Anatomy of neck space by Dr. Milan

1. Radiological Approach to Neck Spaces
Dr. Milan Silwal
Resident, Radiodiagnosis

2. Background:
• Head and neck lesions are a very challenging subject
due to the complex anatomy and wide ranging
pathology.
• Cross sectional imaging is commonly used for clinical
evaluation of head and neck lesions.
• The anatomical location and borders of head and
neck lesions are vital in narrowing radiological
differential diagnosis and allowing formation of an
appropriate clinical management plan.

3. Neck Spaces:
Described in relation to the hyoid
• Suprahyoid (SHN)
• Infrahyoid (IHN)

4. Fascia of the neck
• Key to understanding
neck spaces is fascia.
• 2 major fascial layers of
the neck: superficial and
deep cervical fascia.

5. • Deep cervical fascia comprises three distinct layers:
• Superficial layer splits to enclose a number of muscles (including
sternomastoid and trapezius) and contributes to formation of the carotid
sheath.
• Middle layer envelops the anterior infrahyoid strap muscles, and splits to
enclose the contents of the visceral space. It forms the anterior wall of the
retropharyngeal space and contributing to formation of the carotid
sheath.
• Deep layer encircles the paraspinous and prevertebral muscles and
associated structures. Attaching to the transverse processes, the deep
layer subdivides the perivertebral space into the prevertebral space and
the paraspinal space

6. • PPS lies in a central location in the
deep face
• PMS is medial to the PPS
• MS is anterior to the PPS
• PS is lateral of the PPS
• CS is posterior to the PPS
• RPS is posterior to PPS
• Perivertebral space is posterior to
the RPS

7. • Axial graphic depicting the fascia and spaces of the infrahyoid neck. The three
layers of deep cervical fascia are present in the suprahyoid and infrahyoid
neck. The carotid sheath is made up of all 3 layers of deep cervical fascia (tri-
color line around carotid space). Notice the deep layer completely circles the
perivertebral space, diving in laterally to divide it into prevertebral and a
paraspinal components.

8. Coronal graphic of parapharyngeal space. The parapharyngeal spaces are paired fat-
filled spaces in the more lateral aspect of the suprahyoid neck. This space abuts the
skull base between the masticator and pharyngeal mucosal spaces. There are no
important structures at the point of intersection between the PPS and the skull base.
Inferiorly the PPS communicates inferiorly with the posterior submandibular space.
The masticator space has the largest area of abutment with the skull base, including
CNV3. The pharyngeal mucosal space abuts the basisphenoid and foramen lacerum.

9. Deep neck spaces
• suprahyoid neck
– parapharyngeal space
– parotid space
– pharyngeal mucosal space
– masticator space
– buccal space
• infrahyoid neck
– anterior cervical space
– posterior cervical space
– visceral space
• supra- and infrahyoid neck
– carotid space
– retropharyngeal space
– perivertebral space

11. Parapharyngeal space
• PPS: Central, fat-filled spaces in lateral suprahyoid neck (SHN)
around which most of important spaces are located.
• Is shaped like a pyramid, inverted with its base at the skull
base, with its apex inferiorly pointing to the greater cornu of
the hyoid bone.

12. • Importance of PPS is its conspicuity on CT and MR as well as
its direction of displacement by mass lesions of surrounding
spaces PPS displacement pattern helps define actual space
of origin
– PMS mass lesion pushes PPS laterally
– MS mass lesion pushes PPS posteriorly
– PS mass lesion pushes PPS medially
– CS mass lesion pushes PPS anteriorly

13. • Boundaries
• superior margin: base of skull
• inferior margin: greater cornu of hyoid bone
• medial margin: pretracheal layer of the deep cervical
fascia
• lateral margin: investing fascia of the deep cervical
fascia covering the deep lobe of the parotid
• anterior margin: investing fascia of the deep cervical
fascia covering the medial pterygoid muscle
• posterior margin: prevertebral layer of the deep
cervical fascia

14. • Contents
• fat (main component)
• internal maxillary artery
• ascending pharyngeal artery
• pterygoid venous plexus only small portion;
mainly within masticator space
• lymph nodes

16. This image at the level of the nasopharynx shows the four key spaces
surrounding the parapharyngeal space, the pharyngeal mucosal, masticator,
parotid and carotid spaces.

