Lesions of the Petrous Apex
Resident Physician: Nikunj A. Rana, M.D.
Faculty Mentor/Discussant: Dayton Young, M.D.
The University of Texas Medical Branch – UTMB Health
Department of Otolaryngology
Grand Rounds Presentation
January 28, 2015
Series Editor: Francis B. Quinn, Jr., MD, FACS -- Archivist: Melinda Stoner Quinn, MSICS
Outline
I.
II.
III.
IV.
V.
VI.
VII.
Anatomy
Clinical Presentation
Common Lesions
Cholesterol Granulomas
Surgical Approaches
Outcomes
References
Skull Base Tumors





IAC
Jugular Foramen
Mastiod/Middle ear
EAC
Petrous Apex
Axial CT Anatomy
Axial CT Anatomy
•
The petrous apex is the pyramidal, medial projection of
the petrous portion of the temporal bone.
•
The normal petrous apex is relatively simple in form with
only one principal variation: the degree of pneumatization.
•
That is, the apex may be variably pneumatized with
aerated connections to the middle ear or may contain
predominantly marrow fat.
80% adult mastoid aerated
• 30% adult petrous region aerated, 7% asymmetric
(Brackman)
•
Medial View
Medial View
•
The petrous apex is the pyramidal, medial projection of the
petrous portion of the temporal bone.
•
Can be anatomically described as a pyramid- shaped structure
that can be divided in a posterior and an anterior part by a line
passing in the coronal plane through the internal auditory canal
•
Chole, RA. “Petrous apicitis: surgical anatomy,” Annals of Otology, Rhinology and
Laryngology, vol.94, no.3, pp. 254–257,1985.
Axial CT Anatomy
Axial CT Anatomy
•
The petrous apex of the temporal bone is located
anteromedial to the inner ear within the angle created by
the greater wing of the sphenoid bone anteriorly and the
occipital bone posteriorly.
•
The anterior margin of the petrous apex forms the medial
posterior wall of the middle cranial fossa.
Superior View
Superior View
•
The petrous apex of the temporal bone is located
anteromedial to the inner ear within the angle created by
the greater wing of the sphenoid bone anteriorly and the
occipital bone posteriorly.
•
The anterior margin of the petrous apex forms the medial
posterior wall of the middle cranial fossa.
Inferior View
Inferior View
The most inferior and medial exocranial margin of PA is
separated from the clivus by
• the foramen lacerum
•
•
Above the foramen lacerum, the ICA exits the medial
opening of the carotid canal on its way to the cavernous
sinus.
Chapman PR, Shah R, Cure JK, Bag AK. Petrous Apex Lesions: Pictorial Review.
AJR:196, March 2011
Superior View
What makes the petrous apex anatomically complex is its medial location in the skull base
and its intimate relationship to other clinically important structures including:
• the cavernous sinus
• Dorello canal
• Meckel cave.
Outline
I.
II.
III.
IV.
V.
VI.
VII.
Anatomy
Clinical Presentation
Common Lesions
Cholesterol Granulomas
Surgical Approaches
Outcomes
References
Clinical Presentation


Very Broad
Primary Lesions





Bone
Penumatized air cells
ICA
“Down-going” intracranial processes
“Up-going” invasive nasopharyngeal or sinonasal lesions
via sinus of Morgagni
Given its location, the petrous apex is susceptible to multiple pathologic processes including
intrinsic lesions of bone, pneumatized air cells, or the petrous internal carotid artery; invasive
“downgoing” intracranial pro- cesses; or invasive “upgoing” infiltrating nasopharyngeal or sinonasal
lesions.
Chapman PR, Shah R, Cure JK, Bag AK. Petrous Apex Lesions: A Pictorial Review. AJR 2011;
196:WS26–WS37
Clinical Presentation

Close proximity to



Trigeminal Ganglion in Meckel’s Cave
Petrosphenoidal ligament –> Dorello Canal (superior
envagination)  abducens nerve
Gradenigo’s syndrome: retro-orbital pain, otorrhea,
ipsilateral CN VI palsy
• Gradenigo’s syndrome: retro-orbital pain,
otorrhea, ipsilateral CN VI palsy
• Compression of IAC  hearing loss and
vestibular dysfunction
• CN VII: late if slow growing mass, early if
neoplasms or IAC involvement
• Pain more common with neoplasms
• Mastoid: CN IX  neck pain
• Middle Fossa and Superior petrosal region: CN
V  retro-orbital and facial pain
• Posterior Fossa: CN IX/X and first 3 cervical
roots 
Other Cranial Nerves

