10. Extraforaminal L5 Nerve Root Compression (Far-Out Syndrome)
@ProfFishchenkoFar-out syndrome is extraforaminal compression of the L5 spinal nerve outside the intervertebral foramen, particularly between the L5 transverse process and the sacral ala. Nerve compression causes pain and other neurological symptoms.
Causes and Factors Contributing to Compression
• A lumbosacral transitional vertebra (LSTV): an abnormal connection of an enlarged transverse process with the sacrum and bony overgrowth around the pseudoarticulation may compress the L5 nerve.
• Hypertrophy of the L5 transverse process may narrow the space for the nerve.
• An extraforaminal intervertebral disc herniation may additionally compress the nerve in this region.
• Loss of L5–S1 disc height due to degeneration brings the L5 transverse process closer to the sacral ala and may cause compression and irritation of the L5 nerve.
Far-out syndrome may coexist with foraminal stenosis. When planning L5 nerve decompression, we consider both sites of possible compression.
For decompression, we use a posterolateral approach that can be performed with biportal endoscopic spine surgery (BESS/UBE). We determine the extent of decompression according to the location of compression and the anatomical features.
References
1. Wiltse LL, Guyer RD, Spencer CW, Glenn WV, Porter IS. Alar transverse process impingement of the L5 spinal nerve: the far-out syndrome. Spine (Phila Pa 1976). 1984;9(1):31-41. doi:10.1097/00007632-198401000-00008.
2. Tubbs RS, Iwanaga J, Aly I, Moisi MD, Hanscom DR, Chapman JR, et al. Extraforaminal compression of the L5 nerve: an anatomical study with application to failed posterior decompressive procedures. J Clin Neurosci. 2017;41:139-143. doi:10.1016/j.jocn.2017.03.051.
3. Lee S, Kang JH, Srikantha U, Jang IT, Oh SH. Extraforaminal compression of the L-5 nerve root at the lumbosacral junction: clinical analysis, decompression technique, and outcome. J Neurosurg Spine. 2014;20(4):371-379. doi:10.3171/2013.12.SPINE12629.
4. Heo DH, Sharma S, Park CK. Endoscopic treatment of extraforaminal entrapment of L5 nerve root (far out syndrome) by unilateral biportal endoscopic approach: technical report and preliminary clinical results. Neurospine. 2019;16(1):130-137. doi:10.14245/ns.1938026.013.
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