Dr. AHMED REFAEY
FRCR
RADIOLOGIST
Parotid space
* Paired lateral suprahyoid neck
spaces enclosed by superficial
layer of deep cervical fascia
containing parotid glands, lymph
nodes & extracranial CN7
branches.
Image gallery
Graphic of a skull
base shows PS
(green) surrouded by
superficial layer, deep
cervical fascia(yellow
line) . PS abuts
stylomastoid foramen
(arrow) , mastoid tip
(open arrow) & EAC
(curved arrow).
Parotid space anatomy
Axial graphic shows
superficial layer of
deep cervical fascia (
yelow line )
circumscribes PS.
CN7 ( arrow ) divides
parotid gland into
superficial & deep
lobes
Parotid space anatomy
Axial graphic depicts
a deep parotid lobe
mass pushing the
parapharyngeal fat
from lateral to medial
(arrow) & squeezing
through the
stylomandibular notch
(open arrows)
Image gallery
Sagittal graphic of PS
malignancy (arrow)
shows typical perineural
tumor spread retrograde
along CN7 .
Tumor follows CN7
through stylomastoid
foramen (open arrow) &
up mastoid segment
(curved arrow)
Anatomic relationships
Directly medial to parotid space ( PS ) is
parapharyngeal space ( PPS ) .
Anterior to PS is masticator space .
Internal structures
Parotid gland
-superficial lobe represent about 2/3 of parotid space.
-deep lobe projects into lateral PPS
Facial nerve ( CN7)
-surgical plane between superficial and deep lobe.
External carotid artery
Retromandibular vein
Lymph nodes
- Around 20 lymph nodes found in each parotid gland
Parotid duct
-emerges from anterior PS , runs along surface of masseter muscle ,
arches through buccal space to pierce buccinator muscle at level of
upper 2nd molar tooth.
Accessory parotid glands
-project over surface of masseter muscle
-present in about 20% of normal anatomic dissections.
Key concepts or questions
In mass lesions of PS area, is the mass intra or
extraparotid ?
-small , intraparotid masses easy to identify.
Large , deep lobe masses more troublesome
-mass displace PPS medially
-stylomandibular notch is widened.
What is mass relationship to facial nerve?
-designate mass as superficial , deep or in same plane as
intraparotid facial nerve.
-superficial lobe mass removed by superficial parotidectomy while
deep lobe mass requires total parotidectomy.
. or suspected ?
If malignancy in PS known
-T1+C MR should be done to evaluate entire CN7 to
root exit zone of CPA , to role if there is evidence of
perineural CN7 extension.
Is the PS lesion single or multiple? Unilateral
or bilateral ?
-multiple bilateral lesions suggest unique DD
-Sjogren’s syndrome
-BLL-HIV
-Warthon tumor
-NHl
-systemic metastasis
.
Low garde 1ry parotid malignancy may be
well circumscribed , hence the surgical
rule (( all parotid masses must come out)).
Facial nerve plane in parotid can only be
estimated not seen with imaging.
Parotid LNs are first order drainage for
malignancies of adjacent scalp & EAC .
DD of parotid lesions
Congenital
Inflammatory
Neoplasm
* benign
* malignant
- 1ry
- 2ry
Differential diagnosis
Congenital
*1st brancheal cleft cyst
*infantile hemangioma
*lymphangioma
• Inflammatory
*parotiditis
*reactive adenopathy
*BLL-HIV
*Sjogren syndrome
*sarcoidosis
*Kimura disease
• Benign tumor
*benign mixed tumor
*warthin tumor
*oncocytoma
*facial nerve schwannoma
*lipoma
Malignant tumor,primary
*mucoepidermoid carcinoma
*adenoid cystic carcinoma
*acinic cell carcinoma
*malignant mixed tumor
*squamous cell carcinoma
•
Malignant tumor , metastatic
*Non-Hodgkin lymphoma
*systemic metastasis
1st brancheal cleft cyst
Parotiditis, acute
Acute infection of parotid gland
# bacterial--- acute suppurative parotitis, usually
unilateral, more than 50 years & neonates
# viral – acute viral parotitis , more than 75%
bilateral , most common cause is mumps, most
less than 15 years , peak age 5-9 years.
# calculus induced – parotitis 2ry to ductal
obstruction by stone.
CT findings
NECT
- Bacterial and viral – hyperdense enlarged parotid with ill
defined margins.
- Calculus-induced – parotid duct calculus usually
obvious.
CECT
- Bacterial – enlarged diffusely enhancing parotid with
inflammatory stranding of overlying soft tissues.
- Viral – enlarged parotids with mild enhancement.
- calculus-induced – parotid duct dilated with enhancing
walls.
