Impact of Environmental and Seasonal Factors on Spontaneous Pneumomediastinum With and Without Pneumorrhachis.

Spontaneous pneumomediastinum (SPM) with pneumorrhachis is rare but generally benign and self-limiting. However, the impact of environmental and seasonal factors on SPM remains unclear. This study investigated their association with SPM onset and clinical outcomes. We conducted a 12-year retrospective review of SPM cases, comparing clinical characteristics and outcomes between patients with and without pneumorrhachis. A case-crossover design was used to assess short-term associations between environmental exposures and SPM incidence, analyzed via conditional logistic regression. A total of 70 consecutive patients were identified, with 9 classified as SPM with pneumorrhachis and 61 as SPM without pneumorrhachis. While both groups were predominantly managed with hospitalization, those with pneumorrhachis had longer hospital stays (median: 7 vs. 3 days, p = 0.002) and were more often associated with severe-grade SPM and identifiable triggers (p < 0.001 and p = 0.009, respectively). No significant environmental exposure differences were observed between groups. Seasonally, SPM incidence was significantly higher in autumn and winter (p < 0.001), consistent with elevated air pollutant levels. Linear regression showed that standardized β coefficients for PM2.5 were higher in autumn and winter (β = 1.15 and β = 1.18), indicating a seasonal association between PM2.5 and SPM onset. Despite experiencing more triggers and longer hospitalization, patients with pneumorrhachis had similarly favorable clinical courses. The seasonal clustering of SPM and its association with elevated PM2.5 levels suggest that air pollution may be a contributing factor, warranting further investigation.