Lumbar radiculopathy and intraspinal gas.

Gas within the spinal canal is uncommon and has been associated with trauma, infection and disc degeneration and vacuum phenomenon. We report a 73-year-old man with a history of intermittent low back pain who developed sharp low back pain with radiation to the left calf and ankle when ambulating or standing. Relief was obtained with sitting or lying down, which led to the clinical impression of spinal stenosis. The neuromuscular exam was unremarkable and no sciatic nerve tension sign was present. Electrodiagnostic studies were consistent with an acute S1 radiculopathy, while a dermatomal somatosensory evoked potential was interpreted as essentially normal. A CT scan showed gas in the left lateral spinal canal at L4-S1. After 2 weeks, spontaneous improvement occurred and the patient resumed normal activities. A repeat CT scan after 0.5 years showed the intraspinal gas was diminished while the L5-S1 disc vacuum phenomenon had worsened and a right disc extrusion occurred. The natural history of intraspinal gas, disc vacuum phenomenon and related complications are discussed.