PP159: Evaluation atrophy of sternocleidomastoid muscle after neck dissection

Abstract

Purpose Modified and supraomohyoid neck dissections have become common for treatment of oral cancer. In these dissections spinal accessory nerve (SAN) can be conserved. The relationship between SAN conservation and trapezius muscle function has been evaluated. However, sternocleidomastoid muscle (SCM) has not been fully evaluated. The purpose of this study is to evaluate atrophy of SCM about cosmetic and functional aspect. Materials and methods The size of SCM on cross section at the level of hyoid bone and thyroid cartilage using computed tomography (CT) images were measured from 44 (28 men and 16 women) patients who underwent unilateral neck dissection. We classified these patients into three groups, conserving SCM branch of SAN, sacrificing SCM branch and reconstructing SCM branch, including transplantation or resuture. Results Thirty-eight were conserved SCM branch, four were reconstructed and two were sacrificed. The median interval between neck dissection and postoperative CT images was 12 months. On the contralateral side, there were no significant differences between preoperative SCM size and postoperative size. On the other hand, on the ipsilateral side SCM size was decreased to 82.8% at the level of hyoid bone (HT) and to 77.4% at the level of thyroid cartilage (TC) compared to preoperative size. In conserved SCM branch group, SCM size was 86.7% at the level of HT and 79.9% at the level of TC. In reconstructed group, SCM size was 71.8% at the level of HT and 64.1% at the level of TC, whereas in sacrificed group SCM size was reduced to 34.1% at HT and 56.0% at TC. Conclusions The conservation as well as the reconstruction of SCM branch of SAN can inhibit atrophy of SCM in a similar way that the conservation of SAN can inhibit shoulder function, although there are considerable variations in the innervation.