[Lumbar radiculopathy presenting neuralgic amyotrophy with gadolinium-enhanced MRI lesions: a case report].

A 40-year-old man presented with sudden onset of severe left buttock pain that radiated down the thigh to the leg. On examination, he showed moderate weakness and atrophy in the left quadriceps and tibialis anterior muscles, and absence of a left patellar tendon reflex. Needle electromyography revealed an active denervation pattern in the left quadriceps muscles, suggesting neuralgic amyotrophy. Contrast-enhanced MRI showed abnormal enhancement of the left cauda equina. Steroid pulse therapy relieved pain, and subsequent high-dose intravenous immunoglobulin prevented progression of muscle atrophy and weakness. Neuralgic amyotrophy is characterized by attacks of severe neuropathic pain and subsequent patchy paresis in the upper or lower extremities. Since overall recovery is less favourable than usually assumed, early diagnosis is very important. This case was remarkable in that contrast-enhanced MRI revealed abnormal enhancement and thickening of the cauda equina, which may help in achieving early diagnosis and treatment.