Temporal bone E.Khalili - PowerPoint Presentation

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Temporal bone

E.Khalili Pooya

به نام خدا

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Temporal bone

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Hypotympanum

:

Shallow space in floor of

middle

ear cavity

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Epitympanum

(attic)Roof - tegmen tympani

Floor - line between

scutum

and tympanic portion of facial

nerve

Lateral - Prussak

space Posterior - Aditus ad antrum leads to mastoid antrum

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Mesotympanum

* Roof -

epitympanum

* Floor

- line between inferior edge of tympanic membrane and

cochlear

promontory

* Anterior

- Eustacian tube * Posterior - 3 key structures• Facial nerve recess• Pyramidal eminence

•

Sinus tympani* Medial – Lateral semicircular canal – Oval and round windows – Tympanic segment CN VII

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Conductive chain

Tympanic membrane, ossicles, oval windowTympanic membrane

• Pars

flaccida

- upper

1/3

Two

layers

• Pars tensa - lower 2/3 Three layers: ectoderm, mesoderm,

and endoderm.

– More rigid than pars flaccida – Conducts vibrations to ossicles

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Inner Ear: Anatomy

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Perilymph:

Csf like extracellular fluidBetween membranous and

bony labyrinths

Contiguous

with the

subarachnoid space

No appreciable “flow”

Endolymph

:Fluid that fills the membranous labyrinth.

Unique in body - high K

+ “sealed” compartment maintained by ion exchange in endolymphatic

sac

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Cochlear aqueduct

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Cochlear aqueduct

The cochlear aqueduct connects the perilymph with the subarachoid

space

The cochlear aqueduct is a narrow canal which runs towards the cochlea in almost the same direction as the inner auditory canal, but situated more caudally

It is a point where infected cerebrospinal fluid can enter the inner ear

This can happen in patients with meningitis and cause

labyrinthitis

ossificans

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Axial anatomy in CT sections (from

inferior to superior)

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Malleus (yellow arow

)

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Malleus (yellow

arow)Round window (blue arrow)

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Stapes (green arrow) is seen connecting to the oval window

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Malleus (yellow

arow)Round window (blue arrow)

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C=Cochlea, V=Vestibule

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C=Cochlea, V=Vestibule

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Semicircular canals

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Transverse (

falciform

crest)

Bill’s bar

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Variants of Mastoid development

Hyper-pneumatization

Hypo-

pneumatization

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Bulging sigmoid sinus

The sigmoid sinus can protrude into the posterior mastoid. It can be accidentally lacerated during a mastoidectomy

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High jugular bulb

The jugular bulb is often asymmetric, with the right jugular bulb usually being larger than the left

If it reaches above the

posterior semicircular canal

it is called a high jugular bulb

If the bony separation between the jugular bulb and the tympanic cavity is absent, it is termed a

dehiscent jugular bulb

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Important variant: High jugular bulb, defect in

hypotympanic floor

Axial view

Coronal view

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High jugular bulb

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High jugular bulb

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Dehiscent jugular bulb

Enlarged jugular bulb with dehiscence of sigmoid plate and protrusion of jugular vein into the posterior aspect of the middle ear.

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Aberrant internal carotid artery

Pulsative

tinnitus

Can

look exactly like

glomus

tympanicum

on coronal images Check for TUBULARITY on axials! DON’T BIOPSY

!

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Ectopic carotid artery: Posteriorly

displaced canal passing into the middle ear

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Carotid arteriogram, coronal projection

Ectopic carotid artery

Normal

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Ectopic carotid artery

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Petromastoid canal

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Petromastoid canal

The petromastoid canal or subarcuate

canal connects the mastoid

antrum

with the cranial cavity and houses the

subarcuate

artery and vein

Its diameter is around 0.5 mm

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Acute

otitis media and mastoiditis

Air cell clouding

Intact cell wall

Fluid in middle ear

No erosion in attic wall or

ossicles

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Tympanosclerosis:

thickened tympanic membrane with plaque

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Tympanosclerosis

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Cholesteatoma

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Cholesteatoma

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Congenital Cholesteatoma

=aka

epidermoid

Usually pediatric

population

Arise in variety of places in temporal bone. Middle ear involvement

Bone

erosion occurs late in disease Anterosuperior middle ear, adjacent to

eustachian

tube & anterior tympanic ring, medial to ossicles

DDx :

-pars

tensa

acquired middle ear

cholesteatoma

( Ossicles commonly eroded)-Glomus tympanicum paraganglioma

(

No bony erosion

,

+CE on

MRI)

-

Scwannoma

of tympanic portion of CN VII

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Cholesteatoma

: Soft tissue mass in epitympanum, erosion of scutum

&

ossicles

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A small amount of soft tissue (arrow) is visible between the

scutum and the ossicular chain but no erosion is present

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Chronic otitis media vs

cholesteatoma

Erosion of the lateral wall of the

epitympanum

and of the

ossicular

chain is common in cholesteatoma

(around 75%)

