Piriformis Syndrome

Piriformis-MusclePiriformis syndrome is a rare condition in which the muscle pinches off the sciatic nerve. The piriformis is a big muscle in the buttocks that attaches at the hip. Compression of the nerve causes pain sensations traveling through the buttocks to the back of the leg, often with tingling or numbness. This type of pain is called “sciatica.” Usually sciatica is not the result of piriformis compression, but rather a herniated spinal disc. Piriformis syndrome is marked by muscle tension and spasms that affect the sciatic nerve, which passes through the buttocks down the back of the leg, terminating in the smaller nerves at the feet. Most patients report an ache deep in the buttocks, which is intensified by sitting or climbing stairs. Piriformis can be an acute condition that resolves with rest, or a chronic, debilitating problem resistant to treatment.

Pathology

Piriformis-Syndrome-MRIThe piriformis muscle makes walking and the maintenance of balance possible. It’s a large, flat, pyramid-shaped muscle deep underneath the gluteal muscles in the buttocks. Starting at the sacral spine, the piriformis muscle travels to the greater trochanter of each femur, stabilizing the hip and allowing the thigh to move outward from the body. In most people, the sciatic nerve rests underneath the piriformis muscle, but in about 15% of the population, the sciatic nerve passes through the muscle.

Therefore, patients with an atypical sciatic route through the muscle are more disposed to suffering from piriformis syndrome. Researches studied a group of 100 patients who did not have piriformis syndrome, and magnetic resonance imaging (MRI) scans showed S1 nerve roots above the piriformis muscle in 99.5% of patients, while 75% of S2 nerve roots passed through the muscle and 25% passed on top of it, documenting differences in anatomy amongst the individuals studied (Russell et al). Patients affected with a Morton foot may be at increased risk for developing piriformis syndrome. This condition involves anatomical deformity of the second metatarsal that destabilizes the foot during walking, resulting in internal rotation of the leg. The piriformis compensates by contracting repetitively during the push-off phase of walking, which can cause chronic compression of the sciatic nerve.

Repetitive motions performed during activities such as running or lunging, stress the piriformis muscle causing contractions that apply pressure on the sciatic nerve. Prolonged sitting, climbing stairs, squatting or running uphill can also irritate the piriformis. Compression of the sciatic nerve results in inflammation, which exacerbates pain, leading to a chronic condition.

Physical trauma to the area may lead to fibrosis in the muscle that puts pressure on the sciatic nerve.

Other conditions that may result in piriformis syndrome include:

  • Cerebral palsy
  • Total hip arthroplasty
  • Pseudoaneurism in the inferior gluteal artery near the sciatic nerve

Diagnosis

Herniated_DiscA definitive test for piriformis does not exist, so a diagnosis is determined based on a detailed history and physical exam. The physician asks questions to find out when the pain began, how long the pain lasts, and what aggravates the pain. The patient describes the character of the pain, which is often characterized as a dull ache in the center of the affected buttocks. Patients report pain that radiates down the back of the leg that is made worse by sitting or walking up stairs or along an incline. Piriformis syndrome may also present with weakness, numbness or tingling in the lower extremities. By palpating the piriformis, the doctor may determine if it is contracted and tense. The Freiberg test determines involvement of the piriformis muscles when forced internal rotation of the extended thigh results in pain.

Another movement that contracts the piriformis muscle selectively is the Beatty maneuver. Assuming a side-lying position and bending the knee towards the chest, then abducting the thigh activates the piriformis and results in pain. A physical exam may show shortening of the leg length on the affected side, and the patient may also present with a splayed foot on the affected side when lying on their back. An x-ray or MRI (magnetic resonance imaging) may be performed to rule out other problems with the surrounding tissues.

It’s important to rule out other, more common causes of sciatica, such as:

  • Herniated spinal disc
  • Fibrous adhesions of other muscles in the area surrounding the sciatic nerve
  • Hamstring tendinitis

Nerve conduction tests may be helpful in excluding other conditions.

Treatment

Prescription Medication First line treatment focuses on resting the muscle, avoiding activities that aggravate pain and comfort measures. Ice packs applied to the area for 20 minutes every two to four hours are recommended initially for an acute injury. Pain management after the first 24 hours utilizes heat. A heating pad placed on the muscle for 20 minutes at a time may reduce inflammation and pain. The patient may receive a physical therapy consult to learn stretching exercises that relax the piriformis muscle and reduce pressure on the sciatic nerve. These stretches involve moves that flex and adduct the hip. Massage speeds up the heating process by increasing blood flow to the inflamed area and stopping muscle spasms. The physician may prescribe muscle relaxers or anti-inflammatory medications. A holistic treatment plan can incorporate acupuncture to decrease tension in the body.

If pain persists after trying all the interventions mentioned above, the physician may recommend a corticosteroid and anesthetic injection to the area to reduce inflammation and pain. Iontophoresis is a therapy that uses a mild electric current to deliver medication to the muscle through the skin. For this procedure, the electrode containing a medication solution (steroid or other) is placed on the skin and a low voltage current is employed to drive the ions through the skin into the muscle. Another treatment option is the injection of Botox (botulinum toxin) to weaken the piriformis muscle. Botox inhibits nerve signals traveling to the muscle, causing tonal relaxation and inhibiting the involuntary muscle contractions. The effects of Botox are temporary, but interrupting the cycle of muscle tension and nerve inflammation may allow the patient time to rest and recover from piriformis syndrome. Surgery is an extreme measure only taken as a last resort in treating chronic, debilitating pain.

References