Internal Carotid Artery Course Variation in the Neck Dissection of Oral Cavity Cancer Patients.

Accurate knowledge of cervical vascular anatomy is essential during neck dissection (ND) to prevent serious intraoperative complications. While several variations in the cervical course of the internal carotid artery (ICA) have been documented, an ICA coursing posterior to the internal jugular vein (IJV) remains extremely rare and may increase the risk of vascular injury by altering expected anatomic relationships. Therefore, a thorough preoperative imaging evaluation is critical for a safe surgical procedure. This report presents two oral cavity cancer patients who exhibited an uncommon posterior course of the ICA located behind the IJV. In both cases, preoperative enhanced computed tomography (CT) demonstrated a tortuous, posteriorly displaced ICA, which was subsequently confirmed during selective ND. Tumor resection and ND were performed with meticulous dissection around the carotid sheath, allowing safe preservation of the vascular variation. Postoperative healing was uneventful, and no local recurrence or regional metastasis was observed during follow-up. An ICA coursing posterior to the IJV represents a rare but clinically significant vascular variation encountered during ND. Surgeons should recognize that, even when such variations are identified on preoperative imaging, atypical ICA courses may still pose challenges during dissection, particularly within routinely explored cervical regions. Awareness and careful intraoperative identification of these variations contribute to safer surgical outcomes.