Endometriosis of the somatic nerves together with endometriosis of the visceral nerves and visceral nerve plexuses form what is called nervous endometriosis. The incidence of nervous endometriosis is rare, less than 1% of all cases of deeply infiltrative endometriosis.
Endometriosis of the somatic nerves, as the name suggests, affects the functionality of the somatic nerves, i.e. the nerves that innervate the skeletal muscles, the skeletal sciatic muscles, and in principle, affects the presacral plexus. This structure is the origin of the main somatic nerves in the pelvis: the sciatic nerve, the obturator nerve, the pudendal nerve, the femoral nerve and the gluteal nerve branch of the sciatic nerve.
Endometriosis of the sciatic nerves is a difficult pathological entity to treat, because as Prof. Possover said, the pelvis is a black box, i.e. it is an area that no speciality can find itself in. More specifically, a gynaecologist does not have the necessary neurological knowledge, even though gynaecological surgeons who practise advanced surgery have the knowledge of the anatomy of the retroperitoneum, they do not have the knowledge of neurology.
Also, neurosurgeons with knowledge of neurology do not address this area of the body, they mainly treat conditions of the cranial box and spine, less peripheral nerves and never pelvic nerves. And that’s why this pathological entity has somehow been neglected over time, and so to fill this gap neuropelveology appeared, which is an independent specialty founded and developed by Prof. Marc Possover, an area that receives more and more followers.
Regarding endometriosis of somatic nerves, so a chapter of neuropelveology, there are other renowned doctors who developed and supported research in this field, such as Prof. Horace Roman, Prof. Rabischong, Prof. Khazali. Their interest and findings made the path of somatic nerve surgery much clearer and they made the access techniques that give satisfaction easier.
Somatic nerves have two functions: a sensory one and a motor one. The sensory function basically collects the stimuli from the muscle and integumentary structures located in the territory that the nerve serves and transmits them to the brain.
The motor function achieves the voluntary conscious control of the respective muscles that are involved in movement; walking, running or finer motor functions such as erection and voluntary bladder control.
The type of nerve pain is a fixed point pain, a burning sensation, and allodynia. The location of the pain is exact, and depending on the location of the neuropathic pain, we know which nerve is affected.
The characteristic of pain in nervous endometriosis is that this neuropathic pain is a cyclical pain that mainly occurs during menstruation or ovulation, or it is a chronic pain that is exacerbated during menstruation and ovulation.
“In order to diagnose the affected nerve, knowledge of the functional anatomy of the somatic nerves, respectively of the territories they serve, which are called dermatomes, is needed. This also orients the clinician and thus determines the appropriate treatment”
That is why it is very important for the endometriosis surgeon who addresses this pathological entity, to know how to conduct a neurological examination to complement the usual gynaecological examination.
Regarding surgical indication, we must take into account the fact that somatic nerve endometriosis surgery is an extremely difficult and extremely frustrating surgery. Because, on one hand, each somatic nerve is difficult to access, and on the other hand, any nerve destruction is irreversible, so surgery must be as frugal as possible. Some aspects that we often deal with are sequelae lesions, perineural fibrosis following surgery, postoperative scars that can affect the somatic nerve and consequently generate pain similar to the initial pain caused by endometriosis.
So, in other words, even if we establish a correct diagnosis, perform a correct surgery, it may happen that after surgery the patient’s body develops a scar tissue that includes the nerve path, creates a nerve entrapment, and generate pains similar to the initial pains, which nullifies the benefit of the surgical act.
That is why the balance is very fine regarding surgical indication because we have to balance between, as I said before, the delicates of the operation, the surgical risks, the complications given by the postoperative scar, but on the other hand we have to take into account that nervous endometriosis, slowly but certainly, destroys the affected nerve and every mm of the nerve path counts, and in fact, here is another peculiarity of nerve endometriosis surgery, namely, we are dealing with a tissue that does not regenerate, we are dealing with extremely fine structures and it is crucial to intervene at the opportune moment.
“As far as I am concerned I operated on least 40 cases of endometriosis of the nerves, most of them with favourable results”
From my point of view, the indication for surgery in endometriosis of the somatic nerves is a disabling, intractable pain, that does not respond to any kind of analgesics, a pain that practically makes the patient’s life a nightmare, and or especially, if there are signs of defunctionalization of the nerve, respectively muscle atrophy in the territory served by that nerve and with functional impairments of the nerve served.
It is known that the nerve once affected by endometriosis after a certain time can suffer the wallerian degeneration phenomenon, i.e. downstream of the endometriosis lesion the nerve begins to die and this is the moment when motor dysfunction appears in the served territory and the moment when we are obliged to intervene.
Once we establish the indication for surgery, somatic nerve endometriosis surgery must be extremely accurate, the surgeon must have thorough knowledge of the anatomy of the pelvis. The instruments with which the surgeon works around the nerve must be extremely fine, cold instruments are always preferred, the use energies around the nerve its not recommended, because can irreversibly damage the nerve, and most of the time, surgery is good to be done in a multidisciplinary team, meaning that even if they are not part of the operation, it is very good to ask the opinion of a neurosurgeon at the moment we do such an operation, because as I was telling you, they have thorough neurological knowledge.
“When we operate on nerves it is good to ask the opinion of a neurosurgeon, as they have thorough neurological knowledge”
After surgery for endometriosis of the somatic nerves, recovery through physical therapy is very important because these therapies help heal the nerve and help prevent the formation of perineural scar tissue, as mentioned above. Somatic nerve surgery is carried out in a few centres in the world, and is becoming more and more known. I support the centralization of these cases because, as I told you, somatic nerve endometriosis is extremely rare, and then it would be good for these cases to be directed to centres that already have experience in this field, so that the patient benefits from the best experience and expertise.
As far as I’m concerned, I have a series of at least 40 nervous endometriosis surgeries involving all the previously described nerves, sciatic nerve, obturator nerve, pudendal nerve. Most of them had favourable results, but even so, I consider this surgery to be a great challenge and must always be viewed very seriously and even humbly by the surgeon, I might say.