Endoscopic Ultrasound

TRAINING COURSE
Year
: 2019  |  Volume : 8  |  Issue : 4  |  Page : 227--234

EUS of the neck: A comprehensive anatomical reference for the staging of head and neck cancer (with videos)


Malay Sharma1, Amit Pathak1, Abid Shoukat1, Chittapuram Srinivasan Rameshbabu2, Sumit Goyal3, Raghav Bansal4, Rooby Hamza5, Kshitij Charaya6,  
1 Department of Gastroenterology, Jaswant Rai Speciality Hospital, Muzaffarnagar, India
2 Department of Anatomy, Muzaffarnagar Medical College, Muzaffarnagar, India
3 Department of Oncology, Jaypee Hospitals, Noida, Uttar Pradesh, India
4 Mount Sinai Elmhurst Hospital Center, Elmhurst, USA
5 Department of Gastroenterology, MES Medical College, Malappuram, Kerala, India
6 Department of Gastroenterology, Consultant Otolaryngologist, Excel ENT, Meerut, India

Correspondence Address:
Dr. Malay Sharma
Department of Gastroenterology, Jaswant Rai Speciality Hospital, Meerut - 250 001, Uttar Pradesh
India

Abstract

The use of EUS has application in the nodal staging of head and neck cancer. The technique and the anatomy of head and neck region using EUS have not been described. EUS from three stations in thoracic esophagus, cervical esophagus, and hypopharynx can allow imaging of head and neck. In this article we describe the normal structures from the three stations. The EUS imaging of head and neck can give relevant and additional information in malignancies of head and neck.



How to cite this article:
Sharma M, Pathak A, Shoukat A, Rameshbabu CS, Goyal S, Bansal R, Hamza R, Charaya K. EUS of the neck: A comprehensive anatomical reference for the staging of head and neck cancer (with videos).Endosc Ultrasound 2019;8:227-234


How to cite this URL:
Sharma M, Pathak A, Shoukat A, Rameshbabu CS, Goyal S, Bansal R, Hamza R, Charaya K. EUS of the neck: A comprehensive anatomical reference for the staging of head and neck cancer (with videos). Endosc Ultrasound [serial online] 2019 [cited 2019 Oct 18 ];8:227-234
Available from: http://www.eusjournal.com/text.asp?2019/8/4/227/260860


Full Text



 Background



Sonographic imaging of the head and neck is often difficult due to the anatomical complexity; hence, computed tomography (CT) and magnetic resonance imaging (MRI) are usually performed as the imaging techniques of the first choice for assessing the extent and nature of the diseases of this region.[1] However, ultrasonography (US) is still an integral part of the routine diagnosis, treatment, and follow-up of diseases of the head and neck.[2],[3] A major advantage of US, apart from being highly sensitive and nonionizing, is that the attending physician gets the “big picture,” when he performs the examination himself.[4] Each malignancy of head and neck has its unique first echelon and pattern of spread to different nodal stations.[5] Although nowadays positron emission tomography-CT (PET-CT) is playing an increasingly important role in the detection of pathologic lymph nodes (LNs); a cytopathological confirmation is possible only by CT- or US-guided fine needle aspiration (FNA).[6],[7],[8] EUS adds value during esophageal and lung cancer staging.[9],[10],[11],[12] Little information is available regarding the use of EUS and EUS-FNA aspiration cytology (EUS-FNAC) to stage tumors in the head and neck region.[13],[14],[15] No specific probe has been developed for EUS evaluation of the head and neck region.[16],[17] EUS with the help of a modified probe has shown results superior to CT and MRI in the assessment of laryngeal cancer.[1],[3] A special advantage of EUS examination is that the flexible probes can be used for EUS-FNAC of LNs or masses not accessible to CT or ultrasound.[11],[12],[18] The aim of this article is to present the techniques and limitations of EUS in the diagnostic evaluation of structures and LNs of the head and neck.

 Techniques of Imaging



EUS examination of structures of the neck can be done on outpatient basis after conscious sedation using intravenous midazolam and oral xylocaine (10%) spray. The images in this article were procured with a linear echoendoscope (Pentax EG 3830 UT) using Hitachi Avius-processor. Imaging can be done from three stations: the upper part of thoracic esophagus, the cervical esophagus, and the hypopharynx. The scope is generally unstable near the pharyngoesophageal junction; hence, the examination is started after inserting the echoendoscope into the upper part of thoracic esophagus (Station 1). Subsequent withdrawal is done to cervical esophagus (Station 2), and the last part of the examination is done from hypopharynx (Station 3) [Figure 1], [Figure 2] and [Video 1], [Video 2].{Figure 1}{Figure 2}

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Six home bases

A home base is a structure, which can be easily found by manipulation of the scope if the orientation is lost during imaging. The six main home base structures that can be identified at three stations are arch of aorta, trachea, spine, sternocleidomastoid muscle, thyroid gland, and the great vessels of the neck.

