I have been asked about the effectiveness of pre-sacral neurectomy (PSN) in providing pain relief and if it should be routinely performed as a part of endometriosis and pelvic pain surgery. For those of you not familiar with this term (PSN), it is a nerve cutting procedure done during laparoscopy in an attempt to decrease pelvic pain. This should not be confused with another similar procedure, Laparoscopic Uterosacral Nerve Ablation (LUNA) that has been shown in multiple studies to be ineffective and is not recommended.
PSN has been shown to be effective in relieving midline pelvic pain (pain only in the middle of the pelvis behind the pubic bone) but not pain on the sides (in the area wear the ovaries are located). In my experience, a patient’s pelvic pain resulting from endometriosis resolves after appropriate surgical removal and additional treatment is needed. PSN may be most useful in treating pain that is both in the midline and has been present since the first period, the medical term for this primary dysmenorrhea.
Pelvic pain is transmitted through not one or two nerves but many different nerves throughout the pelvis, which is one of the reasons it can be so difficult to treat. This is different than your pinky finger, which is innervated by only one nerve, the ulnar nerve. If a person had chronic pain in their pinky that did not respond to other treatments a nerve block of this nerve would relieve the pain. There is an area inside the body on the front side of the lower back called the superior hypogastric plexus that contains the major sensory nerves from the uterus and cervix but not the ovaries. This is the reason a PSN helps with pain coming from the uterus or cervix (midline) but not from the ovaries (lateral or on the sides).
There are surprisingly few studies on PSN. Information on the efficacy, or how well the PSN works, varies depending upon which scientific study is quoted. Most but not all studies show that when PSN is used in conjunction with other procedures to treat endometriosis or adhesion, about 75% to 80% experience a decrease in pain, especially painful periods (dysmenorrhea) while about 60% patients not receiving PSN as part of the pelvic pain surgery experience a decrease in their pain. Some studies have shown a decrease in painful sex (dyspareunia) following PSN while others have not shown a difference. This may be due to the multiple different causes of pain with intercourse, some of which may be helped with a PSN while others are not.
But like any surgical procedure, PSN has potential risks and complications. The complications associated with this procedure include constipation, urinary urgency and decrease vaginal lubrication with sex, altered sensation bladder fullness. There is also a risk of damage to the ureters, bowel or blood vessels during surgery. The actual risk of developing these complications including constipation is not well documented in the scientific literature. The few studies that we have reported a postoperative rate of constipation to be between 14% and 74% and about 5% of patients experiencing urinary urgency.
The possibility of chronic constipation as a result of PSN is most concerning. So many of my patients have a significant problem with constipation to begin with that adding a procedure which can make this worse is of questionable benefit. A PSN is not reversible if it causes an unacceptable level of constipation. The approach and techniques I use to treat endometriosis and pelvic pain have a level approaching a 90% response rate (at least somewhat better) and thus I usually do not use PSN as an initial treatment. Patients who have always had killer periods from the very start or patients with pain as a result of significant adenomyosis (endometriosis in the muscle wall of the uterus) should consider PSN. Otherwise, I feel, PSN should be reserved for patients with midline pain that is unresponsive to conservative surgery. In conclusion, PSN seems to be effective in relieving midline pain, but with the potential for permanent side effects, conservative use for specific conditions is probably the best approach.