FDG uptake in the cervical muscles after neck dissection: imaging features and postoperative natural course on ¹⁸F-FDG-PET/CT

Purpose This study aimed to assess the imaging features and postoperative natural course of F-18-fluorodeoxyglucose (FDG) uptake in the cervical muscles after neck dissection. Materials and methods This study included 83 patients who underwent preoperative and postoperative F-18-FDG-PET/CT and were diagnosed with head and neck malignancy after neck dissection. Postoperative F-18-FDG-PET/CT was performed within 5 years after neck dissection. Preoperative and postoperative FDG uptake of the trapezius, sternocleidomastoid, scalene, pectoralis major, and deltoid muscles was visually assessed. Increased postoperative uptake was visually defined as higher postoperative FDG uptake than the preoperative one in the corresponding muscle. The maximum standardized uptake value (SUVmax) was measured in cases with increased postoperative uptakes. Results Increased postoperative uptakes were observed in 43 patients (52%). The trapezius (31/83, 37%), sternocleidomastoid (19/83, 23%), and scalene (12/83, 14%) muscles were involved, as opposed to the pectoralis major and deltoid muscles were not. Increased postoperative uptakes were observed on the dissected side in all 43 patients. Significant differences between SUVmax estimated from the mixed-effects model and postoperative months were observed in the trapezius muscle (Coefficient (beta) = -0.038; 95% confidence interval (CI): [-0.047, -0.028]; p < 0.001) and sternocleidomastoid muscle (beta = -0.015; 95% CI: [-0.029, -0.001]; p = 0.046). Conclusions Increased postoperative uptakes in the cervical muscles were observed on the dissected side in approximately half of the patients after neck dissection. The SUVmax in the trapezius and sternocleidomastoid muscles decreased after surgery over time.