The movements

Imaging of structures is done after the apposition of the probe against the wall. A 360° clockwise or anticlockwise rotation is done to change the axis of imaging. In general, a rotation of the scope done in such a manner that it showed structures posterior, lateral, or anterior to the scope in a sequential manner during rotation [Figure 1]a and [Figure 2]. For uniform description in this article, the structures are described while doing a clockwise movement after doing a maximum anticlockwise rotation and visualization of spine, which is a structure in posterior relation to the esophagus and pharynx.

The orientation

A cranial part of image to the right and caudal part of image to the left convention is followed, and examination is done in three steps [Figure 3]a:{Figure 3}

Identify home baseIdentify anatomic landmarksIdentify LNs.

Station 1: Thoracic esophagus

Identification of home bases

The arch of aorta, the trachea, and the spine. The arch of aorta is easily identified at about 20–22 cm distance in the thoracic esophagus as a circular anechoic vascular structure of 1.5–2.0 cm diameter [Video 3] and [Video 4]. A clockwise rotation from this position takes the imaging plane anteriorly toward the trachea and anticlockwise rotation from this position takes the imaging plane posteriorly toward the spine. The trachea is identified by the presence of air and cartilage in the wall of the trachea, both of which create prominent artifacts [Station 1, [Figure 3]b and [Figure 3]c].

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Identification of anatomic landmarks

Posterior imaging

The spine creates a hyperechoic artifact, and the hypoechoic intervertebral discs are seen between two hyperechoic vertebrae [Figure 3]d.

Lateral imaging

On clockwise rotation from the spine, the descending aorta is identified, and the upper margin of the arch of aorta is identified after tracing the descending aorta to the highest point with slight clockwise rotation of the scope.

Anterior imaging

On further clockwise rotation, the origin of the left subclavian artery left common carotid artery, and brachiocephalic trunk can be seen from the upper border of the arch of aorta [Station 1, [Figure 4]a,[Figure 4]b,[Figure 4]c,[Figure 4]d]. The left subclavian artery, which goes close to apex of lung commonly, creates a mirror image artifact. The left common carotid artery runs close to the left wall of the trachea and the brachiocephalic trunk crosses to the right side of the trachea. During the clockwise rotation of the echoendoscope, the imaging axis passes from the left common carotid artery to the trachea, and it is difficult to visualize the brachiocephalic trunk by EUS scope. The left brachiocephalic vein (LBCV) crosses from the left to right side in front of great vessels of neck.{Figure 4}

Identify lymph nodes

The EUS scope provides a good visualization of nodes in this position. Pathological LNs can be evaluated for metastatic disease by EUS-FNA.

Station 2: Cervical esophagus

Identification of home bases: The great vessels of the neck, the thyroid gland, and the sternocleidomastoid muscle

In this position, an ultrasound probe placed externally from the neck reveals the good quality of images to an ultrasonographer. The scope is in an unstable position for EUS-guided FNAC in this position. The cervical LNs in this position can be also visualized from the neck, and it is generally recommended to do direct ultrasound or CT-guided FNAC from the neck [Station 2 and [Figure 5]a]. Once the echoendoscope is placed inside the cervical esophagus, the great vessels of the neck are easily identified and traced cranially into the carotid sheath within the carotid triangle [Station 2, [Figure 5]b and [Video 5]]. The sternocleidomastoid muscle is seen on the far side of the carotid triangle [Station 2, [Figure 5]c and [Video 6]]. A clockwise rotation from this position takes the imaging axis sequentially toward the left lobe of the thyroid gland, trachea, and the right lobe of the thyroid gland.{Figure 5}

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Identification of anatomic landmarks

Posterior imaging

Maximum anticlockwise rotation identifies the spine posteriorly. Slight clockwise rotation identifies the longus colli muscle along with the vertebral artery. The vertebral artery is seen in an area between the two adjacent transverse processes of vertebrae. The transverse processes interrupt the visualization of the entire course of the artery.

Lateral imaging

Further rotation identifies the sternocleidomastoid muscle and the appearance of structures within the carotid sheath. A clockwise rotation beyond the common carotid artery moves the imaging beam toward the anterior compartment. An outward pull shows the course of the left common carotid artery, which enters the carotid sheath. In this position, the branch of subclavian artery (thyrocervical trunk) can be seen in the triangular area between the probe and sternocleidomastoid muscle in the supraclavicular fossa [Station 2, [Figure 5]d and [Video 7]]. The union of LBCV and internal jugular vein marks the lowest boundary of supraclavicular fossa [Station 2, [Figure 6]a,[Figure 6]b,[Figure 6]c,[Figure 6]d and [Video 8]]. The LBCV is seen to cross in front of the great vessels of the neck [Figure 6]a. The course of left subclavian artery can be followed up till it arches and enters the supraclavicular triangle and the arching part of subclavian artery is easily visualized [Station 2, [Figure 6]b and [Video 9]]. Even with EUS, it is occasionally possible to see the brachiocephalic trunk taking origin from the upper part of the arch of aorta and to trace the course till the division into right common carotid and right subclavian artery. Sometimes, it is possible to see the joining of the thoracic duct in the angle between the joining of LBCV and left subclavian vein [Station 2, [Figure 6]c and [Video 5]].{Figure 6}

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Anterior imaging

A clockwise rotation beyond the common carotid artery takes the beam toward the anterior compartment. The visualization of structures anterior to trachea is not possible by EUS.