17. • Related pathiologies in PPS:
– benign mixed tumor (from minor salivary gland rests in PPS),
– lipoma
– atypical second branchial cleft cyst.
– parapharyngeal cellulitis / parapharyngeal abscess
– trigeminal schwannoma
• To say lesion is primary to PPS, it must be completely
surrounded by PPS fat
• In most cases where lesion is thought to be primary to PPS,
careful observation will find connection to one of surrounding
spaces (usually PS)

18. Pharyngeal mucosal space
• Anatomy Relationships
• Airway side of PMS has
no fascial border
• Posterior to PMS is
retropharyngeal space
RPS
• Lateral to PMS is PPS

19. Internal Contents
• Mucosal surface of pharynx
• PMS lymphatic ring: Lymphatic ring of tissue of PMS (Waldeyer ring)
– Nasopharynx: Adenoids
– Oropharynx, lateral wall: Palatine (faucial) tonsil
– Oropharynx, base of tongue: Lingual tonsil
• Minor salivary glands
– Soft palate mucosa has highest concentration
• Pharyngobasilar fascia
– Tough aponeurosis that connects superior constrictor muscle to skull
base
– Posterosuperior margin notch = sinus of Morgagni
• Levator palatini muscle & eustachian tube pass through this notch on way
from skull base to PMS

20. Lesion is designated primary to PMS under following
circumstances
• Lesion center is medial to parapharyngeal space
• mass pushes PPS fat from medial to lateral
• mass disrupts normal PMS mucosal & submucosal
architecture

22. MASTICATOR SPACE
• MS is large SHN space spanning area from
high parietal calvarium (suprazygomatic MS)
above to mandibular angle below
• Suprazygomatic MS: Contains only belly of
temporalis muscle
• Infrazygomatic MS: MS "proper"; containing
masseter, medial & lateral pterygoids, CNV3 &
ramus/posterior body of mandible

23. • Craniocaudal extent of MS is more extensive than
commonly recognized
• On its cephalad margin MS reaches high on parietal
calvarium at top of suprazygomatic MS
• Abuts skull base with foramen ovale & foramen
spinosum included
• MS lesions displace PPS from anterior to posterior
• Masticator space malignancy can spread perineurally via the
mandibular division of the trigeminal nerve into the middle
cranial fossa.

25. BUCCAL SPACE
• BS is pyramidal fat-filled space of midface; forms
padding of cheeks
• No defined fascial boundaries
• BS predominantly fat & small nodes
– Parotid duct traverses BS; pierces buccinator at level
of upper 2nd molar
– Accessory parotid gland found in ≈ 20%
• Majority of BS pathology is nodal disease or
extension of pathology from adjacent structures
& spaces

26. • Related pathology
• parotid duct calculi
• odontogenic infection
• tumours: minor salivary gland tumours,
vascular lesions (eg haemangiomas)

28. PAROTID SPACE
• Paired lateral suprahyoid neck spaces enclosed by superficial
layer of deep cervical fascia containing parotid glands, nodes
& extracranial facial nerve branches
• PS extends from external auditory canal (EAC) & mastoid tip
superiorly to angle of mandible (parotid tail) below
• features to define a primary parotid space lesion:
– Center of lesion is within parotid gland
– If larger mass lesion of deep lobe, mass displaces PPS from
lateral to medial with widening of stylomandibular gap

29. • Boundaries
• superior margin:
external auditory canal;
apex of the mastoid
process
• inferior margin: inferior
mandibular margin
• anterior margin:
masticator space
• Contents
• parotid glands
• intraparotid lymph
nodes
• intraparotid facial nerve
(CN VII)
• external carotid
artery (ECA)
• retromandibular vein

30. Related pathology
• congenital
– agenesis
– first branchial cleft cyst
– hemangioma
– cystic hygroma/lymphangioma
• salivary gland tumours-benign and primary malignant tumour
• metastatic adenopathy
• lymphoma
• parotid cysts
• inflammatory
– sialadenitis
– abscess
– Sjogren's syndrome

32. CAROTID SPACE
• Paired, tubular spaces surrounded by carotid
sheath that contain carotid arteries, internal
jugular veins, cranial nerves (CN) 9-12 (SHN) &
CN10 (IHN)
• extends from skull base (carotid canal and
jugular foramen) to aortic arch below
• divided into its major segments
– Nasopharyngeal, oropharyngeal, cervical and
mediastinal segments

33. • Boundaries
• superior margin: lower border of jugular
foramen
• inferior margin: aortic arch
• anterolateral margin: sternocleidomastoid
muscle

34. CAROTID SPACE
The suprahyoid carotid space contains CN9-12, the internal carotid artery & the
internal jugular vein. The carotid sheath is made up of components of all 3
layers of deep cervical fascia (tri-color line around carotid space). In the
suprahyoid neck the carotid sheath is less substantial than in the infrahyoid
neck. The sympathetic trunk runs just medial to the carotid space.

