ABA Advanced Diagnostics & Troubleshooting 2 — Questions and Answers
Question 1: A patient's ABR shows a prolonged Wave I-III interpeak interval with a normal Wave III-V interval. Where is the lesion most likely located?
- Auditory cortex
- Retrocochlear (CN VIII or lower brainstem) (Correct answer)
- Cochlea
- Middle ear
Correct answer: Retrocochlear (CN VIII or lower brainstem)
A prolonged I-III interpeak interval indicates a conduction delay between the cochlea/CN VIII and the lower brainstem, suggesting retrocochlear pathology.
Question 2: During DPOAE testing, emissions are absent only at 4000 Hz in a patient with a flat audiogram. What is the most likely cause?
- Equipment calibration error
- Localized outer hair cell dysfunction at 4 kHz (Correct answer)
- Middle ear effusion
- Neural hearing loss
Correct answer: Localized outer hair cell dysfunction at 4 kHz
Absent DPOAEs at a single frequency with a normal audiogram suggests focal outer hair cell damage that has not yet shifted pure-tone thresholds.
Question 3: A patient's tympanogram shows an abnormally low static admittance (As) with a normal tympanometric peak pressure. Which condition is most consistent?
- Otosclerosis (Correct answer)
- Ossicular discontinuity
- Eustachian tube dysfunction
- Tympanic membrane perforation
Correct answer: Otosclerosis
Otosclerosis typically produces a low or absent peak (Type As tympanogram) due to stiffening of the ossicular chain, particularly the stapes footplate.
Question 4: An audiologist observes elevated MEMR thresholds bilaterally with normal pure-tone thresholds and normal tympanograms. Which diagnosis is most consistent?
- Conductive hearing loss
- Auditory neuropathy spectrum disorder (Correct answer)
- Central auditory processing disorder
- Noise-induced hearing loss
Correct answer: Auditory neuropathy spectrum disorder
Auditory neuropathy spectrum disorder (ANSD) is characterized by elevated or absent MEMRs with normal cochlear function (OAEs present) and normal middle ear function.
Question 5: When performing electrocochleography (ECochG), an elevated SP/AP ratio (>0.4) is most suggestive of:
- Acoustic neuroma
- Endolymphatic hydrops (Meniere's disease) (Correct answer)
- Benign paroxysmal positional vertigo
- Superior semicircular canal dehiscence
Correct answer: Endolymphatic hydrops (Meniere's disease)
An elevated SP/AP ratio reflects endolymphatic hydrops, as the distended endolymph increases the summating potential relative to the action potential.
Question 6: A patient presents with bilateral low-frequency sensorineural hearing loss and episodic vertigo. ECochG shows SP/AP = 0.5. What is the next most appropriate diagnostic step?
- MRI with gadolinium
- Videonystagmography (VNG)
- Glycerol dehydration test (Correct answer)
- High-resolution CT of temporal bones
Correct answer: Glycerol dehydration test
The glycerol dehydration test can confirm endolymphatic hydrops by temporarily reducing endolymph pressure, improving hearing thresholds in Meniere's disease.
Question 7: During VEMP testing, a patient shows asymmetric VEMP amplitudes with a significantly reduced response on the right side. This finding most directly suggests:
- Right cochlear hair cell loss
- Right saccular or inferior vestibular nerve dysfunction (Correct answer)
- Right superior semicircular canal dehiscence
- Right endolymphatic hydrops
Correct answer: Right saccular or inferior vestibular nerve dysfunction
Cervical VEMPs (cVEMPs) assess the saccule and inferior vestibular nerve; reduced amplitude on one side indicates dysfunction in that pathway.
ABA Advanced Diagnostics & Troubleshooting 2
A patient's ABR shows a prolonged Wave I-III interpeak interval with a normal Wave III-V interval.
Where is the lesion most likely located?