Disorders Affecting the Inner Ear Flashcards
1
Q
What is homeostasis?
A
The ability of an organism or a cell to maintain internal equilibrium by adjusting its physiological processes
2
Q
What is inner ear homeostasis?
A
The process by which chemical equilibrium of inner ear fluids and tissues maintained
3
Q
For proper inner ear function, is a tight control of ions and homeostasis required?
A
Yes
4
Q
What are the functions of the inner ear that could be disrupted if not balanced?
A
Hair cell function
Regulation of extracellular endolymph and perilymph
Conduction of nerve impulses
5
Q
What are the major ions involved in inner ear homeostasis?
A
Sodium
Potassium
6
Q
What other ions also play a significant role in inner ear homeostasis?
A
Chloride
Calcium
7
Q
Is ion homeostasis controlled by numerous ion channels and transporters in plasma membrane of cells, especially cells lining the scala media?
A
Yes
8
Q
Is active transport of H2O across the cell membranes also needed?
A
Yes
9
Q
Before sound is perceived, does it have to be converted to electrical impulses in the auditory nerve?
A
Yes
This process is mediated by the cilia of the inner ear hair cells
10
Q
Does the sound-induced excitatory deflection of the stereocilia causes a mechanoelectrical transduction current to depolarize the hair cells and initiate action potentials?
A
Yes
11
Q
Do endolymph and perilymph must maintain their specific ion concentrations for max sensitivity?
A
Yes
12
Q
Are there several cochlear and vestibular disorders that are transient and recover spontaneously?
A
Yes
13
Q
What are some of these temporary cochlear and vestibular disorders?
A
Sudden-onset hearing loss
Diuretic ototoxicity recovery after stopping drugs
Autoimmune labyrinthitis (transient symptoms)
Meniere’s disease (intermittent symptoms)
14
Q
What is this temporary cochlear loss stemming from?
A
Not the hair cells or sensory nerves, because it comes back
Damage to homeostatic mechanism
15
Q
What are symptoms of cochlear disorders?
A
Hearing loss (constant or fluctuating)
Difficulty with speech perception
Loudness recruitment (abnormal loudness growth)
Aural fullness
Tinnitus
Abnormal or excessive response to sound
Conditions that may be associated with psychological issues
16
Q
What is the hearing loss associated with cochlear disorders?
A
Any severity
Always SNHL, unless superimposed with ME issue
17
Q
What are some conditions that may be associated with psychological issues?
A
Hyperacusis - physical discomfort/pain when a sound is loud but would be tolerable to most people
Misophonia - intense emotional reactions to certain sounds that are not perceived as loud
Noise sensitivity - increased reactivity to sounds including general discomfort and annoyance in regards to loudness
Phonophobia - anticipatory fear of sound, can cause comorbid conditions (tinnitus) to worsen
18
Q
What are the most common causes of SNHL?
A
Aging
Exposure to toxic levels of noise
19
Q
What are some other causes of SNHL?
A
Genetic syndromic and non-syndromic SNHL
Ototoxicity
Infections of the inner ear
Autoimmune conditions that affect the inner ear
20
Q
What are most infections of the inner ear caused by?
A
Viruses
21
Q
Can bacteria also cause serious diseases?
A
Yes, such as meningitis
22
Q
What are the two known kinds of viruses for the inner ear?
A
Ribonucleic acid (RNA) virus (covid 19 and flu)
Deoxyribonucleic acid (DNA) virus
23
Q
What are RNA viruses?
A
Contain ribonucleic acid in their genome
High mutation rates compared to DNA viruses because RNA polymerases lack the proofreading ability
24
Q
What are DNA viruses?
A
Contain deoxyribonucleic acid in their genome
More stable
25
What are some examples of DNA viruses?
Smallpox, herpes, and chickenpox
26
What is effected in the cochlea from these viruses?
Organ of corti is affected at basal turn (high freq SNHL)
Individual hair cells damaged or missing
Stria vascularis may become atrophied
Tectorial membrane appears shriveled
Complete collapse of Reissner's membrane
27
Is rubella virus an RNA virus?
Yes
28
What is rubella virus?
Has adverse affects on fetus
Responsible for German measles
Greater affect on the auditory system if contracted when auditory system is developing (initial part of the 2nd trimester)
29
What can rubella lead to?
