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M. A. AlShawabkeh et al.
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Fig. 1.2 (a) Normal speech audiogram. (b) Speech
audiogram for a patient with CHL. (c) Speech audiogram
for a patient with a cochlear lesion notice that WRS has
reached a plateau and maintained at that level. (d) Speech
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audiogram for a patient with retrocochlear lesion, notice
how WRS did not maintain at that plateau, and it fell
down; this condition is called Roll Over
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Air pressure in mmH
Fig. 1.3 Different types of tympanogram: Type A: nor-
mal tympanic compliance, Type As: increased stiffness of
the tympano-ossicular system indicative of ossicular xation, Type Ad: hypermobile drum indicative of ossicular
discontinuity. Type B: suggestive of a glue ear. Type C:
negative pressure in the middle ear space (nasal congestion, or ear infection). (Adapted from Mansour S., Magnan
J., Nicolas K., and Haider H. (2018). Middle ear disease)
+200
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1 General Audiology
9
called Acoustic reex. It will occur if the sound’s
intensity is 70–100dB SL.The Arc of this reex
is like the following:
• The sound will pass to the cochlea, and then
it will go to the ipsilateral cochlear nucleus
via CN VIII. From there, it will go to the
trapezoid body. Then the signal will pass
from the trapezoid body to the bilateral superior olives. After that, it will go to the facial
nuclei, and then it stimulates the stapedial
muscle via CN VII.
• The acoustic reex is an objective study. It is
measured by introducing a sound at different
frequencies (500, 1000, and 2000Hz) in any
of the ears, and the change of compliance for
both ears will be detected via a probe.
Acoustic Reex Interpretation
1. In the case of unilateral SNHL: if hearing loss
is more than 60dB in one ear, then acoustic
reex will be absent in both ears if the signal
was introduced in that ear. However, there will
be bilateral acoustic reex if the signal was
presented in the normal ear.
2. In the case of unilateral CHL: the reex will
be absent in both ears if the sound is introduced in the ear with the CHL.However, if the
sound is introduced in the normal ear, the
reex will be only in that ear and absent in the
other ear (as ossicles cannot transmit the stapes signal to the TM).
3. In the case of unilateral facial nerve palsy:
If the signal is introduced in the ipsilateral
ear with the facial palsy, then acoustic reex
will be absent in that ear but present in the
other ear. If the signal is introduced in the
other ear, bilateral acoustic reex will happen. Acoustic reex can be valuable in cases
of facial palsy, as the return of that reux
can indicate the return of the facial nerve
function, and that will show a favorable
prognosis.
4. In the case of brainstem injury: Acoustic
reex will happen only in the stimulated ear,
that is, there will be no crossover of the
signal.
Stapedial reex decay: It happens in CN VIII
lesion. In that condition, if the signal is introduced to the diseased ear 10dB above the acoustic reex threshold and it is sustained for 10s, the
reex amplitude will go down to 50%.
Other uses of acoustic reex are in testing
infants and young children and detecting
malingering.
1.4 Special Tests ofHearing
1.4.1 Otoacoustic Emissions (OAE)
The normal outer hair cells will emit lowintensity sounds, either spontaneously (which is
called spontaneous OAE and presents in 40–60%
of the normal ears) or acoustic stimulation
(called evoked OAE). The spontaneous OAE is
present in 40–60% of normal. The evoked OAE
can be:
1. Stimulus Frequency OAE: It is generated after
a stimulus with a particular frequency
(low-tone).
2. Transiently Evoked OAE (TEOAE): It is gen-
erated after a broadband tone stimulus (click),
which is presented at 80–85dB SPL.It is indi-
cated in cases of neonatal screening as its
presence will suggest a hearing threshold of at
least 20–40dB.
3. Distortion Product OAE (DPOAE): It is gen-
erated after applying two stimuli with two dif-
ferent pure-tone frequencies. DPOAE can test
hearing at higher frequencies (1000–8000Hz).
It is indicated in neonatal screening, noise-
induced hearing loss, and ototoxicity [5].
OAE is absent in cases of cochlear SNHL
>30dB, and middle ear diseases.
OAE is an objective study and can be used in:
1. Neonatal screening.
2. Monitoring Ototoxicity.
3. Noise-induced hearing loss.
4. Distinguishing cochlear from retrocochlear
hearing loss.
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M. A. AlShawabkeh et al.
5. Detecting Auditory Neuropathy; a condition
where the patients have abnormal ABR but
normal OAE.
