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242 Disorders of the Auditory System
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Medical Recommendations
and Management
The patient underwent intratympanic
steroid injections and a short of course of
oral prednisone as well.
Additional Information
The patient responded well to treatment
with complete recovery of auditory function in the affected ear noted during a posttreatment evaluation and no subsequent
return of the hearing loss (Figure 5–11B).
Case 5–12: Sudden
Sensorineural Hearing Loss
History
A 31-year-old female who was 29 weeks
pregnant at the time of evaluation was
seen for evaluation due to a sudden leftsided hearing loss without any known
precipitating causes. She reported aural
fullness, mild tinnitus, and episodic vertigo. No other significant history was
reported.
Audiology
Medical Examination
The patient presented with an essentially
normal otolaryngologic examination.
Impression
Sudden left-sided hearing loss with unknown etiology.
Audiologic Recommendations
and Management
It was medically recommended that the
patient follow up with otolaryngology for
medical management.
Medical Recommendations
and Management
After consultation with her OB/GYN, the
patient underwent a short course of oral
prednisone and intratympanic steroid
injections.
Additional Information
The patient responded well to treatment
with complete recovery of auditory function and no residual hearing loss reported
(Figure 5–12B).
An otoscopic check was unremarkable.
Tympanograms were performed and revealed normal pressure, volume, and compliance for both ears, suggesting normal
middle ear status bilaterally (Figure 5–12A).
A comprehensive audiologic evaluation
demonstrated normal peripheral hearing
sensitivity in the right ear and a moderate low-frequency sensorineural hearing
loss in the left ear. Word recognition was
excellent bilaterally, and speech recognition thresholds were in good agreement
with the pure-tone averages.
otheR disoRdeRs
affecting the cochlea
There are many diseases/disorders that
can affect inner ear function, many of
which have been discussed earlier in this
chapter. In this section of the chapter,
some additional diseases/disorders are
discussed and/or expanded upon briefly.
Several of these conditions have been
mentioned in connection with some of the
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A
Figure 5–12. Pure-tone thresholds and speech audiometry for a 31-year-old female (Case 5–12)
at the time of an initial audiologic evaluation for a sudden sensorineural hearing loss (A) and then
following recovery (B). continues
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B
Figure 5–12. continued
5. Inner Ear Disorders 245
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disorders covered previously, but specific
information regarding topics such as etiologies, site of lesion, audiologic and/or
medical evaluation procedures, and management of these disorders were not necessarily discussed. The following is not
intended to be a comprehensive coverage
of the disorders included, but rather a
brief introduction to additional disorders
that can affect the inner ear to increase
awareness of these disorders and the need
to follow patients with these conditions
audiologically and/or medically.
Enlarged Vestibular
Aqueduct Syndrome
Enlarged vestibular aqueduct syndrome
(EVA), also referred to large vestibular
aqueduct, was first described by Valvassori and Clemis in 1978. They indicated
that a vestibular aqueduct was considered
enlarged if the aqueduct (the narrow canal
that courses from the inner ear into the
skull) becomes abnormally large (greater
than 1.5 mm in diameter from anterior to
posterior). The vestibular aqueduct itself
is housed within the temporal bone and
courses from the vestibule to the posterior
cranial fossa. The diagnosis of EVA normally occurs in childhood. While some
children with EVA present with relatively
stable hearing, the hearing loss can also
be progressive in nature in other children.
The exact incidence of EVA is unknown.
However, it is estimated that 15% of children with bilateral sensorineural hearing loss have EVA (Dabrowski, Myers, &
Daniliova, 2009) and that bilateral EVA is
six times more likely to occur than unilateral EVA (Mori, Westerberg, Atashband, & Kozak, 2008). The causes of EVA
are not fully understood, but it is known
that it may be a result of a mutation in
the SLC26A4 gene. There also is a strong
genetic link to Pendred syndrome (see
Chapter 9 for review). This gene is important for the cellular transport of iodine,
chloride, and bicarbonate anions (Gopen,
Zhou, Whittemore, & Kenna, 2011).
