Distal Lesions of the Pudendal Branches.
The pain is neuropathic, mostly reported as allodynia located in a specific area of one of the distal branches of the pudendal nerve. This generally involves the dorsal branch (rectal branch) or the middle branch (perineal branch) when the lesion is secondary to an episiotomy or proctological procedure. A trigger point is found by palpation of the area of pain while vaginal/rectal palpation of PN is painless. Pelvic dysfunctions, especially neurogenic incontinences never occur. When sub dermal infiltration with local anesthesia produces significant improvement, infiltration with botulinum toxine is a promising treatment option which may control pain efficiently for several months.
When the genitofemoral nerve is affected, pain may be felt in the inguinal area with irradiation in the internal aspect of the thigh (never below the knee) and in the genital area. Lesions of the genital branch of the genitofemoral nerve induce vulvodynia or pudendal pain located selectively in the anterior portion of the vulva (clitoris). Surgical access to the inguinal region (appendectomy, herniorraphia, introduction of lateral trocar for laparoscopy…) exposes patients to risk for injuries to the genitofemoral nerve. Neurologic symptoms are then restricted to sensory changes except in injuries to the genitofemoral nerve in males that can also induce troubles or loss of cremastic reflex. Pain is located not only in the groin area and the ventral genital area (as in lesion of the ventral branch of the PN) but also in the internal aspect of the tight (lesion of the femoral branch), never below the knee. Since the genital branch is only sensitive, neither bladder dysfunctions nor urinary incontinence occur. Inguinal nerve blockade with anesthetic agent is then the method of choice for diagnosis.
Contracture/Spasm of Bulbospongiosus Muscles.
In females, dyspareunia is located in the distal third of the vagina, increased by vaginal penetration. Vaginal palpation of the bulbospongiosus muscles is painful while the muscles are generally under massive tension forming like a “tente” in upper part of the vagina. Relaxation of the muscles can be easier obtained by botulinum toxine infiltration.
Incidences of sacral radiculopathies are widely underestimated obviously because of lack of awareness that such lesions may exist, lack of diagnosis and acceptance, and lack of declaration and report of such lesions. The most probable reasons for neglecting pelvic nerve pathologies in medicine are the complexity of the pelvic nerve system, the difficulties of etiologic diagnosis and - probably the main reason - the limitations in access to the pelvic nerves for neurophysiologic explorations and neurosurgical treatments. Neurosurgical procedures techniques are well established in nerve lesions of the upper limb but pelvic retroperitoneal areas and surgeries to the pelvic nerves are still unusual for neurosurgeons . In one of our own series of 136 consecutive patients suffering from pudendal pain, only 18 had presented a true PN entrapment while all other patients were suffering from a sacral radiculopathy involving the pudendal fibers contained in S#2-4/5.
The semiology may include pudendal pain but frequently involves other different “pelvic symptoms” such as pelvic pain, dys/apareunia, troubles/loss of vesical and/or rectal sensation with “non-pelvic symptoms”. These include low-back-pain (lumbosacral trunk, L5), pudendal pain (S2-4), vulvo-vaginodynia and coccygodynia (S3-4), sciatica (L5-S2), distal pain, and/or abnormal sensations in the legs or buttock.
In massive lesions of the SNR (plexopathy), loss of strength in hip extension, knee flexion, and dorsal plantar flexion of the foot can be detected. Because the vesical parasympathetic nerves (pelvic splanchnic nerves) are contained in the SNR #3-5, vesical symptoms are quasi constant. In extrinsic nerves irritation, bladder hypersensitivity is quasi systematic, but also bladder overactivity is even not unusual. In neurogenic damages of the nerves, behind loss of sensitivity or even numbness in corresponding dermatomes, ultrasonography shows usually postvoid residual urine while urodynamic testing confirm detrusor hypo- or even atonia as well as a detrusor hyposensitivity and an augmentation of bladder capacity.
In surgically induced sacral radiculopathies, correlation of clinical information with the surgical steps of the procedure permit a precise anatomical localization of the neural lesion, which is essential for adapting the therapeutic strategy. Perineal procedures induce pathologies of the pudendal nerve, abdominal/laparoscopic procedures of the sacral nerve roots while vaginal surgeries can induce both .
When nerve injuries have occurred, laparoscopic exploration not only offers an anatomic and functional exploration of the nerves, but may also result in effective neurosurgical treatment using techniques of nerve(s) decompression or reconstruction also by the laparoscopic approach. In non-postsurgical damages, systematic laparoscopic exploration has showed that not only pelvic cancers can induce nerve damage. In addition, frequent pathologies, such as deeply infiltrating endometriosis, uterine myomas or ovarian processes, or retroperitoneal vascular abnormalities (vascular entrapment) and retroperitoneal fibrosis may induce pelvic neuropathies, that can be treated by laparoscopic nerve decompression/neurolysis. Moreover, neurogenic lesions are accessible to laparoscopic implantation of electrodes for neuromodulation of the SNR . Laparoscopy is therefore the essential and logical step in the management of pelvic nerve pathologies that must be indicated as soon as possible, before the nerve damage becomes irreversible and before the process of “pain chronification” starts.
The greater sciatic notch provides egress for the piriformis muscle. The pudendal nerve exits the pelvis at the inferior aspect of this muscle. In the athlete, flexion and abduction of the thigh are common motions, and they may lead to hypertrophy of the piriformis muscle. If the sciatic notch is narrowed because of the posterior orientation of the ischial spine, the cross-sectional area of the greater sciatic notch is reduced. Concomitant hypertrophy of the piriformis muscle may cause compression of the pudendal nerve against the posterior edge of the sacrospinous ligament. The piriformis syndrome is diagnosed primarily on the basis of symptoms and on the physical exam. There are no tests that accurately confirm the diagnosis, but MRI may be necessary to exclude other pathologies. Behind medical treatments and physiotherapy, injection of corticosteroid into the piriformis muscle may be tried, as well as infiltration with botulinum toxine A. Laparoscopic exploration with decompression of the sacral plexus or eventually partial resection of the piriformis muscle may be undertaken as a last resort.