Extraspinal causation of sciatic pain is not common, but as chiropractors who often diagnose and treat "sciatica" on a daily basis, we must constantly be aware of the possibilities. The extraspinal lesion which may be a soft tissue tumor or bone tumor usually presents with symptoms that are very similar to the more frequent causes of sciatica.1 Other extraspinal causes besides tumors have been reported as heterotopic ossification around the hip; misplaced intramuscular injections; myofascial bands in the distal thigh; myositis ossificans of the biceps femoris muscle; compartment syndrome of the posterior thigh; posttraumatic or anticoagulant-induced extraneural hematomas; and as a complication from total hip arthroplasty.2
We are all very concerned with patients who complain of back and/or sciatic pain that is unrelated to trauma, constant, progressive and unresponsive to change in position or bed rest, or accompanied by night pain. A recent article in Spine2 explains an "alarming sign" which is the ability of a patient to attribute a sciatic pain to a specific extraspinal point.
The authors state that more than half of the 32 patients with extraspinal lesions were able to locate the sciatic pain during the straight leg test to a specific point along the extraspinal course of the sciatic nerve distal to the sciatic notch. A mass was noted in 13 of the 32 patients, but the history and alarm sign allowed the diagnosis of a probable tumor as the cause of the sciatica in 22 patients.
Some locations of the soft tissue tumors affecting the sciatic nerve distribution were located in the buttock, gluteus maximus muscle, sciatic notch, mid-thigh, distal thigh, sciatic nerve bifurcation, common peroneal nerve, lateral aspect of popliteal fossa, mid-thigh, popliteal space and medial gastrocnemius. Plain radiographs of the pelvis, mid-femur and proximal fibula revealed 13 of 17 bone lesions. Other bone lesions located in the pelvis were found by CT scans. MRI found all of the suspected soft-tissue lesions.
The authors2 stated that it was very important to radiograph all patients with sciatic pain and that the radiograph not be a coned-down or "screened-down" view, since it is important for the view to extend far enough to the side to include the sacroiliac complex.
Due to the presence of intestinal gas, it is often difficult to recognize early bone tumors in the pelvic ring or sacrum.3 If extraspinal soft tissue tumors are suspected, the authors2 recommend MRI for soft tissue lesions along the entire course of the sciatic nerve.
References
- Sim FH, Dahlin DC, Stauffer RN, Laws ER. Primary bone tumors simulating lumbar disc syndrome. Spine 1977;2:65-74.
- Bickels J, Kahanovitz N, Rubert CK, et al. Extraspinal bone and soft-tissue tumors as a cause of sciatica: clinical diagnosis and recommendations: analysis of 32 cases. Spine 1999;24(15):1611-1616.
- Paulson EC. Neoplasms of the bony pelvis producing the sciatic syndrome. Minn Med 1951;11:1069-74.
