Far-out syndromeと腰部脊柱管狭窄症によりL5神経根症を呈した1例

A Case with L5 Radiculopathy Caused by Far-out Syndrome and Lumbar Canal Stenosis

Ⅰ．はじめに

　Far-out syndrome（以下，FOS）は，L5-S椎間レベルにおいて仙骨翼と横突起で囲まれた椎弓根外側のfar-lateral zoneでL5神経根が絞約されて症状を呈する稀な病態である．今回，われわれは腰部脊柱管狭窄症（以下，LCS）とFOSの合併によるL5神経根症を呈した症例を経験し，除圧術のみで症状を改善させることができた．文献的考察を加えて報告する．

　Far-out syndrome (FOS) is caused by L5 nerve root entrapment at the L5-S1 extraforaminal area surrounded by the sacral alar and the transverse process. Here, we report a case with right L5 radiculopathy caused by L4-5 lumbar canal stenosis (LCS) and FOS. A 57-year-old man suffered from progressing right sciatica and leg pain in the L5 nerve root distribution. MR images showed canal stenosis and a slight disc herniation at the L4-5 level. He underwent surgical decompression for LCS, but he only obtained partial pain relief. Multiplanner reformatted CT scans showed that the right L5 nerve root was entrapped by the sacral alar and lateral disc bulging at the L5-S1 level. Selective radiculograpy demonstrated L5 nerve root compression in the far-lateral area, and a nerve root block provided temporary pain relief. He received a second operation for decompression of the L5 nerve root in the far-lateral zone by partial removal of the sacral alar and the transverse process. He was relieved completely from pain after the operation. He left our hospital on the 9th postoperative day, and returned to work on the 16th day. Visual analogue scales of pain and numbness were 8.7 and 8.7 respectively at first examination. These scores decreased to 5.5 and 3.7 two months after the first operation for LCS, and to 0 and 0 one month after the second operation for FOS. We recommend that more attention be paid to FOS when patients with L5 radiculopathy are diagnosed.