Spinal Cord Stimulation

Spinal Cord Stimulation Bruce D. Nicholson, MD

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Learning Objectives Review indications for spinal cord stimulation Discuss how spinal cord stimulation works Review trial and implantation techniques Discuss successful outcomes for spinal cord stimulation

Pain Definitions  The IASP defines pain as “an unpleasant sensory and emotional experience associated with actual or perceived tissue damage or described in terms of such damage”1  Pain can be classified according to primary etiology2 – Nociceptive – Neuropathic – Mixed neuropathic and nociceptive

 All types of pain can also be classified by duration3 – Acute: less than 6 weeks – Sub-acute: between 6 weeks and 3 months – Chronic: lasting > 3-6 months

1 1: 11111111:Merskey H, Bogduk N, eds. Classification

of Chronic Pain, 2nd Ed. IASP Press Seattle, 1994

2: Cole AJ. In Low Back Pain Handbook, 2nd ed. 2003; pg 361-374 3: Koes BW, et al. Br Med J. 2006;332:1430-1434

Pain  Unpleasant sensory or emotional experience  2 types of pain: acute and chronic  Chronic: – Nociceptive • Somatic • Visceral

– Neuropathic • Central • Peripheral

– Mixed Pain • Many patients have a combination of both because disease or trauma has damaged both nerve cells and other tissues

Nociceptive Pain Somatic pain arises from bone and joint, muscle, skin, and connective tissue • Aching or throbbing • Localized

Visceral pain arises from visceral organs such as GI tract and pancreas • Tumor involvement • Obstructive

Neuropathic Pain Abnormal processing of sensory input by the peripheral or central nervous system Centrally generated pain Peripherally generated pain

Definition of Chronic Pain Frequent or constant pain that does not respond to the usual treatments Unlike acute pain, which gets better and goes away in a short time, chronic pain persists for at least several months

Indications for Neurostimulation and Intrathecal Drug Delivery Therapy

Cole AJ. In Low Back Pain Handbook, 2nd ed. 2003; pg 362. Refer to full prescribing information for Medtronic Neurostimulation Systems and Synchromed速 II and Isomed速 Drug Infusion Systems

Many Americans Suffer Approx. 300,000 back surgeries are performed in the U.S. per year to treat chronic lumbar pain with failure rates as high as 40%1 The success rate decreases significantly with each subsequent back surgery2 1: Deer T, et al. Pain Med. 2004; 5:6-13; 2: Miller B, et al. Pain Practice. 2005;5:190-202

Failed Back Syndrome  Structural causes can be identified post-operatively by CT scan, MRI, myelogram, or x-ray  If no structural cause can be found, persistent pain may be neuropathic—caused by the prolongation of the original condition and/or by the additional physical impact of invasive surgery  Patients may be candidates for neuro modulation therapy

Complex Regional Pain Syndrome (CRPS) Chronic pain syndrome characterized by severe pain with autonomic changes in the painful region Affects up to 1.2 million Americans1-3 Develops in response to a traumatic physical event (e.g., accident or medical procedure) May respond to neurostimulation therapy 1:Stanton-Hicks MD. An update interdisciplinary clinical pathway for CRPS: report of an expert panel. Pain Practice 2002; vol 2, no. 1. 1-16 2:Reflex Sympathetic Dystrophy Syndrome Association (RSDA). CRPS Treatment Guidelines. June 2006 3: RSDA. CRPS/RSD Fact Sheet, CRPS Treatment Guidelines. June 2006

Patient Selection

Pain Management Treatment Options Patients With Chronic Pain Often Seek a Myriad of Opinions and See Numerous Physicians of Varying Disciplines for Treatment

Oral Meds

Chiropractic Care

Nerve Blocks

Fixation Surgery

Corticosteroid Injections

Repeated Surgeries

Physical Therapy

De AndrĂŠs J, Van Buyten J-P. Pain Practice. 2006;6:39-45

History of Neurostimulation  1962  1967  1970s  1980  1982

First carotid sinus nerve stimulator First “dorsal column” stimulator Spinal cord stimulator widely used Medtronic introduces first programmable electrode system in the US First clinical implant of totally implantable neurostimulator

Neurostimulation Indication Neurostimulation is indicated for treatment of chronic, refractory neuropathic pain of the limbs, including unilateral or bilateral pain

Benefits of Neurostimulation Reduces or eliminates pain medications Non-destructive and less invasive than surgical alternatives Reversible – can be discontinued or surgically removed Systems are user friendly –Reprogrammable –Rechargeable

Patient control within physician-set limits Kumar K, Nath RK, Toth C. Deep Brain Stimulation for Intractable Pain: A 15-year experience. Neurosurgery. 1997

Neurostimulation: How Does it Work?  Neuromodulation is the electrical or chemical modulation of the central nervous system to manage chronic pain or improve neurologic function

Neurostimulation Therapy  Electrode is placed in epidural space  Delivers electrical stimulus to the dorsal tracts of spinal  Inhibits pain signals before they reach the brain and replaces them with a tingling sensation that covers the specific areas where pain is experienced

Spinal Cord Stimulation (SCS)  Implanted medical device therapy that delivers electrical pulses to nerves in the dorsal aspect of the spinal cord that can interfere with the transmission of pain signals to the brain and replace them with a more pleasant sensation called paresthesia

CNS Pain Management (Theory)  Gate Control Theory  Melzack and Wall, 19652 C FIBER INHIBITORY INTERNEURON

AaAb FIBERS

PROJECTION NEURON

Gate Control Theory  When sensory impulses are greater than pain impulses  “Gate” in the spinal cord closes preventing the pain signal from reaching the brain C FIBER

