Imaging in Oncology (Answer)

Evan W. Harris, MD
Assistant Professor of Radiology,
H. Lee Moffitt Cancer Center & Research Institute

Answer:

5. right vocal cord paralysis/buckling with medial deviation of the right aryepiglottic fold. This is secondary to metastatic adenopathy involving the recurrent laryngeal nerve on the right (Fig 3).

Clinical examination including indirect laryngoscopy and/or direct fiberoptic laryngoscopy is used to evaluate the patient with hoarseness for laryngeal mass lesions and vocal cord palsies. If vocal cord paralysis is seen, if focused clinical examination (including evaluation of cranial nerve function) demonstrates recurrent laryngeal nerve dysfunction, and if no laryngeal mass lesion is identified, then additional imaging may help to further localize and define the causative lesion. However, the underlying etiology may not be determined in approximately 10% of patients who present with vocal cord paralysis.

The course of the recurrent laryngeal nerve extends to the aortopulmonary window on the left and to the level of the subclavian artery on the right. A chest radiograph may provide helpful information in screening for lesions in these locations. If the chest radiograph does not reveal an abnormality that explains the clinical findings satisfactorily, as in this case, more sophisticated imaging is required. For evaluation of the infrahyoid part of the neck, enhanced computed tomography provides both excellent spatial and soft tissue resolution.

Isolated hoarseness/vocal cord paralysis may be due to lesions involving either the recurrent laryngeal or the superior laryngeal nerve, both of which are branches of the vagus nerve. The recurrent laryngeal nerve innervates all muscles of the larynx except the cricothyroid muscle. Recurrent laryngeal nerve dysfunction is the most common cause of vocal cord paralysis. If this is clinically suspected, then imaging should include the lower neck. If the palsy is left-sided, imaging should be continued caudally to the level of the aortopulmonary window. If the palsy is right-sided, imaging should be performed to the inferior aspect of the right subclavian artery. The superior laryngeal nerve preserves function of the cricothyroid muscle. If superior laryngeal nerve palsy is clinically suspected, then imaging should include the base of skull/posterior fossa and the upper neck. If the nerve involved is unclear, then imaging should cover the skull base/posterior fossa through the aortopulmonary window.

The present study demonstrates medial deviation/buckling of the right true vocal cord, medial displacement of the right aryepiglottic fold, and dilatation of the right pyriform sinus. Together, these findings represent the characteristic radiographic appearance of vocal cord paralysis.[1,2] The abnormal 1.7-cm soft tissue density with enhancing margins and central low attenuation seen in the right tracheoesophageal groove in the expected location of the right recurrent laryngeal nerve is consistent with the appearance of level 7 metastatic lymph adenopathy.

Below the level of the jugulodigastric node, the sites of cervical lymph nodes are classified as follows:

Level 1: submandibular and submental nodes
Level 2: internal jugular chain above hyoid bone
Level 3: internal jugular chain between hyoid bone and cricoid cartilage
Level 4: internal jugular chain below cricoid cartilage
Level 5: spinal accessory chain
Level 6: nodes related to thyroid gland
Level 7: central compartment below the hyoid (tracheoesophageal groove and anterior cervical chain)

The findings in this case are relevant because this area (level 7 lymph adenopathy) may be clinically inaccessible. In addition to location, lymph nodes are classified by size and internal imaging architecture. Lymph nodes in the neck greater than 15 mm in diameter and/or showing central low attenuation (necrosis) are consistent with metastatic disease. As in this case, associated nerve dysfunction implies invasion/malignant disease.

The remaining answer choices are incorrect because the imaging demonstrates deformity of the vocal cords and the aryepiglottic folds rather than an abnormal focal mass. The radiographic findings were confirmed at laryngoscopy. Answer #4 also is incorrect because the abnormality involves the glottic and supraglottic larynx without involvement of the subglottic larynx. The larynx extends from the vallecula to the space between the cricoid and first tracheal ring. The supraglottis begins with the tip of the epiglottis and ends at the laryngeal ventricle. The glottis is the true vocal cords. The infraglottis extends from the undersurface of the true vocal cords to the bottom of the cricoid.

Radiation therapy was planned for local tumor control; however, it is unlikely that full vocal cord function will return.

References

1. Agha FP. Recurrent laryngeal nerve paralysis: a laryngographic and computed tomographic study. Radiology. 1983;148:149.
2. Jacobs CJM, Harnsberger HR, Lufkin RD, et al. CT and MR in the evaluation of vagal neuropathy. Radiology. 1987;164:97.