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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4518_Библиотеки_им_академика_М_И_Перельмана
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12 Head andNeck Pathology
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12. Asa SL, etal. Middle ear “adenoma”: a neuroendocrine tumor with predominant L cell differentiation. Endocr Pathol. 2021;32(4):433–41.
13. Majewska A, Budny B, Ziemnicka K, Ruchała M, Wierzbicka M.Head and neck paragangliomas- a genetic overview. Int J Mol Sci. 2020;21(20):7669.
14. Thompson LDR, Magliocca KR, et al. CAIX and pax-8 commonly immunoreactive in
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15. Bai Y, Kakudo K, Jung CK.Updates in the pathologic classication of thyroid neoplasms: a
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Part IV
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Otology
Chapter 13
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Basic Science oftheTemporal Bone
andAudiology
StanleyPelosi
Pearls
• Differences in the embryonic origin and timing of gestational development mean
that disorders affecting the inner ear are less likely to have coexisting external
ear/middle ear abnormalities.
• The pure tone average (PTA) is the average of hearing sensitivity at 500, 1000,
and 2000Hz.
• Cochlear implants convert sound into an electrical signal to stimulate the cochlear
nerve directly.
Basic Science oftheTemporal Bone
• External/middle ear embryology
– Auricle
Begins development in the fth to sixth gestational week
Six hillocks of His are derived from rst/second branchial arches
First arch→hillocks 1–3→tragus, helical crus, helix
Second arch→hillocks 4–6→antihelical crus, antihelix, antitragus
– External auditory canal, tympanic membrane, middle ear
External auditory canal develops from rst branchial groove (ectoderm,
begins in the sixth week)
Eustachian tube and middle ear develop from rst branchial pouch
(endoderm)
S. Pelosi (*)
Long Island Jewish Medical Center, Donald and Barbara Zucker School of Medicine at
Hofstra/Northwell, New Hyde Park, NY, USA
© Springer Nature Switzerland AG 2023
F. Y. Lin, Z. M. Patel (eds.), ENT Board Prep,
https://doi.org/10.1007/978-3-031-26048-3_13
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Tympanic membrane: derived from rst branchial groove ectoderm (epithelium), mesoderm (brous layer), rst branchial pouch endoderm
(mucosa)
Malleus: rst arch, head and neck (epitympanic portions); second arch,
manubrium
Incus: rst arch, body and short process (epitympanic portions); second
arch, long process
Stapes: second arch, suprastructure and middle ear portion of footplate;
otic capsule, vestibular portion of footplate, annular ligament
• Inner ear embryology
– Ectodermal thickening → otic placode (third week) → otic pit (fourth
week)→otic vesicle (end of fourth week).
– Otic vesicle forms membranous labyrinth.
– Mesenchyme surrounding membranous labyrinth forms otic capsule (ninth
week, initially cartilage and then ossies later in gestation).
– Vestibular side of stapes footplate develops from the otic placode and is one
of the most common sites for development of otosclerosis (ssula ante
fenestrum).
– Differences in embryonic origin and timing of gestational development mean
that disorders affecting the inner ear are less likely to have coexisting external
ear/middle ear abnormalities.
S. Pelosi
• External auditory canal and temporal bone surface anatomy
– External auditory canal
Lateral third is cartilage; medial two-thirds is bone.
Multiple cranial nerves contribute to auricle/external auditory canal sensation including V3, VII, IX, X, greater auricular nerve, and lesser occipital nerve.
Tympanic bone forms incomplete ring, tympanomastoid suture (posteriorly), and tympanosquamous suture (superiorly/anteriorly).
Fissures of Santorini: vertically oriented ssures in the anteroinferior cartilaginous canal that allow spread of infection or tumor between the EAC
and parotid gland.
Persistent foramen tympanicum (foramen of Huschke) occurs in approximately 5% of population, results from incomplete fusion of tympanic ring,
and provides a potential communication for spread of infection or tumor
from the external auditory canal to the infratemporal fossa.
