A painful, burning sensation on the outer side of the thigh may mean that one of the large sensory nerves to your legs, the lateral femoral cutaneous nerve (LFCN), is being compressed. This condition is known as meralgia paresthetica.

The body brings information to the brain about the environment through the sensory nerves, while the motor nerves transmit messages from the brain to activate muscles. To do this, nerves must pass over, under, around, and through your joints, bones, and muscles. Usually, there is enough room to permit easy passage. In meralgia paresthetica, swelling, trauma, or pressure can narrow these openings and squeeze the nerve. When this happens, pain, paralysis, or other dysfunction may result.

Causes

Most cases have no identifiable cause. It can however, be caused by direct injury to the lateral cutaneous nerve of the thigh accidentally. For example:

A seat belt injury from a car accident – Inadvertently, during medical or surgical procedures; or keyhole (laparoscopic) hernia repairs and treatments. Various sports and physical activities such as gymnastics, football, bodybuilding and strenuous exercise.

Rarer causes include a neuroma – Neuromas are non-cancerous (benign) growths (tumours) on a nerve. Pelvic or intra-abdominal tumours (including cancerous ones), could also compress the nerve and cause this problem; but this is rare.

Other possible causes include lying down for long periods of time in a curled-up position. Diabetes can affect nerves in general, and although it would be unusual simply to have this one nerve affected, the lateral cutaneous nerve of the thigh could potentially become damaged.

Symptoms

• Pain on the outer side of the thigh, occasionally extending to the outer side of the knee
• A burning sensation, tingling, or numbness in the same area
• Occasionally, aching in the groin area or pain spreading across the buttocks
• Usually only on one side of the body
• Usually more sensitive to light touch than to firm pressure

Who develops Meralgia Paraesthetica?

Anyone can develop it; however, it is a very uncommon condition. It is more common in men than in women. Generally, it occurs between the ages of 30-40 years. It is much rarer in children. Risk factors include obesity and pregnancy.

Examination

During the appointment, your doctor or podiatrist will ask about recent surgeries, injury to the hip, or repetitive activities that could irritate the nerve. If they suspect meralgia paresthetica, questions will be asked to help determine what might be putting pressure on the nerve. Restrictive clothing and weight gain are two of the more common causes of pressure. Your doctor may ask if you consistently wear tight stockings/ compression, or whether you wear a heavy tool belt at work.

Physical Examination

Your doctor or podiatrist will also check for any sensory differences between the affected leg and your other leg. To verify the site of the burning pain, he or she will put some pressure on the nerve to reproduce the sensation. You may need both an abdominal and a pelvic examination to exclude any problems in those areas.

The pain can usually be provoked by getting you to extend your hip. Hip extension is the movement of the leg backwards. The main buttock muscle (gluteus maximus), tightens when you make this movement.

Tests

X-rays will help identify any bone abnormalities that might be putting pressure on the nerve. If your doctor suspects that a growth such as a tumor is the source of the pressure, he or she may ask for a magnetic resonance image or a computed tomography (CT) scan. An ultrasound scan may be requested. In some cases, a nerve conduction study may be advised.

Treatment

Treatments will vary, depending on the source of the pressure. Generally, the prognosis is good.  The goal is to remove the cause of the compression. This may mean resting from an aggravating activity, to losing weight. It may take time for the burning pain to stop and, in some cases, numbness will persist despite treatment. Other treatments, manipulation, massage, stretching exercises, using NSAIDS, and painkillers may help as well. In more severe cases, your doctor may give you an injection of a corticosteroid preparation to reduce inflammation. This generally relieves the symptoms for some time. In rare cases, surgery is needed to release the nerve.

 

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