Congenital hearing loss
Congenital cataracts
Cardiovascular problems
Possible intellectual disability
30
Is paramyxovirus an RNA virus?
Yes
31
What is paramyxovirus?
Responsible for mumps
Inflammation of the parotid gland (salivary glands)
Can cause males to be infertile
Can cause permanent SNHL, typically unilateral
32
Is cytomegalovirus (CMV) a DNA virus?
Yes
33
What is CMV?
A common double-stranded DNA virus that belongs to the herpes virus family
Found in other mammals too
One of the most common viral diseases
Common all over north america
34
Does about 50 to 80% of the U.S. population carry CMV antibodies by age 35 to 40?
Yes
35
Can CMV result in decreased life expectancy?
Yes
36
Can CMV cause enlarged organs?
Yes
37
Can CMV result in a blueberry rash (reddish blue to magenta)?
Yes
38
Can CMV cause decreased immunity to the flu vaccine?
Yes
CMV has the most genes compared to any other known human virus (large genome)
Our immune system expends a lot of energy fighting this virus all life long
39
Is CMV the most common viral disease among newborns?
Yes
1 in 200 newborns has CMV
About 20% of newborns diagnosed with CMV will develop hearing loss
75% babies born with CMV can manifest delayed onset SNHL even as adults
40
How is CMV passed down to a fetus?
Through the placenta and is teratogenic to the fetus
nfected mothers may only exhibit symptoms of a common cold/mild ‘flu
In 2023, Minnesota became the first state to screen ALL newborns for CMV
41
What kind of hearing loss does CMV result in?
A progressive profound permanent SNHL with the final stage being reached by 3 to 5 years
Many of these children are CI candidates
42
Are newborns with CMV detected during NBHS?
No, due to late onset progressive loss
43
How can CMV show up in infants, older children, and adults?
Can be silent or symptoms may mimic common cold
Cause no permanent damage
44
What other neurological or other complications can CMV cause when it occurs in vitro?
Cardiovascular problems
Neurological problems
Blindness
Intellectual disability
45
Are infected newborns considered contagious?
Yes, can be passed to clinicians
Problem for pregnant clinicians
46
Can CMV also be transmitted through breastmilk?
Yes
But there is no evidence to suggest that it produces a SNHL past about 3 weeks of age
47
How is CMV diagnosed?
Urine polymerase chain reaction (gold standard)
Histologic examination
CT scan
48
What is urine polymerase chain reaction?
Laboratory technique for rapidly producing millions of copies of a specific DNA segment
Done to study things in greater detail
49
What is a histological examination for CMV?
Put saliva sample under microscope, look for specific inclusion bodies
Inclusion bodies are common in many virus infections
50
How does CMV show up on a CT?
Can show intracranial calcification
51
What is AIDS caused by?
The microbe human immunodeficiency virus (HIV)
52
Is HIV a retrovirus?
Yes
53
What are retroviruses?
Retroviruses rely on their enzyme reverse transcriptase to perform the reverse transcription of its genome from RNA into DNA (normal transcription is from DNA to RNA)
Embeds itself into the host's cells
The virus then replicates as part of the infected cell's DNA
54
Can people be HIV positive and not express any signs and symptoms?
Yes
55
Is HIV neurotropic?
Yes
It attacks the nervous system
56
Is HIV lymphotropic and immunotropic?
Yes
It attacks the lymph glands, both T and B cells, and the immune system
57
In populations at risk for HIV, should the condition be considered in all cases of sudden bilateral or unilateral HL?
Yes
58
What are some otologic signs and symptoms associated with AIDS?
OME with or without CHL; SNHL during later stages
Otalgia
Vertigo
Tinnitus
Aural fullness
Reduced OAEs (OHCs affected)
Delayed ABR interwave latencies (central effects)
59
Besides AIDS itself, what might the auditory symptoms be due to?
Ototoxic effects of the AIDS drugs
Recurrent/chronic OME and other opportunistic infections that attack the ear due to the suppressed immune system
60
Can HIV be transmitted through the placenta?
Yes
61
Is there a latent or dormant period for the AIDS virus in infants?
No
Can also have congenital or early-appearing encephalopathy that can damage the brain and CNS
62
Is edema of the brain tissue present with pediatric AIDS?
Yes
63
Is there a greater incidence of otitis media with poorer prognosis in children with AIDS?