– Tympanic membrane
Layers: squamous epithelium, radiating and circular brous layers, mucosal layer
~1cm diameter
Pars tensa: organized brous layer, stiff
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Pars accida: disorganized brous layer, less stiff, and therefore prone to
retraction and primary cholesteatoma formation
Annulus brosus: thickened peripheral rim of the pars tensa
Notch of Rivinus: small posterosuperior defect in bony annular ring
– Temporal bone surface and mastoid
Temporal line: approximates level of tegmen
Spine of Henle: used to identify posterior wall of external auditory canal
Suprameatal (Macewen’s) triangle: external landmark for antrum
Köerner’s septum: bony plate separating squamous and petrous air cells of
temporal bone
Donaldson’s line: imaginary line from lateral canal posteriorly through
posterior canal to sigmoid, identies endolymphatic sac just inferior to line
Facial recess: triangle formed by incudal buttress, facial nerve, and
chorda tympani
Arcuate eminence: bony prominence in middle fossa suggesting location
of superior semicircular canal
– Middle ear anatomy
Malleus: subunits include manubrium (handle), umbo (tip of handle), neck
(attaches to tensor tympani), and head (articulation with incus); has anterior, superior, and lateral malleolar ligaments (can ossify causing malleus
xation).
Tensor tympani muscle (innervated by V3): muscle is parallel to eustachian tube; muscle tendon attaches to malleus neck via cochleariform
process.
Incus: subunits include body (articulates with malleus), short process, long
process, and lenticular process (articulates with stapes head).
Stapes: head, neck (attaches to stapedial tendon), anterior/posterior crus,
footplate.
Stapedial muscle (innervated by CN VII) is parallel and medial to
facial nerve.
Stapes attaches to bony oval window via annular ligament.
Eustachian tube: posterior third osseous, anterior two-thirds cartilage; tensor veli palatini (V3) dilates eustachian tube and tenses soft palate, levator
veli palatini (CN X) attaches to eustachian tube and elevates soft palate,
more horizontal in young children (predisposes to reux of secretions and
serous otitis media); muscles do not function properly in children with
cleft palate; predisposes to serous otitis media.
Promontory: prominence of bone overlying cochlea on medial wall of
middle ear, contains Jacobson’s nerve (from glossopharyngeal nerve, contains salivary bers to parotid gland).
Sinus tympani: portion of posterior middle ear medial to facial nerve
between the subiculum and ponticulus; common site of residual cholesteatoma due to difcult visualization.
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Epitympanum: Prussak’s space bordered laterally by pars accida
(Shrapnell’s membrane), medially by head of malleus, inferiorly by malleus lateral process, anteriorly/superiorly by lateral malleal fold; most
common site of primary acquired cholesteatoma.
Ponticulus: bony ridge from pyramidal eminence to promontory.
Subiculum: bony ridge bordering round window niche posteriorly
Iter chordae anterior (canal of Huguier) and posterior: anterior and posterior sites of chorda tympani entry to mesotympanum.
– Inner ear anatomy
Perilymph is similar to cerebrospinal uid and extracellular uid, high in
sodium, and positive for beta-2 transferrin.
Endolymph is similar to intracellular uid and high in potassium.
Bony labyrinth encloses membranous labyrinth, separated by perilymph.
Vestibular aqueduct contains endolymphatic duct, which courses from
medial wall of vestibule (inferior to otolithic organs) to region of thickened
posterior fossa dura called endolymphatic sac.
Cochlear aqueduct contains periotic duct, which is continuous with subarachnoid space of posterior fossa, courses inferior and parallel to internal
auditory canal, and opens into inner ear at base of scala tympani.
Cochlea and saccule joined by segment of membranous labyrinth called
ductus reuniens.
Cochlea
S. Pelosi
• Has 2.5 turns.
• Modiolus is central cochlear nerve-containing region; osseous spiral
lamina forms bony cochlear framework medially.
• Spiral ligament forms lateral wall of cochlea and contains stria vascularis that produces endolymph.
• Scala vestibuli and scala tympani contain perilymph, connected by
helicotrema.
• Scala media contains endolymph and organ of Corti, separated from
scala vestibuli by Reissner’s membrane.
Organ of Corti
• Sup orted by basilar membrane (separates scala media and scala
tympani).
• Tectorial membrane: gelatinous structure which contacts with stereocilia of hair cells; vibration of basilar membrane→tectorial membrane
displacement→hair cell stimulation.
• Inner hair cells: provide most afferent auditory information to the brain
(90%); 15 neurons synapse on each inner hair cell.