Medically, EVA is diagnosed with
either MRI and/or CT. Each imaging
modality provides different diagnostic
advantages. The MRI provides information regarding the membranous labyrinth, whereas CT reveals the bony labyrinth anatomy. It is recommended that
imaging be obtained for children with
a sudden change in hearing, asymmetric or unilateral hearing losses, or those
with hearing loss of unknown origin. The
audiologic evaluation is also a critical
component of the evaluation and subsequent management of patients with EVA.
Age-appropriate test procedures should
be employed and close monitoring of the
hearing loss should be provided.
Hearing loss associated with EVA has
a range of presentation. It is typically sensorineural in nature, with some patients
demonstrating a mixed loss. It can range
from mild to profound in severity. Reports
vary significantly regarding the stability and progression of the hearing loss
(Gopen et al., 2011). Mori and colleagues
(2008) report stable hearing in 67% of
affected ears and fluctuating hearing loss
in 33% of ears with this condition. There
is also significant variability in the report
of vestibular symptoms such as episodic vertigo and imbalance. Prevalence
rates for vestibular symptoms vary from
14% to 73% (see Ralli, Nola, Sparvoli, &
Ralli, 2017).
What has been relatively well established is the strong link to hearing loss
associated with head trauma (Colvin,
Beale, & Harrop-Griffiths, 2006; Okumura,
Takahashi, Honjo, Takagi, & Mitamura,
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1995). It is widely recommended that individuals diagnosed with EVA reduce exposure to head trauma by restricting certain
high-risk activities. For example, it may
be advised that contact sports be avoided.
While head trauma may not always be
avoidable, it is recommended that precaution be taken to avoid these events.
There is currently no standard medical treatment or intervention to halt the
progression of (or restore) hearing loss in
individuals with EVA. Hearing aids are
the first choice for audiologic management of individuals with EVA. However,
in patients with a progressive hearing
loss, hearing aids may not prove beneficial. In these instances, cochlear implantation is often recommended.
Barotrauma
Barotrauma is an injury that results from
increased air or water pressure. An estimated 80% of diving injuries affect the
head and neck (Klingmann, Praetorius,
Baumann, & Plinkert, 2007). This type of
injury is frequently associated with scuba
diving or flying, but it can also be caused
by blast exposure or hyperbaric oxygen
therapy. When it occurs in connection
with a scuba diving or flying activity,
the damage typically occurs as a result
of ascending or descending too quickly.
While barotrauma can affect multiple
systems (i.e., whole body decompression
sickness, pulmonary hemorrhage, sinus
injury etc.), this discussion will focus
solely on auditory involvement, which is
the most commonly reported occurrence.
As compared to other disorders of the
auditory system, the physiologic manifestation of barotrauma is relatively uncomplicated. Common symptoms associated
with barotrauma include otalgia (ear
pain), aural fullness, tinnitus, and a need
to “pop” the ears. In more severe cases,
vertigo and otorrhea (drainage of the ear)
can occur. Peripheral hearing impairment
can also be present, with the presence
and degree of hearing loss dependent on
the severity of the barotrauma (Glazer &
Telian, 2016).
There is a fundamental principle
referred to as Boyle’s law that is applied
to barotrauma. Boyle’s law states that
pressure of a given mass is inversely proportional to its volume if temperature
remains constant and the amount of gas
remains unchanged in a closed system.
A descending diver will experience an
increase in pressure resulting in a compression of the gas volume. This is why
divers are taught to perform a Valsalva
maneuver. This maneuver acts to equalize pressure between the outer ear and the
middle ear space. If one recalls the anatomy and physiology of the middle ear, in
an ideal environment, there is equal pressure on both sides of the tympanic membrane (i.e., middle ear versus external
auditory canal). In the case of barotrauma,
there is an inability to equalize pressure
between the atmosphere and the middle
ear. This results in a pressure differential
across the tympanic membrane where the
pressure in the ear canal and the middle
ear are no longer equal. Ear-related barotrauma can take on several forms. The
most common form of barotrauma is
middle ear barotrauma, also referred to as
barotitis media or “middle ear squeeze.”
