Piriformis Syndrome - Symptoms, Causes and Treatment

Piriformis is a flat, band-like muscle located in the pelvic region. It is attached to the base of the spine, and to the upper end of the thigh bone (femur).

It enables us to maintain balance on one foot, shift weight from one foot to the other, and also helps in rotating the hip and leg. In 17-22% of the people, this muscle is innervated by the roots of sciatic nerve that runs from the lower back, through the buttock, and into the lower limb.

When these nerve roots get impinged by the piriformis muscles, it leads to sciatica, which is characterized by pain, tingling, numbness and weakness in the buttocks and legs. The set of symptoms thus arising due to the compression or irritation of sciatic nerve by the piriformis muscle are referred to as piriformis syndrome.

Piriformis syndrome is classified as primary and secondary on the basis of the underlying cause.

Primary piriformis syndrome refers to the set of symptoms that arise due to an anatomical cause like:

► Split piriformis muscle
Generally, the sciatic nerve exits the greater sciatic foramen and passes along the inferior surface of the piriformis muscle. In case of split piriformis muscle, the sciatic nerve passes through the belly of piriformis muscle.

► Split sciatic nerve
In this type of variation, the sciatic nerve splits into its two arms -- tibial nerve and common fibular nerve -- while passing through the piriformis muscle. The tibial branch passes either superiorly or inferiorly with respect to the muscle.

► Abnormal sciatic nerve path
Any other anomalies in the paths taken by the sciatic nerve through or around the piriformis muscle may also lead to compression of the sciatic nerve or its branch.

Secondary piriformis syndrome refers to the set of symptoms that arise due to precipitating causes like:

• Injury due to accidents and mishaps
• Repetitive motion injury (RMI) arising due to overuse of the muscle
• Excessive long-distance walking, running or biking

• Chronic trauma as a result of sitting on hard surfaces
• Sitting for long periods of time
• Improper postures while sitting, swimming, etc.
• Local ischemia (lowered or restricted blood supply)

The initial symptom for this condition is pain in the buttock which then spreads to the lower back and legs. Other symptoms include:

• Numbness and weakness in lower extremities
• Tingling sensation in lower limbs
• Pain while sitting, standing or lying for more than 20 minutes (Such pain does not subside on changing the position)

• Pain that worsens in case there is lack of movement
• Difficulty in walking
• Headache
• Neck pain

There is no definitive criteria for the diagnosis of this syndrome. However, the patient's medical history, lifestyle, habits, etc. along with a physical examination for tenderness or presence of palpable mass in the buttocks is useful. Radio-imaging techniques are useful to identify enlargement or abnormalities in the piriformis muscle, but are more useful for excluding other conditions like herniated disc and vertebral abnormalities.

The following signs and tests are often used to identify the presence of sciatic pain, and aid the diagnosis of piriformis syndrome:

► Piriformis sign
Here, the patient is asked to lie down, and is tested for the presence of tonic pain during passive external rotation of the leg.

► Freiberg test
It is similar to the Piriformis sign except that pain during passive internal rotation of the hip is checked for.

► Beatty's test
In this method, selective contraction of piriformis muscles is carried out. The patient is asked to lie on the unaffected side, lift up the painful leg, and hold the knee about 4 inches above the table.

► FAIR (Flexion, Adduction and Internal Rotation) test
In this test, the examiner rotates and adducts the hip of the patient in different positions, namely supine, seated and lateral recumbent.

► Lasègue test (Straight Leg Raise)
Here, the patient is asked to lie flat on his back, and the examiner lifts each leg of the patient at an angle of 90 degrees, while maintaining an extended position of the knee.

Initially, the patient is prescribed with non-steroidal anti-inflammatory drugs (NSAID), muscle relaxants, and is also asked to perform certain muscle stretches. Botulinum toxin (BTX) treatment and physical therapies are also prescribed for relieving the compressed nerve, and alleviating the symptoms. Severe cases may be treated with ligament reconstructive therapy and surgeries.

Piriformis syndrome is an uncommon condition that arises due certain anatomical anomalies as well as physical stress and trauma. It is characterized by sciatic pain, numbness and weakness in the lower extremities, and is often difficult of diagnose.

As such, more research is being performed to understand the anatomical features, and develop unique diagnostic methods for this condition.

Disclaimer: This story is for informative purposes only, and should not be used as a substitute for professional medical advice.