This presentation deals with the anatomy of the different spaces of the neck and the common lesions encountered in individual spaces.

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CT NECK
A PRACTICAL APPROACH
Dr. Hazem Abu Zeid Yousef (MD)
May 2007

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INDICATIONS FOR CROSS
SECTIONAL IMAGING OF
THE NECK

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STANDARD TECHNIQUE
“Scanning protocol”

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NORMAL ANATOMY
Cervical triangles.
Cervical spaces.
Lymph nodes

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The cervical spaces
The cervical spaces of the suprahyoid and
infrahyoid neck include the sublingual
space, submandibular space, buccal space,
parotid space, parapharyngeal space,
carotid space, masticator space,
pharyngeal mucosal space, visceral space,
retropharyngeal space, posterior cervical
space, and prevertebral space

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The sublingual space
The paired sublingual spaces are located in the
floor of the mouth and are defined by the mandible
anteriorly and laterally, the hyoid bone posteriorly,
the oral mucosa superiorly, and the mylohyoid
muscle inferiorly. Dividing the sublingual spaces
are the paired midline geniohyoid muscles, and the
paired genioglossus muscles. Separating these
muscles sagittally is a midline low density plane or
septum. Lateral to the genioglossus muscles is a
lateral low-density plane that contains fat, the
submandibular duct, and the sublingual salivary
glands.

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Typical lesions seen in the sublingual space
include carcinomas extending from the floor
of the mouth and tongue; ranulas, which are
retention cysts of the sublingual salivary
gland; dermoids and epidermoids;
hemangiomas and lymphangiomas; lingual
thyroid glands and thyroglossal duct cysts;
abscesses; lymphadenopathy; and calculi in
the submandibular duct

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Submandibular Space
The submandibular space is posterolateral to the sublingual
space and contains the superficial lobe of the
submandibular salivary gland and lymph nodes. The
submandibular space communicates freely with the
sublingual. Congenital lesions such as cystic hygromas,
branchial cleft cysts, dermoids, epidermoids, and
thyroglossal duct cysts may occur in the submandibular
space. Abscesses are associated with skin thickening,
edema of the fat, and gas in over 50% of cases. Calculi
commonly occur in the submandibular glands. Tumors of
the submandibular gland, present as soft-tissue masses
within the gland. The submandibular lymph nodes are
important sentinels in the spread of floor of mouth
infections and malignancies and may be involved with
lymphom

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Buccal Space
The buccal space is a small region anterior to
the masseter and lateral to the buccinator
muscle. This space contains the buccal fat pad
and is most commonly involved with infection.
Deeply invasive skin cancers also may involve
this space.. Infections and neoplasms from
adjacent spaces, such as the parotid and
masticator space, also may secondarily involve
the buccal space

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Parotid Space
The parotid space is located posterior to the masseter
muscle. This space extends from the external auditory
canal and the mastoid tip superiorly to the angle of the
mandible below. It contains the parotid gland, intra-and
extra-parotid lymph nodes. The gland contains
about 20 intraglandular lymph nodes which are
considered normal if their transverse diameter is less
than 8 mm. The gland also contains extracranial
branches of the facial nerve, and vessels: the external
carotid artery and the retromandibular vein just
behind the mandibular ramus

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Evaluation of masses within the parotid region begins
with determination of the lesion as intraparotid or
extraparotid. Lesions are considered intraparotid if
50% or greater of the circumference is surrounded by
parotid tissue and the epicenter is lateral to the
parapharyngeal space. Intraparotid masses displace the
parapharyngeal fat medially. Identification of a fat
plane between the lesion and the parotid indicates a
parapharyngeal space site of origin, whereas direct
contiguity of mass to gland indicates a deep parotid
lobe origin.
Intraparotid lesions must then be localized to either
the superficial or deep parotid lobes. The
retromandibular vein is chosen as an alternative
landmark for demarcation. The margins of the lesion
also should be evaluated. Sharply defined margins tend
to favor a benign tumor diagnosis, whereas indistinct
margins favor a malignant or inflammatory diagnosis.
Finally, determination of the number of lesions is
helpful in suggesting a diagnosis.

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Parapharyngeal Space
The parapharyngeal space is shaped like an inverted
pyramid and extends from the skull base to the hyoid bone.
This space is triangular on transaxial images with the apex
pointing towards the nasopharynx. Anterolaterally, it is
bounded by the medial pterygoid fascia, which separates it
from the masticator space. Medially, the parapharyngeal
space is bordered by the pharyngobasilar fascia. At the level
of the nasopharynx, this space is subdivided into prestyloid
and poststyloid compartments. The prestyloid compartment
contains branches of the internal maxillary and ascending
pharyngeal arteries, fat, salivary rests, and minor salivary
glands. The poststyloid compartment is also known as the
carotid space as it extends below the hyoid bone.

