Embolization of Intracranial & Skull Base Tumors (Paragangliomas)

Embolization of
Intracranial & Skull Base
Tumors
(Paragangliomas)
Mohamed M.A. Zaitoun, MD
Interventional Radiology Consultant, Zagazig University Hospitals, Egypt
FINR-Switzerland
zaitoun82@gmail.com
Interventional Radiology Unit,
Zagazig University, Egypt

Knowing as much as possible
about your enemy precedes
successful battle and learning
about the disease process
precedes successful
management

Paragangliomas
-These are benign neuroendocrine tumors that
arise from chromaffin cells in paraganglia or
chromaffin-negative glomus cells derived from
the neural crest
-Paraganglia are normal structures that develop
from the neural crest , they accompany cranial
nerves and cluster around cranial nerve ganglia
, tumors of the paraganglia are called
Paragangliomas
-They have been given several names including
chemodectoma , glomus tumors , nonchromaffin
paraganglioma & neurocristopathic tumor

-The ascending pharyngeal artery supplies the
autonomic nervous system in the neck and links
the sites of paraganglioma development , thus
its branches supply tympanic , jugular , vagal &
carotid body tumors
-Multiple tumors in 5-10 %
-Familial autosomal dominant disorder :
*Less than 10 % of cases
*Multicentricity in 30-50 % affected
*Associated with defects on chromosome 11q23

-Four common locations :
1-Carotid Body Paraganglioma
2-Glomus Vagale Paraganglioma
3-Glomus Jugulare Paraganglioma
4-Glomus Tympanicum Paraganglioma

GT=Glomus Tympanicum , GJ=Glomus Jugulare , GV=Glomus Vagale
, CBP=Carotid Body paraganglioma

1-Carotid Body Paraganglioma :
a) Incidence
b) Location
c) Clinical Picture
d) Classification
e) Radiographic Features

a) Incidence :
-Commonest site for paragangliomas in the
head & neck

b) Location :
-At the common carotid artery bifurcation
-Splays the ICA & ECA and completely fills
the carotid bifurcation

c) Clinical Picture :
-Non tender , enlarging lateral neck mass
which is mobile , pulsatile & associated
with a bruit

d) Classification : Shamblin Classification
-Based on involvement of the carotid arteries
1-Shamblin Class I CBTs : Non-adherent
-Are localized tumors with splaying of the carotid bifurcation
but little attachment to the carotid vessels , complete
surgical resection is generally possible with only minimal
risk of vascular or cranial nerve complications
2-Shamblin Class II CBTs : Adherent
-Partially surround the carotid vessels and complete
resection is more challenging
3-Shamblin class III CBTs : Encasting
-intimately surround the carotid
-Complete resection is very challenging and often requires
temporary interruption of the cerebral circulation for
vascular reconstruction , the risk of permanent vascular
and neural defects is significantly higher than for Class I
and Class II tumors

The Shamblin classification is based on involvement of the carotid arteries which are
shown by white arrows in A-C , The tumors are indicated by yellow arrows
(A) CBT (class I) : T2 shows a CBT in a typical location , bulging of the left carotid
bifurcation without any encasement of the carotid vessels , (B) CBT (class II) : T2
shows a right-sided CBT with a partial encasement of the internal and external carotid
artery , (C) CBT (class III) : CT-angiography reveals a huge left-sided CBT with a
complete encasement of the carotid vessels

e) Radiographic Features :
1-CT
2-MRI
3-Angiography

1-CT :
-Contrast enhanced CT is excellent at depicting
these lesions
-Typical appearances are :
*Soft tissue density on non-contrast CT (similar to
muscle)
*Bright and rapid (faster than schwannoma)
enhancement
*Splaying of the ICA and ECA

CT+C shows an intensely enhancing left carotid space mass (m) that splays
the ECA (short arrow) from the ICA (long arrow)

CT+C shows intensely enhancing tumor in the post-styloid space (star)
causing splaying of internal and external carotid artery (arrows)

CT+C shows hyperenhancing mass measuring 1.2 cm in diameter
(arrow) is seen in left carotid space , where tumor is typically located
between left internal carotid artery and external carotid artery

2-MRI :
*T1 :
-Iso to hypointense compared to muscle
-Salt and pepper appearance representing a
combination of punctate regions of hemorrhage
or slow flow (salt) and flow voids (pepper)
*T2 :
-Hyperintense compared to muscle
-Salt and pepper appearance also seen on T2
*T1+C :
-Enhances

T1 shows tumor (arrow) of isointensity at left common carotid bifurcation , note
multiple flow voids (arrowheads) within tumor

T2 shows heterogeneous high signal intensity of tumor (arrow) in left
carotid space , Salt-and-pepper appearance is noted in tumor

T1+C shows heterogeneously enhancing tumor mass
(arrow) in left carotid space

T1+C with fat saturation shows right carotid body
paraganglioma

3-Angiography :
-The splaying of the carotid vessels (lyre sign) is identified
with an intense blush in tumor & enlarged feeding
arteries with and (early vein) seen due to arteriovenous
shunting
-The principle arterial blood supply is from muscular spinal
branches of the ascending pharyngeal artery and tumors
may recruit from branches of the lingual artery , superior
laryngeal artery , ascending cervical artery or deep
cervical artery
-Embolization can be performed transarterially or by
percutaneous puncture into the tumor vessels

-Lateral left common carotid
artery injection , normal 2D
appearance of the left
common carotid artery
bifurcation region
1 common carotid artery
2 internal carotid artery
2b carotid bulb
3 external carotid artery
4 ascending pharyngeal
5 occipital artery
6 posterior auricular artery
7 superior thyroid artery
9 lingual artery
10 facial artery
11 superficial temporal
12 internal maxillary artery

-Lateral 2D view
following
selective external carotid
artery injection , there is
a hypervascular mass
adjacent to the proximal
ECA
This is the typical
appearance of a carotid
body tumor (glomus or
paraganglioma)
6 occipital artery
9 lingual artery
10 facial artery
11 superficial temporal
artery
12 internal maxillary
artery
13 middle meningeal
artery

-Lateral 3D view following
left common carotid artery
injection , note the
hypervascular mass typical
of a carotid body tumor
(glomus or paraganglioma)
situated between the
proximal internal and
external carotid arteries
1 common carotid
artery
2 internal carotid artery
3 external carotid
artery
4 ascending
pharyngeal artery
7 superior thyroid
artery

-Medial 3D view following
left common carotid artery
injection , note the
hypervascular mass
typical of a carotid body
tumor (glomus or
paraganglioma) situated
between the proximal
internal and external
carotid arteries
1 common carotid
artery
2 internal carotid
artery
3 external carotid
artery
4 ascending
pharyngeal artery
7 superior thyroid
artery

Lateral angiogram of left common carotid artery shows splaying of
internal carotid artery and external carotid artery by hypervascular
mass (arrow)