Image gallery
Axial CECT shows
diffusely enlarged and
increased in density
compared to right
side (open arrow)
Image gallery
Axial CECT shows
early changes of
acute parotiditis. Note
subtle asymmetry of
parotid density with illdefined contours and
subcutaneous
stranding (arrow).
Parotid duct is normal
( open arrow)
Image gallery
Axial CECT revealed
intraparotid abscess
as irregular area of
low density (arrow).
Note extension of
inflammation with
carotid space
involvement and
compressed or
thrombosed jugular
vein ( open arrow).
Image gallery
Axial CECT shows
calculus-induced
parotiditis. Note
proximal ductal
calculus (arrow) with
intraglandular ductal
radicle enlargement
(open arrow). The
parotid is enlarged &
enhancing without
abscess.
Benign lymphoepithelial lesions- HIV
( BLL-HIV)
Mixed cystic and solid bilateral intraparotid
lesions found in HIV +ve patients.
Best diagnostic clue : multiple cystic and solid
masses enlarging both parotid glands usually
associated with tonsilar hyperplasia & cervical
reactive adenopathy.
Thin rim enhacement of cystic lesions with
heterogenous enhancement of solid lesions.
5% of HIV+ve patients develop BLL of parotids.
BLL-HIV
Axial graphic shows
classic findings of
BLL-HIV as bilateral
intraparotid cysts
mixed with bilateral
solid lymphoid
aggregates (arrows).
Note associated
adenoidal
hypertrophy (open
arrows)
BLL-HIV
Axial CECT at level of
soft palate shows
benign
lymphoepithelial
lesion of HIV as
hypodense cystic &
mixed cystic-solid
lesions of both parotid
glands with thin
peripheral
enhancement.
Image gallery
Axial CECT reveals
bilateral parotid
enlargement 2ry to
lymphoepithelial
lesions of HIV. Note
both cystic (arrows)
and solid (open
arrows) lesions
bilaterally affecting
the parotid glands.
Image gallery
Axial STIR MR shows
bilateral intraparotid
hyperintense cystic
lymphoepithelial
lesions of HIV. Notice
both superficial and
deep lobes are
involved. Arrows
marks associated
reactive occiptal
nodes.
Image gallery
Axial T1 +C MR
shows bilateral cystic
and solid intraparotid
lesions of HIV.
Palatine (faucial)
tonsils (arrows) are
hyperplastic and
associated with
reactive lateral
retropharyngeal
nodes (open arrows)
Sjogren’s syndrome
SJS – chronic systemic autoimmune
exocrinopathy that causes salivary and
lacrimal gland tissue destruction.
* 1ry SJS – dry eyes , dry mouth , no
collagen vascular disease.
* 2ry SJS – dry eyes , dry mouth , with
collagen vascular disease, most
commonly rheumatoid arthritis.
.
Best diagnostic clue: CT shows bilateral
enlarged parotids with multiple cystic and solid
intraparotid lesions with or without intraglandular
calcification.
Imaging appearence :
* early stage – parotids may appear normal
* intermediate stage – miliary pattern of small
cysts diffusely throughout both glands.
* late stage – larger cystic and solid masses in
both parotids.
Sjogren syndrome
Axial CECT reveals
classic imaging
findings of later stage
sjogren syndrome
with bilateral
enlargement,
heterogeneity &
increased CT density
of parotid glands.
Note punctate
calcifications.
Sjogren syndrome
Axial STIR MR
demonstrates early
stage MR imaging
findings of Sjogren
syndrome as bilateral
parotid enlargement
with miliary diffuse
high signal cystic
intraparotid lesions.
Image gallery
Axial T1W MR shows
multiple low signal
cystic lesions
involving both parotid
glands diffusely. This
“ miliary pattern” of
diffuse involvement is
seen in early stages
of Sjogren syndrome.
Benign mixed tumor BMT
( pleomorphic adenoma )
Most common benign parotid space tumor- 80%
Age: most common above 40 y.
Size– variable, may grow to 6-8 cm when in
deep lobe.
Large , asymptomatic mass arising from deep
lobe of parotid is almost always BMT
80-90 % of parotid BMT involve superficial lobe.
Multicentric BMT rare ( less than 1%) , but
recurrent BMT typically from incomplete
resection tends to be multifocal.
Best diagnostic clue:
* small BMT– sharply marginated, intraparotid
ovoid mass with uniform parenchymal
enhancement.
* large BMT– more than 2 cm , lobulated mass
with inhomogenous enhancement representing
foci of necrosis and old hemorrhage.
* deep lobe BMT– pear- shaped ,
inhomogenous mass pushing parapharyngeal
space medially.
BMT
Axial graphic depicts
a small predominently
superficial lobe BMT.