Compression of IAC




Facial Nerve



Hearing loss
Vestibular Dysfunction
Facial paralysis
Early with IAC involvement or neoplasms
Late with slow growing mass
Mastoid: CN IX  neck pain
Implications of Complex Anatomy


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Broad, non-specific presentations
Clinical presentations NOT enough
Imaging Studies Key

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
CT- bone evaluation
MRI T1 weighted – Fat hyperintense
MRI T2 weighted – CSF/water hyperintense
Implications of Complex Anatomy
•
Clinical presentations of these lesions, therefore, can be
quite variable and depend largely on involvement of
numerous intimately adjacent intra- and extracranial
structures, especially the cranial nerves.
•
Given this variability, petrous apex lesions cannot be
diagnosed accurately on the basis of clinical findings alone.
•
Fortunately, many of these lesions have characteristic MRI
and CT appearances that can often allow a precise
diagnosis.
Outline
I.
II.
III.
IV.
V.
VI.
VII.
Anatomy
Clinical Presentation
Common Lesions
Cholesterol Granulomas
Surgical Approaches
Outcomes
References
Razek AA, Huang BY. Lesions of the Petrous Apex: Classification and
Findings at CT and MR Imaging. RadioGraphics 2012; 32:151–173
Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatoma
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony
preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile
smooth border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatoma
1. Loss of normal
air cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile
smooth border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony
erosion
Hypointense
Hyperintense
No
PA Effusion

The petrous apex air cell system may develop an effusion
associated with an upper respiratory tract infection. This
may be apparent in an asymptomatic patient who has a
MRI for an unrelated condition.
PA Effusion
PA Effusion
Petrous apex effusions are non-enhancing, non-expansile,
petrous apex lesions which demonstrate
 Fig. 3.
 Radiological imaging of petrous apex effusion.
(a)Axial computed tomography image showing preservation
of intact trabeculae (arrows); distinguish from CG
(b)Axial, T1-weighted magnetic resonance imaging (MRI)
showing a non-expansile lesion with low signal intensity.
(c)Axial, T2-weighted MRI showing a non-expansile lesion
with high signal intensity.
(d)Axial, T1-weighted, post-contrast MRI showing a nonenhancing lesion.

PA Effusion
The petrous apex air cell system may develop an effusion associated with an upper respiratory tract
infection. This may be apparent in an asymptomatic patient who has a MRI for an unrelated
condition.
Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatoma
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Petrous apex mucoceles
•
Petrous apex mucoceles are uncommon. Similarly to mucoceles found
elsewhere in the head and neck, they are most likely caused by
postinflammatory obstruction of a pneumatized petrous apex air cell.
•
An obstructed air cell containing respiratory epithelium that maintains its
ability to secrete mucous.
•
The continued production and accumulation of mucoid material within the
obstructed air cell, along with the associated inflammatory response: 
expansion, remodeling, and ultimately permeative erosion or destruction of
the bony margins.
•
CT of mucoceles shows a smoothly expansile bone lesion that may cause
septal erosion and can be difficult to distinguish from a cholesterol
granuloma.
Mucocele
Mucocele

CT of mucoceles shows a smoothly expansile bone lesion that
may cause septal erosion and can be difficult to distinguish
from a cholesterol granuloma.
Radiological imaging of petrous apex mucocele.
(a) Axial, T1-weighted magnetic resonance imaging (MRI) showing
bilateral petrous apex mucoceles exhibiting smooth expansion
and low signal intensity.
(b) Axial, T2-weighted MRI showing bilateral petrous apex
mucoceles with characteristic high signal intensity (isointense
to fluid).
(c) Axial, diffusion-weighted MRI showing that these lesions are
not diffusion-restricted, which distinguishes them from petrous
apex epidermoids.

Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatom
a
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Petrous apex cholesteatomas
Petrous apex cholesteatomas and epidermoids make up 4%–9%
of all petrous apex lesions.
• Cholesteatomas may be classified as acquired or congenital,
with congenital cholesteatomas of the petrous apex being more
common.
• Congenital cholesteatomas arise from aberrant ectoderm that
is trapped during embryogenesis; at histologic analysis, they
consist of cysts lined with stratified squamous epithelium and
filled with keratinous debris
•
•
These lesions classically occur in children and young adults.
Mafee MF, Kumar A, Heffner DK. Epidermoid cyst (cholesteatoma) and cholesterol
granuloma of the temporal bone and epidermoid cysts affecting the brain.
Neuroimaging Clin N Am 1994;4(3): 561–578.
Cholesteatoma
Cholesteatoma

Radiological imaging of petrous apex epidermoid (right
ear).
(a) Axial
computed tomography image showing an expansile
lesion in the right petrous apex.
(b) Axial, T1- weighted magnetic resonance imaging (MRI) showing
an expansile lesion in the right petrous apex with low signal
intensity.
(c) Axial, T2-weighted MRI showing an expansile lesion in the right
petrous apex with high signal intensity.
(d)Axial, T1-weighted, post- contrast MRI showing a nonenhancing lesion.
Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatom
a
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Cholesterol Granuloma
Cholesterol Granuloma
Radiological images of petrous apex cholesterol
granuloma.
(a)Axial computed tomography image showing erosion of
trabeculae and smooth expansion in the petrous apex.
(b)Coronal, T1-weighted, pre-contrast magnetic resonance
imaging (MRI) showing a non-enhancing, expansile lesion
in the petrous apex with high signal intensity.
(c)Axial, T1-weighted, post- contrast MRI showing an
expansile lesion with high signal intensity which does not
enhance.
(d)Axial, T2-weighted MRI showing an expansile petrous
apex lesion with high signal intensity.

Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatom
a
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Encephalocele
Encephalocele
Radiological imaging of petrous apex cephalocoele.
(a) Axial computed tomography image showing bilateral smooth erosion
extending from Meckel’s cave to the petrous apex.
(b) Axial, T1-weighted, pre-contrast magnetic resonance imaging (MRI) showing
bilateral lesions isointense to cerebrospinal fluid (CSF) (low-signal
intensity).
(c) Axial, T2-weighted MRI showing bilateral lesions isointense to CSF (high
signal intensity).
(d) Axial, T1- weighted, post-contrast MRI showing bilateral lesions which do
not enhance.
(e) Axial, constructive interference in the steady state (‘CISS’) MRI focused on
the right petrous apex cephalocoele, showing a lesion isointense to CSF.
(f) Axial, constructive interference in the steady state MRI focused on the left
petrous apex cephalocoele, showing the trigeminal nerve embedded
within the cephalocoele.

Lesion
CT
T1 Weighted
MRI
T2 Weighted
MRI
Enhancement
PA Effusion
1. Bony preservation
2. Intact trabeculae
Hypointense
Hyperintense
No
Mucocele
1. Hypodense
2. Expansile smooth
border
3. Normal bony
architecture
Hypointense
Hyperintense
No
Cholesteatoma
1. Loss of normal air
cells
2. Non-enhancing
3. Isointense CSF
Hypointense
Hyperintense
No
Cholesterol
Granuloma
1. Expansile smooth
border
2. Occasional rim
enhancement
3. Isointense with
brain
Hyperintense
Hyperintense
No
Encephalocele
Smooth bony erosion
Hypointense
Hyperintense
No
Bone Marrow
Non-expansile
Hyperintense
Hypointense
No
Bone Marrow
Bone Marrow

Radiological imaging of petrous apex marrow.
(a) Axial
computed tomography image showing a non-expansile
lesion in the left petrous apex.
(b) Axial, T1-weighted, pre-contrast magnetic resonance imaging
(MRI) showing a left-sided lesion isointense to fat (bright
signal).
(c) Axial, T2-weighted MRI showing a left-sided lesion isointense
to fat (dark signal).
(d)Axial, T1-weighted, post-contrast MRI with fat suppression,
showing suppression of the fat signal in the marrow.
Cholesterol Granuloma
Composition

Cystic lesions containing cholesterol crystals surrounded
by




Foreign body giant, fibrous tissue reaction,
Chronic inflammation
More liquid in nature
Cyst wall:



Fibrous connective tissue
NOT keratinizing squamous epithelium (cholesteatoma)
Therefore complete excision not necessary
Cholesterol Granuloma



