Proportion and Clinical Relevance of Intraspinal Air in Patients With Pneumomediastinum.

Objective: The purposes of this study were to determine the incidence of pneumorrhachis among patients with pneumomediastinum, determine whether its proportion correlates with the extent of pneumomediastinum, and ascertain its clinical relevance.

Materials And Methods: The radiologic database was searched for CT reports between January 2009 and September 2013 containing the term "pneumomediastinum" or "mediastinal air." Scans were examined for pneumomediastinum, pneumorrhachis, pneumothorax, sternotomy, and distribution of pneumomediastinum. The age and sex of the patient and probable cause of the abnormality were recorded. Cases that might have had another cause were excluded.

Results: The search yielded 422 CT scans. Among these, 242 instances of pneumomediastinum in 241 patients were found. Fifteen of these patients had pneumorrhachis. One was excluded because of recent traumatic spinal penetration. There was no significant difference in age or sex between patients with and those without pneumorrhachis. After application of the exclusion criteria, there were 14 cases of pneumorrhachis, yielding a proportion of 5.8%. Pneumorrhachis was observed more frequently in cases of the most severe grade (grade C) of pneumomediastinum; however, that relationship was not statistically significant (11 cases [8.2%]; p = 0.304). Pneumorrhachis was found significantly more frequently in patients with distribution of air in all three mediastinal compartments (13 cases, 16.2%, p < 0.001). Pneumorrhachis was overrepresented among subjects with spontaneous compared with those with secondary pneumomediastinum, although the trend did not reach statistical significance.

Conclusion: Pneumorrhachis was present in 5.8% of patients. It is significantly more common in patients with the broadest distributions of mediastinal air and nonsignificantly more common in association with spontaneous as opposed to secondary pneumomediastinum. Pneumorrhachis in patients with pneumomediastinum is a generally benign, self-resolving condition.