New Paradigms in Spinal Cord Stimulation Steven Falowski MD
Objectives Background of SCS Mechanisms of Action Indications Equipment Placement
Introduction Spinal cord stimulation (SCS) delivers electrical current to the spinal cord Ideal for Neuropathic Pain Adjustable Non- Destructive Neuromodulatory
Indications Most Common Post-laminectomy syndrome Complex regional pain syndrome (CRPS) Ischemic limb pain Angina Other visceral/abdominal pain cervical neuritis pain spinal cord injury pain post-herpetic neuralgia neurogenic thoracic outlet syndrome
Background Initially all unipolar electrodes Set Programming Only radio-frequency (RF) driven passive receivers were available.
Background 1970 s: Pulse Generator 1980 s: Percutaneous electrode Waltz et al 1982: First percutaneous quadripolar electrode 2004: Rechargeable Battery
1980-1990 1990 Mechanism of Action Holsheimer,, Coburn, and Strujik: Distribution of the electrical fields within the spinal structures 1997- Holsheimer et al: : Effect of anode- cathode configuration on paresthesia coverage in spinal cord stimulation
Mechanism Of Action Barolat 1993: : Mapping of sensory responses Barolat 1998: : Anatomical and electrical properties of the intraspinal structures and clinical correlations
Mechanism of Action Foreman et al. 1976 Primate Studies Linderoth et al. 1992 Rat Studies At the chemical level, animal studies suggest that the SCS triggers the release of serotonin, substance P, and GABA within the dorsal horn?descending Inhibition
Mechanism of Action-Electrodes
Indications Post Laminectomy Syndrome CRPS Angina Abdominal/Visceral Pain 50% pain relief in 50-60% of the patients Maintained over several years
Post- Laminectomy Syndrome Etiology: Pain in Center Lower Lumbar Area Pain in Buttocks Radicular Pain Also included: Arachnoiditis Epidural Fibrosis Radiculitis Microinstability Recurrents Disc Herniations Infections
Stimulation of the Low Back Single vs Dual Electrode Law et al: Multiple Bipole Arrays North et al: Midline Quadripolar Electrode Tripole Electrode Steer Current Sharan 2007: : Lateral anodes increase discomfort threshold
Post- Laminectomy Syndrome Marchand et al: Pain scores reduced with SCS Prospective RCT Acted as Own Control Small Study Group
Post- Laminectomy Syndrome North et al-1991: SCS is superior to repeat surgery 50 patients Average 3 surgeries for FBSS prior to SCS 53% of patients had pain relief at 2.2 years Patient Satisfaction North et al-1995: Better outcomes with SCS Prospective RCT Repeat back surgery vs SCS Allowed Crossover
Post- Laminectomy Syndrome Turner-1995: Systematic Review of Literature 41 articles from 1966-1994 1994 50-60% of patients had greater than 50% pain relief Burchiel et al-1996: 55% Successful Stimulation Prospective Multi- Center one year trial
Post- Laminectomy Syndrome Cameron 2004-JNS: 51 studies Total of 3,700 patients SCS had a positive, symptomatic, long-term effect in cases of: refractory angina pain, severe ischemic limb pain secondary to peripheral vascular disease, peripheral neuropathic pain, and chronic low-back pain
Complex Regional Pain Syndrome Pain and swelling in a single body part Pain may start after an injury Pain will usually gradually worsen Usually affects the hands, feet, elbows or knees Two Types: Type I: May not have cause Type II: Always follows an injury
Complex Regional Pain Syndrome
Complex Regional Pain Syndrome Challenges: Pain is not well defined Difficult to cover affected area with stimulation May aggravate original pain
CRPS-Early Work Barolat et at-1989 Pain reduction in 10 of 13 patients Short follow up Kumar et al- 1997 41 month follow up of 12 patients All patients with pain relief
CRPS-More Recent Data Kemlar -1999: 78% pain relief 23 patients Kemlar- 2000: SCS vs Physical Therapy 54 Patients randomized 67% pain relief at 6 months Improved VAS scores Kemlar- 2006: Diminished effectiveness over 5 year follow up
