When the sciatic nerve gets compressed or irritated by the piriformis muscle, this is termed as the piriformis syndrome. The tingling and numbness is felt in the buttocks, descending down into the leg, along the path of the sciatic nerve. Piriformis syndrome is different from sciatica caused by the compression of the spinal nerve roots resulting in irritation and inflammation radiating down to the leg. Overuse or strain, or some anatomical variations in the relationship between the muscle and the nerve may be the root cause of the syndrome.
The piriformis is a pyramidal shaped flat muscle within the pelvis. It lies against the pelvis’ posterior wall, and can be found at the back of the hip-joint. In cases of sciatica where it has been proven that a herniated disk or spinal compression is not causing the problem, the probability is that piriformis syndrome is the reason behind the sciatic symptoms. Trauma or overuse causes the piriformis muscle to spasm and shorten, and strangle the sciatic nerve beneath it. This condition is known as entrapment neuropathies or nerve entrapment although there are instances where the sciatic nerve is passing through the piriformis muscle instead of underneath it. This group of people who comprises 15-30% of the population have a greater chance of contracting piriformis syndrome. The piriformis muscle plays an important part in walking because it rotates the extended thigh and responsible for abducting the flexed thigh. Abduction of the flexed thigh is the action of shifting the body weight to the opposite site of the foot, keeping a person from falling.
Piriformis syndrome is also seen on people with inactive gluteal muscles. This syndrome can result from sitting all day at work which can deprive the gluteals of activity. Work related constant positions may also result in the hamstrings, adductor magnus and piriformis muscles to work harder, resulting in enlarged muscles causing the compression of the sciatic nerve. This is also true for constant activities that use the legs which may result in piriformis syndrome due to overuse injury. For athletes like bicyclists, runners and rowers, the activities should be balanced by lateral leg movements as their constant forward movements will weaken the hip and tighten abductor muscles. Disproportionately weak muscles combined with abnormally tight muscles can have a shortening and contracting effect on the piriformis muscle. When the piriformis muscle has increased in size considerably, the sciatic nerve is impinged and the piriformis muscle gets strained.
There are also incidences of impingement of both the sciatic nerve and the pudendal nerve due to the piriformis muscle spasm. The muscles of the bowels and the bladder are controlled by the pudendal nerve and entrapment of this nerve will result in the numbness and tingling of the groin area. Fecal incontinence and urinary problems will result from this impingement, and a doctor should be consulted immediately.
Stretching and strengthening exercises is an effective and easy treatment for piriformis syndrome which should be alleviated in a few days. A specially designed exercise regimen which targets the hip adductor and gluteus medius muscle groups is recommended. Piriformis syndrome may also be the result of a falling injury. In severe cases of pain, corticosteroids are injected into the piriformis muscle. Explorative surgery is the last resort if the pain continues and becomes intolerable.