MRI of the Sciatic Nerves
Basics: What is an MRI of the Sciatic Nerves?
One of the most common complaints that brings patients to their physicians, is the development of shooting pain down their lower extremities, into their buttocks, hips, lower legs, and to their feet. Pain like this is called radiculopathy, a technical term that means something is pressing on a radicular nerve, or nerve root. This type of problem is commonly caused by disc herniations in the lumbar spine that press on a nerve root that connects to nerves travelling down the leg. Additionally, bony spurs can press on the nerve roots and cause the same symptoms. The cause of this pain is best identified by obtaining an MRI of the lumbar spine, which demonstrates the lumbar nerve roots leaving the spinal canal as they begin to course down the legs. Lumbar MRI is excellent for demonstrating a disc herniation, or a bone spur pressing on a nerve root. Sometimes however, a patient has an obvious radiculopathy, but the lumbar spine MRI is normal. So what now?
Less commonly, there can be something wrong with the nerve root well after it leaves the spinal canal. Sometimes, the sciatic nerve takes an unusual course through a muscle in the pelvis, the pyriformis muscle, which can lead to the muscle pressing on the nerve root. Sometimes, there can be inflammation of the nerve root outside of the canal, or even a tumor pressing on it or invading it. Evaluating these latter causes of radicular pain has traditionally been difficult, and most imaging centers do a poor job of imaging the sciatic nerve outside of the lumbar spine.
We have spent a tremendous amount of time and energy developing several sequences that give us an outstanding look at the sciatic nerves outside of the spine, as they form in the pelvis, and as they travel down the leg. We use 3D volume techniques, and another newer technique called MR Neurography (see images above).