What is piriformis syndrome?
Piriformis muscle is located deep in the buttock and helps to rotate the leg outwards. It extends from the side of sacrum and tailbone to the upper part of thigh bone. One of the main nerves of the leg (sciatic nerve) runs in close relation to this muscle. Problems of the piriformis muscle such as spasms or swelling, can cause irritation of the sciatic nerve leading to sciatica like symptoms. This condition is addressed as piriformis syndrome (PS). Other names for this condition include extra-spinal sciatica, deep gluteal syndrome or wallet neuritis.
What are the symptoms of piriformis syndrome?
Most patients present with buttock and leg pain which is worse on sitting and with hip movements. Pain is described as a dull ache, shooting or burning sensation associated with buttock tenderness. Most patients sit with the affected side tilted upwards. Some patients complain of a swelling, sausage shaped lump sensation in the buttock. Pain commonly radiates towards hip or down the back of the thigh, leg. Walking upstairs or on inclines can increase pain, with relief on lying down. Sometimes when pain is severe it may cause individuals to limp while walking. In females there may be pain during sexual intercourse (dyspareunia).
What causes piriformis syndrome?
PS is six times more common in women and middle ages. Individuals sitting for prolonged periods (long-distance bikers, office workers) and occupations such as truck & taxi drivers, tennis players are at a higher risk. Variations in the anatomy of piriformis muscle, sciatic nerve or its path can predispose to the irritation of the nerve. In majority of individuals the nerve travels below the muscle, it may however travel through or over the muscle or may be split into two. Other causes of piriformis syndrome include
- Trauma or Injury to the muscle such as after a fall onto the buttock, surgery or lumbar and sacroiliac joint pathologies.
- Overuse and microtrauma such as during intense downhill or long-distance running/walking. This can cause muscle spasm and shortening.
- Direct compression as during sitting on hard surfaces may cause repetitive trauma
- Compression due to direct pressure from a tumour invasion, or abnormal dilatation of a nearby blood vessel (inferior gluteal artery aneurysm)
- Post-radiotherapy fatty atrophy of the piriformis muscle
- Altered leg, back or pelvis biomechanics
How is piriformis syndrome diagnosed?
The commonest cause of sciatica is the irritation of the nerves in or near the spine. PS represents an extra spinal cause where the site of nerve irritation lies outside the spine although the symptoms are similar. Correct diagnosis helps to offer targeted treatment and increases the probability of a successful outcome. Another nearby muscle (obturator internus) can cause similar symptoms and this needs to be differentiated from the PS.
Diagnosis begins with a comprehensive history and physical examination. An MRI is useful for detailed evaluation of the lumbar spine & pelvis and ruling out other conditions with similar presentation. X-rays can be used for the evaluation of neighbouring bony structures such as the hip and sacroiliac joints. Electromyography (EMG) may help in differentiating PS from pain originating from the spine.
A local injection into the piriformis muscle is often used to confirm the diagnosis. This is discussed in the treatments section.
What are the treatment options for piriformis syndrome?
Treatment involves a combination of the following;
- Short term rest and activity modification
- Lifestyle modification
- Physical therapy including stretching exercises of the piriformis, hamstring muscle and strengthening of the abductor and abductor muscles
- Medications including anti-inflammatories, muscle relaxants, neuropathic medications (ones used for nerve pain).
If these measures fail to resolve symptoms, then the next step is injections.
Ultrasound Guided Injections
Steroid injections are the most commonly used injection option. As stated previously injections can not only provide relief, but also help in confirming the diagnosis. Using ultrasound helps to improve accuracy and reduce chances of complications. X-rays guidance is an alternative, although ultrasound is preferred as it can be performed in outpatient settings and offers other advantages such as visualisation the piriformis muscle, blood vessels and the sciatic nerve. Local anaesthetic and steroid mixture is used for the injection. Local anaesthetics help to relax the muscle and steroids aid in reducing inflammation thus prolonging the effect of the injection.
Botox injections work by paralysing and relaxing the piriformis muscle, thereby taking the pressure off the sciatic nerve. The effect of these injections can last for a few months proving an opportunity to address the root cause and engage in physical therapy.
Surgery may be considered for severe cases not responding to other measures. It involves either cutting the piriformis tendon from its hip attachment or cutting through the piriformis muscle to take pressure off the sciatic nerve.
Return to sports and activities varies between individuals and depend on the time taken in reduction of the symptoms. Too early a return has the potential to cause worsening of injury and reoccurrence of the symptoms.
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