Implantable Spinal Devices Neel Mehta, MD Director, Outpatient Pain Medicine Clinical Instructor, Department of Anesthesia New York Presbyterian Hospital Weill Cornell Medical College 1
Lunch is on the way!
Disclosures No financial disclosures to report. No off label use of products will be discussed.
Presentation Will Review Neuromodulation Spinal Cord Stimulators Intrathecal Pumps
Pain Treatment Ladder Device therapies are now considered earlier in the treatment continuum
Case HPI: 52 y/o F p/w severe low back and leg pain for 4 years. The pain is constant and described as burning, sharp and stabbing in character. Current VAS 5/10, increasing to 7/10 with activity Meds: Opana ER, Oxycodone, Amitriptyline, Lyrica PSH: Lumbar Laminectomy L4 S1 PE: +SLR b/l, b/l lumbar paravertebral tenderness, motor/sensory intact, reflexes intact Poor pain control and functional ability! Goals for pain control: Going for walks in the park, interact with 10 y/o granddaughter, reduce medications (feels sedated)
What is Spinal Cord Stimulation? Well established, reversible therapy for certain types of chronic pain Electrical energy is applied to specific regions of the epidural space in spinal cord Interrupts pain messages transmitted from spine to brain May restore some of the abnormal chemical processing present in the CNS present in chronic pain conditions 7
Spinal Cord Stimulator Percutaneously placed electrodes in the epidural space, connected to a pulse generator Stimulator leads Stimulation of electrodes interrupts pain sensation going from periphery to CNS Neurostimulator Patient has to be involved and learn how to use it
Mechanism of Action 1965 by Ron Melzak and Patrick Wall Gate Theory Mechanism most likely differs based on type of pain being treated Neuropathic pain secondary to stimulation induced suppression of central excitability Ischemic pain secondary to stimulation induced inhibition of sympathetic outflow (decrease in peripheral vasoconstriction) which increases blood flow to ischemic areas and decreases O 2 demand
Framework for the way in which SCS exerts its effect on pain.
Indications FDA has approved SCS as a tool in managing chronic, intractable pain of the trunk or limbs associated with Failed back surgery syndrome (FBSS) Intractable low back pain Upper extremity or Lower Extremity Pain Higher probability of SCS success has been associated: Postlaminectomy pain Radiculopathy/Spinal Stenosis Plexopathy Arachnoiditis Epidural Fibrosis Painful peripheral neuropathy (Diabetic, Chemo/radiation) CRPS
Favorable Patient Characteristics Success of SCS dependent on patient selection Basic selection criteria include: Radicular, not central pain Anatomically limited pain Poor response to conservative treatment for at least 6 months No untreated bleeding disorders No active systemic infection or infection at the site of implant No untreated drug addiction issues Psychologically stability Successful 3 8 day screening trial
Results Recent systemic review of 49 studies between 1981 2001 with success rate by diagnosis showed long term results of stimulation use with >6 month follow up: 57% improvement for back and leg pain 83% improvement with CRPS 67% FBSS/stump pain/peripheral neuropathy 77% in patients with ischemic limb pain 82% in patients with post herpetic neuralgia
Evidence Reduction in pain by ranges of 40 80% Reduced use of opiates Increased ability to perform activities of daily living (61%) Return to work (25%) Potential cost effectiveness for batteries lasting over one year Stimulation devices may be trialed and permanent implants can be reversed. Practical component in the patient s decision making process and assessment of efficacy.
Spinal Cord Stimulation Trial Under fluoroscopic guidance, an electrode is inserted through an epidural needle Electrode is then connected to an external generator controlled by the patient Purpose of Trial: Help clinician and patient determine whether permanent implant would be useful A successful 3-8 day screening trial of SCS 50% reduction in pain scores Improvement in functional quality 5/23/2012 15
Lead Types Type of leads used dependent upon the patient s pain generators, physician preference and ability, and co morbidities.
Transition to Permanent Trial period is 24 hours to 2 weeks based on patient response and physician preference Adequate assessment of efficacy and reduces risk of fibrosis which hinders placement of a permanent leads. Temporary leads are most often removed and replaced. Pulse generator is placed subcutaneously in a comfortable locations that is determined beforehand.
Neurostimulation Risks The most frequently reported problems following the spinal cord stimulator implant surgery include: infection, lead movement, pain at the implant site, loss of therapy effect, and therapy which did not meet the patient's expectations. Risks: epidural hemorrhage spinal fluid leakage paralysis.