BMT
Axial T1W MR shows
small , superficial lobe
BMT (arrow). Low
signal compared to
surrounding parotid is
typical. Lateral margin
of retromandibular
vein (open arrow)
marks CN7 plane.
Image gallery
Axial garphic reveals
a pear-shaped BMT
of the deep lobe of
the parotid gland.
Notice that despite
the size of this tumor,
the parapharyngeal
fat can still be seen
(arrow) being pushed
superomedially.
Image gallery
Axial T1+C MR with
fat-saturation shows a
large , pear-shaped
BMT extending from
the deep lobe
anteromedially.
Notice the lesion has
pushed the right tonsil
into the high oral
cavity (arrow)
Image gallery
Axial T1+C MR shows
a left parotid tail
intermediate sized
BMT with
inhomogenous
enhancement (arrow).
As these lesions
enlarge , their signal
tends to become
more inhomogenous
on all MR sequences.
Image gallery
Axial CECT shows
recurrent BMT as
multiple lesions
resulting from
intraoperative spillage
of tumor cells. A
larger deep (arrow) &
2 smaller superficial
(open arrow)
recuurent BMTs can
be seen.
Warthin tumor
Benign parotid tumor, sharply marginated ,parotid tail
mass with stricking parenchymal inhomogeneity.
Location– most comonly within parotid tail superficial to
angle of mandible.
Size– 2-4 cm
Morphology – round to ovoid, wellcircumscribed,encapsulated mass or masses ( 20% ).
Parenchymal inhomogeneity is characterestic.
Cystic component in 30% with thin, uniform walls & CT
density of 10-20 HU , with minimal enhancement of solid
component.
General features
2nd most common benign parotid tumor.
20% multicentric, unilateral or bilateral.
Mass is painless, slowly growing.
90% of patients are smokers.
Increase incidence with radiation exposure
Age– mean age = 60 years.
Image interpretation pearls
Be sure to carefully examine for multiplicity
and bilaterality.
Well-circumscribed heterogenous multiple
or bilateral parotid masses in
asymptomatic patient should be
considered warthin tumor.
Warthin tumor
Axial graphic depicts
bilateral mixed solidcystic parotid tail
Warthin tumor. Larger
left intraparotid tumor
is cut in insert to show
characteristic
parenchymal cystic
changes (arrow).
Warthin tumor
Axial CECT shows
mildly enhancing
bilateral parotid tail
Warthin tumor. Note
marked hetrogeneity
of left parotid lesion
(arrow) & solid
composition of right
parotid lesion (open
arrow)
Image gallery
Axial CECT shows a
warthin tumor within
the tail of the
superficial lobe of the
left parotid over the
angle of the mandible
with classic marked
hetrogeneity and
hetrogenous contrast
enhancement.
Image gallery
Coronal T1+C MR
reveals a warthin
tumor in the left
parotid tail (arrow) .
Note the significant
parenchymal
hetrogeneity with both
low and intermediate
signal areas seen
Image gallery
Axial CECT shows a
primarily cystic
warthin tumor of left
parotid tail (arrow).
Note the mural nodule
within the posterior
portion of the lesion ,
differentiating it from
1st branchial cleft cyst
Image gallery
Axial CECT
demonstrates a large
, homogenously
dense, solid Warthin
tumor of superficial
lobe of left parotid
(arrow). Lesions this
size almost always
show significant
parenchymal
inhomogeneity.
Mucoepidermoid carcinoma
Best diagnostic clue:
-low grade MECa: ovoid, well circumscribed,
inhomogenous mass
-high grade MECa : ill-defined, infiltrating mass with
associated malignant nodules.
Location : superficial lobe more than deep lobe.
Malignant adenopathy often present
- 1st order nodes = jugulodigastric nodes ( level 2 )
- intrinsic parotid nodes and parotid tail nodes also
involved.
Imaging recommendations:
- deep tissue spread and perineural tumor through CN7
are better defined by MRI , T1 + C delineate MECa
because high signal fat of normal parotid tissue provides
natural contrast.
Clinical issues
-age : usually 35 – 65 y
- Low grade
painless, mobile , slowly enlarging
- High grade
painfull, non-mobile, rapidly enlarging
Image interpretation pearls
Low grade MECa may exactly mimic
pleomorphic adenoma
High grade MECa has non specific
invasive mass appearance.
Mucoepidermoid carcinoma
Axial CECT shows
well-defined
heterogenous mass in
the right parotid gland
MECa
* axial T1W MR shows
invasive parotid
MECa (arrow) filling
base of stylomastoid
foramen (open arrow)
Image gallery
Axial T1W MR shows
low grade MECa as a
homogenous
intermediate signal
mass (arrow) in
superficial parotid
lobe. Notice how
sharply circumscribed
the tumor is relative to
adjacent parotid gland
Image gallery
Axial T2W MR in
same patient shows
well-defined high
signal MECa (arrow)
in superficial lobe left
parotid. A well
circumscribed, high
signal intraparotid
mass is more
suggestive of BMT.
