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K. Orhan (ed.)Ultrasonography in Dentomaxillofacial Diagnosticshttps://doi.org/10.1007/978-3-030-62179-7_6
6. Sonographic Anatomy and Pathology: Cervical Lymph Nodes
UltrasonographyLymph nodesPathology
6.1 Introduction
Lymph nodes are small bean-shaped structures that constitute a major part of the body’s immune system [1, 2]. Lymph nodes filter substances that travel through the lymph fluid, and contain lymphocytes (white blood cells) that help the body fight infection and disease. There are hundreds of lymph nodes found throughout the body [1, 3]. They are connected to one another by lymph vessels. Clusters of lymph nodes are found in the neck, axilla (underarm), chest, abdomen, and groin [1–4].
6.1.1 Basic Anatomy
Normal lymph nodes are small anatomical oval or kidney-shaped structures with a size ranging from 0.1 to 2.5 cm in size. They are surrounded by a thick connective tissue capsule extending with diaphragms inside the lymph nodes covering multiple compartments [1, 3].
The parenchyma of the lymph nodes is distinguished in the cortical, subcortical, and medullary sections. Enclosed areas of the cortical section form the primary follicles containing a large number of B- and T lymphocytes, mononuclear, and macrophages. B lymphocytes produce antibodies, T lymphocytes destroy antigens, and macrophages perform phagocytosis [1, 3, 4].
A small opening in the middle of the glands creates an area rich in fibrous and fatty tissue designated as the hilum. The medullary section surrounds the hilum and is separated from the cortical section by insertion of the transitional zone of the subcortex. The blood supplying artery enters through the hilum and the corresponding vein and the lymph nodes exit through it [1–4].
The accessory lymph nodes collect the lymph from the adjacent tissues and centrally discharge into the capsule of the lymph nodes. The transported lymph infiltrates the lymph nodes, which act as “refineries” of blood, destroying germs, viruses, cancer cells, and harmful foreign substances before eventually entering the venous circulation.
The lymph nodes are innervated by autonomic nervous system fibers and their innervation include the capsule, the inner diaphragms, and the smooth muscle of the blood vessels [1–4].
6.1.2 Regional and Functional Classification of Lymph Nodes
Based on the older and more recent historical data cervical lymph nodes are classified at least in six different anatomical levels (level I–VI) with different varying subclassifications aiming to the more accurate classification of the pathology, the more detailed surgical planning, and the better programming of the treatment of cervical and even head and neck cancer [5–7].
Classification of the neck regions based on lymph node groups. Courtesy of Aikaterini Spanou
The major lymph node groups of the head region are described together with their topographic location and the structures they drain [5–7].
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Facial: Skin and mucosa of the eyelids, the nose, the buccal area, the temporal and subtemporal region, and rinopharynx
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Parotid: Skin of the temporal and frontal region. The maxilla, the buccal area, the external acoustic meatus and eardrum, the eyelids, and section of the nose.
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Retroauricular: Side section of the hairy part of the skin behind the ear, the skin at the external acoustic meatus region, and the external ear
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Suboccipital: Posterior section of the hairy part of the head
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Submental: Lower lip, tongue tip, gums, and anterior teeth
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Submandibular: Upper and lower lip, intraoral mucosa, tongue, mandible gums, and teeth
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Jugulodigastric: Lingual and pharyngeal tonsils, hard palate, sections of the tongue
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Deep cervical: Larynx, trachea, thyroid gland, parathyroid glands, and upper esophagus
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Supraclavicular: Anterior thoracic wall, armpit region, shoulder, and upper limb
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Superficial cervical lymph nodes are lying on the surface of the sternocleidomastoid muscle, they drain the skin, and the superficial tissues and flow into the deep cervical lymph nodes.
When one is talking about varying levels of classifications, the most frequently followed divisions of the cervical lymph nodes are those according to the American Academy of Otolaryngology which classifies them as follows:
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Level Ia: Submental, within the triangular boundary of the anterior belly digastric muscles and the hyoid bone.
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Level Ib: Submandibular triangle—within the boundaries of the anterior belly of the digastric muscle, the stylohyoid muscle, and the body of the mandible.
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Level IIa: Anteriomedial to the vertical plane of the accessory nerve
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Level IIb: Posterolateral to this plane.
Level III: Middle jugular nodes—around the middle third of the internal jugular vein, from the inferior border of the hyoid to the inferior border of the cricoid cartilage. Anteromedially they are bounded by the lateral border of the sternohyoid muscle and posterolaterally by the posterior border of the sternocleidomastoid.
Level IV: Lower jugular nodes—around the lower third of the internal jugular vein from the inferior border of the cricoid to the clavicle, anteromedially by the lateral border of the sternohyoid and posterolaterally by the posterior border of the sternocleidomastoid.
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Level VA: Above the horizontal plane formed by the inferior border of the anterior cricoid arch, including the spinal accessory nodes.
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Level VB: Lymph nodes below this plane, including the transverse cervical nodes and supraclavicular nodes (except Virchow’s node which is in IV).
Level VI: Anterior compartment nodes—Pretracheal, paratracheal, precricoid (Delphian), and perithyroid nodes, including those on the recurrent laryngeal nerve. The upper border is the hyoid, the lower the suprasternal notch, and the lateral borders the common carotid arteries
The American Joint Committee on Cancer (AJCC) system differs from the above by including Level VII, which is based on the 2002 American Academy system, although the boundaries are defined slightly different [5]
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Level IA: Symphysis of mandible, Body of hyoid, Anterior belly of the contralateral digastric muscle, Anterior belly of ipsilateral digastric muscle
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Level IB: Body of mandible, Posterior belly of digastric muscle, Anterior belly of digastric muscle, Stylohyoid muscle
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Level IIA: Skull base, Horizontal plane defined by the inferior border of the hyoid bone, The stylohyoid muscle, Vertical plane defined by the spinal accessory nerve
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Level IIB: Skull base, Horizontal plane defined by the inferior body of the hyoid bone, Vertical plane defined by the spinal accessory nerve, Lateral border of the sternocleidomastoid muscle
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Level III: Horizontal plane defined by the inferior body of hyoid, Horizontal plane defined by the inferior border of the cricoid cartilage, Lateral border of the sternohyoid muscle, Lateral border of the sternocleidomastoid or sensory branches of cervical plexus
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Level IV: Horizontal plane defined by the inferior border of the cricoid cartilage, Clavicle, Lateral border of the sternohyoid muscle, Lateral border of the sternocleidomastoid, or sensory branches of cervical plexus
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Level VA: Apex of the convergence of the sternocleidomastoid and trapezius muscles, Horizontal plane defined by the lower border of the cricoid cartilage, Posterior border of the sternocleidomastoid muscle or sensory branches of cervical plexus, Anterior border of the trapezius muscle
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Level VB: Horizontal plane defined by the lower border of the cricoid cartilage, Clavicle, Posterior border of the sternocleidomastoid muscle, Anterior border of the trapezius muscle
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Level VI: Hyoid bone, Suprasternal notch, Common carotid artery
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Level VII: Suprasternal notch, Innominate artery, Sternum, Trachea, esophagus, and prevertebral fascia
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