Yes
Due to compromised immune system
Higher rate of recurrence of infection
Higher failure rate of response to treatment
64
What is meningitis?
Inflammation of the meninges (duramater, arachnoid mater, and pia mater) surrounding the brain and spinal cord
65
What is the etiology for meningitis?
Various viruses
Bacteria (haemophilus influenzae most common and pneumococcus pneumonia causes most cases of hearing loss post-meningitis)
66
What are the two kinds of meningitis?
Primary and secondary
67
What is primary meningitis?
Disease originates in the meninges
68
What is secondary meningitis?
OME leading to mastoiditis/labyrinthitis and then meninges
Cholesteatoma that spreads to the meninges
69
What are the initial symptoms of meningitis?
High fever
Neck rigidity
Malaise (blah)
Nausea/vomiting
In severe cases, coma and death
70
What can severe cases of meningitis lead to?
Blindness
Paralysis due to damage of the motor centers of the brain
Hearing loss/deafness (one of the most significant causes of acquired SNHL, can cause permanent abnormal cochlear bone formation)
Vertigo and balance problems
71
What is the treatment for meningitis?
Antibiotics
Mastoidectomy
Amplification or CI
72
Why is a mastoidectomy done as treatment for meningitis?
If the infection is related to middle ear disease and is not resolved by antibiotics
73
When can CIs be used for meningitis cases?
If severe to profound loss has occurred
Need to ensure there is enough space in the cochlea to place the implant because of abnormal bone growth
Bony growth in cochlea can continue after the CI and may compromise implant
74
What is a perilymphatic fistula?
An abnormal connection (a tear or defect) in either or both the oval and round window that separate the air filled ME and the fluid filled perilymphatic space of the inner ear
Opening that shouldn't be there
75
What causes perilymphatic fistula?
Idiopathic
A history of straining or lifting; feeling the ear “pop”
Can occur during the early or late period following stapedectomy
Spontaneous PLF also discovered at the time of surgery for Meniere’s disease
76
What are the 4 recognized patterns of symptoms for perilymphatic fistula?
Episodic vertigo without hearing loss
Hearing loss without vertigo
Symptoms maybe virtually indistinguishable from Meniere’s disease, i.e., tinnitus, SNHL, vertigo, aural fullness
Miscellaneous symptoms with disequilibrium but not episodic vertigo
77
What is the diagnosis for perilymphatic fistula?
Presentation of a symptom complex
High index of clinical suspicion
Dix Hallpike positional testing can result in nystagmus and vertigo
78
What is the treatment for perilymphatic fistula?
Middle ear exploration (exploratory tympanotomy)
Surgical repair for obvious traumatic perilymph leak and sealing of the round or oval window
Patients cautioned against heavy lifting following repair surgery
79
Repair of the perilymphatic fistula may result in what?
Improve/preserve hearing
Resolve vertigo/disequilibrium
Improve tinnitus symptoms
80
Are humans particularly susceptible to noise induced hearing loss in the audible region?
Yes
Between 500 to 8000 Hz
81
Does the A-weighted network follow the human audibility curve?
Yes, has the heaviest weight between 500 and 8000 Hz
Used in sound level meters
82
Can damage to human hearing occur when subjected to an > 8-hour daily exposure of continuous sound at 85 dBA over a period of many years?
Yes
83
Is noise induced hearing loss caused by both dose (level of noise) as well as duration (amount of time)?
Yes
84
What is noise defined as?
Unwanted sound
85
Is the ability of noise to cause a hearing loss related to its desirability or unpleasantness?
No
Classical music played loud enough and long enough can cause as much damage as a chainsaw
86
Are high frequency sounds (up to 5000 Hz) more hazardous than low frequency sounds for NIHL?
Yes
Hearing protection devices also provide greater attenuation of high frequencies and less protection from low frequency sounds
87
Are very narrow-band sounds (such as pure tones) more hazardous than broad-band sounds?
Yes
Concentrated and more damaging
Broad-band noise over a longer duration, however, can cause widespread cochlear damage
88
What is the classic pattern for NIHL?
Noise notch
89
What is a noise notch?
Greatest threshold shifts are noticed at the basal end of cochlea between the 3000 and 6000 Hz region in response to BBN
Peak loss is typically at 4000 and 6000 Hz, improving at 8000 Hz
All sound has to go through basal end
Noise is rarely narrow band
90
Why is the noise notch vulnerable in the 3-6 kHz region?
