Transcript Infectious and Inflammatory Processes of the Temporal Bone

Infectious and Inflammatory
Processes of the Temporal Bone
Neelmini Emmanuel, MD1 and John L. Go, MD, FACR1,2,3
Division of Neuroradiology1 and Departments
of Radiology and
2
Otolaryngology
Keck School of Medicine
University of Southern California
House Ear Clinic3 of St. Vincent Medical Center
Los Angeles, CA
Purpose

This exhibit will familiarize the attendees with
the infectious and inflammatory disorders of the
temporal bone
Design: This exhibit will divide and explore the infectious and
inflammatory disorders of the temporal bone by region and
disease entities within each region :
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Pinna and External
Auditory Canal (EAC)
Acute otitis externa
 Chronic otitis externa
 EAC
cholesteatoma/keratosis
obturans
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Acute otitis media
 Chronic otitis media
 Cholesteatoma
 Tympanosclerosis
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Simple mastoiditis
Coalescent mastoiditis
Complications of
mastoiditis
Petrous apex
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Middle ear cavity (MEC)
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Mastoid region
Petrous apicitis
Cholesterol granuloma
Inner Ear
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Labyrinthitis
Labyrinthitis ossificans
Pinna and EAC
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Otitis externa may be subdivided into acute and chronic otitis
externa. Acute otitis externa is inflammation of the soft tissue
of the external auditory canal. With repeated episodes of
inflammation and periostitis, concentric narrowing of the
external auditory canal may form. This is commonly referred
to as surfer’s ear, and is an example of chronic otitis externa.
Soft tissue may fill the external auditory canal, leading to
medial meatal fibrosis.

Malignant otitis externa refers to inflammation away from the
external auditory canal, typically inferior to the EAC. The
fissures of Santorini represent small channels containing veins
draining the EAC. Thrombophlebitis of these veins leads to
extension of infection below the EAC.
Acute Otitis Externa
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Presentation
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Pain
Erythema
Swelling
Tragal and auricular motion
tenderness
Organisms
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Pseudomonas aeruginosa
Staphylococcus Aureus
Fungal
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A
Candida
Aspergillus
Viral
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Ramsey Hunt syndrome
B
Axial (A) and coronal (B)
CT demonstrates
circumferential soft tissue
thickening within the EAC.
Note no evidence of bony
erosion. Soft tissue
thickening is also associated
with the tympanic
membrane
(myringosclerosis).
Chronic Otitis Externa
Axial CT demonstrates concentric bony narrowing of the EAC bilaterally, known
as surfer’s ear, and is related to repeated episodes of otitis externa and periostitis.
Medial Meatal Fibrosis
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Chronic stenosing
external otitis
60% bilateral
Fibrous plug
Etiologies
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Trauma
Radiation therapy
Inflammation
Axial CT demonstrates soft tissue filling the bony external auditory canal
medial to the external auditory meatus.
Malignant Otitis Externa
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Seen in diabetics, immunosuppressed, postchemotherapy, HIV
Pseudomonas aeruginosa
Mortality rate up to 42% in HIV, 4% in diabetics
Infection spreads inferiorly to TMJ and below
skull base
Middle cranial fossa: Intracranial complications
Skull base involvement: Cranial neuropathy,
osteomyelitis, sinus thrombosis
Malignant Otitis Externa
A
B
Non-contrast axial CT at the level of the left EAC (A) and 1 cm inferior (B) demonstrating
soft tissue mass filling EAC with bony erosion of EAC . Note inflammatory changes
associated with the parotid, masticator and parapharyangeal spaces (red arrow).
Malignant Otitis Externa
A
B
C
MRI of same patient: axial T1WI (A), post contrast (B) and fat saturated T2WI (C)
demonstrates extensive inflammation and enhancement of the left EAC, periauricular region,
masticator, parotid and parapharyngeal spaces. These areas are hyperintense on T2WI. Note
mastoid airspace disease. This can be mistaken for an aggressive tumor.
Malignant Otitis Externa and
Subdural Empyema/Abscess
A
B
C
Post contrast T1WI at the level of the right EAC (A) and 1 cm superior (B) demonstrates
enhancement of the EAC and extensive pachymeningeal enhancement along the temporal
convexity. Note non-enhancing fluid collection (yellow arrows) along the convexity which
demonstrates diffusion restriction on trace diffusion images (C) representing subdural empyema.
