Defining and classifying “spontaneous” pneumomediastinum

Abstract

Introduction: spontaneous pneumomediastinum (SPM) is an uncommon condition with a significantly variable definition and classification in the literature. This inconsistency complicates diagnostic interpretation, study comparisons, and conceptual clarity. The goal of this review was to evaluate the consistency between SPM definitions and classification systems published since 2000.

Methods: a systematic review was performed on PubMed, Scopus, and LILACS. Studies that explicitly described SPM definitions or classifications were included. Two independent reviewers selected and extracted the data. A conceptual analysis matrix was applied to evaluate semantic coherence, clinical validity, and pathophysiological alignment. The process followed the 2020 PRISMA guidelines.

Results: out of 167 records identified, five studies met the inclusion criteria. Marked heterogeneity was found in the use of the terms “spontaneous,” “primary,” “idiopathic,” and “non-traumatic.” Three studies included predisposing or trigger factors within SPM, causing semantic and clinical inconsistency. Only one article presented an explicit definition based on the lack of predisposing or triggering factors, describing it as non-traumatic mediastinal air in healthy individuals. The classification systems were mainly etiological and lacked standardized operative criteria.

Conclusions: there is a notable lack of standardization in the definition and classification of SPM in the medical literature. A unified conceptual framework is needed to clarify the terminology and provide diagnostic reproducibility and comparability between studies. This review proposes operative criteria that could serve as the basis for future consensuses.