Lateral angiographic view obtained after a left CCA injection reveals
splaying of the ECA from the ICA by a hypervascular mass (arrows)
that extends to the bifurcation

Lateral angiographic view obtained after a selective left ascending
pharyngeal artery injection reveals the hypervascular mass (arrows)
with primary vascular supply from this artery

Pre (A) and post (B) embolization angiogram of a carotid body tumor

2-Glomus Vagale Paraganglioma :
a) Incidence
b) Location
c) Clinical Picture
d) Radiographic Features
e) Differential Diagnosis

a) Incidence :
-Glomus tumors that occur along the path of
the vagus nerve (CN X)
-Rarest of head & neck paragangliomas
(2.5%)

b) Location :
-At the high retrostyloid parapharyngeal
(carotid) space in the suprahyoid neck ,
well above the carotid bifurcation
-Within the carotid sheath , it displaces the
ICA anteriorly (as the vagus nerve is
located posterior to the artery within the
sheath) and the IJV posteriorly with no
widening of the carotid bifurcation

CT+C shows intensely enhancing vagale tumor (star) causing anterior
displacement of the internal carotid artery (arrow)

-Painless neck mass which may result in
dysphagia & hoarseness

d) Radiographic Features :
1-CT
2-MRI
3-Angiography

1-CT :
-As Carotid Body Tumor
-Displaces the ICA anteriorly & the IJV
posteriorly

CT+C shows intensely enhancing glomus vagale tumor (gv) displacing
the ICA (ic) anteriorly and the IJV (ij) posteriorly , the tumor makes
the lateral pharyngeal wall bulge into the pharyngeal lumen

CT+C shows intense enhancement of a left carotid space
mass (m)

CT+C shows mild heterogeneous enhancement of a large left carotid
space mass (m)

CT+C shows a well-defined right carotid space mass (m) with smooth margins
and enhancement

2-MRI :
-As Carotid Body Tumor

T1 shows lobulated mass (arrows) with isointensity in right
parapharyngeal space

T2 shows tumor (arrows) with inhomogeneous high signal
intensity

T1+C shows enhancing tumor extending from skull base down to level
of common carotid bifurcation , note multiple flow voids
(arrowheads) within tumor

T2 shows the tumor shows the hyperintense tumor (salt) interspersed with
signal voids of tumor vessels (pepper) , the tumor widely separates the ICA
(ic) and the IJV (ij)

(A) TOF shows the internal (i) and external (e) carotid arteries anterior
to the tumor and the internal jugular vein (v) posterior to the tumor ,
(B) TOF shows the normal internal (i) and external (e) carotid
arteries at the carotid bifurcation

MIP shows anterior displacement of the internal (i) and external (e)
carotid arteries and posterior displacement of the internal jugular
vein (v)

3-Angiography :
-Intense tumor blush
-The arterial supply is also from the muscular
branches of the ascending pharyngeal artery
and the neuromeningeal trunk (if the tumor
involves the skull base) as well as muscular
branches of the occipital artery
-Preoperative embolization is performed
transarterially with particles or with multiple
percutaneous injections of Onyx or NBCA

Lateral angiographic view obtained with a left CCA injection
demonstrates the hypervascular mass (arrow) displacing both the
ECA and ICA anteriorly

Lateral angiographic view obtained after an ECA injection reveals an
enlarged ascending pharyngeal artery as the primary supply to the
hypervascular mass (arrow)

Very vascular tumor surrounding the internal (i) and external (e) carotid arteries
and displacing the internal carotid artery anteriorly , a hypertrophied
ascending pharyngeal artery (solid arrows) supplies the tumor , the tumor
extends to the skull base (open arrows) but not through it , the carotid
bifurcation is normal

Pre (A) and post (B) embolization angiogram of a glomus vagale tumor

e) Differential Diagnosis :
-A mass between the ICA and IJV usually arises from one
of the structures within the carotid sheath or poststyloid
parapharyngeal space :
1-Lymph Nodes
2-Carotid Body Tumor
3-Glomus Jugulare Tumors
4-Schwannoma (Neurilemoma)
5-Metastases
6-Hemangioma
7-Aneurysm of the extracranial internal carotid artery

1-Lymph Nodes :
-Not found within the carotid sheath , so
adenopathy would be an unlikely cause of
splaying of these vessels , though a large
node could insinuate itself between the
vessels , vascular (enhancing) lymph
nodes may be found in Castleman disease
, angioimmunoblastic lymphadenopathy
and Kaposi sarcoma

2-Carotid Body Tumor :
-Also lies between two vessels , as does a glomus vagale
tumor , however , a glomus vagale tumor splays the IJV
and the ICA , a carotid body tumor splays the internal
and external carotid arteries
-The carotid bifurcation is normal in a patient with a glomus
vagale tumor , unless the patient also has a carotid body
tumor
-Glomus vagale tumors occur higher in the neck than
carotid body tumors
-The hyoid bone is a useful landmark for the carotid
bifurcation and so for carotid body tumors
-Carotid body tumors rarely grow up to the skull base

(A) Carotid body tumor , CT+C shows the intensely enhancing tumor (T)
between the left internal (i) and external (e) carotid arteries , j = IJV , (B)
Glomus Vagale , TOF shows the internal (i) and external (e) carotid arteries
anterior to the tumor and the internal jugular vein (v) posterior to the tumor

(A) Carotid Body Tumor , splaying of internal and external carotid artery at the
carotid bifurcation , (B) Glomus Vagale , normal internal and external carotid
arteries at the carotid bifurcation

Right CCA arteriogram shows a small carotid body tumor (black arrow) at the bifurcation
of the internal (I) and external (E) carotid arteries , there is also a large glomus vagale
tumor (white arrow) displacing the internal carotid artery anteriorly , the vagale tumor
separates the ICA from the IJV (J) , the vein can be seen as a black structure
because a venous-phase mask was used to create this subtraction image

3-Glomus Jugulare Tumors :
-It may be more difficult to differentiate a large glomus
vagale tumor from a glomus jugulare tumor
-Glomus jugulare tumors arise in the jugular fossa and
erode the jugular fossa before growing up into the middle
ear and down into the neck
-Glomus jugulare tumors grow into the internal jugular vein
, whereas glomus vagale tumors displace the vein
-Only very large glomus vagale tumors grow up into and
erode the jugular fossa , Jugulare and Vagale tumors
have a similar blood supply , the surgeon can sometimes
determine whether the tumor arose from the vagus nerve
but when the tumor is very large , its origin remains
obscure

4-Schwannoma (Neurilemoma) :
-A Schwannoma , or Neurilemoma , of one of the nerves
within the carotid sheath can mimic a glomus vagale
tumor , displaces the carotid artery anteriorly & IJV
posteriorly
-The nerve sheath tumor often but not always enhances
less intensely than a glomus tumor
-Cranial nerves and the sympathetic trunk all give rise to
nerve sheath tumors , even the surgeon may not be able
to tell the nerve of origin , though Horner syndrome after
surgery strongly suggests an origin from the cervical
sympathetic trunk

