非特異的腰痛に対して上殿皮神経の神経剝離術が有効であった1症例

Non-Specific Back Pain due to Superior Cluneal Nerve Entrapment Neuropathy Treated with Neurolysis:A Case Report

Ⅰ．はじめに

　腰痛の原因は多岐にわたり，神経症状を有し画像などの検査で原因が同定できる特異的腰痛と，神経症状を伴わず原因が同定できない非特異的腰痛に大別される．非特異的腰痛は，腰痛の実に70〜90%を占め，日常診療においてときに保存的治療に抵抗し慢性化しやすい^7,14,15)．その背景に精神医学的問題や心理社会的問題が関与していたり，またさまざまな疾患が併存していることにより診断が困難な場合がある．正確な診断が得られない場合には，投薬，理学療法においても一般的な腰痛治療を行うにとどまり，疾患特異的な治療や原因を改善する方法をとることができず，その結果，治療効果が乏しい結果にもつながるため，腰痛診療における原因疾患の同定は，他疾患と同様に重要である．

　今回われわれは，急性腰痛を繰り返し，治療困難な非特異的腰痛として扱われていた上殿皮神経（superior cluneal nerve：SCN）の絞扼性障害（SCN entrapment neuropathy：SCNE）に対し，神経剝離術を行い良好な臨床経過をたどった1例を経験したので報告する．

　A 43-year-old man with a 10-year history of low back pain（LBP）had been conservatively treated elsewhere with medications for non-specific back pain. He presented to our institute with LBP and difficulty in standing up, sitting down, and sitting for prolonged periods. His Numerical Rating Scale score, due to LBP, was 8 out of 10. He had numbness on the lateral aspect of his left thigh. A lumbar radiography and magnetic resonance imaging studies revealed mild degenerative changes and mild canal stenosis in the lumbar spine. Palpation over the left posterior superior iliac crest, 8 cm from the midline over the iliac crest, revealed severe tenderness. A superior cluneal nerve（SCN）block performed at the trigger point in both the buttocks resulted in complete pain abatement and disappearance of the radiating pain. Therefore, we diagnosed SCN entrapment neuropathy（SCNE). However, the pain reappeared a few days later and subsequent treatments failed to relieve it；therefore, we decided to perform surgery. The SCN penetrates the thoracolumbar fascia through an orifice just before crossing over the iliac crest. We opened the orifice with microscissors in a distal to rostral direction along the SCN and released the entrapped nerve. After surgery, the symptoms were relieved and the patient experienced no recurrence in the last 4 years after the treatment. SCNE should be considered as a causative factor of LBP, and its treatment using minimally invasive surgery yields excellent clinical outcome.