Piriformis syndrome
Overview
Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle causing pain, tingling and numbness in the buttocks and along the sciatic nerve. There is no definitive way to diagnose the syndrome which may result from anatomical variations in the muscle-nerve relationship, or from overuse or strain. Uncontrolled studies have suggested theories about the disorder. However, a large scale formal prospective outcome trial using Class A study design as outlined by the American College of Physicians, found the weight of the evidence-based medicine is that piriformis syndrome should be considered as a possible diagnosis when sciatica occurs without a clear spinal cause
Causes
Approximately 50% of patients with piriformis syndrome have a history of trauma, with either a direct buttock contusion or a hip/lower back torsional injury. The remaining 50% of cases are of spontaneous onset, so the treating physician must have a high index of suspicion for the problem, lest it be overlooked.
Diagnosis
There is no definitive way to diagnose the syndrome, however indications include sciatica - radiating pain in the posterior thigh and lower leg - and the physical exam finding of tenderness in the area of the sciatic notch. Magnetic resonance neurography is a medical imaging technique that can show the presence of irritation of the sciatic nerve at the level of the sciatic notch where the nerve passes under the piriformis muscle. Neurography can also determine whether or not a patient has a split sciatic nerve or a split piriformis muscle - this may be important in getting a good result from injections or surgery. Image guided injections carried out in an Open MRI scanner can accurately relax the piriformis muscle to test the diagnosis. Other injection methods such as blind injection, flouroscopic guided injection, ultrasound, or EMG guidance can work but are not as reliable. Unlike spine injections, there is no bony target that can show up on X-ray, so fluoroscopy can't show the injection target. It has been difficult to achieve reliable injections with EMG and ultrasound because these methods are not specific to the piriformis muscle. CT guided injections can work well but provide a very high dose of radiation to the pelvis and there is no possibility of shielding sensitive tissues from the radiation
Treatment
Treatment usually begins with stretching exercises and massage, and avoidance of contributory activities, such as running and bicycling. Some clinicians recommend formal physical therapy, including the teaching of stretching techniques, massage, and strengthening of the core muscles (abs, back, etc.) to reduce strain on the piriformis. Stretching exercises will target the piriformis, but may also include the hamstrings and hip muscles, in order to adequately reduce pain and increase range of motion. Patients with piriformis syndrome may also find relief from ice and heat. Ice can be helpful when the pain starts, or immediately after an activity that causes pain. This may be simply an ice pack, or ice massage. Alternating heat and ice is often helpful. Failure of piriformis syndrome treatment may be secondary to an underlying obturator internus muscle injury