Stronger mechanical forces due to cochlear geometry (more force generated at that area)
More tenuous blood supply of the cochlea (not as robust)
Just a hypothesis
91
Where is the maximum damage from noise exposure?
About 1/2 an octave above the stimulating frequency
For e.g., a 1000 Hz exposure frequency would cause a hearing loss at 1500 Hz
92
What is a threshold shift?
A change in hearing sensitivity from baseline
93
What are the two types of noise-induced threshold shifts?
Noise-induced temporary threshold shift (TTS)
Noise-induced permanent threshold shift (PTS or NIPTS)
94
What is a noise-induced temporary threshold shift (TTS)?
Reversible increase in auditory threshold following exposure to loud noise – swollen rootlets of stereocilia + hair cells
95
When does most TTS resolve?
After about 15 minutes but can persist for about 14 hours
96
What are the new findings about TTS?
Loud noise can result in hidden hearing loss (synaptopathy)
No permanent change to hearing thresholds
Damage to nerve or IHC
Residual problems
97
What is PTS?
A persistent change in hearing sensitivity persisting after ~14 hours
Permanence is assumed if change still observed on a 30-day follow up hearing test – tip links break; fractured and detached stereocilia
98
Does TTS and PTS vary with frequency, intensity, and temporal properties of the noise?
Yes
99
Does initial noise exposure result in TTS?
Yes
Experienced as a dull or muffled sound quality
For example, at the end of a work shift or loud concert
100
Does a daily dose of noise exposure cause TTS or PTS?
PTS
101
Are both TTS and PTS accompanied by tinnitus?
Yes
Temporary tinnitus after noise exposure may be a useful warning that PTS will occur if exposure continues without use of hearing protection devices (HPDs)
102
Is injury to the ME from noise rare?
Yes
Occurs only with extremely high levels of noise
103
What noise level can result in TM perf?
At or greater than 165 dB SPL
104
What noise level can result in an ossicular chain injury?
At or greater than 190 dB SPL
105
Can TM perfs be used as a sign of possible concussion in human victims of bomb blasts?
Yes
If the TM is perforated, more likely that the person has sustained a concussion from the blast
106
Can exposure to loud noise result in tinnitus?
Yes
107
What structure is most susceptible to noise in the cochlea?
OHCs
Initially, stereocilia lose their stiffness and, therefore, their ability to vibrate in response to sound
The result is a reversible hearing loss or TTS
After repeated hazardous levels of exposure, permanent damage occurs to stereocilia
Hair cell death ensues with PTS
108
T/F: The more intense and prolonged the exposure, the greater the degree of hair cell loss
True
Eventually, IHCs and auditory nerve fibers are also damaged/lost
109
Can noise levels that cause NIHL cause vestibular system injury?
Doubtful
110
Can acoustic trauma (different category of noise exposure) cause vestibular system injury?
Yes
Most patients present with a history of noise trauma and balance symptoms
For e.g., dizziness and vertigo
111
Can acoustic trauma patients also have coincidental causes for their vestibular problems?
Yes
112
Is clinical history crucial for diagnosing NIHL?
Yes
113
Should you do a medical examination to rule out NIHL from other causes of HL?
Yes
114
Is NIHL usually symmetrical?
Yes
But asymmetries of 15 dB HL of greater are not uncommon
Left sided hearing loss with right-handed shooting of weapons
Other causes of asymmetric SNHL (e.g., vestibular schwannoma) should be ruled out
115
Is profound SNHL rare in purely NIHL?
Yes
116
In NIHL, are low frequency thresholds are rarely worse than 40 dB HL?
Yes
117
In NIHL, are high frequency thresholds are rarely worse than 75 dB HL?
Yes
118
Can cessation of noise exposure cause a slower progression of the hearing loss?
Yes
119
Is most NIHL symmetric?
Yes especially if caused by occupational or recreational noise exposure
120
Can asymmetry be greater in the high frequencies (3000 to 6000 Hz)?
Yes, especially with long-gun firearm use because of the head shadow
121
When presbycusis meets NIHL, does the HL flatten?
Yes
122
What is the treatment for NIHL?
No effective treatment
123
What is the best management for NIHL?