1.4.2 Auditory Brainstem Response
(ABR)
Other names for this test are Brainstem Auditory
Evoked Response or potential (BAEP) and
Brainstem Evoked Response Audiometry
(BERA).
Auditory stimulation will generate an electri-
cal response in the VIII cranial nerve and the
brainstem. ABR is a test that can detect this
electoral response. It is composed of three electrodes, a positive electrode put on the high forehead, a negative electrode put on the ipsilateral
mastoid, and a common electrode put on the
contralateral mastoid. ABR utilizes a stimulus
that will generate a stimulus that travels all
through the auditory pathway. The stimulus can
be a broadband frequency spectrum (click ABR)
or frequency specic 500, 1000, 2000, and
4000Hz (tone burst ABR). The response will be
collected as waves; each wave will indicate a
specic anatomical site from which it was generated as the following:
• Wave I: Distal part of CN VIII.
• Wave II: proximal part of CN VIII.
• Wave III: Cochlear nucleus.
• Wave IV: superior olivary complex.
• Wave V: Lateral lemniscus.
• Waves VI and VII: inferior colliculus.
• Normal values for interpeak I–III intervals
is 2ms, III–V is 2ms, and I–V is 4ms.
3. Interaural wave V latency:
• It is abnormal if more than 0.4ms.
1.4.2.2 ABR Interpretation
1. Wave I is absent or delayed: cochlear lesion.
2. Wave V is absent or delayed: upper brainstem
lesion.
3. I–III inter-peak latency prolongation: lower
brainstem lesion.
4. III–V inter-peak latency prolongation: upper
brainstem lesion.
5. I–V inter-peak latency prolongation: whole
brainstem lesion.
1.4.2.3 ABR Interpretation According
totheType ofHearing Loss
1. Normal hearing: all the parameters are within
normal values.
2. CHL: delayed absolute latencies, especially
for wave I.
3. Sensory hearing loss: Delayed absolute latencies. Wave I is absent. Interpeak latencies are
within normal limits. Waves have poor
morphology.
4. Neural hearing loss: Delayed absolute latencies except for wave I, which is within normal
limits. Interpeak latencies are delayed. Waves
have poor morphology.
ABR threshold testing: by utilizing Click
stimuli: 1000–4000Hz. Trace Wave V starting at
an 80dB, and then continue down until wave V is
no longer seen (30–20dB).
1.4.2.1 Parameters Used inABR
1. Absolute latencies, look at Table1.6.
2. Interpeak intervals (interwave latencies):
Table 1.6 ABR absolute latencies
Wav e Latency (ms)
Wav e I 1.5
Wave II 2.5
Wave III 3.5
Wave IV 4.5
Wav e V 5.5
Wave VI 6.5
1.4.2.4 Factors Aecting ABR
1. Age: In infants, the absolute latency of wave
III and V is longer than adults [6].
2. Gender: females have shorter latencies for the
waves III and V [7].
3. Some pharmacological medications like phenytoin, lidocaine, and alcohol can affect
ABR. However, sedatives, general anesthetics, and neuromuscular blocking agents do not
affect ABR.
4. Body temperature: the decreased temperature
will increase the latencies [8].
1 General Audiology
11
1.4.2.5 Application ofABR
1. Auditory threshold testing.
2. Identifying the hearing loss.
3. Classication of type of deafness (conductive
or sensorineural).
4. Neonatal hearing screening.
5. Identication of retrocochlear pathology.
6. Neurosurgical interoperative monitoring.
1.4.3 Electrocochleography (ECoG)
An electrode is inserted at the promontory
through the TM; it will measure the electrical
potential that arises from CN VIII and the
cochlea. These potentials are:
1. Cochlear microphonic (CM): it is the alternating current that arises from the outer hair
cells.
2. Summating potential (SP): it is the direct current that arises from the stria vascularis and
the hair cells.
3. Compound action potential (AP): it is the
summation potential of many nerve bers.
Clinical Applications of ECoG
1. Diagnosis and monitoring patients with
Meniere’s disease: the SP/AP ratio will be
above 30%.
2. Intraoperative monitoring of peripheral auditory pathway.
3. Auditory neuropathy detection.
4. Differentiates cochlea from retrocochlear
lesions.
5. Detecting hearing threshold for infants and
young children.
1.4.4 Other Tests Like
(a) Alternate binaural loudness balance test: It
is a test to detect recruitment. In this test, a
tone is applied to the deaf and normal ears in
an alternating way. The intensity of the sound
in the deaf will start at 20dB above its threshold, and then it will be increased by 20dB
until the loudness will match the normal ear.
