neck triangles

Neck triangles and neck

dissectionMaryam Majid Al-ezairej

Rak medical collageMBBS III

TRIANGLES OF THE NECK

The side of the neck presents a somewhat quadrilateral outline . It is limited above by the lower border of the body of the mandible

,and an imaginary line drawn from the angle of the mandible to the mastoid process.

Below ,it is limited by the upper border of the clavicle. Medially ,by the midline of the neck. Posteriorly , by the anterior border of the Trapezius muscle .

Quadrilateral outline in the neck

The Sternocleidomastoid muscle

This quadrilateral space is divided by the Sternocleidomastoid muscle into two main triangles .

The Sternocleidomastoid muscle passes obliquely upwards and backwards from its site of origin at the clavicle and sternum to its point of insertion on the mastoid process and the occipital bone .

The triangle in front of this muscle is the anterior triangle and the one behind it is the posterior triangle .

Anterior and posterior triangles

Anterior Triangle

Posterior triangle

Posterior triangle

This is formed by : The Sternocleidomastoid musc.,anteriorly. The Trapezius muscle, posteriorly. The Clavicle ,inferiorly. The apex of the triangle is formed by the occipital

bone.

The ROOF of the posterior triangle is formed by:

Skin Superficial fascia Platysma muscle Investing layer of the deep cervical fascia

The FLOOR of the triangle is formed by the following muscles from above downwards:

Splenius Capitis Levator scapulae Posterior scalene Middle scalene Anterior scalene

Subdivisions of the posterior triangle The posterior triangle is further divided into two smaller triangles by the Inferior

belly of the Omohyoid muscle .

These are the : Supraclavicular

triangle Occipital

triangle

Supraclavicular triangle It is formed by the Inferior belly of the Omohyoid , the Clavicle , Sternocleidomastoid muscle.

The Occipital triangle

The Occipital triangle is formed by the

Inferior belly of the Omohyoid The Trapezius muscle

Sternocleidomastoid muscle.

CONTENTS OF THE POSTERIOR TRIANGLE

NERVES and PLEXUSES: Spinal acessory nerve. Branches of Cervical plexus Roots and trunks of brachial plexus.

Contents of the posterior triangle

VESSELS: Subclavian artery Transverse Cervical artery Suprascapular artery External jugular vein (terminal part)

LYMPH NODES: Occipital Supraclavicular

MUSCLES: Inferior belly of Omohyoid muscle

CLINICAL SIGNIFICANCE OF THE POSTERIOR TRIANGLE

The Accessory Nerve may be damaged ,while taking lymph node biopsy.

The External Jugular Vein is present in a superficial location here and this makes it vulnerable to injury.

THE ANTERIOR

TRIANGLE

ANTERIOR TRIANGLE

BOUNDARIES: Anterior border of the SCM muscle midline of the neck inferior border of the mandible ROOF: Skin Superfacial fascia and platysma muscle Investing layer of deep cervical fascia

SUBDIVISIONS OF ANTERIOR TRIANGLE

SUBDIVISIONS OF THE ANTERIOR TRIANGLE The anterior triangle is divided into four

smaller triangles:1. SUBMENTAL TRIANGLE2. SUBMANDIBULAR TRIANGLE3. CAROTID TRIANGLE4. MUSCULAR TRIANGLE

SUBMENTAL TRIANGLE

Formed by the :

anterior midline of neck

hyoid bone anterior belly

of digastric muscle

SUBMANDIBULAR TRIANGLE Formed by:

Inferior border of the mandible

Anterior belly of the digastric muscle

Posterior belly of the digastric muscle

CAROTID TRIANGLE

FORMED BY: Superior belly of

the Omohyoid muscle

Sternocleidomastoid muscle

Posterior belly of the digastric muscle

MUSCULAR TRIANGLE

Formed by: midline of the

neck

superior belly of the Omohyoid

sternocleidomastoid muscle

Contents of the anterior triangle

CONTENTS OF THE ANTERIOR TRIANGLE VESSELS: carotid system(CCA,ICA, ECA) Internal Jugular vein

NERVES: Cranial nerves 7,9,10,11,12 Cervical plexus

MUSCLES: Suprahyoid muscles: (Digastric ,

Mylohyoid,Stylohyoid,Geniohyoid )These elevate the hyoid bone , and the floor of the mouth ,and depress the mandible .