It has been reported to account for more
than 40% of head-related diving injuries
(Klingmann et al., 2007). This may result
in middle ear edema and hemotympanum can occur (Glazer & Telian, 2016).
In more severe cases, the tympanic membrane may rupture. The most obvious
symptom at the time of rupture is severe
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otalgia. Barotrauma may also affect the
inner ear. This is considered far more
serious because of the potential for permanent damage to both the cochlear and
vestibular systems. Symptoms associated
with inner ear trauma include tinnitus,
vertigo, and sensorineural hearing loss.
This may be a result of a rupture of Reissner’s membrane, a fistula, or an inner ear
hemorrhage (Parell & Becker, 1985).
Unfortunately, there is little evidencebased guidance regarding the diagnosis
and treatment of barotrauma; however,
Livingstone, Smith, and Lange (2017) do
provide some recommendations for the
diagnosis and treatment of patients who
experience this condition (the reader is
referred to this reference for a full review).
Given the large range of clinical presentations, medical evaluation and management can vary significantly. For some
patients, they may self-diagnose and their
symptoms may resolve without medical
intervention. For others, particularly those
with more severe symptoms or symptoms that last a longer duration of time,
it is recommended that they seek medical
evaluation. Formal diagnosis is based on
the history and physical exam. This will
often include a thorough otoscopic and
audiologic (including tympanometry)
examination. If middle ear involvement
is present, treatment may include decongestants, and in more severe cases where
otorrhea is observed, antibiotic drops
are prescribed. If a tympanic membrane
perforation occurs, it may spontaneously heal within 1 to 3 months (Glazer
& Telian, 2016); however, in cases where
the tympanic membrane does not heal
on its own, a tympanoplasty procedure
may be indicated. In cases with inner ear
trauma, treatment can range from observation to surgical intervention, depending
on the extent of involvement. Whether it
be due to a diving incident or other activity where changes in pressure occur, clinicians are likely to encounter patients who
have experienced barotrauma.
Meningitis
A discussion of meningitis has been
included in this book due to the significant consequences it can have on the
auditory system. Meningitis occurs when
there is inflammation of the membranes
(meninges) surrounding the spinal cord
and brain. There are several causes but
the two most common types are a result of
either a viral or a bacterial infection, with
the later demonstrating the most devastating impact on the auditory system. For
this reason, the following discussion will
focus on bacterial meningitis as it relates
to the auditory system.
While rare, it is estimated that there
are approximately 4,100 new cases and
500 deaths per year associated with bacterial meningitis (Thigpen et al., 2011). In
adults, symptoms associated with meningitis include nausea and vomiting and
altered mental status. In infants and small
children, symptoms may include fever,
headache, irritability, and general lethargy. Hearing loss is common in children
and adults who have bacterial meningitis. The degree of hearing loss can range
from mild to profound. The incidence
rate in patients with bacterial meningitis
has been reported to be 14%, with 5% of
these patients presenting with profound
hearing loss and 60% with bilateral hearing losses (Rodenburg-Vlot, Ruytjens,
Oostenbrink, Goedegebure, & van der
Schroeff, 2016).
Evidence suggests that in cases where
hearing loss occurs, it does so early on in
its course (Richardson, Reid, Tarlow, &
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Rudd, 1997). Timely audiologic and otologic evaluation of individuals diagnosed
with bacterial meningitis is critical. This is
due to the fact that there can be partial or
complete obliteration of the cochlea in the
form of ossification. In patients who present with hearing losses severe enough to
meet cochlear implant candidacy requirements, implantation can be challenging,
if not impossible, especially if significant
ossification of the cochlea has occurred. It
is recommended that cochlear implantation occur prior to the onset of ossification
in order to optimize outcomes (Durisin
et al., 2015).