CT+C shows heterogeneously enhancing schwannoma (S) medial to
the internal (I) and external (E) carotid arteries and the internal
jugular vein (J)

T1+C shows an intensely enhancing sympathetic schwannoma (S)
between the right internal (I) and external (E) carotid arteries , the
relationship of the tumor to the arteries is similar to that in a carotid
body tumor but this is higher in the neck than the bifurcation , at a
level more typical of a glomus vagale tumor,J = internal jugular vein

5-Metastases :
-A vascular metastasis could mimic a glomus
vagale tumor , but other metastases and a
primary tumor might also be found
6-Hemangioma :
-Might contain phleboliths
7-Aneurysm of the extracranial internal carotid
artery :
-Rare

3-Glomus Jugulare Paraganglioma :
a) Incidence
b) Location
c) Clinical Picture
d) Classification
f) Differential Diagnosis
g) Endovascular Treatment

a) Incidence :
-2nd most common
-Seen in adults , typically between 40 and 60 years
of age
-Three times more common in women
-It doesn’t involve the middle ear , when a large
glomus jugulare tumor extends into the middle
ear , the term (Glomus Jugulotympanicum) is
used
-N.B. : Temporal paraganglioma entails tympanic
& jugular paragangliomas

b) Location :
-At the skull base in the region of the jugular
bulb , most common tumor of the jugular
foramen
-Paragangliomas arising in the jugular
foramen from Jacobson’s nerve of the
glossopharyngeal nerve or Arnold’s nerve
of the vagus nerve are termed (Glomus
Jugulare Tumors)

-N.B. :
*Jacobson Nerve :
-Is the tympanic branch of the glossopharyngeal
nerve (CN IX) and arises from the inferior
ganglion of the glossopharyngeal nerve
-It enters the middle ear cavity via the inferior
tympanic canaliculus and contributes to
the tympanic plexus located on the cochlear
promontory , the parasympathetic fibers leave
the plexus as the lesser petrosal nerve

-N.B. :
*Arnold's Nerve :
-Is the auricular branch (also known as the
mastoid branch) of the vagus nerve (CN X)
-Arnold's nerve originates from the superior
ganglion of the vagus nerve and also has a
small contribution from the inferior ganglion of
the glossopharyngeal nerve
-It ascends through the mastoid
canaliculus (located lateral to the jugular fossa)

Jugular fossa adjacent to middle ear , Jacobson nerve (J) , a branch of the
glossopharyngeal nerve , Arnold nerve (A) , a branch of the vagus nerve
Glomus tympanicum occur along the Jacobson nerve in the middle ear adjacent to the
cochlear promontory (CP)
Glomus jugulare occur along Jacobson or Arnold nerves within the jugular fossa

-Pulsatile tinnitus , hearing loss or vertigo
-A variety of symptoms related to adjacent
cranial nerves (glossopharyngeal , vagus
& spinal accessory) involvement is seen
late in the clinical course of these lesions

d) Classification :
1-Fisch & Valavanis Classification
2- Glasscock Jackson Glomus Tumor
Classification

1-Fisch & Valavanis Classification :
-A : Tumor in the tympanic cavity only
(mesotympanum) , i.e. glomus tympanicum
-B : As A plus extension into mastoid bone
(hypotympanum) with intact jugular bulb
-C1 : Tumor with minimal erosion of the vertical
portion of the carotid canal
-C2 : Tumor with extensive (complete) erosion of
the vertical portion of the carotid canal

-C3 : As C2 with erosion of the horizontal portion of the
carotid canal
-C4 : Involvement of the entire carotid canal including the
foramen lacerum & cavernous sinus
-De1/2 : Paragangliomas with intracranial but extradural
extension , on CT+C the enhancing dura is seen as an
uninterrupted line on the medial surface of the tumor
D1/2 according to displacement of the dura , De1=less than
2 cm , De2=more than 2 cm
-Di1/2/3 : Paragangliomas with intracranial & intradural
extension , CT+C shows focal interruption of the linearly
enhancing dura and nodular tumor extension through
interrupted dure
Di1=less than 2 cm , Di2=between 2 & 4 cm , Di3=more
than 4 cm

*N.B. :
-Epitympanum : this lies above the
level of the eardrum , it contains
the body of the incus and the head
of the malleus
-Mesotympanum : this lies at the
level of the eardrum , it contains
the malleus handle and neck , the
long process of the incus , the
stapes and many more things
-Hypotympanum : this part of the
middle ear space lies below the
eardrum , it is usually empty but
will sometimes have the jugular
bulb within it
-Portion of middle ear around the
eustachian tube orifice is
sometimes called protympanum

Class A , Tympanic paraganglioma (Fisch class A) : axial CT scan of a
tympanic paraganglioma (bone window) on the right promontory ,
note the absence of any bony erosion

Class B , Tympanic paraganglioma (Fisch class B) : the axial CT scan reveals
a left-sided tympanic paraganglioma surrounding and partially destroying
the ossicles , the malleus and stapes could not be discriminated , the tumor
had also invaded the hypotympanum , there was no destruction of the bone
wall to the jugular bulb

Class C , Jugular paraganglioma (Fisch class C) : axial CT scan showing a left-
sided jugular paraganglioma , note the bone destruction between the jugular
bulb and the soft tissue tumor in the hypotympanum

C2 , Left sided glomus jugulare class C2 involving the jugular foramen
and the ascending vertical course of internal carotid artery

C3 , Left sided glomus jugulare class C3 involving the genu and
extending partially to the horizontal portion of internal carotid artery
along its petrous course

C4 , Right sided glomus jugulare class C4 involving the internal carotid
artery up to the intracavernous course

CT+C shows intracranial extradural extension of tumor , linearly
enhancing dura is seen as uninterrupted line on medial tumor
surface (arrows)

CT+C shows erosion of horizontal segment of carotid canal (large arrow)
indicating type C3 : moderate extradural extension (short arrows ) indicating
type De2 and moderate intradural extension (white arrowheads) through
interrupted dura (two long arrows) indicating type Di2

2-Glasscock Jackson Glomus Tumor
Classification :
*Glomus Jugulare :
Type I : Tumor involving jugular bulb , middle ear
and mastoid
Type II : Tumor extending under internal auditory
canal
Type III : Tumor extending into petrous apex
Type IV : Tumor extending beyond petrous apex
into clivus or infratemporal fossa

*Glomus Tympanicum :
Type I : Tumor limited to promontory
Type II : Tumor completely filling middle ear
space
Type III : Tumor filling middle ear extending
into mastoid
Type IV : Tumor filling middle ear extending
into mastoid may extend anterior to
internal carotid artery

