PIRIFORMIS SYNDROME

What is the Piriformis Syndrome

Anatomical relationships between the sciatic nerve and the piriformis muscle
It is a very rare disorder in which the sciatic nerve is compressed by the piriformis muscle. This is, a flat, pyramid-shaped and oblique muscle  located deep in the buttocks, that runs between the femur and the iliac bone. It help in the external rotation of the hip. It can be the cause of severe sciatic pain and disability, especially if not diagnosed soon.  Common sciatic nerve pain (i.e. lumbar disc hernia) is much more prevalent than Piriformis syndrome.
Anatomical relationships between the sciatic nerve and the piriformis muscle
 

What Causes Piriformis Syndrome

Among the reasons for development of piriformis syndrome are:

  • Sitting for extended periods of time

  • Sitting with a large wallet in the rear pocket
  • Repeated forward movements
  • Running
  • Bicycling
  • Stiff sacroiliac joints
  • Foot overpronation
  • Morton’s toe (the second toe next to the big toe is longer than the big toe)
  • Falling injury

The primiformis muscle, if overused, becomes tight and compresses on the sciatic nerve with resulting sciatic pain.

Approximately one-half of piriformis syndrome cases are caused by trauma and the remainder are spontaneous onset of sciatica nerve pain.

Symptoms

Pain distribution in the piriformis syndrome
They are similar to sciatica nerve pain. Pain starts in the buttocks and may travel the length of the leg through the back of the thigh and calf and into the foot. The patients might experience tingling, numbness, burning and weakness. The sciatic pain may worsen with sitting or with activities that press the piriformis against the sciatica nerve, such as running, cycling or hose riding.
Pain distribution in the piriformis syndrome
 

Most often, people suffering from piriformis syndrome, do not have lower back pain.

Diagnosis

It is usually made through physical examination.  Certain tests may elicit sciatica nerve pain indicating the presence of the syndrome, especially the interna rotation of the hip with the knee in full extension.  Your foot on the side where the sciatica nerve pain is may be splayed when you lie on your back.

On MRI examination it is possible to see the sciatic nerve with oedema when crossing under the piriformis muscle.

Treatment

Conservative treatment is most often recommended for treatment of the sciatic pain due to piriformis syndrome. Alternate ice and heat treatment may give relief, especially after engaging in an activity that aggravates the sciatic nerve pain. Ultrasound treatment may be beneficial as ultrasound heat penetrates deep into the muscle loosening the tightness and thereby alleviating sciatica nerve pain. Stretching exercises to target the primiformis muscle, along with the hamstrings and hips muscles, will help increase range of motion and decrease the sciatica nerve pain.

If all these treatments prove unsuccessfull, injection of toxinum botulin in the piriformis muscle under CT or MRI guidance, can be attempted. In case of failure, surgical intervention with removal of the piriformis muscle or the offending fibrous band, is in order.

Fibrous tract inducing the piriformis syndrom
Fibrous tract section in piriformis syndrome
Fibrous tract inducing the piriformis syndrome
Fibrous tract section in piriformis syndrome

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