Commentary: Descending necrotizing mediastinitis: Reclassifying a rare disease.

Swara Bajpai, MD, and Benjamin Wei, MD

This analysis of descending necrotizing mediastinitis demonstrates the utility of adding a proposed IIC category (isolated posterior lower mediastinitis) to the existing classification system.

See Article page 633.

Descending necrotizing mediastinitis (DNM), although rare, is the most severe form of mediastinal infection with high mortality (up to 40%) often due to delay in diagnosis or inadequate surgical drainage. Research is fairly limited on this condition and no definitive guidelines on the optimal treatment of DNM exist.1, 2, 3 Sugio and colleagues conducted a multi-institutional study to assess clinical features and surgical outcomes of DNM and suggest a new classification system. Their retrospective study looked at 225 DNM patients who underwent surgical drainage over a period of 4 years from an impressive 131 centers in Japan.

DNM was first classified by Endo and colleagues in 1999 according to the degree of mediastinal extent; infections limited to the area superior to the carina were defined as Type I, whereas those spreading to the lower mediastinum (LM) were defined as Type II with subdivisions of Type IIA for involvement of the anterior LM and Type IIB for involvement of both anterior and posterior LM. Sugio and colleagues propose a new classification system with an additional category of Type IIC for infections limited to the posterior LM. The study revealed that Type I and IIC more frequently underwent cervical drainage, whereas Type IIA and B were treated more often with thoracotomy. Although more than 70% of their patients received a tracheostomy and the median length of hospital stay was 47 days, 30- and 90-day mortality rates of the entire cohort were only 3.6% and 5.3%, respectively. Type II infections had a higher likelihood of 90-day mortality with a trend toward better short-term survival in Type IIC. Sugio and colleagues attributed their low short-term mortality rate to an overall decrease in disease severity due to their inclusion of Otolaryngology institutions in the analysis. Early surgical intervention (median of 2 days from initial assessment to drainage) and a focus on thorough source control (20% and 30% of patients underwent repeat mediastinal and cervical drainage operations, respectively) could have contributed to their low mortality rate as well.

Reports stress that it is important to take the extent of infection into account when selecting surgical approaches. Previous studies have proposed that diffuse anterior and posterior DNM as in Type IIB demands complete mediastinal drainage via thoracotomy. In comparison, infection that has spread to only posterior mediastinum, although typically categorized as Type IIB, may not mandate aggressive drainage. Along those lines, this study looked at the previously unreported category of extension limited to the posterior mediastinum (ie, new category IIC), which comprised more than one-third of their Type II cases, for which effective drainage was often performed via video-assisted thoracoscopic surgery or transcervical approach. Because of the lack of consensus in the optimal surgical approach for this disease, any clarification in DNM classification will be beneficial in guiding surgeons toward minimal versus aggressive treatment. Sugio and colleagues, in a report that will likely become a benchmark study on DNM, provide a detailed descriptive analysis of the patterns of DNM infection, especially with regard to route of spread and the differing attributes and surgical approaches to such infections. Hopefully, this article can serve as a reference point for development of future guidelines for treatment of DNM.