Piriformis Syndrome and Sciatica
Piriformis syndrome is a medical condition that causes sciatica symptoms of leg pain usually caused by lumbar radiculopathy. Sciatica is a collection of symptoms caused by nerve root compressions at the level of the spine. A herniated intervertebral disc is the most common cause of sciatica symptoms while piriformis syndrome is caused by compression of the nerve below the pelvis.
The sciatic nerve is the largest nerve in the human body made by the collection of the nerve roots L4, L5, S1, S2, and S3. The nerve originates in the lower spine, and as it travels down the pelvis, it lies in front of the piriformis muscle. The nerve exits below the piriformis muscle and lies deep beneath the biceps femoris muscle at the back of the thigh.
Sagittal and axial sections of the lumbar MRI
The sciatic nerve continues down the thigh and at the knee joint’s level, divided into two branches, the tibial nerve, and the common peroneal nerve. The sciatic nerve provides motor supply to major muscles in the thigh, leg, and feet. The nerve supplies the muscles responsible for bringing the thighs together, bending the knee, bending and extending the ankle and the toes. Besides the motor supply, the sciatic nerve carries the sensory input from the legs and feet.
The piriformis muscle is a small muscle originating from the inner aspect of the sacral bone. The muscle extends outwards and attaches to the prominence on the hip bone’s outer side (greater trochanter). The muscle primarily functions to rotate the hip joint outwards (external rotation) and aid in moving the hip to the side (abduction). External rotation and abduction movements help us in our day-to-day activities such as walking, sitting, running, etc.
Causes of Piriformis Syndrome
Piriformis syndrome occurs due to compression or irritation of the sciatic nerve as it passes under the muscle. The compression may occur as a result of muscle spasm in the piriformis due to irritation.
The piriformis spasm may occur due to excessive training without adequate stretching or repetitive action irritating the muscle. Piriformis tightening or swelling may occur as a result of direct injury to the buttock. The nerve may get entrapped inside the piriformis due to initial injury leading to adhesion of the nerve to the muscle.
There may be anatomical variations in the nerve’s relation to the piriformis muscle. The nerve may split into two parts, passing below it and the other passing above it. The split nerves join below the piriformis to continue down the thigh. One of the divided nerves or the whole sciatic nerve may also pass through the piriformis muscle.
The anatomical variation may make the sciatic nerve more vulnerable to compression or irritation at the piriformis muscle level. The entrapment may occur at the bony ischial tuberosity level or between the piriformis and the gemellus obturator internus muscle complex.
The piriformis syndrome usually causes buttock pain that may or may not radiate down the thigh. The pain is generally exacerbated by activities such as sitting or walking for prolonged periods. The patients may especially be intolerant to sitting. In some cases, patients may experience sciatica symptoms during bowel movements as the muscle originates in the pelvis.
The sciatica symptoms caused by lumbar radiculopathy typically occur with activities such as raising your leg while laying down. Additionally, as sciatica is one of the many symptoms caused by the pathology at the spine level, the symptoms may be related to the cause of narrowing the spine. In the herniated intervertebral disc, activities such as bending forward, coughing, sneezing, etc., may worsen the symptoms. In the case of spinal stenosis, activities that involve bending the spine back make the symptoms worse.
The consulting spine surgeon will extract a thorough history regarding the onset of the symptoms and the activities that make the symptoms better or worse. Through a physical examination, the physician will try to localize the pathology causing the sciatica symptoms, which may be coming from the spine or the piriformis muscle.
Physical examination may involve a straight leg raise test, Pace test, and FAIR (flexion, abduction, internal rotation test). The Pace sign is the demonstration of pain from resisted external rotation and abduction. A positive FAIR test involves demonstrating pain as the physician tries to adduct and internally rotate the affected hip.
The straight leg raise test is usually positive in the case of sciatica resulting from lumbar radiculopathy. The test usually involves a demonstration of pain in the back as one lifts the affected leg in the range of 30 to 70 degrees. The test may also be positive in the case of piriformis syndrome.
Additionally, the physician looks for pain on pressing the area of the sciatic notch. The physician may request radiological investigations and neurodiagnostic studies to differentiate the sciatica symptoms.
The treatment of piriformis syndrome is mainly conservative. Conservative management involves anti-inflammatory medications, physical therapy, heat, and cold therapy, etc. The majority of the patients experience an excellent relief of symptoms. NSAID (nonsteroidal anti-inflammatory) medication such as naproxen and ibuprofen act to reduce the inflammation at the site of entrapment/compression/irritation.
Physical therapy is aimed to strengthen and stretch the piriformis muscle to reduce the tightening of the muscle. To improve the patient’s physical therapy participation, the surgeon may inject corticosteroid medication near the sciatic nerve to provide relief from symptoms. Very rarely, operative management may be needed to cut the muscle and release the nerve.