1-CT :
-Soft tissue mass with intense enhancement
-Growth of these tumor is in a number of directions ,
typically they extend into the mastoid air-cells and middle
ear and Eustachian tube
-CT is most useful at assessing the bony margins of the
tumor which are typically irregularly eroded with a moth-
eaten pattern
-Eventually as the tumor enlarges the jugular spine is
eroded and the mass extends into the middle ear , as
well as inferiorly into the infratemporal fossa
-CT is excellent at assessing the integrity of the ossicles
and bony labyrinth

*N.B. : Jugular Spine
-Is a small sharp bony ledge
which separates the two parts
of the jugular foramen :
1-Pars nervosa anteriorly ,
contains the glossopharyngeal
(IX) and Jacobsen's nerve
together with the inferior
petrosal sinus
2-Pars vascularis posteriorly ,
contains the IJV , vagus (X) ,
spinal accessory (XI) and
Arnold's nerve
-It is an important landmark , as
masses of the jugular foramen
(e.g. glomus jugulare) will
erode this spine, helping
distinguish them from
an asymmetrically large jugular
bulb

Erosion of the jugular spine on the left side , note the
normal jugular spine on the right side

Axial CT image (bone window) shows a left jugular foramen mass (m) with
mildly irregular margins

Soft tissue mass lesion in the jugular fossa with irregular destruction of
the jugular fossa (white arrow) , jugular spine , adjacent bone and
extension of the mass into the middle ear cavity (black arrow)

(A) CT+C shows left jugular foramen mass (arrow) with irregular
margins and lytic changes of surrounding temporal bone , Axial CT
scans obtained 5 mm (B) and 10 mm (C) cranial to (A) show well-
enhanced tumor mass (arrowhead) extending through jugular
foramen into posterior cranial fossa

(A) Soft tissue CT+C shows a glomus jugular tumor on the right side with small
intracranial extension , (B) Bone-windowed CT+C shows a large expansile
mass in the right jugular fossa protruding into the right hypotympanum ,
note the infiltration of the vertical carotid canal , as well as (moth-eaten)
borders of the adjacent petrous bone and clivus

CT shows bulky tumescent lesion whose epicenter is located in the
jugular foramen with intense homogeneous enhancement by
contrast and extensive permeative bone

2-MRI :
*T1 :
-Low signal
*T2 :
-High signal , salt and pepper appearance is seen on both
T1 and T2 , the salt representing blood products from
hemorrhage or slow flow and the pepper representing
flow voids due to high vascularity , not typically seen in
smaller glomus tumor
*T1+C :
-Marked intense enhancement

(A) T1 , (B) T1+C and fat-suppression show invasive slightly hyperintense
lesion with marked enhancement in postcontrast images , note the typical
(salt-and-pepper) appearance of the tumor in the postcontrast image

3-Angiography :
-Intense tumor blush with the most common
feeding vessel being the ascending pharyngeal
-Early draining veins are also noted due to intra-
tumoral shunting
-Angiography also has a role to play in
preoperative embolization which is typically
carried out 1-2 days prior to surgery , however
care must be taken to fully evaluate feeding
vessel

Selective external carotid artery angiogram of the same patient (lateral
view) is shown , the characteristically hypervascular tumor with a
coarse blush is supplied by the hypertrophic ascending pharyngeal
artery and the occipital artery (arrows) , note the early draining vein
during the midarterial phase

f) Differential Diagnosis : Masses in the jugular
fossa :
a) Intrinsic Lesions
1-Vascular Normal Variants involving the Jugular
Bulb
2-Jugular Vein Thrombosis
3-Nerve Sheath Tumors
4-Jugular Foramen Meningioma
5-Vascular Metastases
b) Extrinsic Lesions
1-Chordoma
2-Chondrosarcoma
3-Osteomyeitis
4-Rhabdomyosarcoma

a) Intrinsic Lesions :
1-Vascular Normal Variants involving the
Jugular Bulb :
a) Asymmetrically Large Jugular Bulb
b) High Riding Jugular Bulb
c) Dehiscent Jugular Bulb

a) Asymmetrically Large Jugular Bulb :
-Entirely normal and asymptomatic , its only significance is
to distinguish it from pathology
-The size of the jugular bulbs is variable with the right side
being significantly larger than the left in two-thirds of
people
-A normal but large bulb will have an intact jugular spine ,
normal bony margins and have proportionately large
ipsilateral internal jugular vein and sigmoid sinus
-Its dome will not extend above the floor of the internal
acoustic meatus (IAM) thus distinguishing it from a high
riding jugular bulb
-Due to turbulent flow in the jugular bulb, signal on MRI can
be confusing and it must not be mistaken for a tumor

Marked asymmetry with the right jugular bulb being much larger than
the left , the asymmetrically large jugular bulb (right > left) is easily
appreciated , note the enlarged ipsilateral sigmoid sinus

Asymmetric jugular bulb (asterisk)

b) High Riding Jugular Bulb :
-Distinguished from an asymmetrically large
jugular bulb by its dome (roof) reaching above
the internal acoustic meatus (IAM) , it need not
be larger than the contralateral bulb but usually
is
-Has an intact sigmoid plate , a thin plate of bone
separating the jugular bulb from the middle
ear cavity
-If the sigmoid plate is deficient, the bulb is free to
protrude into the middle ear cavity and is then
known as a dehiscent jugular bulb and is a
common cause of a retrotympanic vascular
mass

High-riding jugular bulb (white arrow) extending over basal turn of the cochlea

c) Dehiscent Jugular Bulb :
-Present when the sigmoid plate between a high
riding jugular bulb and the middle ear is absent ,
allowing the wall of the jugular bulb to bulge into
the middle ear cavity
-It is one of the causes of pulsatile tinnitus and is a
common cause of a retrotympanic vascular
mass , clearly , if it is mistaken for a middle ear
tumor and biopsied then the consequences can
be disasterous (as is biopsying an aberrant
internal carotid artery)

Bony defect between the jugular bulb and middle ear cavity

Jugular bulb protruding in the middle ear

On the left a dehiscent jugular bulb (blue arrow) , note also the bulging sigmoid
sinus (yellow arrow)

2-Jugular Vein Thrombosis :
-MRV is a useful tool for diagnosing thrombosis of
the jugular bulb by showing lack of flow related
signal in the involved jugular vein
-Lack of normal flow void
-Acute thrombus is usually hyperintense ,
subacute thrombus may have isointense to
hypointense signal
-Acute clot shows avid diffuse enhancement or
peripheral enhancement , whereas there is lack
of enhancement in a more chronic clot

T2 shows normal flow void in the right sigmoid sinus and jugular vein
(blue arrow) , on the left there is abnormal high signal as a result of
thrombosis (red arrow)

Magnetic resonance venography confirmed thrombosis (black arrows) of right
transverse and sigmoid sinuses and jugular vein