38. • CS mass displacement pattern
– Nasopharyngeal CS mass: PPS displaced anteriorly,
styloid process displaced anterolaterally
– Oropharyngeal CS mass: PPS displaced anteriorly,
posterior belly of digastric displaced laterally
– Infrahyoid neck CS mass: Surrounds CCA
• May separate CCA from IJV

39. RETROPHARYNGEAL SPACE
• RPS is fat-filled space in posterior midline of
neck that can be identified on imaging from
skull base to upper mediastinum
• Upper-most RPS (nasopharyngeal portion) is
“narrow"
– In RPS abscess path of least resistance is inferiorly
• RPS nodes only found in suprahyoid neck

41. • Pharyngeal mucosal space (PMS) is anterior
• Danger space (DS) is directly posterior to RPS
• Carotid space is lateral to RPS
• Fat is primary occupant of SHN RPS
• RPS lymph nodes
– Lateral group:Also called nodes of Rouviere
– Medial group: Less often visible on imaging

42. • radiologic findings to define a lesion as
primary to RPS:
– Centered posteromedial to parapharyngeal space
(PPS) & directly medial to carotid space
– Encroaches on PPS from posteromedial to
anterolateral

43. • Retropharyngeal space (RPS) is immediately posterior
to pharynx & anterior to prevertebral muscles
• Distension of space results in biconvex, bow tie, or oval
configurations
• Plain film cannot distinguish RPS from prevertebral
space process
• Consider abscess 1st in differential of low density RPS
mass
– Delay in diagnosis and treatment can have grave
consequences
• Airway compromise
• Abscess spreads to danger space and then mediastinum

45. Danger space
• Danger space is a potential space located behind the
true retropharyngeal space, which connects the
deep cervical spaces to the mediastinum.
Boundaries:
• anteriorly - alar fascia
• posteriorly - prevertebral fascia
• superiorly - extends from the clivus
• inferiorly - posterior mediastinum at the level of
the diaphragm

46. • It is a potential path for
spread of infections from
the pharynx to the
mediastinum.
• In healthy patients, it is
indistinguishable from
the RPS.
• It is only visible when
distended by fluid or pus,
below the level of T1-T6,
since the retropharyngeal
space variably ends at this
level.
Expected location of the danger
space (green)

47. Perivertebral space
• Cylindrical space surrounding vertebral column
extending from skull base to upper mediastinum
bounded by deep layer, deep cervical fascia subdivided
into prevertebral & paraspinal components
• Prevertebral-PVS sits directly behind retropharyngeal
space
• Paraspinal-PVS is deep to posterior cervical space &
posterior to transverse processes of cervical spine

49. • Imaging findings to define a mass lesion as
primary to prevertebral-PVS:
– Mass is centered within prevertebral muscles or
corpus of vertebral body
– Mass lifts prevertebral muscles anteriorly (RPS
mass pushes them posteriorly)
• Most PVS lesions originate in vertebral body
(infection or metastatic tumor) or Vertebral
body is usu. Involved when PVS lesion is found

50. • Prevertebral-PVS disease may involve epidural space
• 1st barrier to spread is deep layer of deep cervical
fascia
• Path of least resistance of spreading pus or tumor is
deep through neural foramen into epidural space
• When prevertebral PVS disease is found on imaging,
always check for epidural space extension!

53. Infrahyoid neck space

54. Infrahyoid neck space
• The infrahyoid neck is
divided into 6 anatomical
compartments or spaces
by the various layers of the
cervical fascia.
• These spaces are well
recognized in the axial
plane and therefore suited
for analysis on axial CT or
MR.

55. Visceral space
• Location: anterior, within
the middle layer of deep
cervical fascia.
• Contents: Thyroid &
parathyroids, paratracheal
nodes, esophagus, trachea,
recurrent laryngeal nerve
• Importance: Trachea &
esophagus traverse
Visceral space

58. Multinodular goiter
• The swelling is adjacent
to the left lamina of the
thyroid cartilage.
• The strap musculature
seems to be draped over
the lesion (blue arrow).
• Therefore this lesion lies
within the visceral space.

59. • Anterior cervical space and posterior cervical spaces:
– They are predominantly fat filled, so these spaces typically provide
symmetric imaging landmarks on axial imaging. Posterior cervical
space contain CN XI.
– Posterior cervical space contains the spinal accessory lymph node
chain also, so it is commonly affected by both inflammatory and
malignant nodal disease

60. Anterior cervical space
• small infrahyoid compartment of the head and
neck. It is not enclosed by fascia.
• Contents-areolar fat
• Related pathology
• lipoma(most common)
• second branchial cleft cysts

62. The mass has the signal intensity of fat on a T1-
weighted image and the signal is completely suppressed
with fat suppression.

63. To conclude:
• Head and neck anatomy is described reflecting the
importance of fascia lined spaces in confining various
pathologies.
• Neck has been divided into a number of 'deep spaces‘;
suprahyoid and infrahyoid with some of the spaces having
continuation in both the region.
• Knowledge of neck spaces allows for better communication
and aids in diagnosis as each space has a distinct group of
pathologies.

64. References:
• Textbook of Radiology and Imaging-David sutton
• Head and neck spaces: Where and what? By K. J. Au
Yong et al; doi: 10.1594/ecr2009/C-468
• Radiology Assistant

65. Thank You!