533 - Treatment of Neuropathic Pain by Sensory Nerve Stimulation of the Lumb...

#533 Treatment of Neuropathic Pain by Sensory Nerve Stimulation of the Lumbar DRG Using a Percutaneous Transforaminal Approach: A Pilot Study

Oral Posters: MIS

Presented by: A. Yeung

Author(s):

A. Yeung (1)
L. Perryman (2)

(1) DISC, Phoenix, AZ, USA
(2) Stimwave Technologies, Scottsdale, AZ, USA

Abstract

Objective: The lumbar exiting nerve and dorsal root ganglion (DRG) contain small diameter sensory nerve fibers (SNFs) that convey pain information from peripheral nerves. Neuromodulation of SNFs can provide inhibitory effects on pain signals. Stimulator placement at the exiting nerve and DRG provides a targeted treatment to the pain generator. A Sensory Nerve Stimulator (SNS) can be placed transforaminally along the exiting nerve at targeted levels where painful spinal segments require inhibition. The hypotheses are:

1) A SNS placed with a needle via the transforaminal approach can reduce pain associated with Failed Back Surgery Syndrome (FBSS);

2) migration of the SNS lead is negligible with respect to pain relief.

Methods and materials: Five FBSS patients with dissatisfactory back and leg pain following fusion or lumbar discectomy were implanted with a wirelessly powered four electrode SNS lead at a single or multi-level in the axilla of the foramen containing the traversing and exiting nerve of the suspected painful level. A 14 gauge bent tip Tuohy needle was used to guide the implant under fluoroscopy from the ventral aspect of the superior articular process targeting the formen, ending medial to the exiting nerve and the DRG along the lateral aspect of the thecal sac. The angled tip of the Touhy needle was is used to direct the SNS lead to the proper position. After functional verification and reported pain relief, the needle was retracted and the lead was sutured subdermally. With the wireless SNS, the lead is completely embedded in the foramen with no percutaneous connection. Patients were sent home to continue the stimulation regimen for up to 14 days before explantation. Anterior-posterior and lateral X-rays were reviewed every four days to estimate lead migration.

Results: All five patients reported successful stimulation as defined by at least 80% reduction of pain by overall VAS and 80% paresthesia coverage of the pre-operative pain distribution. Baseline VAS scores averaged 8.5. VAS at the end of the trial period averaged 2.3. Anterior/Posterior lead migration was negligible and lateral migration of the lead ranged from 1.1 mm to 5.4 mm after 14 days.

Discussion: Four of the five patients with midline or bilateral pain received only one SNS lead placed on one side of the dorsal column. A result of using a single lead was that patients may report only partial coverage of their total pain area, suggesting that the optimal treatment may require multiple SNS leads to achieve bilateral or multi-level stimulation. All SNS leads in this study were anchored by suturing the proximal end of the tubing to the epidermis. Although a degree of lead migration was observed in all patients, the SNS electrode coverage area overcompensated for any migration effects being over 4 cm in length.

Conclusion: A wirelessly powered SNS fully implanted lead without a percutaneous connection, implantable pulse generator, or hermetically sealed RF receiver; enables direct transforaminal implantation to be successfully placed directly at the pain generator locations to achieve pain relief in FBSS patients. Wireless SNS is a practical and simplified therapy that may provide a viable treatment option for chronic low back and/or leg pain from FBSS.