Surgical Treatment of Extraforaminal Gas-Containing Pseudocyst Compressing L5 Nerve Root by Using Unilateral Biportal Endoscopy.

BACKGROUND: Most gaseous lumbar pseudocysts have been previously reported to be located in the spinal canal and successfully treated by several therapeutic methods. By comparison, a gas-containing pseudocyst in the lumbar extraforaminal area is rare. Here, the authors report a case of symptomatic gas-containing cyst located in the lumbar foramen. It was successfully treated with unilateral biportal endoscopic (UBE) surgery. CASE DESCRIPTION: A 75-year-old man presented with severe left leg pain and tingling sensation refractory to conservative treatment that aggravated with weight bearing and position change. Computed tomography and magnetic resonance imaging showed a gas-containing cyst compressing the left L5 nerve root ganglion in the foramina area at the L5-S1 level. Gaseous extraforaminal pseudocyst was successfully removed by UBE surgery via the paraspinal approach. Vivid and clear endoscopic operative imaging of pseudocyst in detail was obtained during the operation. The patient's symptom was significantly improved after the operation. CONCLUSIONS: A gas-containing pseudocyst in the lumbar foraminal area is not common. Combined use of preoperative magnetic resonance imaging and computed tomography can help diagnose a gaseous pseudocyst and differentiate other pathologies. A UBE technique that provides good operative visualization and delicate operative manipulation is a less invasive therapeutic method to treat a foraminal gas-containing pseudocyst.