CT+C shows jugular vein thrombosis (black arrow) , R-ICA indicates
right internal carotid artery ; L-ICA, left internal carotid artery ; R,
right ; and L, left

3-Nerve Sheath Tumors :
-CT :
*They appear with smooth enlargement of the foramen
without associated destruction or invasion of the bony
labyrinth
*May show a dumbbell shape with intracranial &
extracranial components
*Larger lesions are heterogenous & contains areas of
cystic degeneration
*No calcifications
-MRI :
*Hypo in T1 , Hyper in T2 and intense enhancement
*No salt & pepper appearance
-Angiography :
*Either avascular or hypovascular masses

Schwannoma of the left jugular foramen , (A) Bone-window CT shows
significant enlargement of the JF on the left side , the jugular spine is well
delineated , (B,C) Adjacent axial CT+C show a fairly well-enhanced lesion
(arrow) in the left JF extending extracranially and compressing the
neighboring jugular vein (curved arrow)

(A) Glomus vagale , Bone-windowed CT (after contrast agent administration)
shows a large expansile mass in the right jugular fossa protruding into the
right hypotympanum , note the infiltration of the vertical carotid canal as well
as (moth-eaten) borders of the adjacent petrous bone and clivus , (B)
Schwannoma of the JF , Bone-windowed CT shows significant
enlargement of the JF on the left side , the jugular spine is well delineated

4-Jugular Foramen Meningioma :
-Defined as primary when centered in the JF (intrinsic
lesions) and secondary when centered in the posterior
fossa with extension into the JF
-Dural based , well-circumscribed mass with areas of
calcification
-CT :
*The adjacent cortex shows sclerosis , remodelling or
erosion in rare cases
-MRI :
*Hypointense to isointense on T1 , Hyperintense on T2 and
shows moderate to high degree of enhancement
-Angiography :
*Hypovascular or avascular

Primary meningioma of the right jugular foramen (JF) , CT+C shows a large
centrifugally growing , nonhomogeneously enhancing lesion in the right
cerebellopontine angle , the JF and the infratemporal fossa , the ventral
borders of the tumor are ill defined indicating an infiltrative pattern of spread
toward the nasopharynx

Secondary meningioma of the right jugular foramen (JF) (extrinsic lesion) , T1+C shows a
small meningioma (arrow) originating from the right JF (arrowhead) and extending
medially into the cerebellopontine angle cistern (not shown) with an en plaque growth
pattern , the tumor lacks the (salt-and-pepper) pattern of paragangliomas , note the
presence of a (dural tail sign)

5-Vascular Metastases :
-Vascular metastases to the jugular foramen
originate from renal & thyroid carcinomas
-Appears as aggressive with extensive bone
destruction

Metastasis of breast cancer in the left jugular foramen , (A) CT soft tissue
shows hypodense tumor located in the left jugular fossa extending into the
ventral aspect of the petrous bone , (B) The corresponding bone-windowed
shows demineralization of the adjacent petrous apex which has irregular
borders

b) Extrinsic Lesions :
-Extrinsic lesions involving the JF are either
derived from the brain (above) or the deep facial
spaces (below)
-These lesions could be expected to affect the
temporal bone , brain or carotid space more
than the contents of the JF
-In reality , extrinsic lesions often have a complex
presentation and mimic intrinsic lesions of the JF

6-Chordoma :
-Rare bone tumors arising from remnants of the cranial end
of the embryologic notochord
-They are usually found in the clivus and spheno-occipital
synchondrosis that extend laterally into the JF
0Chordomas produce accentuated irregular bone
destruction and are hypointense on T1 , markedly
hyperintense on T2 and have a typical lobulated shape
with peripheral contrast enhancement where bone has
been infiltrated , Intratumoral calcification is common and
seen in 50% as speckling on CT or as a signal void with
MRI

Axial CT scan of the skull base demonstrates the lesion with a clival
origin and extension to the prepontine cistern with typical trabecular
entrapment (arrow) , dystrophic calcification is also seen
(arrowhead)

7-Chondrosarcoma :
arise from embryonal rests , endochondral bone or
cartilage
-They are usually extradural and have a peak age of
presentation between 20 and 40 years , not dissimilar to
that of chordomas
- Chondrosarcomas are parasellar tumors, whereas
chordomas are infrasellar skull base tumors
- The radiological features of chondrosarcomas are similar
to those of chordomas and differentiation between the
two entities is sometimes not possible on the basis of
radiological appearances alone

CT Showed peripheral Calcification

8-Osteomyeitis :
-Osteomyelitis around the JF may be unilateral
and caused by otitis externa or a deep fascial
abscess or it may be bilateral and secondary to
systemic infections
-Initial CT scans reveal abnormal soft tissue in this
region
-MRI is useful when extensive infiltration of the JF
contents is clinically evident , the imaging
characteristics may be similar to those of tumors
and in these cases the clinical history helps to
differentiate

CT scan showing the soft tissue obliterating left external auditory canal
left mastoid , infra-temporal fossa , skull base and involving the left
TMJ

9-Rhabdomyosarcoma :
-Rhabdomyosarcoma is the predominant tumor (embryonal
histologic type) of the nasopharynx and masticator space
in children , the tumors infiltrate the skull base and
parapharyngeal tissues
-Hyperintense on T2 and muscle isointense on T1 ,
although intratumoral hemorrhage is uncommon ,
subacute or chronic hemorrhagic foci may appear bright
on T1 & T2
- A muscle can always be recognized as its site of origin
and the tumor mass is typically homogenous with
destruction of adjacent bone
-Shows a moderate to marked homogenous enhancement
after contrast agent administration
-Intratumoral calcification is rarely seen in
rhabdomyosarcoma

Rhabdomyosarcoma in the right infratemporal fossa , (A) T1 shows a well-
circumscribed muscle isointense mass in the right infratemporal fossa , the
mass extends into the right jugular foramen (JF) (arrow) , note the marked
bilateral cervical lymphadenopathy , (B) T1+C shows the predominately
hyperintense mass extending into the JF (arrow)

g) Endovascular Treatment :
1-Indications
2-Preprocedure Assessment
3-Embolization Technique

1-Indications :
a) Preoperative embolization to reduce
surgical bleeding and facilitate resection
b) Tumor shrinkage , embolization of large
inoperable lesions can provide
symptomatic relief and be repeated , could
be combined with radiotherapy , there are
reports of the efficacy of radiotherapy with
cure rates of up to 90 %

2-Preprocedure Assessment :
-Imaging assessment , MRI is best to show the
location & spread of temporal tumors , it will
show the distribution of large masses , their
relationship to the carotid canal & involvement of
soft tissues
-HRCT will show bone erosion & destruction
-CTA or MRA can assess the degree of vascularity
& ICA narrowing
-Evidence of involvement of the ICA , i.e. (classes
C3,C4 & D) is an indication for preoperative test
occlusion & possible pre-resection endovascular
occlusion of ICA

