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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. Anatomy

II. Clinical Presentation

III. Common Lesions

IV. Cholesterol Granulomas

V. Surgical Approaches

VI. Outcomes

VII. 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. Anatomy


III. Common Lesions



VI. Outcomes

VII. 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 processes; 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


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

Hearing loss

Vestibular Dysfunction

Facial paralysis

Facial Nerve

Early with IAC involvement or neoplasms

Late with slow growing mass

Mastoid: CN IX neck pain

Implications of Complex Anatomy

Broad, non-specific presentations

Clinical presentations NOT enough

Imaging Studies Key

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. Anatomy


III. Common Lesions



VI. Outcomes

VII. References

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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


Cholesteatoma 1. Loss of normal air

cells

2. Non-enhancing

3. Isointense CSF


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


MRI

T2 Weighted

MRI

Enhancement

PA Effusion 1. Bony

preservation




2. Expansile

smooth border

3. Normal bony

architecture


Cholesteatoma 1. Loss of normal

air cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile

smooth border

2. Occasional rim

enhancement

3. Isointense with

brain


Encephalocele Smooth bony

erosion



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 non-

enhancing 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.


MRI

T2 Weighted

MRI

Enhancement





2. Expansile smooth

border

3. Normal bony

architecture



cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile smooth

border

2. Occasional rim

enhancement

3. Isointense with brain




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.


MRI

T2 Weighted

MRI

Enhancement





2. Expansile smooth

border

3. Normal bony

architecture


Cholesteatom

a

1. Loss of normal air

cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile smooth

border

2. Occasional rim

enhancement

3. Isointense with

brain




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 non-

enhancing lesion.


MRI

T2 Weighted

MRI

Enhancement





2. Expansile smooth

border

3. Normal bony

architecture


Cholesteatom

a


cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile smooth

border

2. Occasional rim

enhancement

3. Isointense with

brain




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.


MRI

T2 Weighted

MRI

Enhancement





2. Expansile smooth

border

3. Normal bony

architecture


Cholesteatom

a


cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile smooth

border

2. Occasional rim

enhancement

3. Isointense with

brain




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.


MRI

T2 Weighted

MRI

Enhancement





2. Expansile smooth

border

3. Normal bony

architecture



cells

2. Non-enhancing

3. Isointense CSF


Cholesterol

Granuloma

1. Expansile smooth

border

2. Occasional rim

enhancement

3. Isointense with

brain




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.


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


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 mucosa-

lined 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.

http://journals.lww.com/otology-neurotology/toc/2003/01000

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

Inflammatory

Granulomatous

Reaction

• 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

Problems with Obstruction-Vacuum

Hypothesis

Impaired ventilation of mucosa-lined pneumatic tracts

Middle ear

Mastoid

Paranasal sinuses

Lung

Extraordinary levels of t-bone pneumatization in PA CG

cases

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

HemorrhagePA Outflow

Obstruction

Hemosiderin + Lipids 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)






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

SNHL + tinnitus

Followed by vertigo + dizziness

Type II: Superior PA

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) = non-

surgical

• 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. Anatomy


III. Common Lesions



VI. Outcomes

VII. References

Surgical Approaches

Serviceable Hearing: Air cells + otic capsule

Above

MCF approach: pros/cons

Attic

Root of zygomatic arch

Below

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. Anatomy


III. Common Lesions



VI. Outcomes

VII. 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%,

most common epistaxis, 1 CSF leak

Restenosis 20% (9/45),

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.

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 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

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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

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