Transcript Prussak`s Space

Build-A-Box
A STEPWISE APPROACH TO
MIDDLE EAR ANATOMY
J McCarty | J Dornhoffer | R Riascos | E Angtuaco | RT Fitzgerald
#1444
eEdE-156
PURPOSE & DISCLOSURE
ANATOMY
IMAGING
PATHOLOGY
MCQ’S
To provide a step-by-step approach to the
complex anatomy of the middle ear –
building the tympanic cavity “box” and all
of its contents from the ground up.
John L. Dornhoffer, MD - inventor of the Olympus Dornhoffer Interpositional
PORP Prosthesis, Dornhoffer HAPEX PORP/TORP & Dornhoffer Micron
Titanium Footplate Shoes
The remaining authors have no disclosures.
THE BOX
Introduction
The tympanic cavity and its contents comprise the middle ear.
Although irregularly shaped, this cavity
within the temporal bone has been
compared to a box with 6 sides.
However, the tympanic cavity floor & roof
are more spherical, bowing outward from
the center of the cavity.
THE EAR
Introduction
The ear is divided into 3 parts.
+
+
External
Middle
Inner
Pinna & External
Auditory Canal
Tympanic Cavity & All of
Its Contents
Cochlea, Vestibule,
Semicircular Canals
Sound
Collection
Sound
Conduction
Nerve Impulse
Formation
It is useful to keep a broad understanding of ear anatomy and function in mind when
studying the detailed subject of otology.
STEP 1: OSSICULAR CHAIN
The middle ear aids in sound conduction.
Ossicles
The tympanic
membrane converts
sound collected by
the external ear into
vibrations.
The ossicles then
transmit and amplify
sound towards the
oval window and
inner ear.
Ossicular Chain = Malleus + Incus + Stapes
OSSICULAR CHAIN ANATOMY
Ossicles
Head of the
Malleus
Anterior Process of the
Malleus
Lateral Process of the
Malleus
Manubrium of the
Malleus
Tympanic
Membrane
LATERALLateral
Short Process of the
Incus
Long Process of the
Incus
Footplate of the
Stapes
Anterior Crus of the
Stapes
Lenticular Process
of the Incus
MEDIAL
CT OF THE OSSICULAR CHAIN
3DVR
Ossicles
Axial
Coronal
Head
MALLEUS
Lateral
Process
Short
Process
Body
Long
Process
Lenticular
Process
Capitellum
Anterior
Crus
STAPES
Posterior
Crus
Head
Handle
Handle
Lateral
Process
INCUS
Head
Head
Neck
Sagittal
Footplate
Body
Long
Process
Short
Process
Capitellum
Posterior
Crus
Anterior
Crus
Body
Short
Process
Body
Lenticular
Process
Anterior
Crus
Capitellum
Posterior
Crus
CASE BASED MULTIPLE CHOICE QUESTION (MCQ)
CASE 1
Case 1 is an example of a:
Ossicles
Malleal &
incudal
prosthesis
Coronal
“TORP” = Total Ossicular Replacement
Prosthesis
“PORP” = Partial Ossicular Replacement
Prosthesis
A.
B.
C.
D.
Foreign body
Stapedial prosthesis
PORP
TORP
The most common repairable
cause of ossicular prosthetic
failure is:
A. Migration
B. Recurrent cholesteatoma
C. Trauma
Native
stapes
Axial
Prostheses may migrate or dislocate. Stapes
prostheses most commonly migrate inferiorly.
Occasionally one may migrate medially
through the oval window
STEP 2: MUSCULATURE
Muscles
STAPEDIUS
TENSOR TYMPANI
Dampens Sound
Dampens Sound
Attaches to Head of
the Stapes
Attaches to Neck
of the Malleus
Innervation: CN VII
Innervation: V3
Two Muscles: Stapedius + Tensor Tympani
AXIAL IMAGING
Muscles
The tensor tympani is a thin elongated
muscle that resides superior to the
Eustachian tube. Only a small portion of this
muscle traverses the tympanic cavity.