3-Embolization Technique :
a) Angiographic Evaluation
b) Choice of Embolic Material & Delivery
Techniques

a) Angiographic Evaluation :
-Paraganglioma confined to the jugular foramen
would be supplied exclusively by the
neuromeningeal trunk , however the majority of
tumors are compromised of multiple
compartments (85%)
-Typical angiographic features are :
1-Moderately enlargement of feeding arteries
2-Early intense irregular tumor blush
3-Rapidly filling veins

-The angioarchitecture is unusual because proximal
arteries are smaller than more distal (intratumor) arteries
, this has obvious implications for the selection of
embolization particles
-The angiographic protocol is to inject both vertebral
arteries (VA) , ICAs & ECAs with selective injections to
the ipsilateral ascending pharyngeal arteries (APA) ,
posterior auricular artery & occipital artery
-The branches of the APA that supply temporal
paraganglioma are the hypoglossal , jugular & inferior
tympanic arteries
-Bilateral APA injections are advised by some authors

-The arterial supply to four regions of spread
of temporal paragangliomas is well
described by Valavanis :
1-Infra-medial
2-Posterior-lateral
3-Anterior
4-Superior

1-Infra-medial : Hypotympanum & Jugular fossa
Inferior tympanic artery
Jugular artery of the APA
Secondary : Lateral clival branch of ILT
2-Posterior-Lateral : Posterior tympanic cavity &
mastoid
Stylomastoid artery
Secondary : Mastoid branches of occipital artery

Injection of ascending pharyngeal artery , opacification of inferomedial
compartment via dilated inferior tympanic artery (long arrow) and
neuromeningeal trunk (short arrow)

Injection of stylomastoid artery , opacification of
posterolateral compartment

3-Anterior : Protympanum & Pericarotid
Anterior tympanic artery of the internal maxillary
Caroticotympanic artery of the ICA
Secondary : Cavernous branches of ICA , Anterior
division of APA
4-Superior : Superior part of the tympanic cavity
(Epitympanum)
Superior tympanic artery which arises from petrous
branches of middle meningeal artery

Injection of internal maxillary artery at level of branching of middle meningeal
artery (curved arrow) , opacification of anterior compartment (thin arrows)
via anterior tympanic artery (long thick arrow) and of superior compartment
(arrowheads ) via superior tympanic artery (short thick arrow)

-The extradural extension of type De and Di
paragangliomas is supplied centrally by the meningeal
branches of the ascending pharyngeal artery and
posteriorly by the recurrent meningeal (or mastoid)
branch of the occipital artery
-The central extradural portion represents the intracranial
extension of the inferomedial compartment and the
posterior extradural portion represents the intracranial
extension of the posterolateral compartment
-If the extradural extension is large , the anterior
intracranial portion of the tumor is supplied by the clival
and even the cavernous branches of the ICA , the
superior extradural extension is supplied by the petrous
branch of the middle meningeal artery

(A) Vertebral angiogram shows opacification of intracranial extradural tumor extension
(arrowheads) via recurrent meningeal branch (thin arrow) of occipital artery filling
through vertebrooccipital anastomosis (thick arrow) (B) Injection of occipital artery
shows opacification of posterolateral compartment (white arrowheads) through
stylomastoid artery (short arrow) and of extradural extension (black arrowheads)
through recurrent meningeal branch (long arrow)

-The intradural portion of type Di paragangliomas is
constantly supplied by parenchymal branches of the
vertebrobasilar system , intradural extensions at the level
of the jugular foramen receive their blood supply from
the posterior inferior cerebellar artery (PICA) and
intradural extensions into the cerebellopontine angle
receive their blood supply from the anterior inferior
cerebellar artery (AICA)
-A careful inspection of the late phase of the dominant
vertebral artery injection is advised to assess the late
venous flow pattern to decide if the jugular vein is
occluded because of the confounding effect of tumor
venous drainage

(A) Vertebral angiogram shows opacification of intradural extensions via AICA
(arrow) and PICA (arrowhead) , (B) Injection of internal maxillary artery
shows opacification of anterior compartment (thin arrow) of superior
compartment (thick arrows) and of intradural extension into cerebellopontine
angle (arrowheads)

b) Choice of Embolic Material & Delivery
Techniques :
-Transarterial embolization is usually performed
with particles (140-250 μm)
-Smaller particles shouldn’t be used because of
possible cranial nerve damage
-Liquid agents (NBCA or Onyx “ev3”) may be used
for treatment of inoperable tumors where a
higher risk of morbidity due to collateral tissue
damage is acceptable

-They may be delivered transarterially or by direct injection
-Percutaneous direct injection into the tumor vascular
spaces is now the preferred route
-It is axiomatic that embolization with liquids in the APA
causes complications even in the very best hands
-Transarterial embolization of transpial pedicles (from AICA
& PICA) for tumors with intradural spread is usually
performed with particles but should be reserved for
cases of malignant histology or when excessive
hypervascularity prevents surgical excision
-In such cases , injection may be best performed with a
balloon inflated in the distal VA to prevent reflux of
emboli

4-Glomus Tympanicum Paraganglioma :
a) Incidence
b) Location
c) Clinical Picture
d) Classification
f) Differential Diagnosis
g) Endovascular Treatment

a) Incidence :
-Most common tumor of the middle ear ,
however
-More common in middle aged women (40-
60 years of age)

b) Location :
-At the tympanic cavity , classic more specific
location is on the cochlear promontory
-Mass arising from the middle ear and not
involving the jugular foramen
-Benign tumor arising from glomus bodies found
along the inferior tympanic nerve (Jacobson
nerve) , a branch of the glossopharyngeal nerve
on the cochlear promontory

The inferior tympanic branch or Jacobson nerve (J) of the glossopharyngeal
nerve (IX) arises from and travels anterior to the IJV (JV) toward the middle
ear where it lies against the cochlear promontory , the auricular branch or
Arnold nerve (A) of the vagus nerve (X) follows a path posterior to the IJV
on its way to the facial canal , Glomus tympanicum occur along the
Jacobson nerve in the middle ear adjacent to the cochlear promontory (CP)

-Pulsatile tinnitus (90%) , conductive hearing
loss (50%) & facial nerve paralysis (5%)
-Known for its appearance as a red
retrotympanic mass on otoscopic exam
-One must be careful to assess for presence
of an aberrant ICA , which also presents
with pulsatile tinnitus & a red
retrotympanic mass

d) Classification :
-See Jugular Paraganglioma

1-CT :
-Appear as a small soft-tissue nodule
classically located at the cochlear
promontory and confined to the middle ear

(A) Axial CT showing the glomus tumor growing from the medial wall of the
middle ear , (B) Coronal CT showing the glomus tympanicum tumor growing
from the medial wall of the middle ear

