Compound Muscle Action Potentials and Spontaneous Electromyography Can be Used to Identify and Protect the Femoral Nerve During Resection of Large Retroperitoneal Tumors

Neurophysiological Monitoring Service, University of California San Francisco, 533 Parnassus Avenue, U-491, Box 0220, San Francisco, CA 94143-0112, USA.
Annals of Surgical Oncology (Impact Factor: 3.93). 07/2008; 15(6):1594-9. DOI: 10.1245/s10434-008-9903-4
Source: PubMed


Resection of large retroperitoneal neoplasms may injure the femoral nerve, thereby causing a permanent neurological deficit. We used electrical neurophysiological monitoring to identify, map, and preserve the femoral nerve during surgical resection to reduce the risk of neurological deficit.
Seven patients with retroperitoneal neoplasms underwent eight resections. Compound muscle action potentials (CMAPs) were recorded from needle electrodes placed in the iliacus, quadriceps, and sartorius muscles. Spontaneous electromyography (EMG) was continuously monitored from the same muscle groups. A handheld monopolar stimulator was used to elicit evoked EMG responses to identify and map the course of the femoral nerve. A stimulating strength of 10 mA was used to map the nerve. The stimulation threshold was tested after neoplasm resection to predict postoperative femoral nerve function.
Electrical stimulation with CMAP recording and a stimulating strength of 10 mA successfully localized the femoral nerve in six cases. Monitoring with a stimulating threshold between 0.6 and 1.6 mA predicted postoperative femoral nerve preservation after tumor resection in four of the six cases.
Neurophysiological monitoring using CMAP and spontaneous EMG can protect the femoral nerve during resection of large retroperitoneal neoplasms.

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    • "To help identify and avoid iatrogenic injury to the ureter, ureteral stents were placed by urologists before laparotomy in 35% of resections. Intraoperative femoral nerve monitoring, which we described previously [10], was done in 11% of cases to help identify the femoral nerve and prevent postoperative disability when involvement was suspected based on the location of the tumor and/or symptoms (e.g. paresthesias, pain, weakness). "
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    ABSTRACT: Retroperitoneal tumors are often massive and can involve adjacent organs and/or vital structures, making them difficult to resect. Completeness of resection is within the surgeon's control and critical for long-term survival, particularly for malignant disease. Few studies directly address strategies for complete and safe resection of challenging retroperitoneal tumors. Fifty-six patients representing 63 cases of primary or recurrent retroperitoneal tumor resection between 2004-2009 were identified and a retrospective chart review was performed. Rates of complete resection, use of adjunct procedures, and perioperative complications were recorded. In 95% of cases, complete resection was achieved. Fifty-eight percent of these cases required en bloc multi-organ resection, and 8% required major vascular resection. Complete resection rates were higher for primary versus recurrent disease. Adjunct procedures (ureteral stents, femoral nerve monitoring, posterior laminotomy, etc.) were used in 54% of cases. Major postoperative complications occurred in 16% of cases, and one patient died (2% mortality). Complete resection of challenging retroperitoneal tumors is feasible and can be done safely with important pre- and intraoperative considerations in mind.
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