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Sister Ruth Kennedy of Ethiopia named Presidential Guest Speaker for 2007 Annual Meeting

From the Editor: Spinal Cord Stimulation

New Members

Spinal Cord Stimulation:
Successful Revision of Failed Laminectomy Placed Leads And Percutaneous Leads with a Current Controlled Multi-Channel Stimulator

By Mark W. Scioli, M.D.

Spinal Cord Stimulation is an advanced method of treating pain of neurogenic origin, (chronic intractable back and or leg pain) associated with peripheral neuropathy, failed back surgery, or chronic regional pain syndromes. 1, 2

Impulses produced by a generator or radiofrequency driven receiver implanted in the flank or buttock, are sent to leads placed into the epidural space. These leads may be implanted percutaneously or via a laminectomy usually between the 8th and 10th thoracic vertebra. Patients must undergo a successful “trial” placement of percutaneous leads connected to an external generator. If 50% or more relief of pain is achieved, the patient becomes a candidate for permanent lead placement either percutaneously or by laminectomy. 2, 3.

Current and voltage delivery to the leads varies by manufacturer. Advanced Bionics and ANS utilize constant current, variable voltage, while Medtronic uses constant voltage, variable current. 2 Advanced Bionics utilizes a current driven system which can automatically adapt to local scarring resulting in effective stimulation despite the natural scarring process. 2

Pain relief via spinal cord stimulation is thought to occur via several mechanisms of action, most notably by “closing the gate” leg antidromic activation of large-diameter afferent nerve fibers. 4 Activation of other neural pathways are also proposed to suppress or inhibit sensory input.

Complications of spinal cord stimulation include lead migration, infection, hematoma, spinal fluid leak, nerve injury, aberrant stimulation into unwanted dermatome, or gradual loss of pain relief due to scarring. Lead migration is most likely to occur with percutaneous leads. 3

Thus several factors can play a role in spinal cord stimulation losing its initial benefit. Loss of lead position or loss of lead contact by scarring, coupled with each manufacturer technical capability to deliver the stimulus results in loss of pain coverage or aberrant/ineffective sensations of parasthesia “Retrieving pain relief” is patients with failed dorsal column stimulators is indeed challenging. The following case reports illustrate successful pain control in 3 patients, two of whom had initially good results with percutaneous leads, who then failed; necessitating laminectomy lead placement, only to fail again. One case involves a multiply operated back that was treated with percutaneous leads which migrated. In all three cases, a current driven Precision system from Advanced Bionics was used in conjunction with laminectomy lead placement to successfully provide pain relief.

Case #1
A 35 year old male fell 24 feet resulting in a severe bilateral calcaneal fractures.  Multiple surgical procedures were performed on both feet between 1995 and 2002.  Intractable pain into both feet prevented him from being able to walk or stand greater than 30 minutes. In 2002 he underwent successful placement of a Medtronic Percutaneous Dorsal Column Stimulator but due to lead migration his pain recurred. He then underwent a laminectomy for placement of an ANS Lamitrode at T9 in 2003. Pain relief was incomplete and he developed painful shock-like sensations in his perineum and stopped using the device for the next two years. In 2006 under I.V. sedation and local anesthetic, a revision laminectomy and removal of the scarred in Lamitrode was performed. In its place an Artisan lead and Precision IPG were implanted at T­8-9 with an “awake” trial documenting excellent pain relief to both feet minus the perineal shocking sensation. His pain remains controlled with Lyrica 50mg. tid and Combunox taken intermittently.

Case #2
A 59 year old male status post 360 fusion L4 to S1 in 1998 developed intractable back and leg pain. He underwent successful implantation of a dual lead (percutaneous) ANS spinal cord stimulator in 2001. Due to lead migration in the acute post op time frame an attempt was made reposition the leads but was unsuccessful due to spinal canal anatomy. Thus he underwent a T9 laminectomy for placement of an ANS Lamitrode 3 months later. Over the next 4 years there was steady degradation in pain control as well as worsened ability to stand or walk. In 2006 he underwent revision T9 laminectomy with removal of the Lamitrode and had implanted the Artisan lead with Precision IPG from Advanced Bionics. He realized dramatic pain relief and regained his ability to stand, walk and balance without a cane or assistive device.

Case #3
A 24 year old male underwent an IDET at L5 to S1 in 2001 for painful degeneration of the disc. Over the next 3 years his pain worsened steadily resulting in a TLIFF at L5 to S1 in 2004. Within 3 months he developed an acute change in his back and leg pain and radiographs documented posterior migration of the interbody cage. An attempt was made to reposition the cage from posterior approach which failed. The cage was then removed via an anterior approach and an interbody fusion was achieved but he developed persistent back and leg pain. After a successful trial and placement of an ANS percutaneous dorsal column stimulator, he had abrupt loss of pain control. Radiographs revealed severe lead migration. He then had a T10 laminectomy with placement of an Artisan lead and Precision IPG with excellent recovery of pain control to both his back and legs. He returned to work as a fast food clerk 3 months later.

Discussion
Three patients, (2) with complex spinal surgical histories and one with  intractable lower extremity pain, all had successful pain relief from a spinal cord stimulator. Two of the three had lead migration and were converted to ANS Lamitrode which over time failed as well. The third case had ANS  percutaneous leads which migrated and in all three, successful recovery of pain relief was obtained with the Bionics Artisan lead and Precision IPG with its current driven technology.

References:

1. Shealy CN, Mortimer JT, Reswick, JB (1967) . “ Electrical inhibition of pain by stimulation of the dorsal columns: Preliminary Clinical Report” Anesth Analg 46: 489-91.

2. “Spinal Cord Stimulator.” Wikipedia, The Free Encyclopedia. 7 Feb 2007, 05: 55 UTC <http://en.wickipedia.org/w/index.php? title=Spinal_Cord_Stimulator&oldid=106251727

3. Villavicenio AT, Leveque JC, Rubin L. et al. (2000). “Laminectomy  versus Percutaneous electrode placement for spinal cord stimulation.” Neurosurgery  46 (2): 399-405.

4. Oakley JC, Prager JP (2000). “Spinal Cord Stimulation: mechanisms of action.” Spine 27: 2574-83. 

NEXT MEETING:
COS 95th Annual Meeting

September 27-29
The Peabody Hotel
Memphis, TN