腰下肢痛の鑑別診断における坐骨神経ブロックの有用性と限界―梨状筋症候群の診断に主眼を置いて

Sciatic Nerve Blocks for Diagnosis of Piriformis Syndrome

　腰下肢痛患者で，臨床所見と腰椎MRI所見が典型的に一致せず梨状筋症候群(PS)が否定できない188例に対して坐骨神経ブロック(SNB)を行った．効果を著効，有効，無効に分け，最終診断を有効度別に調査し，またPSに対する梨状筋切除術と腰椎疾患除圧術後に症状改善が得られた各群における術前のSNB効果を評価した．最終診断はPS(疑い含む)が56％，腰椎疾患23％で，SNB著効中PS(疑い含む)は81％であった．SNBはPS手術有効群で100％の有効性を示したが，腰椎手術有効群の66％にも有効性があり，PSの確定診断法とは言えなかった．

　We used sciatic nerve block (SNB) to make the differential diagnosis of piriformis syndrome in 188 consecutive patients with sciatica in whom it was impossible to make the diagnosis based on the lumbar MRI findings.　We rated the effectiveness of SNB as excellent (60%), good (25%) and poor (15%).　After performing SNBs, lumbar radicular blocks, and surgeries based on the initial diagnosis, the final diagnoses were piriformis syndrome (56%), piriformis syndrome complicated with lumbar degenerative disease (4%), lumbar degenerative disease (23%), others or unknown (16%).　The prevalence of piriformis syndrome in the excellent effectiveness group was 81%.　SNB was effective in all patients with piriformis syndrome and in 66% of the lumbar degeneration patients.　The diagnostic value of SNB is of limited value for differentiating piriformis syndrome from lumbar degenerative disease.