Image gallery
Axial CECT shows a
holoparotid invasive
high grade MECa
involving the
superficial lobe
(arrow) & deep lobe
(open arrow). Notice
single intraparotid
lymph node (curved
arrow).
Image gallery
Axial CECT in same
patient again reveals
invasive high grade
MECa of parotid with
associated antegrade
perineural tumor on
CN7 (arrow) and
spinal accessory
malignant adenopathy
(open arrow).
Image gallery
Axial CECT shows
high grade MECa in
accessory left parotid
lobe as an invasive
hetrogenous mass
(arrow) anterior to
masseter muscle.
Open arrow: opposite
normal accessory
parotid.
Image gallery
Axial T1W MR
demonstrates an
invasive high grade
MECa of the right
parotid gland (arrow)
with antegrade
perineural tumor on
the facial nerve (open
arrow)
Adenoid cystic carcinoma
Previously called cylindroma
Best diagnostic clue
- low grade ACCa: well-circumscribed, homogenous
enhancing mass
- high grade : infiltrative , enhancing mass with poorly
defined margins
Superficially located, slow growing neoplasm with
propensity for perineural extension
Peak age 50-70y , rare before 20 y
Look carefully for perineural tumor with any parotid
neoplasm, but particularly ACCa.
Imaging findings often non-specific & similar to other
parotid tumors.
ACCa
Axial graphic depicts
high grade parotid
ACCa spreading in
perineural fashion
along proximal CN7
(arrow) & via
auriculotemporal
nerve (open arrow) to
V3 (curved arrow).
ACCa
Coronal T1W MR
shows high deep
parotid ACCa (arrow)
extending through
stylomastoid foramen
with replacement of
foraminal fat pad,
along mastoid
segment of facial
nerve (open arrow).
Image gallery
(Left) axial T1+C MR
demonstrates a high grade
ACCa as an ill defined
enhancement in deep parotid
lobe (arrow) extending
medially to infiltrate masticator
space (open arrow).
(right) coronal T1+C MR
shows intracranial extension of
parotid ACCa through foramen
ovale (arrow) along mandibular
nerve. Spread from CN7 to
CN5 occurred via the
auriculotemporal nerve.
Metastatic disease, nodal,
parotid
Lymphangitic or hematogenous tumor spread to
intraglandulr parotid lymph nodes.
Best diagnostic clue:
- multiple parotid masses in setting of known
head & neck malignancy.
- size : 5 mm- 4 cm
* Consider recurrent BMT in the differential
diagnosis if there is a history of BMT surgical
removal .
General features
Parotid gland has intraglandular lymph nodes ( not
submandibular or sublingual glands )
Normal parotid : up to 32 intraglandular lymph nodes
Parotid nodes are 1st order nodal site for skin of upper
face , external ear , scalp (75%)
Systemic metastasis to parotid nodes rare
Metastasis = 4% of all salivary neoplasm
Clinical presentation usually – external ear, scalp , upper
face skin cancer with enlarging parotid masses.
Age= 7th decade
Image iterpretation pearls
Multifocal unilateral disease is most
suggestive of 1st order nodal disease from
adjacent skin sites
Bilateral nodes suggests systemic disease
or hematogenous metastatic spread.
Metastatic disease
Axial CECT shows
two unilateral
intraparotid
squamous cell
carcinoma nodes
(arrows). Primary
tumor on skin of
ipsilateral forehead
had been treated
multiple times in the
previous year.
Metastatic disease
Axial CECT in same
patient shows cervical
neck metastatic nodal
spread (arrows) in
addition to parotid
nodal disease.
Image gallery
(left) axial CECT reveals left
intraparotid melanoma nodal
mets (arrow) from left temporal
fossa skin primary. Note
posterior lateral margin of node
shows early extranodal
spread.
(right) axial T1W MR shows
ovoid intermediate to high
signal melanoma metastatic
node (arrow). Primary tumor
located on external ear on left.
Parotid nodes are 1st order
drainage for this primary site.
Non-hodgkin lymphoma, parotid
Lymphoma involving intra- and periparotid
lymph nodes as primary site or secondry
in systemic disease.
Best diagnostic clue: multiple, wellcircumscribed, homogenously mildly
enhancing intraparotid masses with
adjacent lymphadenopathy, unilateral or
bilateral
NHL
Axial CECT reveals
multiple right
intraparotid lymph
nodes (arrows)
involved by NHL.