MR Imaging of the Superior Cervical Ganglion and Inferior Ganglion of the Vagus Nerve: Structures That Can Mimic Pathologic Retropharyngeal Lymph Nodes

Abstract

Background and purpose: The superior cervical ganglion and inferior ganglion of the vagus nerve can mimic pathologic retropharyngeal lymph nodes. We studied the cross-sectional anatomy of the superior cervical ganglion and inferior ganglion of the vagus nerve to evaluate how they can be differentiated from the retropharyngeal lymph nodes.

Materials and methods: This retrospective study consists of 2 parts. Cohort 1 concerned the signal intensity of routine neck MR imaging with 2D sequences, apparent diffusion coefficient, and contrast enhancement of the superior cervical ganglion compared with lymph nodes with or without metastasis in 30 patients. Cohort 2 used 3D neurography to assess the morphology and spatial relationships of the superior cervical ganglion, inferior ganglion of the vagus nerve, and the retropharyngeal lymph nodes in 50 other patients.

Results: All superior cervical ganglions had homogeneously greater enhancement and lower signal on diffusion-weighted imaging than lymph nodes. Apparent diffusion coefficient values of the superior cervical ganglion (1.80 ± 0.28 × 10^-3mm²/s) were significantly higher than normal and metastatic lymph nodes (0.86 ± 0.10 × 10^-3mm²/s, P < .001, and 0.73 ± 0.10 × 10^-3mm²/s, P < .001). Ten and 13 of 60 superior cervical ganglions were hypointense on T2-weighted images and had hyperintense spots on both T1- and T2-weighted images, respectively. The latter was considered fat tissue. The largest was the superior cervical ganglion, followed in order by the retropharyngeal lymph node and the inferior ganglion of the vagus nerve (P < .001 to P = .004). The highest at vertebral level was the retropharyngeal lymph nodes, followed, in order, by the inferior ganglion of the vagus nerve and the superior cervical ganglion (P < .001 to P = .001). The retropharyngeal lymph node, superior cervical ganglion, and inferior ganglion of the vagus nerve formed a line from anteromedial to posterolateral.

Conclusions: The superior cervical ganglion and the inferior ganglion of the vagus nerve can be almost always differentiated from retropharyngeal lymph nodes on MR imaging by evaluating the signal, size, and position.

Fig 1.

The coronal (A) and axial (B) views around the superior cervical ganglion according to anatomic reports show the superior cervical ganglion (black arrow), the inferior ganglion of the vagus nerve (white arrow), and the retropharyngeal lymph node (gray arrowheads). IJV indicates inferior jugular vein; ECA, external carotid artery; LCLN, lateral cervical lymph node (black arrowheads); LCM, longus capitis muscle; PG, parotid gland; SMG, submandibular gland; ST, sympathetic trunk; VN, vagus nerve. The magenta circle indicates the right carotid sheath.

Fig 2.

We assessed bilateral superior cervical ganglia (black arrows), the inferior ganglion of the vagus nerve (white arrows), and the retropharyngeal lymph nodes (gray arrowheads) using 3D-STIR (A, maximum-intensity-projection image; B, a section of original coronal images). The artery and vein clearly demonstrate flow voids. IJV indicates inferior jugular vein; LCLN, lateral cervical lymph node (black arrowhead); LCM, longus capitis muscle.

Fig 3.

A 62-year-old man with oropharyngeal cancer with left lymph node metastasis. Bilateral superior cervical ganglia (circles), metastatic lymph node (arrowhead), and cancer (open arrowhead) are noted. Contrast-enhanced fat-saturated T1-wighted image (A) shows stronger enhancement of the SCG than the metastatic lymph node. The T1-weighted image (B) shows almost the same signals. Fat-saturated T2-weighted image (C) shows heterogeneous signal of the metastatic lymph node, whereas the SCG is homogeneous. Diffusion-weighted image shows that the signals of the SCGs are lower than those of the metastatic lymph node. ADC values of the right SCG, left SCG, and metastatic lymph nodes were 1.32, 1.54, and 0.90 × 10⁻³mm²/s, respectively.

Fig 4.

A 58-year-old woman with an intraganglionic hypointense spot (arrow) on the right on T2-weighted image (A). This spot is less evident (arrow) on the gadolinium-enhanced fat-saturated T1-weighted image (B). T1-weighted images in a 65-year-old man show slit-shaped hyperintense areas in the bilateral superior cervical ganglia (C, circles). Signals of these regions are suppressed on the gadolinium-enhanced fat-saturated T1-weighted image (D).

Fig 5.

A, A 14-year-old adolescent with a prominent but normal RPLN. Coronal maximum-intensity-projection image shows the superior cervical ganglia (arrows) and the retropharyngeal lymph nodes (arrowheads). Each SCG was inferior to the RPLN. B, Reconstructed axial MIP image of 15-mm thickness shows that each SCG (arrows) is posterolateral to the RPLN (arrowheads). C, Coronal MIP image shows the SCG (arrows), inferior ganglia of vagus nerve (open arrows), and RPLN (arrowheads) in a 38-year-old man. The SCG is inferior to the IGVN. D, Reconstructed axial MIP image shows that the RPLN (arrowhead), SCG (arrow), internal carotid artery, IGVN (open arrow), and the internal jugular vein (IJV) form a line from anteromedial to posterolateral. B and D, Blurring on the images is because the MIP was used to superimpose the SCG, IGVN, and RPLN. IJV indicates inferior jugular vein.

Fig 6.

Probability maps of the superior cervical ganglion against the C2 transverse process (A, asterisk) and common carotid artery bifurcation (B, asterisk). The SCG was located at the anterior side against the C2 transverse process and superior and posterolateral to the CCAB. The location of bilateral SCGs is similar. R indicates right; L, left; Cor, coronal; Sag, sagittal; Axi, axial.