Tensor
Tympani
Tensor
Tympani
1
2
3
4
1
Eustachian
Tube
2
Eustachian
Tube
The stapedius is not well visualized on CT.
3
4
Sequential axial images (1 = cranial, 4 = caudal)
CASE BASED MCQ
CASE 2
Tumor invasion of the facial nerve
tympanic segment would cause:
Muscles
2
1
A. Hyperaccusis
B. Conductive hearing loss
C. Sensorineural hearing loss
Axial
Damage to the proximal facial nerve could
lead to denervation of the stapedius and
inability to adequately dampen sound.
Facial nerve segments labeled 1 & 2 on
the coronal image are:
A.
B.
C.
D.
Canalicular & genu
Genu & labyrinthine
Labyrinthine & tympanic
Tympanic & mastoid
Coronal
The “snails eyes” are the labyrinthine &
tympanic segments of the facial nerve on
coronal CT.
STEP 3: LIGAMENTOUS SUPPORT
Superior Malleal Ligament
Ligaments
Posterior Incudal Ligament
Anterior Malleal Ligament
Several ligaments stabilize the suspended ossicular chain.
MALLEAL SUPPORT
Anterior Malleal Ligament
TEGMEN TYMPANI
(attachment)
*
Superior Malleal Ligament
Ligaments
SCUTUM
Lateral Malleal Ligament
The malleus has the strongest support of the
3 ossicles.
4 Ligaments + Tensor Tympani Muscle
INCUDAL & STAPEDIAL SUPPORT
Annular
Ligament
Posterior Incudal
Ligament
Stapedius
Ligaments
Incudostapedial
Joint
INCUDAL
STAPEDIAL
The single posterior incudal ligament stabilizes the incus within the
tympanic cavity.
The annular ligament surrounds the footplate of the stapes, and
stabilizes it to the oval window.
AXIAL IMAGING
Anterior Malleal
Ligament
Ligaments
Posterior Incudal
Ligament
The ligaments stabilizing the ossicular chain may not be well visualized on CT.
However, here the posterior incudal and anterior malleal ligaments are seen
CASE BASED MCQ
CASE 3
Incudal
body
Malleal
head
Ligaments
Which ossicle is most commonly
dislocated secondary to trauma?
A. Malleus
B. Incus
C. Stapes
CASE 4
Incudal
body
Malleal
head
The incus is the largest ossicle. It also
happens to have the weakest support.
Axial
Laterally dislocated incus abuts the
lateral wall of the epitympanum.
Ice cream that fell of the cone.
What is the most common ossicular
traumatic injury?
A. Incudal fracture
B. Malleal fracture
C. Malleoincudal joint disruption
D. Incudostapedial joint disruption
Although malleoincudal joint disruption is more
often identified on CT, incudostapedial
disruptions occur more often.
Axial
Disruption of the malleoincudal joint
without lateral incudal displacement.
Ice cream only separated from cone.
STEP 4: NERVES
Nerves
JACOBSON’S N.
CHORDA TYMPANI
Branch of CN IX
Branch of CN VII
Courses over
Cochlear
Prominence
Innervation:
Sensory
Courses b/w Incus
& Malleus
Innervation: Taste
Anterior 2/3 of
Tongue
TRAVERSING NERVES
Nerves In & Around the Middle Ear
Nerves
Course
Innervation
JACOBSON’S N.
CHORDA
TYMPANI
CN IX
CN VII
TYMPANIC
STAPEDIUS N. SEGMENT OF
FACIAL N.
CN VII
CN VII
MASTOID
SEGMENT OF
FACIAL N.