Infrahyoid muscles : (Sternohyoid,Sternothyroid,Thyrohyoid,

Omohyoid ) These depress the hyoid bone and the larynx.

Neck dissection

HISTORY

1888 - Jawdynski described en bloc resection with resection of carotid, internal jugular vein and sternocleidomastoid muscle.

1906 - George W. Crile of the Cleveland Clinic describes the radical neck dissection. The operation encompasses removal of all the lymph nodes on one side of the neck, and includes removal of the spinal accessory nerve (SAN, or CN XI), internal jugular vein (IJV) and sternocleidomastoid muscle (SCM).

1957 - Hayes Martin describes routine use of the radical neck dissection for control of neck metastases.

1967 - Oscar Suarez and E. Bocca describe a more conservative operation which preserves SAN, IJV and SCM.

Last 3 decades - Further operations have been described to selectively remove the involved regional lymph groups

NECK DISSECTION

Cancers in the head and neck region commonly metastasize to cervical lymph nodes. The term "neck dissection" refers to a surgical procedure in which the fibrofatty contents of the neck are removed for the treatment of cervical lymphatic metastases. Neck dissection is most commonly used in the management of cancers of the upper aerodigestive tract. It is also used for malignancies of the skin of the head and neck area, the thyroid, and the salivary glands as depicted in the images below.

Region I: Submental and submandibular triangles. Ia is the submental triangle bound by the anterior bellies of the digastric and the mylohyoid. Ib is the triangle formed by the anterior and posterior bellies of the digastric and body of mandible.

Region II: upper third including the upper jugular and jugulodigastric nodes and the upper posterior cervical nodes. Region bound by the digastric muscle superiorly and the hyoid bone (clinical landmark) or the carotid bifurcation (surgical landmark) inferiorly. IIa contains nodes in the region anterior to the spinal accessory nerve and IIb posterior to the nerve.

Region III: middle third jugular nodes extending from the carotid bifurcation superiorly to the cricothyroid notch (clinical landmark) or omohyoid muscle (surgical landmark).

Level of lymph nodes

Region IV: lower jugular nodes extending from the omohyoid muscle superiorly to the clavicle inferiorly.

Region V: posterior triangle group of lymph nodes located along the lower half of the spinal accessory nerve and the transverse cervical artery. The supraclavicular nodes are also included in this group. The posterior boundary is the anterior border of the trapezius muscle, the anterior boundary is the posterior border of the sternocleidomastoid muscle, and the inferior boundary is the clavicle.

Region VI: anterior compartment group comprises lymph nodes surrounding the midline visceral structures of the neck extending from the level of the hyoid bone superiorly to the suprasternal notch inferiorly. On each side, the lateral boundary is the medial border of the carotid sheath. Located within this compartment are the perithyroidal lymph nodes, paratracheal lymph nodes, lymph nodes along the recurrent laryngeal nerves, and precricoid lymph nodes. 4

Classification

1) Radical neck dissection; 2) Modified radical neck dissection; 3) Selective neck dissection including

supraomohyoid, posterolateral, lateral, and anterior; and

4) Extended radical neck dissection.

Classification

The radical neck dissection is defined as removing all of the lymphatic tissue in regions I-V including removal of the spinal accessory nerve, (SAN), sternocleidomastoid muscle (SCM), and internal jugular vein (IJV). It does not include removal of the suboccipital nodes, periparotid nodes except for infraparotid nodes located in the posterior aspect of the submandibular triangle, buccal nodes, retropharyngeal nodes, or paratracheal nodes

Classification

Modified radical neck dissection (MRND) is defined as excision of all lymph nodes routinely removed by radical neck dissection with preservation of one or more nonlymphatic structures, i.e., SAN, IJV, SCM. 4 Medina subclassifies the MRND into types I-III; where type I MRND preserves the SAN, type II MRND preserves the SAN and IJV, and type III MRND preserves the SAN, IJV, and SCM. Thetype III MRND is also referred to as the "functional neck dissection" as popularized by Bocca, however in his classic description the submandibular gland is not excised

CLASSIFICATION

When the modification involves one or more lymph node groups that are routinely removed in the radical neck dissection, the procedure is termed a selective neck dissection.

The last major subtype is the extended neck dissection defined literally as removal of one or more additional lymph node groups and/or nonlymphatic structures not encompassed by radical neck dissection, such as parapharyngeal, superior mediastinal, and paratracheal. In practice, any of the previous neck dissections may be extended to include other structures. 

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