Most common lesion of PA
30x less common than acoustic neuroma
Etiology


Theory 1 (older): Obstruction-vacuum hypothesis
Theory 2 (new): Exposed Marrow hypothesis Jackler 2003, Hoa
2012
Problems with the Classic (Obstruction-Vacuum) Hypothesis: Impaired ventilation of mucosalined pneumatic tracts in the middle ear, mastoid, paranasal sinuses, and lung are very common,
but CG is rare. The extraordinary levels of temporal bone pneumatization typically observed in
PA CG cases is indicative of excellent ventilation and freedom from inflammatory mucosal
disease. Were underpressure due to gas absorption alone sufficient to trigger hemorrhage, CG
ought to be frequent in otitis media with effusion.
Jackler, RK. Cho, M. A New Theory to Explain the Genesis of Petrous Apex Cholesterol
Granuloma. Otology & Neurotology:January 2003 - Volume 24 - Issue 1 - pp 96-106.
Obstruction-Vacuum Hypothesis
Temporal Bone
Mucosal Swelling
Resorption of Gas
in Petrous Cavity
Negative
Pressure
Hemorrhage into
temporal bone air cells
Degradation of Hemosiderin
+ Cholesterol
• Temporal bone mucosal swelling +
resorption of gas that is present 
• Negative pressure and hemorrhage
into the temporal bone air cells
• Degradation of hemosiderin and
cholesterol which  inflammatory
granulomatous reaction
Inflammatory
Granulomatous
Reaction
Problems with Obstruction-Vacuum
Hypothesis

Impaired ventilation of mucosa-lined pneumatic tracts





Extraordinary levels of t-bone pneumatization in PA CG
cases



Middle ear
Mastoid
Paranasal sinuses
Lung
indicative of excellent ventilation
freedom from inflammatory mucosal disease
If underpressure sufficient to trigger hemorrhage, why
OME  CG?
Exposed Marrow Hypothesis
PA Pneumatization
Hematopoietic Marrow
Budding Mucosa
Bony Interface
Hemorrhage
Hemosiderin + Lipids
PA Outflow
Obstruction
Substrate for CG
Cyst Formation
Jackler RK, Cho M. A new theory to explain the genesis of petrous apex cholesterol granulomas. Otol Neurotol. 2003; 24:96–106.
Exposed Marrow Hypothesis

As cellular tracts penetrate the apex during young adulthood, budding
mucosa invades and replaces hematopoietic marrow. The bony interface
becomes deficient, with coaptation of richly vascular marrow and the
mucosal air cell lining. Hemorrhage from the exposed marrow coagulates
within the mucosal cells and occludes outflow pathways. Sustained
hemorrhage from exposed marrow elements provides the engine
responsible for the progressive cyst expansion. As the cyst expands, bone
erosion increases the surface area of exposed marrow along the cyst wall.
This exposed marrow theory explains the unique proclivity of the healthy
and well-pneumatized PA to form a CG.

Marrow in the petrous apex serves as a source for both hemosiderin and
lipids. Cholesterol crystals that result from both breakdown of these lipids
within the marrow instigate an inflammatory reaction that is believed to be
necessary for formation of these cysts (1,11). Some have suggested that the
variability in aggressiveness of the cholesterol granuloma is related to the
richness of the adjacent blood supply
Hoa M, House J, Linthicum FH. Petrous Apex Cholesterol Granuloma: Maintenance of Drainage Pathway, the Histopathology
of Surgical Management and Histopathologic Evidence for the Exposed Marrow Theory. Otol Neurotol. 2012 August ; 33(6)
Hoa M, House J, Linthicum FH. Petrous Apex Cholesterol Granuloma: Maintenance of Drainage Pathway, the Histopathology
of Surgical Management and Histopathologic Evidence for the Exposed Marrow Theory. Otol Neurotol. 2012 August ; 33(6)
Hoa M, House J, Linthicum FH. Petrous Apex Cholesterol Granuloma: Maintenance of Drainage Pathway, the Histopathology
of Surgical Management and Histopathologic Evidence for the Exposed Marrow Theory. Otol Neurotol. 2012 August ; 33(6)
Clinical Presentation

Most commonly asymptomatic, found due to work up of
other problems (HA)
Hearing loss (64.7%), vestibular symptoms (56%), tinnitus (50%), headache (32.3%),
facial twitching (23.5%), facial paresthesia (20.6%), otorrhea (11.8%), diplopia (5.9%),
facial weakness (2.9%)
Aggressive CG