Also note second abscess in the temporalis muscle (red arrow) with small abscess on the right with
associated inflammatory changes of the muscle.
EAC Cholesteatoma
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10% of acquired cholesteatomas occur in the
external auditory canal
Represent a ball of keratinized, desquamated
epithelial cells
May be associated with prior perforation of the
tympanic membrane
Soft tissue mass associated with adjacent bony
destruction
EAC Cholesteatoma
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CT
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Soft tissue mass with associated bony destruction
MRI
T1WI: iso- to hypointense in signal intensity
 T2WI: mild to moderate hyperintense signal
intensity
 Post contrast imaging: No enhancement
 Diffusion imaging: restricted diffusion
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Keratosis Obturans
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Keratosis Obturans is similar to EAC cholesteatoma
Histologically the same
Demographics, presentation and natural history are different, so the two
entities were separated
Most common location of keratosis obturans is adjacent to the tympanic
membrane inferiorly with localized bony remodelling or erosion of the EAC
Cholesteatoma vs. Keratosis Obturans
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Cholesteatoma
 Unilateral
 Over the age of 40
 Dull, achy pain
 More bone erosion
 Otorrhea
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Keratosis Obturans
 Bilateral
 Under the age of 40
 Sharp pain
 Little bone erosion
 No otorrhea
Cholesteatoma
A
B
EAC cholesteatoma in 2 patients (A) and (B). Note presence of soft tissue mass and associated
bony remodelling and erosion. In B, note that the mass fills the EAC.
Cholesteatoma: MRI
A
B
C
Left EAC cholesteatoma: T1WI (A), T2WI (B), and post contrast T1WI (C) demonstrates a mass
filling the EAC. Note that this mass is isointense on T1WI, hyperintense on T2WI and
demonstrates no enhancement.
Cholesteatoma: MRI, CT
A
B
Diffusion imaging (A) of same case as prior slide demonstrates restricted diffusion.
Coronal CT (B) demonstrates the EAC mass filling the EAC with associated bony erosion
and remodelling.
Keratosis Obturans
A
B
Axial (A) and coronal (B) CT scan in patient with left EAC mass. Note that the mass
abuts the tympanic membrane and floor of the EAC with associated bony scalloping. The
mass was pearly white in appearance and was found to represent keratosis obturans.
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Middle Ear Cavity
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Acute otitis media
(AOM)
Chronic otitis media
(COM)
Cholesteatoma
Tympanosclerosis
Inflammation within the middle ear cavity may
represent acute otitis media, chronic otitis
media, or cholesteatoma.
Effusion within the middle ear cavity does not
equal acute OM.
Effusion within the middle ear cavity with signs
of infection (otalgia, fever, elevated WBC, ESR
or CRP) is indicative of infection.
Acute Otitis Media
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Bacterial infection
Streptococcus pneumoniae
 Haemophilus influenzae
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Less common, higher incidence of meningitis
Proteus
 Pseudomonas
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Mycotic infections: unusual
Acute Otitis Media: Imaging
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CT imaging
Fluid within the MEC
 No ossicular erosion
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MR imaging: Fluid signal intensity on MRI
Hypointense on T1-weighted images
 Hyperintense on T2-weighted images
 No enhancement
 No diffusion abnormality
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Chronic Otitis Media
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Unresolved inflammatory process
TM perforation commonly associated with
retraction pockets
Pseudomonas and Staphylococcus infection
most common organisms
Highly vascularized granulation tissue present
Chronic Otitis Media: Imaging
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CT imaging
Fluid/soft tissue in MEC
 Ossicular erosion or disruption may be present
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MR imaging
Post contrast images demonstrate enhancement
 Diffusion imaging: negative
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Chronic Otitis Media: CT
Serial axial CT images demonstrates soft tissue material within the
mesotympanum. There is no ossicular or bony erosion.
Chronic Otitis Media
A
B
C
D
Same patient as prior slide. MRI T1WI (A), post contrast T1WI (B), T2WI (C) and diffusion
(D) demonstrates isointense material in the right middle ear cavity (MEC) which enhances
in B. This was not well seen on CT and demonstrates no restricted diffusion (D).
