SERVICES:

• Hearing Evaluations
• Hearing Aid Fitting & Repair
• Tinnitus Evaluations & Coping Consultations
• Auditory Brainstem Evoked Response Testing
• Electrocochleography
• Immittance Testing
• Speech Mapping
• Otoacoustic Emissions
• Hearing in Noise Tests
• Assistive Listening Technology
• Occupational/Employment Hearing Tests
• Custom-made hearing protection
• Custom-made ear molds

TESTS OF HEARING FUNCTION

Disorders of hearing loss can be classified according to whether the damage to hearing is PRE-NEURAL or NEURAL. PRE-NEURAL hearing loss is associated with damage to the outer ear, middle ear, and/or inner ear (cochlea).

TESTS FOR PRE-NEURAL HEARING LOSS

Tests that are used to identify PRE-NEURAL lesions are: (1) otoacoustic emissions, (2) Electrocochleography (3) Immittance testing, and (4) diagnostic hearing evaluations. The most frequent cause of PRE-NEURAL hearing loss is noise exposure. Noise exposure can occur in the form of occupational (military, industrial) or recreational (hunting, loud music, motorcycles) A common cause of PRE-NEURAL hearing loss is genetic. We now have identified several hundred genes that result in acquired hearing loss. PRE-NEURAL hearing loss can also be associated with health conditions such as diabetes, autoimmune disease, frequent and chronic ear disease, and Meniere’s disease.

OTOACOUSTIC EMISSIONS

Otoacoustic emissions measure the cochlear microphonic, which is an electrical response produced by the outer hair cells of the cochlea. These outer hair cells are often referred to as the amplifier of the inner ear. The absence of otoacoustic emissions suggests outer hair cell damage, which is a PRE-NEURAL finding and represents 95% of all adult hearing loss.

ELECTROCOCHLEOGRAPHY

Electrocochleography (EcochG) is also a test that records the electrical activity of the cochlea. Abnormal electrical cochlear activity is characteristic of patients with Endolymphatic Hydrops/Meniere’s Disease and represents PRE-NEURAL damage. The presence of normal electrical activity within the cochlea followed by an absent neural response suggests a NEURAL LESION.

IMMITTANCE

Immittance testing is both sensitive and specific for abnormalities of the middle ear, which are considered PRE-NEURAL causes of hearing loss. Fluid or congestion behind the eardrum (Eustachian Tube Dysfunction) can be identified by immittance testing as well as the mobility of the middle ear bones. These conditions can be treated medically and/or surgically and require appropriate medical referral.

HEARING EVALUATIONS

Although hearing evaluations are routinely used in most diagnostic centers, routine hearing tests do not differentiate between PRE-NEURAL and NEURAL lesions without more comprehensive tests.

TESTS OF NEURAL HEARING FUNCTION

NEURAL hearing loss is associated with damage to the auditory nerve and/or its central pathways. Tests that are used to identify NEURAL hearing loss are Auditory Brainstem Response tests (ABR) and Acoustic Stapedial Reflexes (ASR). Causes of NEURAL hearing loss include: (1) space occupying lesions of the VIII hearing nerve, (2) demylenating diseases such as Multiple Sclerosis, (3) inner hair cell loss, and (4) neuropathy of the hearing nerve. Patients with NEURAL hearing loss are not candidates for hearing aids and depending on the degree of hearing loss and etiology may benefit from a cochlear implant. Fortunately, the incidence of neural hearing loss is low.

AUDITORY BRAINSTEM RESPONSE TEST

The auditory brainstem response test (ABR) records brain waves (electrical potentials). These potentials are evoked by an auditory stimulus and occur within the cochlea (wave I), the VIII auditory nerve (wave II), and auditory regions of the brain (waves III-V). NEURAL lesions are associated with the presence of wave I and the absence of subsequent wave forms. This test is completely noninvasive and involves the recording of the sound as the patient rests or takes a nap. Patients with abnormal ABR findings are referred for further medical tests.

ACOUSTIC STAPEDIAL REFLEXES

The acoustic stapedial reflex (ASR) is identified at the lowest intensity required to elicit a stapedial muscle contraction in the middle ear. The neural connections for the reflex arc are located in the lower brainstem but are also influenced by the higher central nervous system structures. A disruption of the reflex arc in an ear that has no middle ear pathology is suggestive of a NEURAL cause for hearing loss. These patients are referred for medical follow up.

Patients with PRE-NEURAL hearing disorders are typically excellent candidates for rehabilitation whereas patients with NEURAL hearing disorders are not candidates for amplification.