CRPS-Limitations Difficult to cover affected area with stimulation Long- term efficacy is yet to be determined Improvement in pain scores, but not necessarily improvement in functional impairment
Angina Factors Involved EKG changes Time to Angina Exercise Capacity Recovery Time Use of Nitrates Anginal Attacks End Results Ischemia Myocardial Flow MI Arrhythmias
Angina-Use of SCS Lower cervical and upper thoracic region Continuous vs cyclical use Often use a low intensity stimulation for several hours per day for prophylactic purposes Eddicks S et al(2007): Continuous sub threshold stimulation RCT demonstrating improved functional status and symptoms Blinded
Angina-Efficacy of SCS DeJongste et al 1994: decrease in anginal attacks and nitrate consumption Treatment group as Control DiPede 2003: Immediate and long- term clinical outcome with SCS Prospective 104 pts with SCS for refractory angina Decrease anginal episodes at rest and with activity
Angina-Efficacy of SCS Vulink et al -1998: Improved pain and quality of life Hauvast et al-1998: Increased exercise duration and time to Angina Decreased Anginal Attacks Decreased use of Nitrates Decreased Ischemic episodes on EKG
Angina-ESBY Study Mannheimer et al 1998-2002: RCT: CABG vs SCS Prospective Non- Blinded Trial SCS/CABG: Both with 30% Improvement NHP scores 5 year Mortality: 27% in both groups No difference in the percentage of cardiac deaths
Angina-ESBY Study Mannheimer et al 1998-2002: Cardiac Events were similar across the groups *More Cerebrovascular events observed in CABG group* Eight in CABG group/two in SCS group Both groups had decrease in anginal attacks and decreased nitrate use No significant inter-group difference
Angina- ESBY Study Study Limitations: Limited number of patients Limited follow-up time Not Blinded
Conclusion of ESBY Study CABG and SCS appear to be equivalent methods in terms of symptom relief SCS may be a therapeutic alternative for patients with an increased risk of surgical complications
Angina-Mechanism of SCS Homogenization of myocardial blood perfusion with SCS Augustinsson et al-1995 1995: : SCS patients have improved heart muscle lactate metabolism, oxygen demand, and blood flow in the coronary sinus Hautvast et al: : No change in HR variability after 6 weeks i.e. autonomic modulation may not be the explanatory mechanism of action
Angina-Mechanism of SCS Foreman/Linderoth Linderoth: Pain Relief from direct inhibition of signal or decrease in ischemia? Decreased activity in Spinothalamic/Sympathetic Tracts in Rat Model Hautvast et al-1996: Positron emission tomography study Redistribution of myocardial flow in favor of ischemic parts of the myocardium Both at rest and after pharmacologic stress induction Demonstrated as a long- term effect of SCS
Angina The role of SCS in the management of refractory angina pectoris seems to be very promising Uniformly good results in the relief of Anginal pain shown in the literature Results maintained in long- term follow up Effects go beyond pain relief
Abdominal/Visceral Pain 20% of the population in United States has abdominal pain Many etiologies gastrointestinal genitourinary musculoskeletal nervous system Treatment modalities Cognitive- behavioral Physical Pharmacological therapies More Invasive: Celiac plexus blocks Celiac ganglia destruction
Abdominal/Visceral Pain-Initial Interest Some studies have demonstrated some localization in the spinal cord for visceral pain secondary to malignancy Hirschberg-1996 1996: : Increased Dorsal Column Activity Midline Myelotomy
Abdominal/Visceral Pain-Initial Case Reports: Ceballos et al-2000: Interest 2000: Mesenteric Ischemia Reduction in pain scores Decrease Narcotic Use Krames et al-2004: Irritable Bowel Syndrome Reduction in diarrhea Initial reduction in pain
Abdominal/Visceral Pain Khan et al-2005: Refractory Abdominal Pain Non- alcoholic pancreatitis,, abdominal wall neuromas,, post splenectomy pain All patients(9) had a significant improvement in VAS scores Decreased narcotic use Placement of the leads at the T5-7 7 level 8 month follow up
