Jervell-Lange-Nielson

Alport

Infectious

Meningitis may lead to the spread of bacteria to the inner ear through the cochlear aqueduct, which can lead to cochlear fibrosis and ossification.

TORCHES infections are congenital and early-onset causes of SNHL. Infec- tious causes may lead to symmetric or asymmetric losses.

Traumatic

Fractures of the temporal bone involving the otic capsule usually lead to profound hearing loss. Leakage of perilymph from the oval or round windows can cause progressive hearing loss and dizziness. Strong Valsalva during heavy lifting, head trauma, or barotrauma may initiate these perilymphatic fistulas.

Neurologic Disease

Multiple sclerosis is well known to cause a myriad of neurologic symptoms including hearing loss. ABR can be helpful in diagnosis, but MRI is more definitive. Cerebrovascular disease leading to brainstem stroke can also cause hearing loss, but usually multiple other neurologic symptoms will also be present.

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Evaluation

History

Pertinent history includes timing of onset, and whether abrupt or gradual, or fluctuating. Perceived severity and possible laterality are important. As- sociated symptoms and signs may be important, especially vertigo, visual disturbance, tinnitus, aural fullness, otalgia, or otorrhea. Past otologic history such as infection or surgery, a family history of hearing loss, and past exposures to noise or ototoxic agents is pertinent. A review of systems for associated neurologic or rheumatologic disease is sought.

Physical Exam

A thorough head and neck examination should be performed. The ear should be examined for any potential cause of CHL, such as cerumen, tympanic perforation, or middle ear effusions. Tuning fork tests may be done to docu- ment laterality and nature of hearing loss.

Imaging

Temporal bone CT is the single most useful test in children; specifically assess cochlea as well as vestibular aqueduct (enlarged vestibular aqueduct syndrome is defined as 1.5 mm anteroposterior [AP] diameter). To assess for retrocochlear pathology, MRI scanning of the head with fine cuts through the internal auditory canals should be performed with and without contrast media. Vestibular schwannomas and multiple sclerosis are typical diagnoses for which imaging studies should be obtained.

Labs

There is controversy regarding laboratory testing. For pediatric hearing loss, one may consider urinalysis (for Alport and branchio-oto-renal syndrome), ECG (for Jervell-Lange-Nielson), RPR or FTA-ABS, toxoplasmosis, cytomegalovirus-related tests, thyroid function testing, ESR, antinuclear antibody testing, rheumatoid factor, liver function tests, CBC, referral for ophthalmology exam if retinitis pigementosa is suspected, Cx 26 gene testing. (Temporal bone CT is the single most useful test in children.)

In adult progressive or fluctuating hearing loss, consider 68-kD antibody testing, ESR, Lyme serology, and RPR.

Other Tests

Pure tone audiometry is the standard for documentation of hearing loss.

Speech testing should also be performed. Patients may also be screened with otoacoustic emission testing and ABR testing. Hearing loss can be clas- sified by its severity:

● Mild (15–30 dB)

● Moderate (30–50 dB)

● Moderate to severe (50–70 dB)

● Severe (70–90 dB)

● Profound (90 dB)

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Treatment Options

Medical

Common forms of hearing loss (presbycusis, noise-induced hearing loss) can be treated with appropriate amplification. New hearing aid technologies include directional microphones, the capacity to filter background sounds, and many other programmable features. For symmetric hearing loss, bilateral aids are best. A CROS aid (contralateral routing of sound) may be used in severe unilateral loss to decrease the head-shadow effect.

Hearing loss associated with Ménière disease may respond to medical therapy with diuretics [Dyazide (GlaxoSmithKline, Brentford, Middlesex, UK) or Diamox (Lederle Laboratories, Philadelphia, PA)] or steroids (oral or possibly intratympanic).

Otoprotective treatment strategies are under study for concomitant use during known ototoxic drug treatments.

Surgical

Patients with profound bilateral loss that is not helped by hearing aids may be candidates for cochlear implantation (see Chapter 2.5.4). Patients with profound unilateral loss can be candidates for osteointegrated bone- anchored hearing devices (BAHAs; see Chapter 2.5.5).

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Outcome and Follow-Up

Frequent adjustments and cleaning of hearing aids will ensure better pa- tient compliance and satisfaction. Yearly audiograms should be performed on patients with identified SNHL to monitor for progression.

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ICD-9 Codes

389.10 Sensorineural hearing loss