Middle Ear Cavity Cholesteatoma
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Imaging similar to epidermoid
CT imaging
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Soft tissue mass with ossicular/bony erosion
MR imaging
Hypointense on T1-weighted images
 Hyperintense on T2-weighted images
 Post contrast images, no enhancement
 Diffusion imaging: Positive
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Pars Flaccida Cholesteatoma
A
B
Axial (A) and coronal (B) CT images demonstrate a mass lateral to the malleus head
with associated erosion of the scutum, classic for a pars flaccida cholesteatoma.
Cholesteatoma
A
B
Axial (A) and coronal (B) CT demonstrating a mass filling the middle ear cavity and
extending laterally into the EAC. Also note superior extension into the mastoid antrum
with erosion of the scutum. Notice in B the erosion of the lateral semicircular canal
representing a perilabyrinthine fistula.
Cholesteatoma: MRI
A
B
C
T1WI (A), post contrast (B), diffusion (C) and T2WI demonstrates
a mass in the MEC which is iso- mildly hyperintense on T1WI, no
enhancement (B), hyperintense on T2WI (D) and with restricted
diffusion (C) consistent with cholesteatoma.
D
Chronic Otis Media and
Cholesteatoma in the mastoid antrum
Fluid, debris or soft tissue fills the middle ear cavity and the
mastoid antrum on these CT images.
Chronic Otitis Media and
Cholesteatoma
A
B
C
D
Sequential T1WI (A, B), and post contrast T1WI (C, D) demonstrates enhancing
material (yellow arrow) in the middle ear cavity and non-enhancing material in the
mastoid antrum (red arrow). See next slide for more images.
Chronic Otitis Media and
Cholesteatoma
A
B
C
Sequential T2WI (A, B) and trace diffusion (C, D)
MR images demonstrate hyperintense material
within the MEC and mastoid antrum. Diffusion
imaging demonstrates restricted diffusion in the
mastoid antrum (D, red arrow). Found to have
chronic otitis media and cholesteatoma in the
mastoid antrum.
D
MR Imaging of the Middle Ear
MRI
Sequence
Acute Otitis Media
Chronic Otitis Media
Cholesteatoma
Post
Contrast
-
+
-
DWI
-
-
+
T1
T2
Tympanosclerosis
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Sequela of chronic otitis media
Noncholesteatomatous erosions
As granulation tissue regresses, a fibrous, calcific or bony
restriction to ossicular movement may occur
A
B
Sequential axial CT images (A) demonstrates fluid within the MEC. Follow up CT six
months later (B) demonstrate heterotopic calcification (red arrow) within the middle ear
cavity and fluid/debris representing chronic otitis media.
Mastoid Region
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Mastoid airspace disease
Effusion within the
middle ear cavity does
not represent mastoiditis
Signs of infection similar
to otitis media represent
acute mastoiditis
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Complications of
mastoiditis
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Coalescent mastoiditis
Abscess formation
Petrous apicitis
Superior extension
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Meningoencephalitis
Sinus thrombosis
Coalescent Mastoiditis
B
A
Sequential axial CT slices through the left temporal bone demonstrates coalescence of air
cells and erosion of the lateral cortex on the left side. B (located below the temporal bone)
demonstrates soft tissue swelling in the post auricular region.
Coalescent Mastoiditis with Post
Auricular Abscess/Air
A
B
Soft tissue (A) and bone window (B) axial CT of the left temporal bone demonstrates
opacification of the mastoid air cells, coalescence of air cells and erosion of the
medial and lateral mastoid cortex (red arrows). Note the extensive periauricular and
post auricular soft tissue swelling and the air collection lateral to the mastoid with
presence of fluid.
Mastoiditis with Abscess
Axial CT at the level of the mastoids demonstrates opacification of the mastoid air
cells and ring enhancing fluid collection in the soft tissues superficial to the base of the
petrous temporal bone (red arrows).
