Neurotology/Audiology Flashcards
Match the terms: Most (efferent/afferent) neurons innervate (inner/outer) Hair Cells.
Efferent neurons predominantly innervate OHCs
Afferent neurons predominantly innervate IHCs
Which of the following have high Na/low K? Select all that apply: Scala tympani, scala vestibuli, cochlea, vestibule, endolymphatic sac
scala tympani, scala vestibuli, endolymphatic sac. (The trick is that endolymphatic sac has perilymph-like concentration despite being named “endolymphatic!”)
What type of OAE is used in neonatal hearing screens?
DPOAEs
How much is a maximal conductive hearing loss?
60dB
What would be the expected results for the following tests in auditory neuropathy: pattern of hearing loss, WRS on audiogram, ABR, acoustic reflexes, tympanometry, OAEs
SNHL, worse WRS than expected compared to PTA, absent ABR, absent ipsilateral and contralateral acoustic reflexes, present OAEs, normal tympanometry
Define: interaural attenuation, crossover, masking.
Interaural attenuation = the loss of sound energy from one side of the skull to another
Crossover = the amount of sound that is heard by the contralateral ear
Masking = sound played to the contralateral ear to account for crossover
Which end of the cochlea is sensitive to high frequencies?
Basal turn. The apex is sensitive to low frequencies.
When should masking be considered for air conduction using over the ear headphones, air conduction using insert earphones, and bone conduction?
10dB for bone (interaural attenuation = 0-10dB)
40dB for over ear
70dB for insert
How do dB HL values correspond to SPL vs SL and which one is used for reference in clinical audiometry?
HL is used in clinical audiometry. HL values are not uniformly/linearly corresponded to SPL values, as human hearing is not equally sensitive at all frequencies. SL is equal to HL but calibrated to the individual’s hearing.
What is the difference between hearing level, sound pressure level, and sensation level?
HL = threshold to hear 50% of stimuli in a “normal” ear. SPL = objective measure of sound intensity calibrated to micropascales. SL = individuals’s threshold
How do cochlear hearing losses impact the ABR at low, flat, or high frequencies?
Low frequency HL does not typically affect. Mild to moderate high frequency HL also does not impact so long as the signal/stimulus is adequate. Flat losses >75dB usually make ABR impossible. Everything in between affects waveform/latency/amplitude but not in a predictable way. (Note from Tiff – I included this because this topic came up in an actual question on the boards when I took them. Showed an audiogram with conductive hearing loss and an ABR with waveform latencies/altered audiogram, wanted to know if this is indicative of a retrocochlear lesion or normal for the audiogram. I don’t know if it was an experimental question).
Which level of ECOLI represents the first point of potential crossover to the contralateral side?
The superior olive.
What is auditory fatigue and how is it tested? What does it signify?
Inability to continuously perceive a note presented at a certain frequency at or slightly above db SL. Indicates VIII nerve lesion. May be tested with tone decay test, acoustic reflex delay, or supra threshold adaptation test.
What is the expected pattern of acoustic reflex responses in clinically significant left otosclerosis?
Absent left reflexes to bilateral stimuli. Present right reflexes to right stimulus. Possible present right reflex to left stimulus provided that degree of CHL < 65dB.
WRSs are usually presented at 30-40dB SL. How does that compare to db HL? (Eg if a person has a speech recognition threshold of 25 dB HL, at how many dB HL will a patient typically be presented with the word list for word/speech recognition?)
SRT in dB HL + 30-40 dB. In the given example, presentation will be at 55-65 dB HL.
Explain the pneumonic ECOLI.
Eighth nerve, cochlear nucleus, olivary complex, lateral lemniscus, inferior colliculus
What are the four sources of impedance matching in the middle ear, and how much is added by that source?
1) area effect of the TM (17:1 size difference TM to oval window)
2) lever action of the ossicular chain (additional 1.3:1)
3) natural resonance and frequency of the middle ear/EAC
4) phase difference between the round and oval windows
What is recruitment? What is its significance?
Disproportionate increase in subjective loudness for a given increase in dB stimulus. Indicates cochlear pathology.
What is the transformer ratio of the middle ear? How many dB does that equal?
22:1 (17 area effect x1.3 lever action); 25 dB
What is meant by the “cochlear amplifier”?
Active feedback mechanism causes OHCs to stiffen/relax the basilar membrane so that a narrow band of IHCs will receive maximal stimulation for a given frequency
When might one see a Type Ad tympanogram? (Try to provide at least 1 example).
Decreased compliance/loose compliance - partial ossicular discontinuity/disarticulation, flaccid TM.
Why is the term “sensorineural” favored over “nerve loss” in SNHL?
Because majority of SNHL is cochlear rather than retrocochlear.
What is rollover and what does it signify?
Decrease in word recognition score with increase in presentation volume. Marked rollover suggests retrocochlear lesion; slight may be seen in SNHL or cochlear lesions.