As with other disorders, audiologic
evaluation is age dependent. In children
who are too young to participate in a traditional audiologic examination, objective
measures such as electrophysiologic and
electroacoustic measures can be administered. If an ABR is completed, it is important to obtain ear- and frequency-specific
information in order to determine the
extent of audiologic involvement. For
older children and adults, a comprehensive audiologic evaluation is warranted.
With respect to the otologic examination,
perhaps the most important diagnostic
tool is imaging. This allows the physician
to determine the presence and extent of
any cochlear ossification. This information, in conjunction with audiologic test
results, will help guide the medical and/
or surgical management of patients with
this particular disorder.
Cytomegalovirus
Cytomegalovirus (CMV) is a common infection. By the age of 40, nearly half of all
adults will have been infected by the virus
(Centers for Disease Control and Prevention, 2019). In fact, it is the most common
intrauterine infection among women in
the United States (Akpan & Pillarisetty,
2019). While many adults may not even
be aware they’ve contracted the virus,
CMV in an infant can have devastating
consequences including hearing loss and
neurodevelopmental disabilities (Cannon,
Griffiths, Aston, & Rawlinson, 2014). The
following discussion will focus for the
most part on congenital CMV (cCMV);
that is, CMV acquired in-utero.
Pregnant mothers with CMV are
often asymptomatic. Approximately 21%
of pregnant women are symptomatic
(Picone et al., 2013). When symptoms do
occur in women, they are similar to those
of mononucleosis (malaise, headache,
lymphadenopathy, hepatosplenomegaly,
arthralgias, rash, and fever). The most
common complication associated with
cCMV is hearing loss, which makes it
the number one cause of nonsyndromic
hearing loss among children. The prevalence rate of cCMV in the United States
is reported to be approximately 40,000
new cases annually (de Vries et al., 2004).
According to the Centers for Disease Control and Prevention (2019), approximately
1 in every 200 infants is born with cCMV
and 1 in 5 will have long-term medical
problems, one of which is hearing loss. In
fact, it has been reported that 10% to 15%
of asymptomatic children will develop
sensorineural hearing loss (Ross, Novak,
Pati, & Boppana, 2011). Additional complications include microcephaly (small
head), intrauterine growth restriction
(low weight), jaundice, rash, hepatosplenomegaly (enlarged liver and spleen),
retinitis, and/or seizures (Centers for Disease Control and Prevention, 2019).
Diagnosis of cCMV can occur either inutero through amniocentesis in the prenatal period or from direct assessment of the
infant in the postnatal period. This can be
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accomplished through a variety of diagnostic approaches, but the recommended
procedure is through the application of a
PCR (polymerase chain reaction) test. This
is accomplished by obtaining a urine or
saliva sample and testing for viral DNA
and/or RNA loads. This approach has been
found to be a sensitive and rapid method
for the detection cCMV in the postnatal
period (Ross et al., 2011). Of note, however, is that diagnosis of cCMV must be
made in the first 21 days of life. After this
time, it not possible to determine if the
cause was congenital or acquired CMV.
The primary medical treatment
approach for infants diagnosed within
3 weeks of life is antiviral therapies
including valganciclovir (administered
orally) or ganciclovir (administered
through intravenous infusion). These
drugs are administered in an attempt to
arrest the progression of sensorineural
hearing loss. Administration of antiviral
therapy was found to either maintain
normal hearing or stop the progression of
hearing loss in 76% of infants when baseline test results were compared to results
obtained 6 months postbaseline (Kimberlin et al., 2003). Unfortunately, this treatment approach has significant side effects
including bone marrow suppression. For
this reason, in cases of severe hearing
loss noted at the time of baseline testing,
antiviral therapy will likely not be implemented due to the severity of the side
effects that may be encountered and the
limited benefits in regard to preservation
of hearing ability that are likely to be realized in these cases.
