DESCENDING NECROTIZING MEDIASTINITIS (DNM) DISGUISING AS A MEDIASTINAL MASS

TOPIC: Chest Infections TYPE: Medical Student/Resident Case Reports INTRODUCTION: DNM is an uncommon infection arising in the head or neck which tracks between the cervical fascial planes into the mediastinum. We report a case of DNM with a challenging presentation. CASE PRESENTATION: A 56-year-old male on chronic hemodialysis recovering from COVID pneumonia, presented to the emergency department with 2 days of shortness of breath. He was hypertensive, tachycardic and hypoxic, in respiratory distress, requiring immediate initiation of noninvasive ventilation. Shortly after arrival, he went into cardiac arrest. Resuscitation efforts were successful. Intensive management included mechanical ventilation, broad spectrum antibiotics, vasopressors and continuous renal replacement therapy for suspected septic shock. Chest x-ray showed mediastinal widening, confirmed by CT, to be due to a 7.5 cm lobulated, soft tissue density in the mediastinum impinging on the trachea. Bronchoscopy via endotracheal tube showed no obstruction except for some dynamic airway collapse. Trans-bronchial needle aspiration of the mediastinal mass was non-diagnostic. In 2 days, he improved, was extubated but then emergently re-intubated due to acute upper airway obstruction. Repeat imaging revealed a large retropharyngeal abscess extending from C1 level to the thyroid gland. It wrapped around anteriorly and communicated with a large collection in the superior mediastinum surrounding the trachea. Also noted was an enlarging pleural effusion. Urgent surgical drainage of the retropharyngeal space, superior mediastinum and pleural fluid was performed. Cultures grew Staphylococcus aureus. Mediastinal exploration and tracheostomy followed. He steadily improved and was discharged. DISCUSSION: DNM is a life-threatening infection that originates in the neck;retropharyngeal abscess in this case. It spreads caudally through cervical fascial planes facilitated by gravity and negative intrathoracic pressures (1). Oral flora are the usual pathogens (2). Diagnosis needs a high index of suspicion to obtain necessary imaging. Favorable outcomes are seen with early diagnosis, airway protection, antibiotics and timely surgical drainage (3).Our patient had narrowing of the proximal trachea due to compression from the fluid collection requiring emergent re-intubation. His initial chest CT reported a soft tissue density concerning for malignancy. It was the second CT that suggested an abscess. Looking back, prior chest x-rays showed progressive mediastinal widening over 10 days, making malignancy less likely. Review of old imaging remains invaluable. CONCLUSIONS: Deep neck infection leading to mediastinitis requires early diagnosis, antibiotic administration as well as operative management for source control. REFERENCE #1: Benedetto C, et al. Catastrophic descending necrotizing mediastinitis of the anterior and posterior compartments: A case report. Radiol Case Rep. 2020;15(10):1832-1836 REFERENCE #2: Brook I, Frazier EH. Microbiology of mediastinitis. Arch Intern Med. 1996 Feb 12;156(3):333-6. Erratum in: Arch Intern Med 1996 May 27;156(10):1112. PMID: 8572845. REFERENCE #3: Ridder GJ, Maier W, Kinzer S, Teszler CB, Boedeker CC, Pfeiffer J. Descending necrotizing mediastinitis: contemporary trends in etiology, diagnosis, management, and outcome. Ann Surg. 2010 Mar;251(3):528-34. doi: 10.1097/SLA.0b013e3181c1b0d1. PMID: 19858699. DISCLOSURES: No relevant relationships by Rana Hejal, source=Web Response No relevant relationships by Willie McClure, source=Web Response No relevant relationships by Tanmay Panchabhai, source=Web Response No relevant relationships by Layla Sankari, source=Web Response No relevant relationships by Apoorwa Thati, source=Web Response