CN VII
Inferior
Mastoid
Arises close
Pyramidal
tympanic
Medial wall of
segment origin to pyramidal
eminence to
canaliculus 
tympanic
 B/w incus & eminence 
stylomastoid
cochlear
cavity
malleus
stapedius
foramen
prominence
Sensory
Taste Anterior
2/3 of Tongue
Stapedius
*
*
AXIAL IMAGING
1
CN VII
Tympanic
segment
3
CN VII
Mastoid
Segment
1
Nerves
2
3
2
CN VII
Posterior
Genu
4
CN VII
Mastoid
Segment
4
Sequential axial images (1 = cranial, 4 = caudal)
CASE BASED MCQ
CASE 5
Malleal
Handle
Nerves
Red
Mass
What are the findings on clinical
otoscopy?
A. Red retrotympanic mass
B. Blue retrotympanic mass
C. White retrotympanic mass
There’s a small red retrotympanic mass
overlying the cochlear promontory without
underlying erosions.
Otoscopy
Retracted
TM
Promontory
Otoscopy
Stapedial
Head
Red
Mass
A.
B.
C.
D.
Rounded mass on
the promontory
Intact middle
ear floor
Coronal
What is the most likely diagnosis?
Glomus tympanicum
Glomus jugulotympanicum
Aberrant carotid artery
Persistent stapedial artery
Glomus jugulotympanicum would have
dehiscence of the middle ear floor & warrant
a different surgical approach.
Specimen
STEP 4: NERVES
Nerves
TYPE
LOCATION
NERVE PARAGANGLIA
Glomus Tympanicum
Cochlear Promontory
CN IX (Jacobson’s)
Glomus Jugulare
Jugular Foramen
CN X
Glomus Vagale
B/w ICA & IJ
CN X
Carotid Body Glomus
Carotid bifurcation
(splaying ICA & ECA)
CN X
“Glomus” = “Paraganglioma”
Arise from paraganglia (normal structures which accompany CN & ganglia)
STEP 5: WALLS
“Roof” or Tegmen Tympani
Pyramidal Eminence
“Posterior” or
Mastoid Wall
Walls
Facial N. Recess
“Medial” or
Labyrinthine Wall
Sinus Tympani
“Floor” or Jugular Wall
“Anterior” or
Carotid Wall
AXIAL IMAGING
Anterior Wall
Anterior Wall
Medial
wall
1
2
Walls
1
CP
AAA
h
2
3
4
E
5
6
Lateral
Wall/TM
CP
FR PE
ST
Posterior
Wall
E
Medial
wall
4
CP
CC
Lateral Wall/
TM
CC
JB
RW
5
6
Floor
AAA = aditus ad antrum, E = Eustachian tube, Co = Cochlea, CP = cochlear promontory, ST = sinus tympani, PE = pyramidal eminence, FR = facial
recess, RW = round window, CC = carotid canal, JB = jugular bulb
CASE BASED MCQ
CASE 6
TM
Stellate
mass
From which structure does the mass
arise?
A. Tympanic Membrane
B. Ossicular Chain
C. Tegmen Tympani
Stellate
mass
A soft tissue attenuation stellate mass arising
from the TM projects into the external
auditory canal.
Walls
A.
B.
C.
This mass arises from the TM – the D.
Coronal
lateral wall of the middle ear – and
protrudes into the EAC.
What is the most likely diagnosis?
Squamous Cell Carcinoma
Cerumen
Verruca Vulgaris
Glomus
A benign cutaneous wart cause by human
papillomavirus (HPV).
Axial
TM involvement is very rare – until
2013, there were no reports of verruca
on the TM in the English literature.
CASE BASED MCQ
CASE 7
Permeative
changes
Rounded
mass
Walls
Coronal
This mass causes permeative
changes of the tympanic cavity
floor and protrudes into the
middle ear.
A.
B.
C.
D.
What is the diagnosis?
Cholesteatoma
Glomus Tympanicum (GTP)
Glomus Jugulotympanicum (GJP)
Metastasis
Mass
A destructive soft tissue mass erodes through
the middle ear floor and extends superiorly –
overlying the cochlear promontory.
This mass arises in association with
which nerve?
A. CN VII
B. CN VIII
C. CN IX
D. CN X
Arnold’s Nerve – a branch of CN X.
