[Pneumorachis: report of three rare causes]. / Pneumorachis: illustration de trois étiologies rares.

The presence of gas in the spinal canal or pneumorachis is a rare imaging finding, typically incidental. Pneumorachis may be due to several degenerative, traumatic, infectious, tumoral or iatrogenic etiologies. We report three cases of pneumorachis in patients with lumbar back pain. A case occurred in a patient with advanced degenerative disk disease. Another was in a patient with posterior facet synovial cyst. The last was in a patient with locally advanced rectal carcinoma complicated by perforation. Pneumorachis was detected on MRI in two cases and on CT in all three cases.