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Carotid Space
The cylindrical carotid space extends from the base of the skull to the
aortic arch. The suprahyoid portion of the carotid space is bordered
anteromedially by the pharynx, posteriorly by the prevertebral fascia,
and anterolaterally by the prestyloid parapharyngeal space. In the
infrahyoid region, this space is surrounded by the visceral and
retropharyngeal spaces medially, the prevertebral and posterior
cervical spaces posteriorly, and the sternocleidomastoid muscle
anterolaterally.
The carotid space contains the carotid artery, internal jugular vein,
glossopharyngeal nerve, vagus nerve, spinal accessory nerve,
hypoglossal nerve, sympathetic chain, and the internal jugular nodes
of the deep cervical chain.

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Masticator Space
This space contains the mandible, the muscles of mastication, and the
mandibular division of the trigeminal nerve. Lesions derived from
these tissues include nerve sheath tumors, mandibular and soft tissue
sarcomas, dental tumors, cysts and abscesses, osteomyelitis,
hemangiomas, lymphangiomas, and lipomas..
The mandibular branch of the trigeminal nerve exits the skull through
the foramen ovale, which is located above the masticator space and has
been termed the "chimney of the masticator space". Lesions within the
masticator space can invade the middle cranial fossa by this route and
intracranial processes, such as meningiomas, can descend into the
masticator space and become extracranial. Signs of perineural spread
along the mandibular division of the trigeminal nerve include:
expansion of the foramen ovale, mass within Meckel's cave, lateral
bulging of the cavernous sinus, and atrophy of the muscles of
mastication.

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Pharyngeal Mucosal Space
The pharyngeal mucosal space includes the mucosal
surfaces and immediate submucosa of the
nasopharynx, oropharynx, oral cavity, and
hypopharynx. Most of this space is surrounded
posteriorly and laterally by a sleeve comprised of
the middle layer of the deep cervical fascia.
Superiorly, this fascia envelopes the posterior aspect
of the pharyngobasilar fascia, which attaches the
pharynx and superior constrictor muscle to the base
of the skull. Also included in this space are
lymphoid tissue, minor salivary glands, and
pharyngeal constrictor muscles.

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The nasopharyngeal portion of the pharyngeal mucosal space
extends from the posterior boundary of the nasal cavity to a
plane defined by the hard and soft palate. For purposes of
cancer staging, the nasopharynx is subdivided into posterior,
superior, lateral, and anterior walls26. The oropharyngeal
portion extends from the inferior margin of the nasopharynx
to the level of the glossoepiglottic folds. It is subdivided into
lateral, posterior, anterior, and superior walls. The oral cavity
consists of the floor of the mouth, the anterior two thirds of
the tongue, the buccal mucosa and gingiva, the hard palate
and retromolar trigone. The hypopharynx is considered in the
section on the visceral space because of its relationship with
the larynx.

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Visceral Space
The midline visceral space is enclosed by the middle layer of
deep cervical fascia and extends from the hyoid bone to the
mediastinum. It contains the larynx and hypopharynx, the
thyroid and parathyroid glands, the trachea and esophagus,
paratracheal lymph nodes, and the recurrent laryngeal nerves.

26. The most common malignant lesion of the pharyngeal mucosal
space is carcinoma.
The lymphoid tissue of the pharyngeal mucosal space includes
the adenoids and tonsils and is collectively named Waldeyer's
ring. Normally, the lymphoid tissue is asymmetric and
involutes with age; therefore, the consideration of neoplasm in
a young patient must be carefully weighed with a history of
recent upper respiratory infection and the likely presence of
normal variability. Non-Hodgkin lymphomas develop from
this tissue. Inflammatory lesions such as tonsillar abscess also
are fairly common and can present with sore throat, high fever,
and a mass in the tonsillar region. Post-inflammatory
calcifications frequently are seen as incidental findings on CT
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Retropharyngeal Space
The retropharyngeal space lies posterior to the visceral space. The
retropharyngeal space extends from the base of the skull to the
mediastinum and serves as a potential conduit for spread of neck
pathology into the chest. The retropharyngeal space is divided into
suprahyoid and infrahyoid compartments. The suprahyoid
compartment contains lymph nodes and fat, whereas the infrahyoid
compartment only contains fat. Therefore, retropharyngeal
lymphadenopathy only occurs above the hyoid and tends to remain
unilateral or bilateral, sparing the midline. In contradistinction,
infections and direct invasion of cancer may involve both the
suprahyoid and infrahyoid portions and the midline "danger space“.

