Transmission & Drivetrain Systems Flashcards

A patient presents with maximum conductive hearing loss (~60 dB HL) and a flat (Type B) tympanogram with large ear canal volume. The most likely cause is:

Answer: Tympanic membrane perforation with ossicular discontinuity

A perforated tympanic membrane connects the ear canal to the middle ear space, inflating the measured ear canal volume, while ossicular discontinuity produces maximum conductive loss.

Which surgical procedure restores ossicular chain continuity by interposing a prosthesis between the stapes and the tympanic membrane or remaining ossicles?

Answer: Ossiculoplasty (PORP/TORP)

Ossiculoplasty uses partial (PORP) or total (TORP) ossicular replacement prostheses to re-establish the mechanical transmission chain from tympanic membrane to oval window.

What does a negative peak pressure on a tympanogram (e.g., −200 daPa) indicate about the transmission system?

Answer: Negative middle ear pressure from Eustachian tube dysfunction

Negative middle ear pressure develops when the Eustachian tube fails to equalize pressure, causing the tympanic membrane to retract and shifting the tympanogram peak into negative daPa.

In the context of acoustic immittance testing, ipsilateral acoustic reflex thresholds that are elevated or absent while contralateral reflexes are normal suggest a lesion at which level?

Answer: Middle ear on the probe side

If the probe-side middle ear is impaired, the stapedius muscle contraction cannot be detected immittance-wise ipsilaterally, while the contralateral pathway (and reflex arc) remains intact.

Which condition is characterized by a mobile stapes footplate but discontinuous ossicular chain, yielding a large air-bone gap and a Type Ad tympanogram?

Answer: Ossicular discontinuity (isolated incus erosion)

Isolated ossicular discontinuity (e.g., incus erosion) allows the tympanic membrane to move freely (Ad pattern) while the broken chain cannot drive the oval window, producing a large conductive loss.

During the acoustic stapedius reflex arc, which cranial nerve carries the efferent signal to the stapedius muscle?

Answer: CN VII (facial)

The facial nerve (CN VII) innervates the stapedius muscle; its integrity is assessed clinically through acoustic reflex testing.

Wideband acoustic immittance (WAI) provides information across a broad frequency range. Which advantage does it have over single-frequency tympanometry?

Answer: It detects middle ear pathologies that appear normal on 226 Hz tympanometry

WAI assesses energy absorbance across 200–8000 Hz and can identify pathologies like ossicular fixation or superior canal dehiscence that present with normal 226 Hz tympanograms.