Nerve monitoring augmented CT-guided cryoablation for neuropathic pain in the anterior femoral cutaneous nerve

1. Understand the anatomy of the anterior femoral cutaneous nerve.


2. Determine optimal cryoablation probe positioning.


3. Explore the utility of nerve monitoring during cryoablation.

We describe a novel technique for CT-guided cryoablation of the anterior femoral cutaneous nerve {1}. This is a 36-year-old male with myxopapillary ependymoma status post thoracic and sacral laminectomies. He developed disease recurrence requiring radiation therapy with persistent dysesthesia and neuropathic pain, particularly along the anterior left thigh, refractory to medical therapy. His pain intermittently reached 7-8/10 in severity with burning sensations, worse in the evening, and prohibitive to activities of daily living.

Clinical Findings/Procedure Details:

The patient underwent diagnostic nerve block 1.5 months prior, in which 3 cc of 0.5% bupivacaine was infiltrated along the anterior femoral cutaneous nerve. He endorsed complete pain relief for the remainder of the day. Given this response, he presented for ablation under general anesthesia. Due to proximity of the left femoral nerve, intraoperative nerve monitoring was used to increase procedural safety {2}.

The area of interest was scouted and nerve monitoring probes were applied to muscle groups above and below the femoral nerve. Under CT guidance, nerve monitoring probes were applied to the left femoral nerve fascicle above and below the area of cryoablation. Lidocaine was infiltrated and an IceSeed 1.5 90-degree probe (Boston Scientific) was advanced to the left anterior femoral cutaneous nerve. Two cycles of freeze/thaw (3 and 2 minutes respectively) were performed with continuous nerve monitoring demonstrating no functional compromise of the femoral nerve. Periodic CT images visualized the extent of the ice ball. Upon completion of the freeze/thaw cycles, the probe was removed and hemostasis was achieved with manual compression. Post-procedural nerve stimulation confirmed no injury to the femoral nerve. The patient was extubated and admitted overnight for observation.

Conclusion and/or Teaching Points:

The patient returned to clinic one week post-procedure and noted significant symptomatic improvement. His pain is dulled, now 3-4/10 with decreased frequency of onset (less than once an hour, previously 3-4 times per hour) and no nighttime episodes, which had disrupted his sleep. He has no neurological deficits in the rest of his lower extremity.

This case demonstrates the efficacy of CT-guided neurolysis via cryoablation of the anterior femoral cutaneous nerve with enhanced safety through the use of intraprocedural nerve monitoring.