Erosion can occur in chronic otitis, but reportedly in less than 10% of patientsDisplacement of the ossicular chain can be seen in cholesteatoma

, not in chronic

otitisCholesteatoma can present with a non-dependent mass while chronic otitis shows thickened mucosal lining

However, in both diseases the middle ear cavity can be completely opacified, obscuring a

cholesteatoma

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Cholesteatoma

: Soft tissue mass between ossicular chain and lateral tympanic wall, which is eroded

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Paragangliomas

:

also known as

glomus

tumors

or

chemodectomas

, are the second most common tumor to involve the temporal bone

(after schwannoma)and the most common tumor of the middle ear. These tumors originate from paraganglia along the tympanic branch of the glossopharyngeal nerve (Jacobson nerve) and the auricular branch of the vagus

nerve (Arnold nerve) and within the

intravagal paraganglia inferior to the foramen. Paragangliomas

are highly vascular. Paragangliomas may have a typical

salt-and-pepper appearance

on T1-weighted and T2-weighed images due to intermixed vascular flow voids and tumor tissue

.

They usually show avid enhancement on gadolinium-enhanced

images.

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Glomus

Tympanicum paraganglioma

Arises

from

glomus

bodies at

cochlear

promontory

Margin abutting cochlear promontory is flat

Engulfs, not erodes

ossicles DDx :

* aberrant course of carotid artery

*

pars

tensa

cholesteatoma* epidermoid

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Glomus Jugulare

paraganglioma

Jugular foramen mass with

permeative

destruction

of the adjacent bone and extension into hypo/

mesotympanum

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Glomus

jugulare: Jugular fossa appears enlarged and the

hypotympanic

floor is eroded. Mass protrudes into the

mesotympanum

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Glomus jugulare

tumor

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Acoustic neuroma

: Left IAC is enlarged by a mass extending into CPA

Bone window

Post-contrast brain window

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Meningioma: Post-contrast CT scan

Partially calcified mass protrudes from IAC into CPA. Hyperostotic changes narrow IAC

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Large vestibular aqueduct

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Large vestibular aqueduct

The vestibular aqueduct is a narrow bony canal (aqueduct) that connects the endolymphatic sac with the inner ear

(vestibule)

Running through this bony canal is a tube called

the

endolymphatic

duct

A large vestibular aqueduct is associated with progressive

sensorineural hearing lossThe large vestibular aqueduct is associated with an absence of the bony

modiolus

in more than 90% of patients

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Mondini

deformity: Instead of the normal two-and-one-half turns, there is only a normal basal turn and a cystic apex

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Labyrinthine ossificans

Ossifcation

of membranous labyrinth as healing response to infection,

trauma

, surgery

Classic presentation is bilateral SNHL in child after meningitis –

Bone depostion in fluid spaces of vestible

, semicircular canals

and cochlea

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Labyrinthitis

ossificans

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Labyrinthitis ossificans

Labyrinthitis ossificans

is seen after meningitis

It is a condition in which the inner ear is filled with fibrotic tissue, which calcifies

It mostly affects the cochlea, but the vestibule and semicircular canals can also be involved

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Otosclerosis

is a genetically mediated metabolic bone disease of unknown etiologyIt is sometimes called otospongiosis

because the disease begins with an

otospongiotic

phase, which is followed by an

otosclerotic

phase when

osteoclasts

are replaced by osteoblasts and dense sclerotic bone is deposited in areas of previous bone resorptionWhen this process involves the oval window in the region of the footplate, the footplate becomes fixed, resulting in conductive hearing loss

However, involvement of other portions of the

otic capsule can result in mixed sensorineural hearing loss

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Otosclerosis

The process starts in the region of the oval window, classically at the fissula ante fenestram

, i.e. in front of the oval window (

fenestral

otosclerosis

)It can also occur around the cochlea (

retrofenestral

otosclerosis)

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Cochlear Otosclerosis

/otospongiosus

Young

adult with bilateral mixed hearing loss

Focal lytic plaques in

pericochlear

bony labyrinth

85% bilateral symmetric – Unknown etiologyTreated with flouride

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Fenestral

and cochlear otosclerosis: double ring appearance

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Otosclerosis

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Fenestral

Otosclerosis/otospongiosus

Adults

with conductive hearing

loss

More common than cochlear

otosclerosis

Similar process involving the oval and round window region

Unknown

etiologyFlouride treatment slows hearing loss.

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Lucency

anterior to the oval window (arrow) and between the cochlea and the internal auditory canal. Combined fenestral & retrofenestral

otosclerosis

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Semicircular canal dehiscence

thinning or absence of bony roof over

superior or

posterior semicircular

canal

Noise

induced vestibular

symptoms

Unknown etiology Affects adults

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Longitudinal fracture, bleeding in air cells

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Coronal view,

Incus dislocation and protrusion into canal

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Transverse fracture involves vestibule and middle ear

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Postoperative ear

Attico-antrotomy : most of mastoid air cells are present

Mastoidectomy

:

Almost all of the mastoid air cells are removed

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Thank you