Gynecologists Beware

Abstract & Commentary

Source: Irvin W, et al. Minimizing the risk of neurologic injury in gynecologic surgery. Obstet Gynecol. 2004;103: 374-382.

New-onset leg weakness or numbness is a common cause for neurologic consultation following gynecologic surgery. Usually such deficits are transient and do not necessitate extensive investigation. Infrequently, long-term disability results. This review addresses issues that would prevent such avoidable surgical complications.

Abdominal hysterectomy is the most common cause of iatrogenic femoral neuropathy. Stretch injury consequent to poor patient positioning or surgical dissection may be causative but, most often, prolonged compression by retractor blades is the cause. Self-retaining retractors appear particularly prone to cause this type of injury, consequent to ischemia resulting from pressure on the vaso nervorum. Recovery occurs anywhere from 3-65 days post-operatively but may be delayed even longer. When hand-held retractors are used, the incidence of femoral neuropathy drops from 7.5% to 0.7% following otherwise identical surgery. Thin patients, poorly developed rectus abdominis musculature, a narrow pelvis, prolonged surgery, and the extended Pfannenstiel incision (bikini line) all increase the risk of femoral neuropathy, and thus the choice of proper retractors in these populations is particularly warranted.

Meralgia paresthetica, consequent to intra-operative lateral femoral cutaneous nerve injury, shares the same etiologies as femoral neuropathy and may be similarly prevented. Genitofemoral neuropathy causes relatively mild sensory symptoms in the ipsilateral mons, labia majorum and femoral triangle and is most likely to occur during surgery for large pelvic sidewall masses or during external inguinal lymph node biopsy. Avoidance of injury can be achieved by identifying the nerve prior to excision of any mass.

Retroperitoneal surgery for malignancy or endometriosis most frequently injures the obturator nerve, resulting in thigh adduction weakness and upper medial thigh numbness. Again, adequate exposure of the nerve will best prevent this injury but may require retraction of the external iliac artery and vein. Sciatic neuropathy, a rare complication of laparotomy and usually due to the repair needed following unexpected pelvic hemorrhage, may similarly be avoided by diligent identification of the nerve before suture placement.

When a low transverse incision is used for pelvic surgery, the iliohypogastric and ilioinguinal nerve are most at risk due to their course between the internal and external oblique muscles in the anterior abdominal wall. Transection of the nerves may occur during the initial incision, they may be entrapped during suture placement, or a delayed-onset neuropathy may occur as a result of normal healing and scarring. Sharp/burning pain radiating from the incision site to the groin/symphysis (ilioinguinal) or mons/labia/upper inner thigh (iliohypogastric) region with paresthesia in the appropriate dermatome and relief after nerve block are the diagnostic triad for these entrapments. Coughing, sneezing, and stretching exacerbate the pain while bending at the knees provides temporary relief. Neurolysis is often necessary for cure. Not extending the surgical incision beyond the lateral border of the rectus sheath will significantly reduce the risk (3.7% following Pfannenstiel incisions) of this complication.

Vaginal surgery may similarly result in neurologic injury. Femoral neuropathy may occur bilaterally and is due not to compression from retractors but from prolonged incorrect lithotomy positioning. Excessive hip flexion, abduction, and external hip rotation allows the femoral nerve to be compressed under the inguinal ligament. Should prolonged surgery be necessary, periodic repositioning is advisable.

Sciatic nerve injury occurs in 0.3% following vaginal hysterectomy and is a result of stretch injury due to its being fixed at the sciatic notch and fibular head, not allowing significant "give." Moderate hip flexion and thigh abduction with minimal hip external rotation is the optimal lithotomy position to prevent this injury.

Postoperative gluteal pain and perineal anesthesia from pudendal neuropathy may occur if the nerve is inadvertently incorporated into a suture line. Reexploration is often necessary to provide relief by releasing the entrapped nerve.

Neurologic injury following gynecologic surgery cannot be eliminated, but its incidence may be decreased by careful patient positioning, careful placement of retractor blades, limiting excisions where possible, and obtaining adequate exposure of the surgical field.

Commentary

Neurologic injury following obstetrical labor and delivery occurs infrequently. Among 6048 women who delivered a live-born child between July 1997 and June 1998, 56 (0.92%) experienced a new nerve injury confirmed by examination (Wong CA, et al. Obstet Gynecol. 2003;101:279-288). Most commonly, mononeuropathy of the lateral femoral cutaneous (n = 24) or femoral (n = 22) nerve was seen, followed by L4, L5, or S1 radiculopathy (n = 5), obturator, common peroneal or lumbosacral plexopathy (n = 3 each), and sciatic neuropathy (n = 2). Recovery occurred in a median of 2 months but ranged from 1 week to more than 18 months. Nulliparity and protracted second stage of labor with prolonged pushing in the semi-Fowler-lithotomy position were found, by logistic regression analysis, to be associated with nerve injury. Regional anesthesia, assisted vaginal delivery, newborn weight, pre-pregnancy basal metabolic index, fetal presentation (cephalad or otherwise), gestational period, and weight gain were not significant risk factors for injury. — Michael Rubin

Dr. Rubin, Professor of Clinical Neurology, New York Presbyterian Hospital-Cornell Campus, is Assistant Editor of Neurology Alert.