Abdominal/Visceral Pain Tiede et al: Multiple abdominal surgeries 2 patients Placed at T2 Relieved postprandial pain Decrease Narcotic Use Patients returned to work Kapural et al: Chronic visceral pelvic pain 6 females Endometriosis/Multiple Surgical Explorations >50% Pain relief Decrease opiate use Decrease VAS score 30 month follow up
Abdominal/Visceral Pain- Viscerotomes Mechanism Sympathetic and Parasympathetic Pathways The sympathetic afferents in the lower thoracic/upper lumbar spinal segments have been shown to transmit painful impulses from the viscera
Equipment
Equipment Rapidly Changing Multiple Stimulation Parameters Multiple Types of Electrodes and Combinations Increased Uses
Pulse Generators Two basic types Internal Pulse Generator Radiofrequency coupled pulse generator Rechargeable Pulse Generator Power Requirement Issues
Pulse Generators IPG: Lithium Battery Activation/Control occur through an external transcutaneous telemetry device Control by patient and physician Battery life: 2.5 to 4.5 years Outpatient surgery to replace
Pulse Generators Rechargeable Systems
SCS Model Large fibers activated near the cathode
Transverse tripolar stimulation (4 pts) Central cathode and two lateral anodes Anodes increase the discomfort threshold over the roots compared to the paresthesia threshold (thus increasing the therapeutic range) Lateral/medial steering advantage by setting different voltages of the flanking anodes Closer spacing = More effective fiber activation
Electrode Configurations - + UB GC LTS-2A LTS-4A LTS-6A 2 anodes 4 anodes 6 anodes
Tripole Paddle-Summary Similar activation ratios were obtained as with trialed percutaneous leads Lower paresthesia thresholds and energy per pulse were seen with the paddle than with the percutaneous array. Trialing with one or more percutaneous arrays can aid in determining the effectiveness of paddle arrays.
Awake versus non-awake Surgery for Placement of Spinal Cord Stimulators
Study Design A retrospective review of 291 internalization operations to determine whether first time awake surgery for placement of spinal cord stimulators is preferable to non-awake placement Electrode implantation can be performed either under monitored (local anesthetic and intravenous sedation) or under general anesthesia
Surgeries Performed BATTERY EOL FAILURE INFECTION NEW STIMULATOR REPOSITION 61% New Implantation 16% Failure 10% Repositioning of the battery or stimulator 7% EOL of the battery 6% are due to infection
Placement of Stimulator 35 30 25 # cases 20 15 10 5 0-5 2002 2003 2004 2005 2006 Year Y # No Wakeup # Wakeup
Monitoring
Failure Rate #cases 90 80 70 60 50 40 No Failure Failure Non Awake Surgical Failure Rate 16% Awake Surgical Failure Rate 31% 30 20 * 10 0 Wakeup No Wakeup * = p<.05
Repositioning #cases 90 80 70 60 50 40 30 20 No Reposition Reposition Non Awake Surgical Repositioning Rate 16% Awake Surgical Repositioning Rate 17% 10 0 Wakeup No Wakeup
Infection Non Awake Surgical Infection Rate 7% Awake Surgical Infection Rate 7% #cases 90 80 70 60 50 40 30 No Infection Infection 20 10 0 Wakeup No Wakeup
Summary Important Points: Radiographical position and motor stimulation responses to assure proper electrode positioning under general anesthesia Performed after a percutaneous trial Conclusion: Non-awake surgery is associated with fewer failure rates and therefore fewer re- operations, making it a viable alternative
SCS-Conclusions Conclusions SCS Technology is improving Equipment and stimulation parameters Reliable and safe modality Goal of neurostimulation is to reduce pain rather than to eliminate pain 50% improvement in pain relief Reduce use of pain medications Increasing amount of uses Importance of selection criteria
Thank You
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