Northeast Florida Medicine
Vol. 66, No. 1 2015
55
Otolaryngology
The ear canal can be the source of a conductive or mixed
hearing loss due to ear canal stenosis, the presence of exos-
tosis, or congenital atresia of the external auditory canal.
Another important potential cause for transient hearing
loss is otitis externa. Acute otitis externa is typically caused
by pseudomonas aeruginosa, which is normally present in
the external auditory canal, and results in infection in the
warm moist environment of the ear canal. This frequently
follows swimming, bathing or other water activities leading
to the accumulation of moisture within the ear canal.
7
It
is important to distinguish acute otitis externa from other
potential causes, and to assess for modifying factors such
as a tympanic membrane perforation, prior tympanostomy
tube placement, diabetes mellitus, immunocompromised
status, or the presence of prior radiotherapy. Assessment
for pain and use of analgesics is appropriate depending
upon the severity of symptoms. The use of oral antibiotics
is inappropriate unless there is evidence of spread of the
infection from the ear canal in the form of cellulitis or
possibly in the case of an immunocompromised patient.
Topical antipseudomonal otic drops are appropriate as
the initial therapy for otitis externa. It is also important
to enhance the medical delivery of the otic drops through
appropriate aural toilet by cleaning the ear canal and also
by the use of an otic wick. Non-ototoxic drops should be
used in the case of a non-intact tympanic membrane or if
a tympanostomy tube has been previously placed. A repeat
assessment is appropriate 48 to 72 hours later for these
patients. Diabetic or immunocompromised patients who
fail to respond to standard treatment should be assessed
for necrotizing otitis externa where osteomyelitis of the
temporal bone has developed.
The middle ear is another potential source of a conductive
or mixed hearing loss. Infectious etiologies predominate
with tympanic membrane perforations, cholesteatoma of
the middle ear, and tympanosclerosis as common problems
resulting in hearing loss. Effusions of the middle ear space
in children are extremely common and will be discussed
in more detail in the article by Drs. Maddern and Simon-
sen. Adults will also develop middle ear effusions, most
commonly due to eustachian tube dysfunction. Temporal
bone trauma may cause ossicular discontinuity resulting in
hearing loss. Congenital ossicular fixation is an uncommon
cause of hearing loss in children.
8
Otosclerosis, the most
common cause of a conductive hearing loss in middle age
adults, is the result of an abnormal balance of the process of
bony remodeling of the osteoclasts and osteoblasts within
the otic capsule.
9
The disproportion of certain cytokines
within the otic capsule is thought to be the cause of this
bony remodeling problem, and has led to the recent use of
bisphosphonates in patients with otosclerosis affecting the
neural function of the cochlea. Stapes surgery in the form
of stapedotomy or stapedectomy, which involves replace-
ment of the stapes bone, continues to be an appropriate
form of therapy for patients with a significant conductive
component to their hearing loss. This yields significant
hearing improvement in 85-90 percent of properly se-
lected patients.
10
Another commonly misdiagnosed form
of conductive hearing loss is that of superior semicircular
canal dehiscence syndrome.
11
These patients appear to
have a low frequency conductive hearing loss, but on CT
scanning of the temporal bone are found to have dehiscence
of the superior semicircular canal resulting in the loss of
sound pressure and noise-induced dizziness. Drs. Lundy
and Zapala discuss this problem in greater detail in their
article in this journal.
Great progress has been made in the diagnosis and treat-
ment of a variety of forms of sensorineural hearing loss.The
most common preventable form of sensorineural hearing
loss is that of noise induced hearing loss.
1
While liability
concerns have resulted in improvement in corporate and in-
dustrial noise exposure, noise exposure frommusic, military
work, and other hobbies such as hunting or woodworking
involve significant noise exposure and continue to be an
ongoing problem. The simple use of foam earplugs will
prevent a significant amount of noise-induced hearing loss.
Genetic causes of hearing loss are myriad and are better
understood than in the past. Studies of single nucleotide
polymorphisms in genome-wide association studies have
led to the identification of many genetic loci responsible
for hearing loss. More than 300 genetic loci have been
implicated with approximately 70 causative genes iden-
tified.
4
Most genetic hearing loss is nonsyndromic with
the majority being of the autosomal recessive variety.
12
The most common autosomal recessive cause is due to
JGB2 chromosomal changes with resultant malforma-
tion in the gap junction proteins within the cochlea.
13
This accounts for as much as 50 percent of patients with
congenital sensorineural hearing loss. Syndromic causes
of hearing loss are also fairly common with Waardenburg
syndrome, Usher syndrome, Pendred syndrome and Jervell
and Lange-Nielsen syndrome. Alport’s syndrome, which
is an X-linked syndromic cause of hearing loss, is asso-
ciated with kidney dysfunction. Mitochondrial genetic
abnormalities have been recently described, which fail to
follow traditional Mendelian genetics. Surprisingly, these
are only transmitted from the female and are as a result
of genetic material within the mitochondria, which may
be disordered. There is a significant variable expressivity
with this type of hearing loss. An excellent information
source for genetic hearing loss is the Hereditary Hearing
Loss Homepage.
14
Ototoxic causes of hearing loss are not uncommon and
thankfully have been reduced in the past several years.
These are primarily related to the use of aminoglycosides,