Type I: CN VIII involvement



Type II: Superior PA



SNHL + tinnitus
Followed by vertigo + dizziness
HA + facial pain
Middle + posterior fossa dural irritation
Type III: Meckel’s Cave


CN V or CN VI
Possible OM from ET compression
Mosnier I, Cyna-Gorse F, Grayeli AB, Fraysse B, Martin C, Robier A et al. Management of cholesterol granulomas of the petrous
apex based on clinical and radiologic evaluation. Otol Neurotol 2002;23:522–8
Aggressive CG
•
•
•
First type, sensorineural hearing loss and tinnitus are the commonest presenting
symptoms, followed by vertigo and dizziness. In such cases, involvement of the
vestibulocochlear nerve is typical.
Second type is related to a cholesterol granuloma located in the superior part of the
petrous apex, in which compressional symptoms such as headache and facial pain are
the principal features; this type is related to middle and posterior fossa dural
irritation.
Third type: involvement of either the trigeminal or the abducens nerve, signifying
compression of the Meckel’s cave region. Rarely, recurrent otitis media can be a
feature, indicating pressure on the eustachian tube.
Mosnier I, Cyna-Gorse F, Grayeli AB, Fraysse B, Martin C, Robier A et al. Management of cholesterol granulomas
of the petrous apex based on clinical and radiologic evaluation. Otol Neurotol 2002;23:522–8
Park KC, Wong G, Stephens JC, Saleh HA. Endoscopic transsphenoidal drainage of an aggressive petrous apex
cholesterol granuloma: unusual complications and lessons learnt. The Journal of Laryngology & Otology (2013),
127, 1230–1234.
To Drain or Not to Drain?







Solid tumors + cholesteatoma
Goal of Drainage?
Sx = surgical; no symptoms = non-surgical
Controversial
Natural hx not well defined for small cysts
Drain large lesions or sx’s CN involvement
Delaying surgery in presence of sx’s = no real advantage
• Solid tumors/cholesteatoma removed when first identified, rather than after symptoms develop b/c these symptoms
frequently reveal further involvement of other vital structures
• Drainage: establish outflow drainiage pathway that is maintained so that CG expansion does not result in recurrence of
patient symptoms
• Sx = surgical, no symptoms (still controversial, b/c symptoms can be cuased by other things, ie non-specific HA) = nonsurgical
• Natural hx not well defined for small cysts
• Drain large lesions or sx’s pain/visual changes, diplopia, hearing loss, vertigo, facial nerve weakness
• Delaying surgery in presence of symptoms offers no real advantage
Outline
I.
II.
III.
IV.
V.
VI.
VII.
Anatomy
Clinical Presentation
Common Lesions
Cholesterol Granulomas
Surgical Approaches
Outcomes
References
Surgical Approaches


Serviceable Hearing: Air cells + otic capsule
Above




Below





MCF approach: pros/cons
Attic
Root of zygomatic arch
Infralabyrinthine
Infracochlear
Anterior
Non-serviceable hearing: translabyrinthine
Infratemporal fossa A/B/C
Approaches
Endoscopic Transphenoidal
 Petrous Angle: 10-20
degrees
 Good for patients in
which there is space
between medial wall of
cyst and lateral wall of
paraclival ICA
 CI in patients where cysts
are hidden behind ICA
Shoman, N. Donaldson, AM Ksiazek, J, Pensak, ML, Zimmer, LA. First Stage in Predicative Measure for Transnasal
Transsphenoidal Approach to Petrous Apex Cholesterol Granuloma. Laryngoscope, 123:581–583, 2013
Approaches –
Endoscopic Transphenoidal
•
Feasablity of endoscopic approach is based on petrous
angle (angle centered at vomer, extending between
medial aspect of the C3 segment of ICA and occipital
protuberance)
•
Majority of temporal bones have petrous angle 10-20
degrees (82.8%)
Neal 2013
Outline
I.
II.
III.
IV.
V.
VI.
VII.
Anatomy
Clinical Presentation
Common Lesions
Cholesterol Granulomas
Surgical Approaches
Outcomes
References
Outcomes


Successful Tx: absence of growth + improvement in symptoms
Open: largest study 82%, smaller studies 90-100%