The initial difference between the deaf ear
and normal ear will be maintained throughout the test in the conductive and neural deafness. However, in cochlear lesion, recruitment
may be seen.
(b) Short Increment Sensitivity Index (SISI): In
this test, a continuous tone will be presented
to the patient at 20 dB above the threshold
and continues for 2min, and every 5s, there
will be an increase in the intensity of the
sound by 1dB.Patients should indicate when
this increase in sound’s intensity will happen. Interpretation: in the cochlear lesion,
SISI score will be 70–100%, while in neural
hearing loss, SISI score will be between 0%
and 20%, and in CHL, SISI score will be less
than 15%. The main concept of this test is
based on the fact that patients with cochlear
hearing loss will have an increased ability to
distinguish smaller changes in sound’s
intensities.
(c) Threshold Tone Decay Test: In this test, a
tone with 4000Hz frequency is presented to
the patient continuously for about 60s. The
intensity of that tone will be 5dB above the
patient’s hearing threshold. The patient
should be able to hear the sound continuously till the end of the 60s. If he is not able
to do that, then the sound intensity will be
increased by 5 dB, and the test will be
repeated similarly until the patient will be
able to hear the sound for the whole period.
The result is expressed of dB decay. If the
decay is more than 25dB, then this indicates
a retrocochlear lesion.
Take-Home Messages
• Audiological tests should always be
taken as a battery of tests and not relying
on a single test as this will help to give a
whole picture of the patient.
• Tuning forks can be used in different
clinical hearing assessment tests like
Weber, Rinne, Bing, Absolute bone conduction, Schwabach, and Gelle tests. It
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M. A. AlShawabkeh et al.
is essential to know how to interpret the
results of these tests, especially the
results of Weber and Rinne tests.
• Pure tone audiometry and speech audiometry are audiometric tests used commonly in clinical practice. Hearing level
is the most common reference used in
audiometers.
• Masking, which is a narrow-band noise
for pure-tone audiometry or wideband
noise for speech audiometry applied to
the non-tested ear, will prevent the
crossover of the signal from the tested
ear to the other ear; it is used in some
instances.
• Tympanometry and acoustic reex are
Immittance/Impedance tests. There are
ve types of tympanogram graphs: A,
As, Ad, B, and C.
• Patients with recruitment, which is an
abnormal growth of loudness, have a
reduced dynamic range, and they are
poor candidates for hearing aid.
• OAE spontaneous or evoked. The
evoked OAE is either Transiently
Evoked OAE or Distortion Product
OAE.OAE is an objective test that can
be used in neonatal screening, monitoring ototoxicity, noise-induced hearing
loss, distinguishing cochlear from retrocochlear hearing loss, and detecting
Auditory Neuropathy.
• Other nomenclatures for ABR are
Brainstem auditory evoked response or
potential (BAEP) and brainstem evoked
response audiometry (BERA). It is an
objective study that measures the electrical response in the VIII cranial nerve
and the brainstem after a signal stimulation. It can be used for testing the auditory threshold, identifying hearing loss,
classication of the type of deafness
(conductive or sensorineural), neonatal
hearing screening, identication of retrocochlear pathology, and during neurosurgical interoperative monitoring.
• Electrocochleography has a clinical
application in diagnosis and monitoring
patients with Meniere’s disease, where
the SP/AP ratio will be above 30%.
• Alternate binaural loudness balance
test, Short Increment Sensitivity Index
(SISI), and Threshold Tone Decay Test
are other audiological tests sometimes
used in clinical practice.
References
1. Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd ed. Sunderland, MA: Sinauer
Associates; 2001. The Audible Spectrum.
2. Hearing loss and deafness: normal hearing and
impaired hearing. InformedHealth.org [Internet].
Cologne, Germany: Institute for Quality and
Efciency in Health Care (IQWiG); 2006. 2008 May
15 [Updated 2017 Nov 30].
3. Wahid NWB, Attia M. Weber Test. [Updated 2020
Feb 14]. In: StatPearls [Internet]. Treasure Island, FL:
StatPearls Publishing; 2020. Available from: https://
www.ncbi.nlm.nih.gov/books/NBK526135/
4. Flint P, Haughey B, Lund V, Niparko J, Robbins K,
Regan Thomas J, Lesperance M.Cummings otolaryngology. 6th ed. Philadelphia: Elsevier; 2014.
5. Abdala C, Visser-Dumont L.Distortion product otoacoustic emissions: a tool for hearing assessment and
scientic study. Volta Rev. 2001;103(4):281–302.