Axial (A) and coronal (B) thin-section CT scans of temporal bone (bone
window) show 5-mm soft-tissue mass (arrow) filling hypotympanum
of left middle ear cavity

(A) Coronal CT with no contrast enhancement shows a small oval soft
tissue mass (arrow) on cochlear promontory , (B) Axial CT shows
small glomus tympanicum in typical location (arrow)

Coronal image of the left temporal bone shows focal soft tissue on the
cochlear promontory (white arrow)

2-MRI :
*T1 : low
*T2 : high
*T1+C : marked contrast enhancement

(A) T1 , (B) T1+C of the left temporal bone show soft tissue mass over
cochlear promontory with enhancement following contrast

3-Angiography :
-Same as Glomus Jugulare Paraganglioma

Superselective angiography of the right external carotid artery shows a hypervascular
tumor mass in the right middle ear supplied by the internal maxillary artery , posterior
auricular artery , ascending pharyngeal artery and tympanic branch of first part of
maxillary artery

f) Differential Diagnosis : Middle ear
masses :
1-Aberrant Internal Carotid Artery
2-Persistent Stapedial Artery
3-Adenoma
4-Facial Nerve Schwannoma
5-Cholesteotoma

1-Aberrant Internal Carotid Artery :
a) Incidence
b) Radiographic Features

a) Incidence :
-Collateral pathway that occurs as a result of agenesis of
the first embryonic segment of the ICA
-The inferior tympanic branch of the ascending pharyngeal
artery anastomoses with the caroticotympanic artery
(hyoid artery remnant) of the ICA
-The aberrant ICA variant may therefore be more
accurately referred to as (the inferior tympano-
caroticotympanic variant)
-The inferior tympanic artery passes through the inferior
tympanic canal (Jacobsen canal) at the skull base with a
resultant characteristic narrowing of the vessel

b) Radiographic Findings :
1-Soft tissue mass in the middle ear
2-Defective thin bonny membrane around
the mass
3-Absent or hypoplastic vertical segment
of carotid canal
4-Enlarged inferior tympanic canal
5-Reduced diameter and lateralization of the
ICA

CT of the temporal bone showing the aberrant carotid artery entering
the tympanic cavity through a dehiscent carotid plate

Normal inferior tympanic canaliculus

(A) Bilateral aberrant ICAs , (B) bilateral hypoplastic carotid canals
(horizontal arrows) and enlarged bilateral inferior tympanic canals
(vertical arrows) through which the aberrant ICA (inferior tympanic
artery portion) passes

(A) Left aberrant ICA (B) Normal right carotid canal (horizontal arrow
on the patient’s right) , a hypoplastic carotid canal (horizontal arrow
on the patient’s left) & the inferior tympanic canal (vertical arrow)
with the aberrant ICA

CT Shows reduced diameter and lateralization of the left
ICA compared to the right ICA

2-Persistent Stapedial Artery :
a) Incidence
b) Anatomy
c) Radiographic Findings

a) Incidence :
-PSA is a rare congenital vascular anomaly of the
middle ear
-Usually manifests as a pulsatile mass in the
middle ear cavity , an incidental finding during
middle ear surgery or pulsatile tinnitus
-Can be associated with an aberrant internal
carotid artery or other middle ear anomalies

b) Anatomy :
-The stapedial artery is transiently present in fetal
life and connects the branches of the future
external carotid artery to the internal carotid
artery
-The stapedial artery arises at 4-5 weeks of fetal
life from the hyoid artery which is a derivative of
the second branchial arch , near its origin from
the proximal internal carotid artery (third
branchial arch)

-The stapedial artery gives rise to two branches
after entering the cranial cavity :
1-The upper , or supraorbital branch becomes the
middle meningeal artery and also transiently
anastomoses with the ophthalmic artery
2-The lower , or maxillomandibular division has
two branches , a mandibular branch and an
infraorbital branch which persist in adult life as
inferior alveolar and infraorbital arteries
respectively
-Anastomosis forms between ventral pharyngeal
artery (precursor of external carotid artery) and
lower division of stapedial artery

-As the ventral pharyngeal artery supplies flow to middle
meningeal artery , stapedial artery regresses leaving
small caroticotympanic artery
-Persistence of the stapedial artery in postnatal life leads to
the middle meningeal artery typically arising from it , the
foramen spinosum remains hypoplastic or aplastic which
is an indirect sign of PSA
-Variant stapedial remnants giving rise to distal external
branches with significant input to the ophthalmic artery
are important to recognize before undertaking what
would be otherwise routine external carotid
embolizations (as embolizations of a tumor supplied by
the external carotid artery “ e.g. meningioma or
hemangiopericytoma ” can result in blindness)

A , The hyoid artery arises from the
ICA , the stapedial artery arises
from the hyoid artery near its
origin , the stapedial artery
branches into upper and lower
divisions after passing through the
stapes , the ventral pharyngeal
arteries are the precursors of the
definitive ECA , the stapedial
artery is the only supply to the
upper and lower divisions
B, Anastomosis forms between the
ventral pharyngeal artery and the
lower division branches
C, The stapedial artery decreases in
size
D, Normal adult anatomy with
involution of the stapedial artery
E, Anatomic configuration of typical
PSA

Axial HRCT image showing absence of foramen spinosum
on the left side compared to the normal right

-The PSA arises from the petrous part of the internal
carotid artery , enters the anteromedial hypotympanum
and is contained in the Jacobson canal
-After leaving the osseous canal , it crosses the cochlear
promontory and passes through the obturator foramen of
the stapes
-It then enters the fallopian canal through a dehiscence just
behind the cochleariform process and travels anteriorly
in the anterior facial canal
-This leads to prominence of the tympanic part of the facial
nerve , another indirect imaging sign of PSA
-Finally , the PSA exits just before the geniculate ganglion
entering into the extradural space of the middle cranial
fossa

-Axial Images (A-H) from superior to
inferior
-The small vascular channel can be
seen leaving the vertical carotid
at G (arrow) and can be followed
along the lower medial wall of the
middle ear (D-F) (arrows)
-Level C is at the plane of the
stapedial crura
-The vessel cannot be clearly
separated from the anterior crus
of the stapes
-After following the facial nerve canal
, the small vascular channel
reaches the middle cranial fossa
at level B (arrowhead)
-Level A represents the position of
the geniculate ganglion turn of
the facial nerve canal

-Coronal images (A–D) , from
posterior to anterior
-The narrow presumed vascular
structure is seen at B (arrowheads)
coursing along the promontory
-At level A , the small vascular
structure (arrows) crosses the oval
window niche to end in the lower
inferomedial aspect of the
tympanic segment of the facial
nerve canal
-This small channel is also seen at B
(arrow)
-More anteriorly (C and D) , the small
canal (arrows) courses just inferior
to the tympanic segment of the
facial nerve canal in a separate
channel as it passes toward the
floor of the middle cranial fossa
-The small soft-tissue structure
immediately inferior to this canal is
the tensor tympani muscle within
its semicanal