Symptoms improvement 90% (71/79, 6 studies)
Recurrence 12.5% (15/120, 9 studies)
Complication rate: 24.3% (n=115, 9 studies)


Hearing loss/CSF leak
Endoscopic:


resolution rate 98.5%,
complication rate 13.2%,


Restenosis 20% (9/45),


most common epistaxis, 1 CSF leak
symptomatic/recurrence 7.5% (4/45)
Stent: 45% (23/45)


1/23 developed symptoms after (4.3%)
As opposed 10.7% if non-stented
Outcomes

Absence of continuous growth in combination with an
improvement in symptoms
Eytan DJ, Kshettry VR, Sindwani R, Woodard TD, Recinos PF. Surgical outcomes after endoscopic
management of cholesterol granulomas of the petrous apex:
a systematic review. Neurosurg Focus 37 (4):E14, 2014
Outcomes


Successful Tx: absence of growth +
improvement in symptoms
Endoscopic:


resolution rate 98.5%,
complication rate 13.2%,
 most common epistaxis, 1 CSF leak


Restenosis 20% (9/45),
 symptomatic/recurrence 8.8% (4/45)
Stent: 51%% (23/45)
 1/23 developed symptoms after
(4.3%)
 As opposed 10.7% if non-stented
 P = 0.6
Outcomes
•
Absence of continuous growth in combination with an
improvement in symptoms
•
Stent more likely to be placed in narrow drainage
pathway; sample bias?
Outcomes


CN affected for short period have better prognosis
Follow up MRI of CG shows



cyst remains full of fluid but hypointense T1,
return of hyperintense T1 suggest inadequate drainage in a
symptomatic lesion
Radiologic characteristics = successful long term drainage




Stable size- maximal diameter
Presence of cyst aeration
Placement of drainage stent
***sx recurrence can occur with re-accumulation within cysts
w/o enlargement; therefore stable size may not be best
Outcomes
•
CN affected for short period have better prognosis
•
Follow up MRI of cholesterol granuloma shows cyst remains full
of fluid but hypointense T1, return of hyperintense T1 suggest
inadequate drainage in a symptomatic lesion
•
Lesion size, resolution of patient symptoms, occurrence of
complications and presence of aeration have been reported
•
Most common cause of recurrence is obstruction of the
drainage site by fibrous tissue
Long Term



Lesion size, resolution of patient symptoms, occurrence
of complications, and presence of aeration have been
reported
Most common cause of recurrence is obstruction of the
drainage site by fibrous tissue
Revision rate of surgery 41% (7/17)



18% revision with stent (2/11)
83% revision w/o stent (5/7)
p=.035
Post-operative Imaging
Magnetic resonance imaging characteristics of petrous apex cholesterol granuloma:
Left Image: drainage catheter leading from the petrous apex cholesterol granuloma cyst
cavity to the middle-ear cavity, on coronal, T2-weighted image.
Hoa M, House J, Linthicum FH. Petrous Apex Cholesterol Granuloma: Maintenance of Drainage Pathway, the Histopathology
of Surgical Management and Histopathologic Evidence for the Exposed Marrow Theory. Otol Neurotol. 2012 August ; 33(6)
Final Thoughts








Lesions of PA present broadly
Imaging key to dx
CG can be incidental findings
Operate on CG only if large OR sx’s of CN involvement
Endoscopic management is safe option (anatomy)
Stent placement may be beneficial
Long term f/u with MRI
Future works: mucosal flaps + gel foam
Faculty Discussion: Dayton Young, MD - Page 1