Due to the high incidence of hearing
loss among infants with cCMV, newborn
hearing screening can play an integral role
in early identification of the virus. One
approach that has been recommended and
implemented in some hospitals is targeted
screening for a cCMV infection whenever
a newborn fails his or her newborn hearing screening. Fowler and colleagues
(2017) studied nearly 10,000 infants across
7 medical centers in the United States over
a 5-year period. They found that 7% of
cCMV-positive infants did not pass their
newborn hearing screenings. Followup diagnostic testing confirmed hearing
loss in 65% of the infants who failed their
hearing screening. They also reported
that 3.6% of the infants who passed their
newborn hearing screening but who were
cCMV-positive on the screening test for
this viral condition were found to have
sensorineural hearing loss upon outpatient diagnostic follow-up (Fowler et al.,
2017). A more recent study that used targeted cCMV screenings in infants who
failed their newborn hearing screenings
reported a cCMV prevalence rate of 3.64%
(Beswick et al., 2019). In 2013, Utah was the
first state to mandate cCMV screening for
infants who failed their newborn hearing
screening. Currently, five states including
Connecticut, Iowa, New York, Utah, and
Virginia require targeted screening for
infants who fail their newborn hearing
screening. Illinois requires that CMV testing be offered to parents of infants who
fail their newborn hearing screening. In
addition to these statewide screening
programs, a number of birthing hospitals
in other states across North America have
adopted targeted CMV-screening programs (National CMV Foundation, 2019).
The audiologic presentation in individuals with cCMV varies significantly.
For individuals who acquire hearing loss
as a result of cCMV, the severity can range
from mild to profound, and both unilateral and bilateral involvement has been
observed. The risk of hearing loss is certainly higher in symptomatic infants as
compared to those who are asymptomatic.
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Hearing loss is the only indicator of the
virus in asymptomatic infants. Due to
the potential latent onset of hearing loss,
long-term and frequent audiologic monitoring is recommended for cCMV-positive
infants. Interestingly, the pathogenesis
of hearing loss has yet to be elucidated
(Cheeran, Lokensgard, & Schleiss, 2009).
Congenital CMV is a prime example
of a disorder that requires a multidisciplinary (infectious disease, otolaryngology, neurology, primary care, audiology,
etc.) team approach. The audiologist
plays an integral role in the evaluation,
management, and surveillance of infants
with cCMV. When an infant is diagnosed
with cCMV, the audiologist will be called
upon to perform an ABR to determine if
hearing loss has developed, and if so, to
what degree. Audiologic findings will
often guide the medical decision-making
process (i.e., to treat or not to treat). Once
a child is diagnosed with hearing loss,
appropriate audiologic management and
surveillance is crucial. Some children are
managed with hearing aids; however,
those with severe to profound hearing loss
may require cochlear implantation.
Congenital CMV is not only the most
common intrauterine infection, but is one
that can have devastating consequences.
There is a strong association between
cCMV and sensorineural hearing loss,
and for that reason, it is important for
the audiologist to have a comprehensive understanding of the disease and its
impact on auditory function.
Diabetes Mellitus
The information on hearing loss and/or
vestibular problems related to diabetes
is rather limited. One would think that
because of the well-known effects that
diabetes has on vision, reports on the
effects on the auditory system would be
as common, but this does not seem to be
the case. Certainly, there are individuals
with diabetes who likely have hearing
loss related to the disease, but these associations are not easily documented.
Data from the Centers of Disease
Control and Prevention (2017) revealed
that in 2015, an estimated 30.3 million
people in the United States had diabetes and an estimated 84.1 million adults
in the United States had prediabetes.
The most common subtypes of diabetes
include type I and type II diabetes. Type I
is an autoimmune disease where the cells
that generate insulin are destroyed. This
type of diabetes is sometimes known as
juvenile-onset diabetes, but it can occur
at any age; however, the onset of type I
diabetes is typically under 40 years of age.
Individuals with type I diabetes usually
must inject themselves with insulin daily.
