How is electrodiagnostic testing performed in the evaluation of femoral nerve entrapment?

Updated: Oct 15, 2019
  • Author: Minoo Hadjari Hollis, MD; Chief Editor: Thomas M DeBerardino, MD  more...
  • Print
Answer

Electrodiagnostic testing may be performed for diagnosis. With nerve conduction studies, the technique includes using a bar electrode for recording and reference. This can be performed with either antidromic (conduction against the direction of sensory fiber conduction) or orthodromic (conduction in the direction of nerve conduction) methods. The antidromic study is usually easier to perform, though on occasion, response may be absent bilaterally. In obese patients, the response is small and difficult to obtain.

A needle stimulation electrode may be needed. The sensory response is absent in 71% of patients with meralgia paresthetica and is prolonged in 24% of patients with this condition. EMG test results with the needle are normal in patients with this diagnosis, which may help to differentiate it from an upper lumbar radiculopathy.

Technically, the sensory test is a difficult study, and a response must be present on the opposite side to determine entrapment. It may be nearly impossible to obtain a response in an obese patient or a patient with a large abdomen without using a needle for stimulation. Unfortunately, the test may be difficult for the patient to tolerate because of the large amount of current (with respect to more peripheral nerves) required to stimulate a nerve that lies under adipose tissue.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!