Introduction:
Deep neck infections (DNIs) are potentially life-threatening conditions due to their rapid progression and risk of severe complications. Although odontogenic infections are well-known sources, the extension of infection into the posterior mediastinum with the formation of a cervical fistula is rare. Early diagnosis and multidisciplinary management are essential for improving patient outcomes.

Aim:
This case report aims to present a rare and severe complication of an odontogenic infection leading to descending mediastinitis, emphasizing the importance of timely intervention, appropriate antimicrobial therapy, and surgical drainage.

Case study:
A 44-year-old female patient presented with neck swelling, pain, dysphagia, and trismus one week after a tooth extraction. Physical examination revealed a 3 × 2 cm abscess-like lesion extending from the left submandibular region to the anterior and posterior neck spaces. Imaging confirmed a deep neck abscess with posterior mediastinal extension. Despite empirical antibiotic therapy, her condition worsened, necessitating surgical drainage and intensive care management. A fistula tract was identified between the gingiva and the superior sternal notch. The patient was successfully treated with a combination of broad-spectrum antibiotics, surgical intervention, and supportive care, leading to full recovery.

Results and discussion:
DNIs can lead to descending mediastinitis with high morbidity and mortality. Early imaging, multidisciplinary care, and timely surgery are crucial. This case underscores the need for vigilance in dental infections to prevent severe complications.

Conclusions:
(1) Odontogenic infections may rarely cause descending mediastinitis. (2) Early diagnosis and airway protection are essential. (3) Broad-spectrum antibiotics and timely surgery improve survival.