Thigh Pain Diagnosis
Wearing skinny jeans and keeping your cell phone in your front pocket can put you at risk of developing meralgia paresthetica, a common cause of thigh pain.
The diagnosis of meralgia paresthetica is often a clinical one. This means that in the presence of appropriate risk factors and consistent signs and symptoms, no specific testing is needed to make the diagnosis.
The physical examination should include careful assessment of the area involved. Often the clinician will use a pen or marker to delineate the involved area. Consistently, a fairly well-defined oval will emerge--extending from the hip, outer thigh to above the knee (see Affected Area, Figure 1).
The top condition this can be confused with meralgia paresthetica is nerve pain originating from the lower back (lumbar spine), or sciatica. Most people think sciatica is a very specific type of pain experienced in the leg, but it is actually a general term used to describe any nerve pain experienced as a result of a problem in the lumbar spine.
A herniated disc is a common cause of sciatica. If the herniation is at the appropriate part of the spine (lumbar level L3-L4) pain can be experienced in the front and side of the thigh and in a manner similar to meralgia paresthetica. However, it is not nearly as well defined and will often follow a more variable course than that of meralgia paresthetica.
What Tests to Expect
If testing is needed to help sort out an unclear presentation, the most useful tests are EMG/NCS and MRI. EMG/NCS stands for an electromyelogram / nerve conduction study. This test uses tiny needles inserted into the muscle and pads placed on the skin to determine whether there are alterations in the electrical current of the nerve suggesting that it has been damaged.
EMG/NCS is not 100% accurate for meralgia paresthetica, and are highly dependent upon the expertise of the practitioner administering the test. However, this test can be very useful in sorting out whether nerve pain is from meralgia paresthetica or from another source, such as the lumbar spine or a condition called neuropathy.
MRI, or magnetic resonance imaging, is the test views to determine whether there is a pinched nerve originating in the lumbar spine. This is not the first test of choice and is best used when the EMG suggests a pinched nerve in the back over MP is the source of pain.
A new diagnostic test making its way into more physician offices is musculoskeletal ultrasound. It uses the same technology used for years to image developing babies and look for blood clots, but has defined to get in a close look at nerves, muscles, tendons and ligaments. Ultrasound helps determine whether the lateral femoral cutaneous nerve is abnormally enlarged, or whether it is trapped under a ligament in the pelvis.
Finally, if the cause of your pain is less obvious, your doctor may order other tests such as an x-ray of the hip to make sure the pain is not coming from arthritis or a local problem in the bone. Blood tests can include a study of the thyroid, blood sugar (glucose) levels to check for diabetes, serum lead levels, vitamin B12 and folate, which at low levels can adversely affect nerve function.