Dr. Rana, that was a very good presentation, very thorough. I think you
covered mostly, maybe all the aspects that would come up in this kind of a
case. Petrous apex lesions are different from most lesions that you learn
about in medicine. The diagnosis usually isn’t based on a biopsy, because
it’s so hard to get to. It’s in the middle of the head. So we do rely a lot on
imaging, and we know a lot about imaging. The two lesions that I think
most about as I think back about patients I’ve seen are first of all, the very
common cholesterol granuloma and the other one is bone marrow. So,
these are things which you’ve got to be prepared to look for. You’ll be
asked to interpret an image that’s been found during an otherwise normal
scan, or in the diagnostic search for the cause of a headache. And you will
have to explain that it’s normal bone marrow. Otherwise, that becomes
the focus of the headache, and you want to avoid going down that pathway.
The cases that you’re really going to be looking at are either really big or
associated with some sort of neurological sign.
Faculty Discussion: Dayton Young, MD - Page 2
The other place where I’ve seen these most often is in a postoperative
mastoid. It’s not uncommon to go into a mastoid for a revision surgery and you find a
cholesterol granuloma right there. And it’s probably based on blood products that
were there from the original surgery. There’s often nothing to do about them - you
end up draining them at the time. They are a characteristic brown color when you see
them and usually make no difference clinically.
Surgical approach - You described a number of surgical approaches, a lot of
them had been tried earlier on back when Gradenigo’s syndrome was big and before
antibiotics. A lot of these approaches were developed by people who were draining
abscesses. The surgical approach will be different on every patient, usually based on
the pneumatization of the temporal bone and the sphenoid sinus. If you have a
sphenoid sinus that is well pneumatized and is abutting the petrous apex, it’s a straight
shot into the petrous apex sometimes. Other times in the T-bone scan there’s a well
pneumatized air cell tract right underneath the cochlea. Sometimes there’s plenty of
space to do an infralabyrinthine approach and sometimes in front of the cochlea. It
really does depend on the patient’s anatomy. The middle cranial fossa approach is
probably the least favored approach. The drainage route would be a stent of some
kind placed up underneath the dura and into the middle ear space. It doesn’t work
well because it’s not dependent drainage.
That was a good presentation. Thank you, Dr. Rana.
References
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Chole, RA. “Petrous apicitis: surgical anatomy,” Annals of Otology, Rhinology and Laryngology, vol.94, no.3, pp. 254–
257,1985.
Chapman PR, Shah R, Cure JK, Bag AK. Petrous Apex Lesions: Pictorial Review. AJR:196, March 2011
Razek AA, Huang BY. Lesions of the Petrous Apex: Classification and Findings at CT and MR Imaging. RadioGraphics
2012; 32:151–173
Mafee MF, Kumar A, Heffner DK. Epidermoid cyst (cholesteatoma) and cholesterol granuloma of the temporal bone
and epidermoid cysts affecting the brain. Neuroimaging Clin N Am 1994;4(3): 561–578.
Jackler RK, Cho M. A new theory to explain the genesis of petrous apex cholesterol granulomas. Otol Neurotol.
2003; 24:96–106.
Mosnier I, Cyna-Gorse F, Grayeli AB, Fraysse B, Martin C, Robier A et al. Management of cholesterol granulomas of
the petrous apex based on clinical and radiologic evaluation. Otol Neurotol 2002;23:522–8
Park KC, Wong G, Stephens JC, Saleh HA. Endoscopic transsphenoidal drainage of an aggressive petrous apex
cholesterol granuloma: unusual complications and lessons learnt. The Journal of Laryngology & Otology (2013), 127,
1230–1234.
Brackmann DE, Toh E. Surgical management of petrous apex cholesterol granulomas. Otol Neurotol 2002;23:529–33
Giddings NA, Brackmann DE, Kwartler JA, “Transcanal infracochlear approach to the petrous apex,” Otolaryngology—
head and neck surgery, vol.104, no.1, pp. 29–36,1991.
Shoman, N. Donaldson, AM Ksiazek, J, Pensak, ML, Zimmer, LA. First Stage in Predicative Measure for Transnasal
Transsphenoidal Approach to Petrous Apex Cholesterol Granuloma. Laryngoscope, 123:581–583, 2013
Eytan DJ, Kshettry VR, Sindwani R, Woodard TD, Recinos PF. Surgical outcomes after endoscopic management of cholesterol
granulomas of the petrous apex:
a systematic review. Neurosurg Focus 37 (4):E14, 2014
Isaacson B, Kutz JW, Roland PS. “Lesions of the petrous apex: diagnosis and management,” Otolaryngologic Clinics of North
America, vol. 40, no. 3, pp. 479–519, 2007.
Lesions of the Petrous Apex
Resident Physician: Nikunj A. Rana, M.D.
Faculty Mentor/Discussant: Dayton Young, M.D.
The University of Texas Medical Branch – UTMB Health
Department of Otolaryngology
Grand Rounds Presentation
January 28, 2015
Series Editor: Francis B. Quinn, Jr., MD, FACS -- Archivist: Melinda Stoner Quinn, MSICS