Case Study: Piriformis Syndrome Follow-Up

0812-nervemed-injection-1ABOVE: Open MR interventional scan of the case study patient depicting the MRI needle delivering injectate medication to the piriformis muscle based on MR Neurography targeting.


This month’s case study continues with the success story of a 2008 Piriformis patient who contacted us last month with updates on his progress. This patient has been suffering from right lower extremity neurologic symptoms. Physical exam and imaging indicated involvement of the piriformis muscle and obturator internus muscle.

Based on MR Neurography findings, it does appear the patient would benefit from additional MR guided interventional procedures. The patient has had several injections in the past with little success and is reluctant to have additional injections and prefers to go straight to surgery. However, Dr. Filler explains the benefits of the procedure and the differences in accuracy versus more traditional injection methods.

The patient learns that an Open MR guided injection is designed to be both diagnostic and therapeutic. When a patient has a complex pain syndrome involving more than one soft tissue location then it is especially important to conduct targeted imaging since the reaction or lack thereof becomes an important part of assessment. Even if there isn’t a long term pain relief from this injection, it is targeted in real time imaging so the procedure becomes a planning tool for a minimal access surgery.

A number of T-1 weighted axial images were obtained demonstrating the anatomy of the pelvis. There was some muscle asymmetry appreciated with the piriformis and obturator internus being larger on the right. Once a good location within the muscle was achieved, introduction of treatment agents was commenced. We then see T2-weighted axial images in which hyperintense material is distributed within the piriformis and obturator internus muscles. The distribution demonstrates a linear exclusion, striations, which are suggestive of the presence of muscle spasm, both piriformis and obturator internus mild-to-moderate.

Following the Open MR Guided interventional procedure the patient has had good diagnostic response to the injections but no persisting benefit. So a minimal access surgery is planned a few days later. It was immediately apparent that there were complex fibrovascular bands crossing and restricting the sciatic nerve and also adhering to a capsule around the piriformis muscle. The piriformis muscle was released from the capsule and the fibrovascular bands were carefully coagulated and sectioned ultimately bringing the sciatic nerve into full view. The remnants of these were also coagulated and resected.

Then using the Open Interventional MR imaging sequences the surgeon proceeded inferior and posterior until the obturator internus was identified. The pudendal nerve was also identified and carefully avoided. The nerve to the obturator internus was carefully mobilized proximally into the superior retrosciatic space behind the sciatic nerve and then distally along its branches in the inferior retrosciatic space.Once all this was completed, the area was irrigated copiously with antibiotic solution. Seprafilm was placed as an adhesiolytic agent to all the dissected nerve and muscle surfaces.

At one month out from the surgery, which included resection of the piriformis muscle and neuroplasty of the sciatic nerve and neuroplasty of the nerve to the obturator internus. We were happy to report that the patient was completely pain free. At the time the patient was quite pleased with his progress and hopeful that this situation would continue. It is now more than four years since the surgery and the patient continues to be completely pain free with only the occaisional use of anti-inflammatory medications. The patient case illustrates the complexity of the Piriformis diagnosis and the successful interventional use of MR guidance for treatment planning.


ABOVE: In this Open MRI Guidance image, we can see the medication being delivered to a very small area of the obturator internus and tendon through the MRI needle.