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Femoral nerve compression by an iliopsoas bursal cyst coexisting With lumbar spinal stenosis: a case report

Year: 2026

Type: article

Abstract: Background: Iliopsoas bursal cysts are rare synovial proliferative lesions, most commonly associated with osteonecrosis of the femoral head, osteoarthritis, and rheumatoid arthritis. When a cyst compresses the femoral nerve, it may cause groin pain, radiating anterior thigh pain, and an antalgic gait, closely mimicking lumbar spinal stenosis (LSS). Only approximately 20 comparable cases of femoral nerve compression have been documented worldwide. Concomitant LSS and femoral nerve compression by an iliopsoas bursal cyst have not previously been reported. The coexistence of LSS and femoral nerve compression caused by an iliopsoas bursal cyst may result in delayed or missed diagnosis. Case presentation: We report a patient with concomitant LSS and femoral nerve compression caused by an iliopsoas bursal cyst who was initially treated for LSS alone. After 3 days of integrative conservative treatment for LSS, the low-back, posterior thigh, and lateral calf pain improved substantially; however, the right anterior thigh and groin pain became intolerable. Subsequent hip ultrasonography and magnetic resonance imaging (MRI) demonstrated an iliopsoas bursal cyst adjacent to the femoral nerve. Available electromyography findings showed a reduced right femoral nerve response amplitude. Considering the patient's overall clinical presentation, we considered right femoral nerve injury to be the most likely diagnosis. The patient underwent open anterior cyst excision to achieve complete neural decompression. The anterior thigh pain improved rapidly, with the visual analog scale (VAS) score decreasing from 8 to 2 on postoperative day 1. No symptom recurrence was observed during 12 months of follow-up. Conclusion: This case provides an important clinical warning. In older patients with chronic occupational musculoskeletal overuse, extraspinal femoral nerve compression should be considered when treatment for LSS relieves low-back and posterior thigh pain but severe anterior thigh or groin pain persists or worsens. Hip Doppler ultrasonography, MRI, and electromyography/nerve conduction studies should be performed to exclude extraspinal femoral nerve compression. In patients with severe cyst-related femoral nerve compression, open cyst excision can provide rapid neural decompression.

Source: Frontiers in Surgery

DOI: 10.3389/fsurg.2026.1948532