Introduction: The etiology of lumbosacral plexopathy is often due to compression. One of the less common causes of this is aneurysm of the iliac artery. However, 13% of the patients with this disorder initially have symptoms of plexus irritation or deficit.
Clinical case: We describe the case of a 42 year-old-man, with no previous medical history, who complained of right-sided sciatica for the previous three months. On examination there were clinical signs of a lesion of the right lumbosacral plexus. On CT of the pelvis and MR of the lumbar spine there were images compatible with an aneurysm of the right iliac artery. This diagnosis was confirmed on arteriography. Treatment was surgical (aneurysmography and right iliofemoral by-pass). The pain disappeared and the motor deficit improved considerably.
Conclusion: When a patient presents with lumbosacral plexopathy, an iliac aneurysm should be considered as a possible etiological factor. In such cases early diagnosis is essential, since surgical treatment will usually resolve the clinical problem.