Axial
Involvement of the middle ear floor is
the distinguishing factor differentiating
GTP from GJP and necessitates a
different surgical approach.
STEP 6: SPACES
Epitympanum
Mesotympanum
Spaces
Hypotympanum
The middle ear is further divided into several spaces.
CROSS SECTIONAL IMAGING
Protympanum
Epitympanum
Mesotympanum
Mesotympanum
Posterior Tympanum
Hypotympanum
Spaces
Coronal CT
Axial CT
CASE BASED MCQ
CASE 7
Epitympanic
mass
In which space does the mass reside?
A. Protympanum
B. Mesotympanum
C. Prussak’s
A small soft tissue mass resides in the
epitympanum, eroding the TM.
Spaces
Coronal
This mass extends through
Prussak’s space, blunts the scutum
and abuts the TM.
What is the most likely diagnosis?
A. Cholesteatoma
B. SCC
C. Cerumen
Cholesteatomas can be either congenital (2%)
or acquired (98%).
Epitympanic
mass
Otoscopy
Acquired cholesteotomas are most
often seen in the epitympanum,
medial to the pars flaccida (82%).
PRUSSAK’S SPACE
Malleal
Neck
Lateral Malleal
Ligament
Lateral
Process
Spaces
Prussak’s
Space
Tympanic
Membrane
Coronal
STEP 7: ADJACENT STRUCTURES
Aditus Ad Antrum
Eustachian Tube
Adjacent
Cochlear Promontory
Round Window
Oval Window
AXIAL IMAGING
FN
1
2
Co
CP
AAA
CP
TT
h
1
2
3
4
E
5
E
TM
6
TM
CC
CC
JB
Adjacent
CP
4
FR PE
ST
RW
5
6
AAA = aditus ad antrum, FN = facial nerve, TT = tensor tympani, E = Eustachian tube, Co = Cochlea, CP = cochlear promontory, ST = sinus
tympani, PE = pyramidal eminence, FR = facial recess, RW = round window, CC = carotid canal, JB = jugular bulb
CASE BASED MCQ
CASE 7
Thinned
posterior
wall
What is the most likely diagnosis?
A. High riding jugular bulb
B. Aberrant carotid artery
C. Glomus jugulotympanicum
JB
A.
B.
C.
D.
An enlarged & high riding jugular bulb
Axial
Adjacent
The carotid canal is normal & there is no
permeative destruction of the floor.
What is the most common clinical
presentation?
Sensorineural hearing loss
Conductive hearing loss
Pulsatile tinnitus
Otalgia
extends along the middle ear floor
GTP, GJP, & aberrant ICA’s also present with
tinnitus.
JB
Coronal
The overlying bone is thin and
remodeled.
FINAL MIDDLE EAR BOX
Stapedius
Aditus Ad Antrum
Ossicular Chain
Tensor Tympani
Pyramidal Eminence
Eustachian Tube
Facial N. Recess
Chorda Tympani N.
Sinus Tympani
Cochlear Promontory
Round Window
Final Box
Oval Window
Jacobson’s N.
REFERENCES
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THANK YOU
Jennifer McCarty, MD
Roy Riascos, MD
Twitter: @JMcCartyMD
Email: [email protected]
PGY5 Radiology Resident
Department of Radiology
University of Arkansas for Medical Sciences
Associate Professor of Neuroradiology
Chief, Division of Neuroradiology
The University of Texas Health Sciences Center at
Houston
John L. Dornhoffer, MD, FACS
Professor of Professor and Vice-Chair
Samuel McGill Chair in Otolaryngology Research
Department of Otolaryngology
University of Arkansas for Medical Sciences
Ryan T. Fitzgerald MD
Assistant Professor of Radiology
Department of Radiology, Neuroradiology Division
University of Arkansas for Medical Sciences
Edgardo Angtuaco, MD, FACR
Professor, Department of Radiology
Chief, Division of Neuroradiology and MRI
University of Arkansas for Medical Sciences