下肢に生じたneuralgic amyotrophy（lumbosacral radiculoplexus neuropathy）の1例

A Case of Neuralgic Amyotrophy in the Lower Extremity (Lumbosacral Radiculoplexus Neuropathy)

はじめに

　Neuralgic amyotrophyは1948年Parsonage and Turnerによって提唱された特発性末梢神経疾患である^1）。激しい疼痛に引き続いて筋力低下をきたし，腕神経叢ニューロパチーと考えられている^1－3）。下肢においても同様の病態が報告されlumbosacral（radiculo）plexus neuropathyと呼ばれているが，上肢に比べるとその頻度は少ない^4－9）。われわれは，坐骨神経痛様疼痛で発症しその後筋力低下・筋萎縮を認め，neuralgic amyotrophyと考えられた症例を経験したので，最新の知見を含めて報告する。

Abstract

　We report a 76-year-old man who suddenly had pain in the right buttock that radiated down the back of the leg.　He underwent nerve block therapy, but subsequently noted weakness of the right leg.　On examination, there was moderate weakness of the right gastrocnemius, flexor digitorum longus and extensor hallcis longus, and mild weakness of the tibialis anterior, quadriceps and hamstrings muscles.　The right Achilles tendon reflex was absent.　There was a slight diminution of touch sensation over the right L5-S1 area.　A nerve conduction study revealed reduced motor and sensory action potentials in the right leg.　An electromyography showed evidence of denervation in the right gastrocnemius and tibialis anterior muscles.　Treatment with corticosteroids was effective for alleviating his pain, and muscle strength improved gradually.　One year later, he showed no neurological deficits.　Neuralgic amyotrophy in the lower extremities is rare, but awareness of this disorder helps us avoid unnecessary surgical investigations and leads to possible treatment with immunomodulative therapy.