Axial and coronal CT showing the intracranial course of the stapedial
artery in the bony ridge to the promontary

Coronal image showing enlarged right facial nerve (yellow arrow)
compared to normal (blue arrow)

Sagittal image on the left side showing course of persistent stapedial
artery traversing through the canaliculus to enter the cranial cavity

c) Radiographic Findings :
-Small canaliculus originating from petrous
segment of ICA
-Linear soft tissue density crossing over
cochlear promontory
-Enlarged facial nerve canal or separate
canal parallel to facial nerve
-Aplastic or hypoplastic foramen spinosum

(a) Transverse CT of the left skull base shows absence of the foramen
spinosum posterolateral to the foramen ovale (arrow) ,
(b) Transverse CT of the right skull base shows the normal foramen
spinosum (arrowhead) posterolateral to the foramen ovale (arrow)

A, Axial CT scan of skull base shows a normal left foramen spinosum (straight arrow) ,
the right foramen spinosum is absent , the right ICA is laterally displaced into the
middle ear (curved arrow) , the left ICA is in a normal position
B, Coronal CT scan through right middle ear shows the ICA in the middle ear cavity
(straight arrow) , the soft tissue at the tympanic segment of the facial nerve is
prominent because of the presence of a stapedial artery (curved

A, Axial CT scan shows a normal right foramen spinosum (arrow) and
absence of the left foramen spinosum
B, Coronal CT scan shows the aberrant ICA on the left (straight arrow)
and the soft-tissue density of a PSA (curved arrow)

C, Left carotid arteriogram , lateral view shows a PSA arising from the
aberrant ICA (arrow)
D, Left carotid arteriogram , frontal view shows a PSA arising from the
aberrant ICA (arrow)

A, Axial CT scan shows a normal left foramen spinosum (arrow) and absence of the right
foramen spinosum
B, Axial CT scan through middle ear shows prominent soft tissue representing facial
nerve and PSA (arrow)
C, Coronal CT scan through middle ear shows prominent soft tissue representing facial
nerve and PSA (arrow)

A, Axial CT scan shows a normal left foramen spinosum (arrow) and absence of the right
foramen spinosum
B, Coronal CT scan through right middle ear shows the soft tissue at the tympanic
segment of the facial nerve is prominent because of the presence of a stapedial
artery (arrow)
C, Coronal CT scan through left middle ear shows the tympanic facial nerve is normal in
size (arrow)

Carotid arteriogram , lateral view shows a PSA (curved arrow) arising
from the aberrant ICA which represents the inferior tympanic branch
of the ascending pharyngeal artery assuming the role of the ICA
(straight arrow)

Lateral internal carotid angiogram shows the persistent stapedial artery
arises from the proximal internal carotid artery and ends as the
middle meningeal artery , the middle meningeal artery anastomoses
with the ophthalmic artery

AP internal carotid angiogram shows connection between the
persistent stapedial artery , middle meningeal artery and ophthalmic
artery is demonstrated , when the middle meningeal artery arises in
this manner , it does not enter the skull base in the usual fashion

Lateral internal carotid angiogram shows the persistent stapedial artery
arises from the proximal internal carotid artery and ends as the
middle meningeal artery

AP internal carotid angiogram shows the origin of the persistent stapedial artery
from the proximal intracranial internal carotid is again seen , the persistent
stapedial artery continues as the middle meningeal artery , the middle
meningeal artery lacks its characteristic curve as it does not enter the skull
base in the usual fashion

C, Coronal CT scan through left middle ear shows the ICA in a normal position below the
cochlea (straight arrow) , the tympanic facial nerve is normal in size (curved arrow)
D, Coronal CT scan at level of vestibule shows the entrance of the aberrant ICA into the
right middle ear (arrow)

A, Axial CT scan shows a normal right foramen spinosum (arrow)
and absence of the left foramen spinosum
B, Coronal CT scan shows the aberrant ICA on the left (straight
arrow) and the soft-tissue density of a PSA (curved arrow)

3-Adenoma :
a) Incidence

a) Incidence :
-Middle ear adenoma is a rare benign
epithelial tumor deriving from middle ear
mucosal cells
-The mean age is 45 years with no sex
predominance

b) Radiographic Features :
-CT : Relatively well-circumscribed soft
tissue attenuation enhancing mass is seen
without evidence of bone erosion
-MRI :
*T1 : low to intermediate intensity
*T2 : high intensity
*T1+C : enhances

(A) Axial CT shows the mass (short white arrow) extending over the cochlear promontory
(long black arrow) and into the round window niche , (B) The mass is invaginating
along the long process of the incus (long white arrow) and neck of the malleus with a
portion sitting posteriorly on the pyramidal eminence (white arrowhead) between the
sinus tympani and the facial nerve recess , (C) Coronal CT shows the relationship of
the mass (short white arrow) to the ossicles (long white arrow) and the cochlear
promontory (long black arrow)

4-Facial Nerve Schwannoma :
a) Incidence

a) Incidence :
-Very rare , make up less than 1% of
all temporal bone tumors
-Patients usually of 30-40 years of age
-Facial numbness , facial palsy , hearing
loss and tinnitus raise the clinical
suspicion of facial nerve schwannoma

b) Radiographic Features :
-Enhancing tubular mass (using T1-enhanced MR)
within an enlarged facial nerve canal (using CT)
- Lesion enhancement is likely to be better
appreciated on the MRI than CT
-Key findings :
Smooth expansion of the facial nerve canal
May show enhancement

Coronal CT of the left temporal bone shows soft tissue with smooth
expansion of the facial nerve canal (white arrow)

Axial bone algorithm CT image demonstrating focal enlargement of the
labyrinthine segment of the facial nerve canal from a facial nerve
schwannoma (between arrows)

5-Cholesteotoma :
-CT :
1-Soft tissue mass in middle ear
2-Borders may be well or ill-defined
3-Erosion of incus & scutum common
4-Bone resorption is typical
5-Mastoid air cells are typically
underpneumatized and sclerotic

(A,B) :Coronal and axial CT of the left temporal bone show soft tissue
in the epitympanum (long arrow) with blunting of the scutum (short
arrow) and erosions of the ossicles (black arrow) , there is sclerosis
of the mastoid

-MRI :
*T1 : low
*T2 : high
*T1+C : no enhancement
*DWI : diffusion restriction
DWI is particularly useful when
distinguishing a cholesteatoma from other
middle ear masses , it is the only entity
that demonstrates restriction

(A) MRI delayed T1+C shows absence of contrast uptake , (B) Diffusion
shows high signal compatible with diffusion restriction

g) Endovascular Treatment :
-See Jugular Paraganglioma

Embolization of Intracranial & Skull Base Tumors (Paragangliomas)

Embolization of Intracranial & Skull Base Tumors (Paragangliomas)

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