Selective neck dissection: CT and MR imaging findings

Selective neck dissection (SND) has become a common surgical procedure for selectively treating known or potential metastatic nodal disease from head and neck cancer while preserving functional structures. The purpose of this article is to describe the expected CT and MR findings after SND.

CT (26/27) or MR images (1/27) from 27 consecutive patients treated with SND for either staging or nodal control of head and neck malignancy were retrospectively reviewed by two experienced head and neck radiologists. One patient had bilateral SND. The quantity of deep cervical fat was subjectively assessed, as was patency of the ipsilateral internal jugular vein (IJV) and asymmetry in size and contour of the sternocleidomastoid (SCM), trapezius, and infrahyoid strap muscles. The presence of the submandibular gland was noted.

Twenty-seven of 28 necks had marked decrease in fat beneath the SCM muscle. This resulted in the muscle directly abutting the paraspinal muscles in most cases. The SCM muscle contour and size was asymmetric or flattened and atrophic in 16/28 necks. Atrophy of the infrahyoid strap muscles was seen in 8/28 necks. Six of 28 had no detectable IJV, and it was presumably thrombosed. Submandibular gland was not present in 17/28 cases.

The imaging findings after SND are characteristic and reflect the type of surgery performed. If level I nodes are removed, the submandibular gland is absent. Marked decrease in deep cervical fat is common. Changes in and around the SCM muscle are routinely seen and include posterior and medial displacement of the muscle, distortion and flattening of the muscle, or atrophy, despite surgical preservation of spinal accessory nerve. Finally, although the IJV is not resected in SND, nonvisualization of the vein on postoperative images may reflect thrombosis.