Sensory

INHIBITORY INTERNEURON

Gate Pain AaAb FIBERS

PROJECTION NEURON

Gate Theory and SCS  SCS system implanted in the epidural space stimulates the paininhibiting nerve fibers masking painful sensation with a tingling sensation (paresthesia) C FIBER

Sensory SCS

INHIBITORY INTERNEURON

Gate Pain AaAb FIBERS

PROJECTION NEURON

Tenets of SCS Comprehensive trial Customizable system components Optimized efficiency in programs and design Team approach to patient care

Patient Selection Considerations Patients who have neuropathic pain in a concordant anatomic distribution respond best to neurostimulation (NS) therapy Patients who have nociceptive pain in a concordant distribution respond best to Intrathecal Drug Delivery (IDD)

Pain Patterns

Patient Selection Checklist  Failure of oral/transdermal opiate use or undesirable side effects  More conservative therapies have failed  An observable pathology exists that is concordant with the pain complaint  Further surgical intervention is not indicated  No serious untreated drug habituation exists  Psychological evaluation and clearance for implantation has been obtained  No contraindications to implantation exist Cole AJ. In Low Back Pain Handbook, 2nd ed. 2003; pg 362.

Beware of Painful Patterns

Neurostimulation Trial  Pain Therapy Trial provides an opportunity to measure the effectiveness of neurostimulation without making a long-term commitment – Gauge patient response – Provide an adjustment period – Explore therapy parameters

 The goal is at least a 70% reduction in pain over a 3-5 day trial period – Patient-specific goals should include pain reduction and improved quality of life

Kumar K, et al. Neurosurgery. 2006;58:481-496

Neurostimulation Trial (cont’d)  A percutaneous lead is positioned in the epidural space on the dorsal aspect of the spinal cord at the appropriate nerve root level(s)  Electrical current from the lead generates paresthesias that can be adjusted in intensity and location to achieve the best pain coverage  Leads are attached to an external pulse generator which supplies the current  Patients can adjust stimulation to meet pain management needs

Electrode Placement

How Are Device Factors Evaluated? During a Temporary SCS Trial –External power source is used to evaluate •Pain relief •Paresthesia coverage •Power requirements •Programming needs •System requirements (IPG)

Lead Options for Various Pain Patterns

More Electrodes = More Coverage

Fewer electrodes cover smaller area (fewer nerve fiber targets)

More electrodes cover larger area (more nerve fiber targets)

Neurostimulation

Electrode

Rechargeable Generator

Neurostimulation Implantation Overview

Neurostimulation Implantation An incision is made over the spine to place lead A pocket is formed under the skin to hold the neurostimulator The lead is tunneled under the skin and connected to the neurostimulator

Impulse Transmission

Potential Issues with Neurostimulation Lead migration resulting in loss of pain relief Intermittent or uncomfortable stimulation Stimulation in the wrong location Neurological damage during procedure Risk of infection at implantation Relative contraindication for MRI North R, Kidd D, Zahurak M, et al. Neurosurgery. 1993;32:384-395.

Spinal Cord Stimulation Patient Profiles Chronic Painful Radiculopathy  79 y.o female 10 years S/P lumbar decompression and fusion for L4/5 stenosis  Failed medications and injections  No further surgery indicated  Right leg pain VAS 9/10 with ambulation; no pain at rest

Pain Diagram

Spinal Cord Stimulation Patient Profiles (cont’d) Failed Back Syndrome  44 y.o. male S/P lumbar surgery x2  Failed medications and injections  Left leg pain constant – VAS 7/10 at rest – 10/10 with activity

Pain Diagram

Summary of SCS Therapy  Position electrode in area of specific neural target  Create paresthesia that overlaps painful area(s)  Program for effectiveness, patient comfort, and energy efficiency  Reduce medication, restore function and improve quality of life

References  The National Pain Foundation (a health advocacy group for pain sufferers).  Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov 19;150(699):971–979.  Kumar K, Hunter G, Demeria D. Spinal cord stimulation in treatment of chronic benign pain: challenges in treatment planning and present status, a 22-year experience. Neurosurgery. 2006; 58:481-496.  North RB, Kidd DH, Farrokhi F, Piantadosi SA. Spinal cord stimulation versus repeated lumbosacral spine surgery for chronic pain: a randomized, controlled trial. Neurosurgery. 2005;56:98-106; discussion 106-107.  Barolat G, Oakley JC, Law JD, North RB, Ketcik B, Sharan A. Epidural spinal cord stimulation with a multiple electrode paddle lead is effective in treating intractable low back pain. Neuromodulation. 2001;4:59-66.  Van Buyten JP, Van Zundert J, Vueghs P, Vanduffel L. Efficacy of spinal cord stimulation: 10 years of experience in a pain centre in Belgium. Eur J Pain. 2001;5:299-307.  Cameron T. Safety and efficacy of spinal cord stimulation for the treatment of chronic pain: a 20-year literature review. J Neurosurg Spine. 2004;100(3):254-267.  Alò K, Yland M, Charnov J, Redko V. Multiple program spinal cord stimulation in the treatment of chronic pain: follow-up of multiple program SCS. Neuromodulation. 1999;2(4):266-272.  Taylor RS, Van Buyten JP, Buchser E. Spinal cord stimulation for chronic back and leg pain and failed back surgery syndrome: a systematic review and analysis of prognostic factors. Spine. 2005;30:152-160.  A Prospective Clinical Evaluation of a Rechargeable Implantable Pulse Generator (IPG): An Interim Analysis of Sustainability of Spinal Cord Stimulation Treatment for Chronic Lower Back Pain. Poster presented at the North American Neuromodulation Society (NANS) annual meeting; December 7, 2010; Las Vegas, NV.  Neurostimulation – A Global Strategic Business Report 10/08—Global Industry Analysis, Inc.