6. Sharma M, Bist SS, Kumar S.Age-related maturation
of wave V latency of auditory brainstem response in
children. J Audiol Otol. 2016;20(2):97–101. https://
doi.org/10.7874/jao.2016.20.2.97.
7. López-Escámez JA, Salguero G, Salinero J.Age and
sex differences in latencies of waves I, III and V in auditory brainstem response of normal hearing subjects.
Acta Otorhinolaryngol Belg. 1999;53(2):109–15.
8. Gold S, Cahani M, Sohmer H, Horowitz M, Shahar
A. Effects of body temperature elevation on auditory nerve-brain-stem evoked responses and EEGs
in rats. Electroencephalogr Clin Neurophysiol.
1985;60(2):146–53.
Part II
Otology/Neurology
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Temporal Bone Imaging
Karen Nicolas and Ahmed Elsotouhy
2
Abbreviations
CBCT Cone-beam CT
CPA Cerebellopontine angle
CSF Cerebrospinal uid
CSOM Chronic suppurative otits media
CT Computed Tomography
EAC External auditory canal
IAC Inner auditory canal
IAC Internal auditory canal
LSCC Lateral semicircular canal
LVA Large vestibular aqueduct
MDCT Multidetector-CT
ME Middle Ear
MRI Magnetic Resonance Imaging
OW Oval window
PSCC Posterior semicircular canal
RW Round window
SSCC Superior semicircular canal
TB Temporal Bone
TM Tympanic membrane
K. Nicolas (*)
MEIH Hospital Mount Lebanon and Lebanese
University, Beirut, Lebanon
A. Elsotouhy
Neuroradiology Department, Hamad Medical
Corporation, Doha, Qatar
Key Points
• The main CT Imaging modalities as
MDCT and CBCT are described with
advantages and inconvenients. MRI is
described with its general imaging
characteristics, main sequences for temporal bone imaging, and dedicated
sequences for special pathologies. MRIContraindications are briey reviewed.
• CT-Anatomy and MRI-Anatomy are
demonstrated on several slices through
the main anatomic regions of the temporal bone by both techniques.
• A systematic reading structure is proposed, that approaches the temporal
bone from outside to inside, and determines for each anatomic site the essential structures to evaluate. Key images,
the most adapted reconstruction plane,
and pathologic manifestations at each
anatomic site are described and
illustrated.
• The temporal bone surfaces and surroundings are often involved by spread
of temporal bone pathologies: especially infectious pathologies, as necrotizing otitis externa and chronic
suppurative otitis media (CSOM) with
or without cholesteatoma tend to extend
beyond. Also the tegmen is a predestinated site of weakness in patients with
© Springer Nature Switzerland AG 2021
A. Al-Qahtani et al. (eds.), Textbook of Clinical Otolaryngology,
https://doi.org/10.1007/978-3-030-54088-3_2
15
16
poor mastoid development or lysis and
pathologic communications through
the tegmen are described. Further entities are tumors involving the IAC or
glomus tumors that have been
illustrated.
• Postoperative imaging ndings are
briey illustrated for ossicular reconstructions and stapes prosthesis. The
important role of MRI diffusionweighted imaging for residual/recurrent
cholesteatoma is pointed out, also for
associated complications to be aware of,
during surgical revision. Follow-up after
intervention for vestibular schwannoma
is a long-term survey that needs reproducible exact measurements of slow
growing residues.
2.1 Introduction
Imaging technology has greatly improved over
the last two decades; high-resolution CT has been
overcome by multidetector CT techniques and
more recently complemented by Cone-beam CT
(CBCT) with its lesser radiation and higher resolution for some middle ear structures.
MR imaging has been developed to thinner
slices and 3D imaging, with specic sequences
for otologic and neurotologic pathologies.
Thus, imaging nowadays is one of the basic
diagnostic mainstays of temporal bone pathology
to orient surgical indications and elucidate possible anatomical abnormalities. In consequence,
the preoperative and postoperative counseling of
the patients is rendered more informative and
enlightened.
Principal imaging methods, basic anatomy,
and essential imaging keys are presented.
It remains that adequate communication
between the clinician and the radiologist is a
prerequisite to select the best imaging protocol. Finally, the postoperative feedback from
the clinician to the radiologist constitutes the
main source of improvement of diagnostic
expertise.
K. Nicolas and A. Elsotouhy
2.2 Temporal Bone Imaging
Techniques
2.2.1 MDCT (Multidetector-CT)
2.2.1.1 CT Acquisition and Processing
Acquisition of a data volume of the temporal
bone is actually done by slice thicknesses of 0.5–
0.6 mm or less, that permit standard reformation
of thin slices on each ear alone in the axial
(Fig.2.1) and coronal plane (Fig. 2.2). The standard axial plane is reached when the whole LSCC
is visible on one slice (Fig.2.1d).
