[A case of neuralgic amyotrophy in the lower extremity (lumbosacral radiculoplexus neuropathy)].

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.