• Outer hair cells: provide only 10% of afferent auditory information to
the brain, source of otoacoustic emissions; one neuron synapses on ten
outer hair cells; receive large efferent projection from superior olive in
brainstem (cochlear amplier).
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Semicircular canals
• Three canals on each side; each is oriented 90° to one another
(orthogonal).
• Ampulla: expansion at one end of each semicircular canal near vestibular opening; contains cupula (gelatinous layer), crista ampullaris (hair
cells at base of cupula).
• Superior and posterior canals have common crus.
Otolith organs
• Utricle: senses horizontal linear acceleration
• Saccule: senses vertical linear acceleration; also has some sound sensitivity (basis of vestibulocollic reex).
• Maculae of utricle and saccule contain hair cells and are covered by a
gelatinous otolithic membrane, which contains calcium carbonate
(otoliths).
• Polarity of hair cells is oriented around a central line called the striola.
Vestibular nerve
• Superior vestibular nerve: innervates utricle, superior/lateral semicircular canals
• Inferior vestibular nerve: innervates saccule, posterior canal
• Scarpa’s ganglia: distal vestibular nerve cell bodies
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– Conductive sound pathway
Sound energy from air transferred to inner ear via pinna, external auditory
canal, tympanic membrane, and ossicles.
Each conductive component has an inherent “resonant frequency,” or natural vibrating frequency (pinna 5kHz, external auditory canal 3kHz, tympanic membrane/ossicles 500–2000Hz).
Gain in sound intensity from tympanic membrane to inner ear ~30dB.
Larger surface area of TM relative to footplate more important for intensity
gain than lever action of ossicles.
– Neural sound transduction pathway
Displacement of stapes→endolymph movement→basilar membrane dis-
placement→hair cell stereocilia deected by shearing force of tectorial
membrane→hair cell activation→auditory nerve stimulation
Cochlea is tonotopically organized with higher-frequency sounds causing
greater hair cell stimulation at base and lower-frequency sounds causing
stimulation at the apex
Ipsilateral auditory nerve→ipsilateral cochlear nuclei→bilateral superior
olive→ lateral lemniscus → inferior colliculus→thalamus→temporal
lobe auditory cortex
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S. Pelosi
Audiology
• Decibel: logarithmic unit of measurement used to express sound intensity.
– dB SPL (sound pressure level): magnitude of displacement of sound mole-
cules in air
– dB HL (hearing level): difference in sound intensity compared to average dB
SPL for normal-hearing listeners
– dB SL (sensation level): difference in sound intensity compared to an indi-
vidual patient’s HL threshold
– 10dB difference changes sound intensity by factor of 10 (30dB has 100×
greater sound intensity than 10dB)
• Pure-tone audiometry measures thresholds for pure tone stimuli and speech audiometry for speech stimuli.
– Pure-tone average (PTA): average of hearing sensitivity at 500, 1000, and 2000
• Speech reception threshold/speech recognition threshold (SRT): lowest level at
which a given word can be repeated 50% of the time.
– Uses two-syllable (spondee) words for testing
– Good estimate of pure-tone average to within 10dB
• Speech awareness threshold/speech detection threshold (SAT/SDT): lowest level
at which patient is aware that speech is present.
– Less difcult, used when speech reception threshold cannot be determined
(young children)
• Word recognition score (WRS): percentage of words correctly repeated when
presented with a 50-word list.
– Uses single-syllable, phonetically balanced words (e.g., NU-6)
– Presented at ~40dB greater than patient’s speech reception threshold
• Interaural attenuation: reduction in sound energy when a signal introduced to the
test ear is transmitted through the skull to the non-test ear.
– No sound energy reduction for bone conduction signal, 40dB reduction for
air conduction
• Crossover: sound energy that has exceeded interaural attenuation to stimulate
non-test ear.
• Masking: use of a noise source placed into the non-test ear to prevent the participation of the non-test ear in determining the patient’s audiometric threshold in
the test ear.
– Air conduction testing: mask if signal presented to test ear is 40dB greater
than bone conduction threshold of non-test ear.
– Bone conduction testing: mask if there is any suspected difference in bone
conduction between test and non-test ears.
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– Masking dilemma: occurs when there is a bilateral moderate-to-severe con-
ductive hearing loss. The sound intensity for masking the non-test ear crosses
over to the tested ear and interferes with testing.