Prevention
Environmental controls to reduce noise in the work-place
Use of hearing protection devices to minimize the level of noise exposure
For e.g., earmuffs and ear plugs
Musician earplugs, which can attenuate environmental noise by 15 to 25 dB but allow speech/music to be heard
124
Should you use appropriate amplification when a permanent hearing loss occurs?
Yes, to prevent it from worsening
125
Are the uses of anti-oxidants and other chemicals used to protect against NIHL?
Currently being investigated
126
Is acoustic trauma distinct from other forms of NIHL?
Yes
It is a sudden permanent hearing loss from a single event or exposure without intervening TTS
127
What is most acoustic trauma caused by?
Impulse noise (sudden, short duration very loud sounds)
Bombs/improvised explosive devices (IEDs)
Firearms and other weapons
Industrial blasts
128
What kind of injury does acoustic trauma cause?
Direct mechanical injury to the cochlea with or without perf
129
What sound intensity causes acoustic trauma?
165 to 190 dB SPL
Can rupture or produce hemorrhage of the TM
Disrupt or fracture the ossicular chain
130
Can impact noise greater than or equal to 140 dB SPL peak pressure result in PTS?
Yes
131
What are some signs and symptoms of acoustic trauma?
Visible TM perforation/hemorrhage on otoscopy
Audiometric results following acoustic trauma are similar to NIHL (noise notch at 3000 to 6000 Hz)
Type Ad tymp with absent ARTs if ossicular disarticulation (which can result in a mixed hearing loss)
132
Are there a variety of hearing configurations possible with acoustic trauma?
Yes
High frequency sloping configuration
Flat configuration (more common)
133
Can hearing loss from acoustic trauma improve over a 4 to 6 month period?
Yes
134
May surgery be required to repair TM and ossicles if they are damaged from acoustic trauma?
Yes
135
What are blast injuries caused by?
Indirect impact from a pressure wave generated by an explosion that causes an instant rise in pressure, creating a blast wave that starts at the site of the explosion and travels outward
136
When do blast waves occur?
When the compression of air in front of the pressure wave heats and accelerates air molecules, leading to a sudden increase in overpressure and temperature, which are transmitted into the surrounding environment as a propagating shock wave known as the blast wave
137
What is the most susceptible organ to primary blast injury?
The ear
138
What can blast injuries damage in the ear?
The entire auditory system, resulting in TM perforation, ossicular disarticulation, tinnitus, otalgia, hearing loss, and/or vertigo
139
Are otologic injuries often missed for blast injuries?
Yes
Highest priority is directed toward diagnosis and treatment of life-threatening injuries
140
What is the intracellular potential of hair cells?
-80 mV
The high K+ concentration in the endolymph creates a +80 mV endocohlear potential (EP) that couples with a -80 mV hair cell intracellular potential to create a differential potential of +160 mV
141
What is the endocochlear potential in the vestibular system?
About 5 to 10 mV
Resulting in a much smaller total potential difference
142
What are the two ways that hair cells are diplaced?
Shearing movement of the tectorial membrane (outer hair cells) or
Motion of the endolymphatic fluid (inner hair cells)
143
Does potassium flow down the electrical gradient into the cell from the endolymph, and then out the base of the cell into the perilymph?
Yes
144
What happens when the two fluids in the inner ear are allowed to mix?
Transduction is compromised
Resulting in hearing loss or vestibular dysfunction
Happens in Meniere's disease when the membranous labyrinth ruptures
145
What is responsible for the endocochlear potential?
Tight junction of the vascular endothelial cells and basal stria cells
Limit intercellular leakage
146
Will any cochlear disorder that disrupts the strial cell layers, channels, transporters, or gap or tight junctions reduce the endocochlear potential and result in hearing loss?
Yes
147
What hearing loss results from increased potassium transport in the endolymph or increased endolymph production?
Endolymphatic hydrops (meniere's)
148
What hearing loss results from decreased potassium transport in the endolymph or decreased endolymph production?
Endolymphatic xerosis (JLNS and connexin)
149
Do the majority of genetic disorders cause a permanent hearing loss due to impaired ion transport to the inner ear?
Yes
150
Is endolymphatic xerosis believed to be the most common genetic hearing loss in humans?
Yes
151
What do the connexin genes do?
Abnormalities in connexin gap junctions proteins
152
What do the JLNS genes result in?
They are responsible for producing proteins that make up the potassium channels on the apical stria