Which of the following does not impact latencies on ABR: Age, Gender, Temperature, Medications, State of Arousal, Hearing Loss.
Trick question! They all impact ABR latencies. However, note that it is generally accepted that they are not acutely affected by most sedative anesthesia, drugs, or state of arousal (hence why a sedated ABR is still accepted as reliable)
When might one see a Type As tympanogram? (Try to provide at least 2 examples).
Restricted compliance - stiff TM (tympanosclerosis), otosclerosis, malleolar fixation.
Which of the following would not be helpful in the evaluation of pseudohypoacusis: Stenger test, Lombard test, OAE, Bekesy audiometry, acoustic reflexes.
Trick question! All would be helpful. Presence of TOAEs ensures there is no significant hearing loss >40dB. Stenger is helpful for identifying malingerers (play tone in both ears, louder in the affected ear - malingerer will say they hear nothing). Lombard increases background noise and monitors patient for increasing the volume of their speech. A continuous stimulus line trending above a interrupted stimulus line on Bekesy audiometry suggests pseudohypoacusis. Acoustic reflex present at 5dB above voluntary audiometric threshold suggests pseudohypoacusis.
In what type of hearing loss affecting either the stimulus ear or recording/reflex ear might the stapedial reflex be absent?
Stimulated ear: significant hearing loss > 65dB (conductive or SNHL)
Recording/reflex ear: significant conductive pathology or hearing loss
What are the three types of audiometric testing appropriate for children prior to PAE? At what age is each test appropriate?
Behavioral Response Audiometry up to 6 months. Visual Reinforcement Audiometry from 6 to 30 months. Conditioned play from ~30-36 months of age.
What type of OAE can provide frequency-specific information?
DPOAEs; but DPOAEs may be recorded even in a moderate to severe hearing loss
How is significant ototoxic change defined?
threshold shift of 20dB at a single frequency, threshold shift of 10dB in two adjacent frequencies, loss of response at 3 consecutive frequencies where previous responses were recorded
What are the 3 classifications of noise-induced hearing loss?
Transient threshold shift, permanent threshold shift, or acoustic trauma
Based on OSHA guidelines, how many hours can a person be exposed to 90dB SPL? 95dB SPL? 105 dB SPL?
8 hours; 4 hours; 1 hour
What are the commonly accepted anatomical origins for waves I, III, and V of an ABR?
I. distal eighth nerve
III. caudal brainstem near trapezoid body and superior olivary complex
V. lateral lemniscus as it enters the inferior colliculus
(This always confused me that it doesn’t quite line up perfectly with ECOLI. Just important to realize that it doesn’t – ECOLI is meant to be a mneumonic for the general propagation of auditory signal)
What 3 electric potentials occurring with sound stimuli are measured by ECOG?
Summating potential
Action potential
Cochlear microphonic
(There is also a resting potential, but this is without stimulus)
Is the cochlear microphonic, summating potential, and action potential AC or DC?
CM = AC AP = AC SP = DC
With respect to ECOG, what is the summating potential a reflection of?
It reflects the time-displacement pattern of the cochlear partition in response to the stimulus envelope
What type of SP is expected in endolymphatic hydrops? (Large or small)
Enlarged
On what site is a transtympanic electrode placed?
Cochlear promontory
With respect to ABRs as a screening tool, what type of ABR is better for detection of small tumors?
Stacked ABR
What type of ABR is used for pediatrics, difficult-to-test, and possible non-organic hearing loss?
Threshold ABR
You are performing a threshold ABR in an individual suspected of non-organic hearing loss. At 2000Hz, wave V disappears with a 15 dB HL stimulus. What does this indicate?
You are near the patient’s hearing threshold
What is the generally accepted difference between ABR thresholds and behavioral thresholds?
ABR thresholds are 10-20dB higher than behavioral
What is the clinical implication/significance of the following findings on ABR: [a] delayed wave I latency; [b] small or absent wave I with delayed absolute latencies of other waves; [c] normal wave I with delay of all other absolute latencies; [d] wave I-III interpeak latency; [e] inter-aural (between ears) wave V latency >0.4ms?
a. CHL
b. SNHL
c. neural hearing loss
d. best descriptor of eighth nerve tumor
e. suspicious for unilateral retrocochlear lesion; sensitive for eighth nerve tumor
What electrical neural monitoring test can be used to assess frequency-specific profound hearing loss?
Auditory Steady State Response (Click and tone burst ABR cannot do this, as masking dilemma cannot be overcome). Difficult to do ASSR with bone conduction as well due to masking dilemma.
AKA 40Hz response, envelope-follow, frequency-following, amplitude-modulating-following response
What is Heschl’s gyrus?
The supratemporal plane of the auditory cortex
What does a cVEMP test? Is this ipsilateral or bilateral?
cVEMP is a reflection of the saccule, posterior SCC, inferior vestibular nerve, and central connections. Ipsilateral response.
