Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
The nerves that exit the spine and supply innervation to the legs pass through a collection of nerves called the lumbar plexus, and then branch off and enter to the inguinal region or posterior aspects of the pelvis to the leg. The lumbar plexus lies in the pelvis, near the ovaries, uterus, and other genito-urinary structures. Irritation or damage to the lumbar plexus or its branches can occur from the surgery itself or from positioning during the surgery (such as when the legs are flexed and the knees bent, as in when the legs are placed in stirrups for gynecologic procedures).
Symptoms of neuropathic pain, pain coming from nerves, include burning, tingling, loss of sensation, pins-and-needles, electric pains, etc. One such type of nerve irritation after surgery is called meralgia parasthetica. The symptoms of this condition include tingling, numbness and burning pain in the outer part of the thigh. The cause of is compression of the nerve that supplies sensation to the lateral part (outer part) of the thigh, the lateral cutaneous nerve. This condition has many causes including being overweight, certain surgeries and the positioning that occurred during surgery, pregnancy, very tight clothes, diabetes, trauma. Also, in patients who are bed-ridden for prolonged periods of time in a particular position, this condition may occur.
Treatment of post-operative pain from suspected nerve irritation or damage is often required for several weeks; the pain usually gets better on its own but can be more chronic. It sounds like you are on the right track being evaluated by a pain specialist. Sometimes multiple modalities such as oral medications, topical patches, and other therapy are required to help with the pain.
Regarding the lumbar spine issues, it sounds like the L4-L5 disc has resorbed which is good. The finding of a herniated disc may or may not be of significance. If the disc is pushing on the spinal cord or on the nerves that exit the spine, it could potentially cause symptoms, but if it is an L5-S1 disc, the symptoms would not be in the inguinal region but rather in the back, posterior buttocks, thigh, and leg. Often, herniate discs are asymptomatic, found on MRI looking for the cause of back pain or some other symptom, and they are just incidental. If they are symptomatic (if the neurologist thinks that the disc is causing symptoms), treatment could include pain management, medications for neuropathic pain, medications (non-steroidals such as advil), sometimes steroids if there is swelling (edema), temperature therapy (hot or cold packs), stretching and controlled physical therapy, muslce relaxants, and so on, these are best prescribed by an experienced physician, each has its own indications.
Treatment for neuropathic pain sometimes requires multiple medications that affect different parts or functions of nerves. These medications were invented for other diseases but work well for pain and include some of the antidepressants such as amityrptiline, anti-seizure medications such as neurontin or lyrica, and others.
No abnormalities detected on the EMG/NCS can mean one of two things: (1) there are no nerve problems, (2) or the nerves that are irritated or causing the symptoms are located too deep in the pelvis or inguinal region to be tested (EMG/NCS has its limitations regarding accessibility to nerves).
Continued follow-up with your pain management and neurologist is recommended.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
Thank you very much, Dr. Chahine, for taking the time to thoroughly answer the question. I have to say I knew much of this already as I have researched this thoroughly, but the possibility of irritation to the lumbar plexus was something I did not know and will look into.
After more research, I have several theories and ideas. I have read about an somatosensory evoked potential nerve study which may be able to test nerves which are not easily tested with other nerve studies. I will also be asking the doctor about the possibility of a diagnostic local anesthetic into either the genitofemoral or ilioinguinal nerve, which may at least diagnose which nerve is the problem as I believe the irritation is peripheral and not a nerve root issue.
I have also read abstracts where an NCS was done by comparing the values contralaterally to the values of the healthy nerve on the other side since no average values are known for some of these deeper pelvic nerves.
Being as both MRI's were done after the pain started and the L5/S1 disc was not a problem before and now the L4/L5 disc has resorbed makes me think this is not coming from spinal nerves.
I believe either the genitofemoral nerve or the ilioinguinal nerve is either adhesed or entrapped, but the problem will be convincing the doctor to try some of these things.
Thank you very much for the info and if you have any further thoughts on my ideas, I would love to hear your thoughts.