• Kyongsong Kim, Jun Shimizu, Toyohiko Isu, Daijiro Morimoto, Akatsuki Kubota, Akio Morita, and Yasuo Murai.
• Department of Neurological Surgery, Nippon Medical School, Chiba Hokuso Hospital, 1715, Kamagari, Inzai-City, Chiba, Japan. kyongson@nms.ac.jp.
• Eur Spine J. 2024 Feb 1; 33 (2): 490495490-495.

PurposeThe middle cluneal nerve (MCN) is a pure sensory nerve around the middle buttock. Its entrapment between the iliac crest and the long posterior sacroiliac ligament elicits low back pain (LBP) that can be treated by MCN neurolysis or neurectomy. Because few studies examined the pathology of MCN entrapment (MCN-E) we subjected 7 neurectomized specimens from 6 LBP patients to pathologic study.MethodsWe present 6 consecutive patients (7 sides) with intractable LBP who underwent successful MCN neurectomy. Their symptom duration ranged from 6 to 96 months (average 47.3 months); the follow-up period ranged from 6 to 17 months (average 11.7 months). The surgical outcomes were evaluated using the numerical rating scale (NRS) for LBP and the Roland-Morris Disability Questionnaire (RDQ) score. The resected MCNs underwent neuropathological analysis.ResultsPostoperatively, all 6 patients reported immediate LBP amelioration; their NRS and RDQ scores were improved significantly. Pathological study of the 7 resected nerves showed that the myelinated fiber density was decreased in 6 nerves; we observed marked enlargement (n = 5), perineurial thickening and disruption (n = 6), intrafascicular fibrous changes (n = 5), myelinated fibers separated by fibrous cells under the perineurium (n = 4), and Renaut bodies (n = 3). The 7th nerve appeared normal with respect to the density and size of the myelinated fibers, however, the perineurium was slightly thickened.ConclusionWe present pathological evidence at the MCN compression site of 7 nerves from 6 patients whose LBP was alleviated by MCN neurectomy, indicating that MCN entrapment can elicit LBP.© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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