• Audiometric evaluation in young children.
– Behavioral observation audiometry (birth–6 months): sound is presented;
look for bodily responses to sound (eye widening, eye opening, body
movement).
– Visual reinforcement audiometry (6 months–3 years): child is taught to look
toward a visual stimulus during presentation of a sound; reduce sound and
visual stimulus intensity until minimum hearing thresholds reached.
– Conditioned play audiometry (3–5 years): child is taught to perform a repeti-
tive play task (place peg in pegboard) in response to sound.
• Immitance audiometry.
– Tympanometry: evaluates eardrum mobility, measured with ear canal volume
(normal 0.2–2cm3)
Type A: normal middle ear pressure, normal compliance
• As (shallow or stiff): normal middle ear pressure, decreased compliance
(otosclerosis, tympanosclerosis)
• Ad (deep): normal middle ear pressure, increased compliance (ossicular
discontinuity or accid tympanic membrane)
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Type B: non-mobile tympanic membrane (normal external canal volume
indicates effusion, large volume indicates perforation)
Type C: negative middle ear pressure, normal compliance (Eustachian tube
dysfunction)
– Stapedial reex
Tests integrity of cranial nerves 8 and 7, normally occurs at 70–100dB HL
Reex arc: ipsilateral cochlea→ipsilateral CN 8 → ipsilateral cochlear
nucleus→ipsilateral trapezoid body→bilateral superior olive→bilateral
facial motor nucleus→bilateral CN 7→bilateral nerve to stapedius
Absent reexes:
• Sensorineural hearing loss >65dB, CN 8 cannot initiate reex.
• Any level of conductive hearing loss.
• Facial nerve pathology impairs efferent limb of reex.
• Reex decay test: test stapedial reex 10dB above threshold; <50% of
original amplitude within 10s suggest a retrocochlear lesion.
• Otoacoustic emissions (OAEs).
– Low-energy sounds produced by the cochlea, believed to be generated by
outer hair cells
Spontaneous: present in 75% of normal-hearing patients, but may not be
present with >25dB HL.
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Transient evoked: most sensitive measure, elicited by clicks; response contains multiple frequencies (500–4000 Hz); if present indicates a patient
does not have a sensorineural hearing loss any worse than 20–40dB at
these frequencies.
Distortion product: two pure tones presented simultaneously; response is a
tone at a specic frequency; can test at higher frequencies, useful for testing for noise-induced hearing loss and medication ototoxicity.
Useful for infant screening (transient evoked otoacoustic emissions have
high sensitivity/specicity), disabled individuals who cannot participate in
testing, diagnosis of auditory neuropathy, malingerers.
Able to identify patients with cochlear hearing loss (loss of hair cells), but
does not test for patients with auditory neuropathy or other retrocochlear
pathology (in these cases auditory brainstem response testing is helpful).
Conductive hearing loss and sensorineural hearing loss worse than
20–40dB can eliminate otoacoustic emission responses.
• Auditory brainstem response (ABR)
– Uses surface electrodes to measure the neural response of peripheral and cen-
tral auditory pathways to an auditory stimulus.
– Traditionally obtained in cases of asymmetric hearing loss/tinnitus or unilat-
eral vestibular weakness to evaluate for vestibular schwannoma.
– Can also be used intraoperatively during vestibular schwannoma surgery in
hearing preservation cases to measure integrity of auditory pathway.
– Auditory click initiates neural response; electrical potential measured using
an electrode placed in external auditory canal; each wave represents neural
activity of different parts of auditory pathway.
– Waveforms (Mnemonic “ECOLI”):
S. Pelosi
I Distal eighth nerve
II Proximal eighth nerve
III Cochlear nuclei
IV Superior olive
V Lateral lemniscus
VI Inferior colliculus
– If patient has severe–profound hearing loss in ear to be tested, auditory brain-
stem response may not be measurable.
– Result interpretation:
Prolonged wave I, normal I–V interwave latency may be caused by conductive hearing loss or cochlear sensorineural hearing loss
Retrocochlear pathology
Indicated by abnormal wave V latency relative to opposite ear or
abnormal I–V, I–III, III–V interwave latencies relative to opposite ear or
established norms
Sensitivity not as high as MRI for diagnosing vestibular schwannoma
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