28. Retropharyngeal masses lie anterior to the prevertebral
space, posteromedial to the parapharyngeal space and
medial to the carotid arteries. The prevertebral muscles
may be compressed and laterally splayed. Common
retropharyngeal lesions include inflammatory
lymphadenopathy and abscesses.
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Posterior Cervical Space
The posterior cervical space abuts the carotid space posterolaterally
and is sandwiched by the sternocleidomastoid muscle anterolaterally
and the paraspinal muscles posteromedially The primary components
of this space are fat, the spinal accessory and dorsal scapular nerves,
and the spinal accessory lymph nodes of the deep cervical chain.
Typical lesions arising in this space include spinal accessory
lymphadenopathy from metastatic squamous carcinoma and
lymphoma, lipomas, liposarcomas, cystic hygromas, and branchial
cleft cysts.

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Prevertebral "perivertebral" Space
The prevertebral space is formed by the deep cervical fascia. Fascia
attaches to the transverse processes of the cervical vertebra dividing
this space into anterior and posterior compartments. The anterior
compartment contains the vertebral bodies and spinal cord, the
vertebral arteries, phrenic nerve, and prevertebral and scalene muscles.
The posterior compartment contains the posterior vertebral elements
and paraspinous muscles.. Prevertebral space lesions usually arise in
the vertebral body, intervertebral disc spaces, or prevertebral or
paraspinous muscles. Examples include vertebral osteomyelitis and
metastases, and rarer lesions such as chordoma and nerve sheath
tumors. On imaging, prevertebral lesions anteriorly displace the
retropharyngeal space and anterior border of the prevertebral
muscles and posterolaterally displace the posterior triangle fat.

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Cervical lymph nodes

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33. The outer ring forms the table surface and represents
the “sentinel chains” at the base of the skull
including the occipital, mastoid, parotid,
submandibular, facial, submental, and sublingual
nodal groups. The shaded inner C-shaped structure
represents the deep retropharyngeal nodes that
extend to the hyoid bone. All of these groups drain
into the paired anterior and lateral chains depicted
as the legs of the table.
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34. The submental group is located inferior to the anterior mandible and
mylohyoid muscle and between the digastric muscles
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The submandibular group is located in the submandibular space.

36. The retropharyngeal nodes are located in the suprahyoid
retropharyngeal space, along the lateral borders of the longus capitis
muscle
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The sublingual nodes are found in the sublingual space and drain
the tongue and floor of mouth. A lateral group follows the course
of the lingual artery and a median group lies between the
genioglossus muscles

38. The lateral cervical chain is subdivided into the superficial and deep
lateral cervical nodes. The superficial group follows the course of the
external jugular vein, is easily palpable, and therefore is not usually
examined by imaging. The important deep group is further divided into
the spinal accessory, transverse cervical, and internal jugular groups.
The spinal accessory nodes are found within the fat of the posterior
cervical triangle and posterior cervical space lateral and posterior to
the spinal accessory nerve between the trapezius and the
sternocleidomastoid muscles. The transverse cervical group are seen in
the supraclavicular region.
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39. The internal jugular group is deep to the
sternocleidomastoid muscle and follows the course
of the internal jugular vein. High internal jugular
nodes extend from the base of the skull to the
carotid bifurcation “hyoid bone”.
The middle jugular nodes extend from the carotid
bifurcation to the omohyoid muscle “ cricoid
cartilage”. Finally, the low jugular nodes span from
the omohyoid muscle to the clavicle. The nodes of
Virchow are the most inferior nodes in the deep
cervical chain
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Level I consists of the submental and submandibular nodes.
Level II includes the internal jugular chain extending from
the base of skull to the (hyoid bone).
Level III corresponds to the internal jugular nodes from the
carotid bifurcation to the (cricoid cartilage).
Level IV refers to all nodes in the internal jugular group
from the omohyoid muscle to the clavicle.
Level V consists of spinal accessory and transverse cervical
nodes.
Level VI contains the pretracheal, prelaryngeal, and
paratracheal nodes.
Level VII includes the nodes in the tracheoesophageal
groove and upper mediastinum.

41. Imaging criteria for lymphadenopathy is based on nodal size, internal
heterogeneity, presence of clusters, shape, and associated findings.
Nodes in levels I and II generally are larger compared with nodes in
lower levels.
Internal lymph node heterogeneity is one of the most reliable criteria for
recognizing lymphadenopathy.
Clusters are defined as three or more contiguous, ill-defined nodes
within the same level ranging from 8 to 15 mm in size. Clusters may be
seen in inflammation, cancer, or lymphoma. Small cancerous nodes,
seemingly normal by size criteria, may be clustered with larger
obviously malignant nodes.
Shape is no longer thought to be reliable in differentiating normal from
pathologic nodes. Round nodes tend to be neoplastic whereas elliptical
or bean-shaped nodes are generally normal or hyperplastic; however,
many exceptions may be encountered.
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Thank you