Type II diabetes is the more common type
of diabetes, with 85% of the individuals
with this disease having this type, and it
has a strong genetic factor. It is commonly
treated with diet change, fitness activities,
oral medication, and in advanced cases,
insulin injections (National Institute of
Diabetes and Digestive and Kidney Diseases, 2016).
A third type of diabetes is referred to
gestational diabetes mellitus, which is a
carbohydrate intolerance condition that is
first diagnosed during pregnancy through
an oral glucose tolerance condition test.
Although the carbohydrate intolerance
often returns to normal after the birth, the
mother has a significant risk of developing postpartum glucose intolerance (Kjos
et al., 1990).
The etiology and pathology centers
around elevated blood glucose levels and
alterations of lipids and proteins. These
conditions are likely related to microangiopathy or damage to small blood ves-
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sels and possible atherosclerosis. These
vascular changes may affect the stria
vascularis and other small vessels in the
cochlea and central pathways (Lisowska,
Namysłowski, Morawski, & Strojek, 2001).
The incidence of hearing loss directly
related to diabetes is difficult to determine because it can be a challenge to
distinguish this pathology from other
etiologies that result in hearing loss (i.e.,
aging, noise exposure, etc.). Estimates of
the incidence of hearing loss in individuals with diabetes range from 10% to 55%
of the people diagnosed with the disease
(see Jerger & Jerger, 1981). However, a
more recent study reported a much higher
occurrence of hearing loss in those with
diabetes (Bainbridge, Hoffman, & Cowie,
2011). This study reported that roughly
two-thirds of their diabetes population
had hearing loss with the high frequencies
most commonly affected bilaterally. The
population in this study was in their midto late 50s; hence, hearing loss related to
aging as well as other factors could have
inflated these results.
The pathology in diabetes is vascular
in nature; hence, either the cochlea or the
auditory nervous system can be involved.
Typically, a bilateral sensorineural loss is
noted in individuals with diabetes, but
overall, this trend has been inconclusive.
Dizziness may be present in approximately one-fifth of the patients with diabetes. Tympanograms are usually normal
bilaterally, and results of acoustic reflex
testing vary depending on the site of maximum involvement and the degree of loss
(i.e., they can align with either cochlear or
retrocochlear findings) (Jerger & Jerger,
1981). Auditory brainstem response abnormalities are also common in this
population of patients. Konrad-Martin
et al. (2010) found ABR results to be different for a diabetes group and a control
group that included individuals less than
50 years of age in both study groups. In
this study, the absolute latency of wave V
was found to be delayed, as was the I–V
interwave latency for the diabetes group.
It also has been reported that the ABR
reveals slower conduction times in individuals with diabetes but without hearing
loss (Lisowska et al., 2001). Specifically,
delays of wave I and extensions of the I–V
interwave intervals were reported in this
study, indicating possible cochlear and/or
retrocochlear involvement. Recent work
has also shown that DPOAE fine structure
is reduced (amplitude reduction) in those
with type I diabetes compared to a control group. Hearing sensitivity, however,
between the groups did not differ, which
is a result consistent with the findings
reported in much of the previous literature (Spankovich, Long, & Hood, 2019).
Perilymph Fistulas
Perilymph fistulas, also referred to as perilymphatic fistulas, are leaks of perilymph
usually from either the oval or round window. (Superior canal dehiscence, which
was discussed earlier in this chapter, is
also considered a perilymph leak.) These
leaks can be located at the ligament-type
tissue around the oval window or can be
a result of a tear in the round window.
Leaks in perilymph from either site often
result in symptoms of hearing loss and/or
imbalance or dizziness. These symptoms
may increase with activity and subside
with rest. The diagnosis of perilymph fistula at times is difficult and controversial
because the condition often cannot be
confirmed — even at surgery.
Perilymph fistula is considered a rare
disorder with an unknown prevalence.
The etiology of perilymphatic fistula is
broad based. Chief among possible causes
are head trauma, barotraumas (deep sea
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