What are the expected findings on cVEMP in a patient with [a] SNHL [b] CHL [c] clinically significant SSCD [d] severe otosclerosis?
a. no impact
b. increased thresholds or low amplitudes
c. Increased amplitudes and decreased thresholds/ability to detect despite an ABG
d. expected to be absent
What is Alexander’s Law? Keeping that in mind, if you are speaking to a patient with postoperative vertigo following resection of a right acoustic neuroma, which side should you stand on to reduce/minimize their nystagmus? Which direction will the slow phase of nystagmus be after a left labyrinthectomy?
Alexander’s law states that in a unilateral peripheral vestibular loss, eye movement in the direction of the stronger labyrinth will exacerbate the nystagmus. Hence, you should stand on the right side of a right acoustic neuroma patient with postop vertigo. The slow phase of nystagmus after a left labyrinthectomy will be towards the left.
Gaze-stabilizing reflexes include smooth pursuit, optokinetic nystagmus, and VOR. Which one(s) dominate in slow head movement? Which one(s) for fast movement?
Smooth pursuit +OKN dominate in slow. VOR for fast.
What is the function of the cupula?
The cupula is the gelatinous part within the ampulla of the canal and contains hair cells. Its job (in part) is to block fluid flow by nature of its gelatinous consistency, allowing endolymph from the affected SCC to deflect the cupula (instead of freely floating into the vestibule) and excite the stereocilia of the hair cells causing sensation of head rotation.
How are the SCCs paired in canal planes?
The two horizonal canals are paired. Then LARP (left anterior/right posterior) and RALP (right anterior/left posterior).
Note: The extraocular muscles are also paired. Medial/Lateral recti correspond with horizontal canals, superior/inferior with anterior canals, and obliques with posterior canals.
Contrast the following between the utricle and the saccule: innervation? directionality of sensation for linear acceleration?
Utricle (“Up”) - innervated by the superior VN. Senses horizontal movement. Saccule (ball sack hangs down; lol sorry) - innervated by inferior VN. Senses vertical movement.
Discuss ampullopetal vs ampullofugal. Which SCCs are excited by ampullofugal flow vs ampullopetal flow?
Ampullopetal = toward ampulla Ampullofugal = away from ampulla (like centriFUGAL forsces)
Horizontal is excited by ampullopetal. Anterior/Posterior by ampullofugal.
On what principle with respect to excitatory vs inhibitory responses in the VOR is the head thrust test based?
Excitatory forces at HIGH velocity dominate the VOR. Hence, unilateral vestibular loss/weakness will cause a saccade during head thrust test because the weaker/inhibitory side cannot keep up with the excitatory forces. This asymmetry is masked in normal subjects by reciprocal wiring in the brainstem, but is brought out when only one labyrinth/one peripheral vestibular system is working.
Why doesn’t whole-labyrinth irritative nystagmus (excitatory stimulation of all 3 canals) have a vertical component?
The upward component of the anterior canal cancels out the downward component of the ipsilateral posterior canal. However, both the anterior and posterior canals have the same torsional direction, which is doubled in an pathologic excitatory stimulus.
What nerve is most often affected in vestibular neuritis?
Superior vestibular nerve
Name 2-3 potential vertiginous syndrome diagnoses based on length of episode (more than three accepted): seconds to minutes; minutes to hours; hours to days; constant
seconds to minutes: BPPV, PLF, VBI
minutes to hours: Meniere’s, migraine
hours to days: migraine, vestibular neuronitis
constant: mal de debarquement, uncompensated vestibular hypofunction, psych
What is the likely vertiginous syndrome based on positional triggers:rolling over to side in bed; with neck extension while standing upright; with rapid head movements
rolling: BPPV
neck extension: VBI
rapid head movements: vestibular hypofunction
What is the purpose of Fresnel glasses during bedside examination? What is expected directionality of post-headshake nystagmus evaluation using Fresnel glasses in a patient with left peripheral vestibular hypofunction?
Purpose is to suppress ocular fixation/compensation for underlying vestibular dysfunction. With left peripheral hypofunction, expect drift to left and beat to right.
What is the bedside maneuver for evaluating for lateral/horizontal canal BPPV?
Supine with head slightly extended past level, roll to affected side (affected ear down) and assess for nystagmus. Fix with “Log roll” - roll away from affected ear
What is hennebert’s sign? What is Tullio’s phenomenon? Name 3-5 syndromes that can cause them.
Hennebert’s sign - vertigo with pneumatic otoscopy or tragal pumping. Tullio’s - vertigo with loud noises. Can be caused by SSCD, enlarged vestibular aqueduct, otic syphilis, PLF, lateral/horizontal canal fistula (cholesteatoma)
What syndromes can cause post-hyperventilation nystagmus?
Demyelinating lesions - MS, vestibular schwannoma, compression by a blood vessel (vascular loop- AICA)
What is the purpose of Jongkees formulas? What is the upper limit of normal?
Calculate unilateral weakness or directional prepondarance in caloric testing. Cutoff is 25% for both.