SCS Newer Applications Occipital neuralgia Axial back pain Chronic abdominal pain secondary to multiple surgeries (not IBD) Chronic pancreatitis Vascular lower extremity pain and insufficiency
INTRATHECAL THERAPY
SYSTEMIC VS. SPINAL ANALGESIA
Intrathecal pain therapy Medication delivered to intrathecal fluid The device consists of a catheter and pump Battery powered (10 year) Smaller doses of medication are needed for effective pain relief because drug is delivered directly to the pain receptors
Smaller, Programmable Pumps 20 ml & 40 ml Intrathecal Catheter PTM (Patient Bolus Dose)
Physician Control of Opioids
Less dose needed, Less Side effects! Route of Administration Relative Potency (mg)* Oral Intravenous Epidural Intrathecal 300 100 20 1
Patient Selection Not received adequate relief with conventional therapies Reduce adverse effects from oral opioids such as nausea, vomiting, sedation, and constipation Decrease or eliminate use of oral analgesics Increased ability to perform activities of daily living Patient control of medication within physician set limits May be effective for patients who do not experience relief from neurostimulation therapy
Pre Implantation Trial Medications delivered to spinal canal by injection or infusion Allows assessment of pain relief and evaluation of side effects 50% reduction in pain, side effects, functional ability positive result
Risks Associated with Targeted Drug Delivery surgical procedure drug related adverse events pump or catheter problems can cause serious or fatal drug overdose or underdose, and may require corrective surgery Inflammatory masses can form at the catheter tip and result in serious neurological impairment, including paralysis
Which Therapy?
How to determine which therapy? neuropathic pain with specific anatomic distribution usually respond best to neurostimulation (NS) therapy. nociceptive pain respond best to intrathecal drug delivery (IDD). Patients who do not respond well to stimulation may be candidates for IDD therapy.
Summary for Implantable Devices Intractable pain Intolerable side effects from systemic analgesics Conservative therapies ineffective Patient s functional status declines Surgery may provide little benefit (or residual pain from surgery) Patient wants to get better!
References Coffey RJ, Owens, M, Broste, Steven K, et al. Mortality Associated with Intrathecal Opioid Drug Infusion to Treat Non-Cancer Pain: Risk Factors and Mitigation. Late breaking paper presented at: North American Neuromodulation Society 12th Annual Meeting; December 4-7; 2008; Las Vegas, NV. de Lissovoy G, Brown RE, Halpern M et al. Cost Effectiveness of Long-term Intrathecal Morphine for Pain Associated with Failed Back Surgery Syndrome. Clinical Therapeutics 1997;19(1):96 112. Deer T, Chapple I, Classen A, et al. Intrathecal drug delivery for treatment of chronic low back pain: report from the National Outcomes Registry for low back pain. Pain Med 2004;5(1):6-13. Doleys DM.Psychological factors in spinal cord stimulation therapy: brief review and discussion. Neurosurgical Focus 2006: 21(6):1-6. Doleys DM and Olson K ed. Psychological assessment and intervention in implantable pain therapies. Minneapolis: Medtronic Inc., 1996: 1-20. Follett K and Doleys D. Selection of Candidates for Intrathecal Drug Administration to Treat Chronic Pain: Considerations in Pre-implantation Trials. Minneapolis: Medtronic Inc., 2002: 1-19.
References continued Kumar K, Hunter G, Demaria D. Spinal cord stimulation in treatment of chronic benign pain: challenges in treatment planning and present status, a 22-year experience. Neurosurgery. 2006;58(3):481-496. Loeser JD and Melack R. Pain: an overview. The Lancet 1999;353(9164):1607-1609. 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(1):98-107. Medtronic Implantable Systems Performance Registry (ISPR). 2007 Annual Report. Protocol NSP0010-10000. Report date: October 2, 2008. Roberts LJ, Finch PM, Goucke CR, Price LM. Outcome of intrathecal opioids in chronic non-cancer pain. Eur J Pain. 2001;5(4):353-361. Smith T.J. and Coyne P.J. How to Use Implantable Drug Delivery Systems for Refractory Cancer Pain. J Supportive Oncology 1:1:1-4. Taylor R, Caraway D, Van Buyten JP et al. eds. Spinal Cord Stimulation: Overcoming Barriers to Successful Outcomes for the Complex Pain Patient. Minneapolis: Medtronic Inc., 2006: 1-10. 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(3):299-307.