Clinical Audiology - Acoustic Reflex and Objective Testing

Vocabulary flashcards covering clinical audiology topics including the acoustic reflex, objective electrophysiological tests, and hearing pathologies.

Acoustic Reflex (Stapedius Reflex)

The contraction of the stapedius muscle in the middle ear in response to high-intensity acoustic stimuli.

Stapedius Muscle

A middle ear muscle connected to the neck of the stapes bone, innervated by the Facial Nerve (Cranial Nerve VII).

Tensor Tympani Muscle

A skeletal muscle located in a bony canal above the Eustachian tube, connected to the handle of the malleus and innervated by the Mandibular branch of the Trigeminal Nerve (Cranial Nerve V).

Pennate Type

A specific muscle structure characterized by short, parallel fibers that allow the ear muscles to produce high tension even with minimal movement.

Startle Response

An automatic reaction to sudden or loud sounds involving the Tensor Tympani and muscles of the face and neck.

Binaural Hearing

The physiological principle explain why an acoustic stimulus in one ear causes bilateral stapedius muscle contraction in both ears simultaneously.

Acoustic Immittance

A measurement of the middle ear's ease of movement (compliance) or resistance (impedance) to sound energy.

Acoustic Reflex Threshold Detection

An indication that a reflex has occurred, defined as a minimum compliance change of at least $0.02\,ml$.

Ipsilateral Stimulus (Uncrossed)

A measurement where the acoustic stimulus is presented and the compliance change is measured in the same ear.

Contralateral Stimulus (Crossed)

A measurement where the acoustic stimulus is presented to one ear while the compliance change is measured in the opposite ear.

Superior Olivary Complex (SOC)

The central processing region for the acoustic reflex arc located in the lower part of the brainstem.

Acoustic Reflex Threshold (ART)

The minimum sound intensity in $dB\,HL$ or $dB\,SL$ that triggers a measurable contraction of middle ear muscles.

Reflex Amplitude

The magnitude of the stapedius muscle contraction, which increases linearly with stimulus intensity until reaching saturation.

Saturation

The peak point where the acoustic reflex no longer expands or increases in strength even if the sound intensity is raised.

Reflex Latency

The time duration in milliseconds from the onset of the acoustic stimulus until the beginning of the stapedius muscle contraction.

Reflex Decay (Fatigue)

The weakening of the stapedius contraction during a prolonged acoustic stimulus, usually tested for $10\,\text{seconds}$ at $10\,dB$ above threshold.

Loudness Recruitment

An abnormal perception of loudness characteristic of cochlear damage, where a small increase in intensity leads to a sharp and disproportionate jump in perceived loudness.

Retrocochlear Damage

Damage occurring beyond the cochlea, frequently involving the eighth cranial nerve or the brainstem.

Sensitivity (CDA Model)

The ability of a test to correctly identify and locate a pathology (True Positive rate).

Specificity (CDA Model)

The ability of a test to correctly identify healthy subjects and rule out pathology (True Negative rate).

SPAR (Sensitivity Prediction by the Acoustic Reflex)

A method formerly used to predict the hearing threshold based on the difference between reflex thresholds for Broad Band Noise and pure tones.

Sensorineural Hearing Loss (SNHL)

Hearing loss resulting from damage to the inner ear (cochlea), the auditory nerve, or central pathways, characterized by the absence of an Air-Bone Gap.

Just Noticeable Difference (JND)

The smallest change in stimulus parameters (intensity or frequency) required for a subject to perceive a difference.

Otoacoustic Emissions (OAE)

Acoustic signals (sound waves) produced by the movement of outer hair cells in the cochlea, measured in the external ear canal.

Electromotility

The ability of outer hair cells to contract and expand in length to amplify sound vibrations within the cochlea.

Diplacusis

A perceptual distortion often found in unilateral cochlear loss where a single pure tone is heard differently in each ear.

Alternate Binaural Loudness Balance (ABLB)

A behavioral test used to detect recruitment in patients with unilateral hearing loss by comparing loudness perception between ears.

Rollover Ratio

A calculation in speech audiometry where a result higher than $0.45$ indicates suspected retrocochlear pathology because PB scores drop as intensity increases.

Nyquist Frequency

The requirement that a digital sampling rate must be at least twice the highest frequency of the signal to ensure accurate reproduction without aliasing.

Auditory Brainstem Response (ABR)

An electrophysiological test recording five specific waves ($I$ to $V$) within the first $10\,ms$ after an acoustic stimulus to assess the auditory pathway.

Brainstem Transmission Time (BTT)

The time interval between Wave I and Wave V in ABR, representing neural conduction speed through the brainstem, with a norm of approximately $4.0\,ms\,(\pm 0.4\,ms)$.

Electrocochleography (ECochG)

A procedure for recording electrical potentials from the cochlea (CM, SP) and the auditory nerve (AP) in response to sound.

Ménière’s Disease

A chronic inner ear condition involving low-frequency fluctuating hearing loss, episodic vertigo, tinnitus, and ear pressure, often linked to Endolymphatic Hydrops.

Auditory Neuropathy Spectrum Disorder (ANSD)

A hearing disorder where OAEs and CM are normal, but the ABR is abnormal or absent, indicating impaired neural synchronization.

Stenger Test

A behavioral test utilizing the lateralization principle to detect malingering or functional hearing loss in cases of reported unilateral impairment.

Central Auditory Processing Disorder (CAPD)

A condition characterized by difficulty in identifying, analyzing, and interpreting acoustic stimuli despite having normal peripheral hearing thresholds.