Most common supplementary reformations are
• “Axial stapes” plane: to evaluate the whole sta-
pes and footplate on one image (Fig. 2.3) [1].
• Poeschl plane: to evaluate the bony coverage
of the SSCC (Fig. 2.4), if doubtful on the coronal plan.
• Sagittal plane: to assess relation from malleus
head and anterosuperior wall of the tympanic
cavity.
Injection of iodine contrast is almost never
required, except for suspected vascular lesions.
• Advantages of MDCT: short examination
time, modality almost everywhere available,
providing an overall view on the two temporal
bones, the nasopharynx, most parts of the
sinuses, and the base of skull.
• Inconvenients of MDCT: Considerable radia-
tion exposure, especially in children, and
important metallic artifacts from several prosthesis or cochlear implants.
2.2.2 CBCT (Cone-Beam CT)
It is a recent imaging method based on a cone of
radiation turning around the patient (instead of the
X-ray fan beam rotating spirally around the patient).
Preliminary results of institutions that use already
CBCT in their daily practice conrm its utility [2]
and further implementation as a second and complementary imaging method is predictable.
2.2.2.1 Advantages
• Radiation is less (several former studies esti-
mated the difference at least 3–10 times less
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ab
cd
2 Temporal Bone Imaging
17
Fig. 2.1 Main anatomic structures on consecutive axial
CT cuts from a to d of the middle ear from caudal to cranial. (1) Malleus, (2) Incus, (3) Stapes, (4) Tensor tympani
muscle, (5) Cochleariform process, (6) Last turn cochlea,
(7) Mid turn cochlea, (8) Basal turn cochlea, (9)
Labyrinthine portion N VII, (10) Geniculate ganglion,
(11) Tympanic portion of N VII, (12) Sinus tympani, (13)
Stapedial muscle, (14) Facial recess, (15) PSCC, (16)
LSCC (standard plan), (17) Cog, (18) Modiolus. AER
anterior epitympanic recess, EAC external auditory canal,
M mastoid, RW round window, IAC internal auditory
canal, V Vestibule, OW oval window, A antrum, ATT attic
for CBCT versus MDCT [3, 4]), but exact
evaluation of radiation dose is much difcult,
probably underestimation of the CBCT dose
because of its beam geometry that cannot be
fully evaluated by the standard dose evaluation of MSCT [5–7].
• Strikingly higher spatial resolution for interfaces with high difference of density (air-bone
or air-tissue-contrast) has been shown, especially in cadaveric specimen [8, 9] with excellent visibility of ossicular chain and
articulations [10], also cochlear anatomy and
the facial nerve.
• Much less metallic artifacts than MDCT [8,
11] predestinating CBCT for prosthesis and
cochlear implant controls [12].
18
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abc
K. Nicolas and A. Elsotouhy
Fig. 2.2 Anatomy on coronal CT slices from a to c from
anterior to posterior: (1) Scutum, (2) Malleus handle, (3)
Malleus neck, (4) Incus body, (5) Incudo-stapedial joint,
(6) Stapes, N VII facial nerve, (8) SSCC, (9) LSCC, (10)
a
c
b
Fig. 2.3 Axial stapes plan: (a) on axial CT, the red refer-
ence parallel to the footplate for reconstruction → obtain
(b): Second red reference line along the stapes axis (red
Recess towards the round window. EAC external auditory
canal, Ty tympanic membrane, IAC internal auditory
canal, SPS superior petrosal sinus, OW oval window, RW
round window, Teg tegmen
dotted line) → obtain (c): axial stapes plan with the whole
stapes on one slice. Thin footplate (P) between the two
black arrows
2.2.2.2 Inconvenients
• Although CBCT has high specicity for oto-
• Small eld of view enables only one side
examination per acquisition.
sclerosis, its sensitivity for inactive, sclerotic
foci was found to be very low [13]. Others
stated that more fenestral lesions were found
2.2.3 MR Imaging
by MSCT than by CBCT, whereas retrofenestral lesions were equally diagnosed by both
techniques [14].
• Lack of soft-tissue contrast resolution limits
the use of CBCT in general diagnostic imaging of the temporal bone [10].
2.2.3.1 General MR Imaging
Characteristics
• 1.5 Tesla MRI, most available and providing a
good standard image quality and evaluation of
any anatomic region of head and neck.
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