Petrous Apicitis
A
B
T1WI (A), post contrast T1WI (B) and trace diffusion
(C) demonstrates enhancement of the petrous apex and
adjacent dura. Note area of non enhancement of the
petrous apex which demonstrates diffusion restriction
in C, consistent with a petrous apex abscess. Patient
presented with a sixth nerve palsy.
C
Patient with known mastoiditis
on the right side
A
B
C
D
Post contrast T1WI axial (A), coronal (B), T2WI (C) and diffusion (D) images
demonstrate a ring enhancing fluid collection in the right temporal lobe arising
from the superior aspect of the temporal bone. On T2WI, the fluid collection
demonstrates a hypointense rim, and the contents demonstrate restricted diffusion
on the trace diffusion image consistent with a brain abscess.
Mastoiditis with Dural
Venous Sinus Thrombosis
A
B
C
Axial T1WI (A) demonstrates hyperintensity within the left transverse and sigmoid sinus (red arrows),
concerning for dural venous sinus thrombus. Axial T2WI (B) demonstrates left-sided mastoid airspace
opacification (blue arrow), consistent with mastoiditis. MR Venogram MIP image (C) demonstrates
absence of flow through the left transverse, sinus, left sigmoid sinus and proximal left internal jugular
vein (yellow arrows).
Cholesterol Granuloma
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Expansile lesion, most common petrous apex
May occur in the MEC or mastoids
CT imaging
Expansile without bone destruction
 Typically posterior to ICA
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MRI
Hyperintense on both T1- and T2-weighted images
 No enhancement
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Cholesterol Granuloma
-
Expansile lesion, most common petrous apex
May occur in the MEC or mastoids
Axial CT image
through the right
temporal bone (A)
demonstrates
expansile lesion (*)
in the petrous apex.
*
A
C
B
D
Corresponding to the
finding on CT, axial MR
T1WI (B), T2WI (C) and
fat saturated T1WI (D)
demonstrate T1 and T2
hyperintense lesion within
the right petrous apex
(yellow arrow).
This lesion does not
contain fat, but rather
blood and/or cholesterol
crystals given T1
hyperintensity.
MEC Cholesterol Granuloma
Axial CT image
through the left
temporal bone (A)
demonstrates
expansile lesion (*)
in the middle ear
cavity.
*
A
B
C
D
Corresponding to the
finding on CT, axial MR
T1WI (B), T2WI(C) and
contrast-enhanced T1WI
(D) demonstrate T1 and T2
hyperintense lesion within
the left middle ear cavity
(blue arrows), without
contrast enhancement.
Inner Ear: Labyrinthitis
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Inflammation of the membranous labyrinth
Symptoms include vertigo, hearing loss, or facial palsy.
Diagnosis by MRI, demonstrating enhancement of the
otic capsule and decreased or loss of signal on T2WI.
Route of spread
Tympanogenic
Meningogenic
Hematogenic
Posttraumatic
Agent
Viral
Autoimmune
Bacterial
Luetic
Other
Serous
Suppurative
Labyrinthitis
A
B
E
F
C
D
G
H
Sequential axial high resolution T2 images through the inner ear structures (A-D) demonstrates
alteration of fluid signal in the right cochlea (red arrow), compared to the normal left cochlea (blue
arrow). Sequential post contrast T1WI (E-H) demonstrating no enhancement of the inner ears.
Labyrinthitis
A
B
Sequential T1WI (A) and post contrast T1WI (B) demonstrates avid enhancement of
the cochlea and vestibule in B (red arrows). Also note chronic otomastoid airspace
disease in B with enhancement of the contents of the middle ear cavity and mastoids.
Labyrinthitis Ossificans
A
C
B
Patient with history of
meningitis 2 years prior to
the scan with subsequent
sensorineural hearing loss.
Right (A) and left (B) axial
CT images at the level of
the cochlea demonstrates
non visualization of the
cochlea bilaterally.
Ossification of the cochlea
bilaterally. Axial T2WI (C)
at the level of the cochlea
demonstrates absence of
the fluid signal intensity
within the cochlea due to
ossification.
Conclusion

Infectious and inflammatory disorders may primarily or
secondarily involve the temporal bone. This exhibit has
systematically described the underlying pathophysiology
and imaging findings of these conditions in the various
areas of the temporal bone and utility of different
imaging modalities in evaluating these entities.
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