Meralgia paraesthetica

Meralgia paraesthetica (UK spelling), or meralgia paresthetica (US spelling) (me-ral'-gee-a par-es-thet'-i-ka) — also called Bernhardt-Roth syndrome — is numbness or pain in the outer thigh not caused by injury to the thigh, but by injury to a nerve that extends from the thigh to the spinal column.

This chronic neurological disorder involves a single nerve, namely the lateral cutaneous nerve of thigh (also called the Lateral femoral cutaneous nerve). The term meralgia paraesthetica comprises four Greek roots, which together denote "thigh pain with anomalous perception".

Etiology
The lateral cutaneous nerve of thigh most often becomes injured by entrapment or compression where it passes between the upper front hip bone (ilium) and the inguinal ligament near the attachment at the anterior superior iliac spine (the upper point of the hip bone). Less commonly, the nerve may be entrapped by other anatomical or abnormal structures, or damaged by diabetic or other neuropathy or trauma such as from seat belt injury in an accident.

The nerve may become painful over a period of time as weight gain makes underwear, belting or the waistband of pants gradually exert higher levels of pressure. The pain may be acute and radiate into the rib cage, into the groin and thigh.

Or, weight loss or aging may remove protective fat layers under the skin compressing the nerve against underwear, outer clothing but more commonly by belting. Pressure may also be caused by long periods of standing or leg exercise which increase tension on the inguinal ligament.

Signs and symptoms

 * Pain on the outer side of the thigh, occasionally extending to the outer side of the knee, usually constant.
 * A burning sensation, tingling, or numbness in the same area
 * Multiple bee-sting like pains in the affected area
 * Occasionally, aching in the groin area or pain spreading across the buttocks
 * Usually more sensitive to light touch than to firm pressure
 * Hyper sensitivity to heat (warm water from shower feels like it is burning the area)

Diagnosis
Diagnosis is largely made on the description given by the patient and relevant details about recent surgeries, injury to the hip, or repetitive activities that could irritate the nerve. An examination will check for any sensory differences between the affected leg and the other leg. An abdominal and pelvic examination may be required to exclude any problems in those areas.

Electromyography (EMG) nerve conduction studies may be required. X-rays may be needed to exclude bone abnormalities that might put pressure on the nerve; likewise CT or MRI scans to exclude soft tissue causes such as a tumor.

Treatment
Treatments will vary. In most cases, the best treatment is to remove the cause of the compression by modifying patient behavior, in combination with medical treatment to relieve inflammation and pain. The following treatments are examples. Whatever the cause, recovery typically requires several weeks to months, depending on the severity of nerve damage, and is facilitated by using looser clothing and suspenders rather than belting.

Non-steroidal anti-inflammatory drugs (NSAIDs) will reduce inflammatory pain, plus narcotic pain killers may be required as the level of pain can become disabling and prevent sleep. Reduction of physical activity is mandatory, in relationship to the pain level. Absolute bed rest is required for acute pain levels.

The lateral cutaneous nerve of the thigh can occasionally be damaged during laparoscopic hernia repair, or scarring from the operation can lead to meralgia paraesthetica.

For lower pain levels, treatment may involve:


 * Rest periods to interrupt long periods of standing, walking, cycling, or other aggravating activity
 * Weight loss in overweight individuals and exercise to strengthen abdominal muscles
 * Wearing clothing that is loose at the upper front hip area
 * Heat, ice, or electrical stimulation
 * Nonsteroidal anti-inflammatory medications for 7–10 days

It may take significant time (weeks) for the pain to stop and, in some cases, numbness will persist despite treatment. In severe cases a local nerve block can be done at the inguinal ligament using a combination of local anaesthetic (lidocaine) and corticosteroids to give relief that may last several weeks. Pain modifier drugs for neuralgic pain (such as amitriptyline, carbamazepine or gabapentin) may be tried, but are often not as helpful in the majority of patients.

In persistent and severe cases, surgery may be needed to decompress the nerve or as a last resort to resect the nerve. The latter treatment results in permanent numbness in the area.