Identification of nodes

The important group of LNs in this place includes the lower and middle jugular group along the carotid sheath and Level VI LNs in the anterior compartment. Among the Level VI LNs, the LNs lying anterior to trachea cannot be identified, but the LNs in paratracheal region, especially on the left side can be easily identified. When the LNs are classified according to the International Association of Study of Lung Cancer, the identified subgroups are Station 2L, 2R 3a and 3p [Station 2, [Figure 6]d, [Video 10] and [Video 11]].

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Station 3: Hypopharynx

Identification of home bases

The thyroid gland, internal jugular vein, and sternocleidomastoid muscle. It is easy to locate the common carotid artery and internal jugular vein within the carotid sheath from the hypopharynx on both sides of the neck. The thyroid cartilage creates an artifact in hypopharynx and the upper part of thyroid gland is seen on either side of thyroid cartilage closely related to common carotid artery. The sternocleidomastoid muscle is occasionally seen beyond the internal jugular vein [Station 3 and [Figure 7]].{Figure 7}

Identification of anatomic landmarks

Posterior imaging

Maximum anticlockwise rotation identifies the spine posteriorly. Slight clockwise rotation identifies the longus colli muscle just adjacent to the posterior pharyngeal wall along with the vertebral artery [Station 3, [Figure 8]a and [Figure 8]b].{Figure 8}

Lateral imaging

Further clockwise rotation identifies the sternocleidomastoid muscle and the appearance of structures within the carotid sheath. The common carotid artery is very easily traced upward within the carotid sheath, and sometimes the bifurcation into external and internal carotid artery can be seen in Station 3, [Figure 9]a,[Figure 9]b,[Figure 9]c. The course of internal jugular vein is easily followed within the carotid sheath. Some part of the internal jugular vein is visualized through the upper part of the left or right lobe of thyroid gland.{Figure 9}

Anterior imaging

A clockwise rotation beyond the common carotid artery takes the beam toward the anterior compartment. The visualization of structures anterior to trachea is not possible by EUS, and the visualization of pretracheal LNs is not possible. The lobes of thyroid gland and LNs on the either side of the trachea in paratracheal region (paratracheal LNs) can be visualized.

Identification of nodes

The important group of LNs in this place includes upper jugular LN station - for head and neck cancer and LNs of Station 2L, 3a and 3p for lung cancer [Station 3 and [Figure 10]]. No LNs are present posterior to cervical esophagus in the retropharyngeal space.{Figure 10}

The Diagnostic US of the head and neck is mainly used to assess organs and lesions that lie near the surface, including the salivary glands, the thyroid gland, the major vessels, enlarged superficial LNs, and other superficial pathologic lesions.[19],[20],[21],[22]

Although EUS and EUS-FNA have a well-established role in the assessment and management of gastrointestinal and pulmonary diseases, the data on their value for assessing tumors in the head and neck region are very limited.[23] Traditionally, the mediastinum and lower part of the neck has been evaluated using standard imaging techniques such as CT and MRI. Cervical LN metastases are of overriding importance in predicting the prognosis in these patients.[24] Size has been used as one of the criteria for differentiating benign from malignant LNs. LNs larger than 10 mm in size are considered abnormal but even smaller LNs may harbor metastasis.[25] CT and MRI have suboptimal sensitivity for detecting the smaller size of LNs and patients with false-negative imaging on CT or MRI are generally never referred for EUS. The decision regarding the presence of metastasis in such smaller group of LNs is of importance and EUS-FNA offers a chance to establish the presence of pathology. A comparison of ultrasound and PET/CT for staging and surveillance of head and neck and thyroid cancer found superior sensitivity (96.8% vs. 90.3%), specificity (93.3% vs. 20%), positive predictive value (96% vs. 70%), and negative predictive value (93% vs. 50%) for ultrasound compared to PET/CT.[19] Another comparative study of ultrasound with PET/CT found that the two techniques had equivalent accuracy for surveillance of head and neck cancer, and the authors concluded that ultrasound could be considered complementary to PET/CT for detecting subclinical regional recurrences after head and neck cancer treatment.[21]

EUS and EUS-FNA do have their own limitations. For example, EUS does not allow visualization of the pretracheal and the right paratracheal region.[26] Endobronchial endosonography is helpful in patients where evaluation of the right paratracheal region is needed.[27],[28] Further information is required from prospective studies comparing EUS with different imaging modalities in patients with advanced and metastatic tumors in the head and neck region.[29] The use of ultrasound as a practical tool for head and neck cancer surveillance is still relatively constrained due to the limited number of practitioners who are skilled in head and neck US. The accuracy for the staging of tumors of the neck and pickup of a smaller group of some LNs may improve if EUS is included in the imaging modalities of head and neck cancers. There is a possibility that the use of EUS and EUS-FNA will become a part of multimodality imaging during evaluation of tumors in the head and neck region.

Acknowledgments

We would like Mr. Pran Prakash (Graphic Designer) for making line art diagram and animation videos in this article.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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