Neuromodulation; A new Frontier for Neuroradiologists Bassem A. Georgy, M.D., North County Radiology Assistant Clinical Professor, University of California, San Diego

Consultant; DePuy Spine, Arthrocare Inc., Dfine Advisory Board; Osseon LLC, Spine Aligns Multiple pending Patents Financial Disclosure

Overview History Gate Theory Indications Implantation techniques SCS and Neuroradiology

What is Neurostimulation? Delivery of electrical impulses to the spinal cord to block pain signals transmission Induce Paresthesia Patient feels a tingling sensation in the usual area of pain Any kind of neuropathic pain refractory to other treatments and not candidate for further surgical procedures

Types of Pain Neuropathic Pain –Radiculopathy –Herpetic Neuropathy –Diabetic Neuropathy Nociceptive Pain –Discogenic pain –Facet and SI pain Mixed Pain –FBSS –Cancer pain

What is a Spinal Cord Stimulator? Electrical lead implanted in the epidural space Lead is tunneled under the skin Lead is connected to a charger that is implanted in a subcutaneous pocket Patient control the charger from outside

Types of SCS Procedures SCS trial –Subcutaneous lead implantation and outside charger Percutaneous implantation –Subcutaneous lead implantation, subcutaneous pocket for charger Surgical implantation –Laminectomy for lead implantation

Gate Control Theory -Proposed by Melzack & Wall in A non-painful stimulus that acts likes gates can block the transmission of a painful stimulus.

The Gate Control Theory There is a gate in the spinal cord that controls the flow of noxious pain signals to the brain. The theory suggests that the body can inhibit these pain signals or "close the gate" by activating certain non- noxious nerve fibers in the dorsal horn of the spinal cord. The neurostimulation system, implanted in the epidural space, stimulates these pain-inhibiting nerve fibers, masking the sensation of pain with a tingling sensation (paresthesia) Stimulate the large diameter A fibers not small C fibers

Mechanism of Action GABAergic effects Dorsal Column Stimulation Increased blood flow Neurotransmitters metabolites concentration in the CSF

Indications Failed back surgery Syndrome RSD Arachnoiditis Peripheral Neuropathy Axial pain Post herpetic Neuralgia Peripheral Vascular diseases Angina

13 Percutaneous Lead Placement Local anesthesiaLocal anesthesia Insert 14G Touhy needle into the epidural spaceInsert 14G Touhy needle into the epidural space Confirm needle location with fluoroscopy and loss of resistanceConfirm needle location with fluoroscopy and loss of resistance Introduce guidewireIntroduce guidewire Insert leadInsert lead Confirm lead location with fluoroscopyConfirm lead location with fluoroscopy 13

18 Dual Lead Placement Insert second needle one level below/contralateral to firstInsert second needle one level below/contralateral to first Place lead tips at same level or staggeredPlace lead tips at same level or staggered 18

22 Intraoperative Screening 22 Connect lead and screenerConnect lead and screener Test by trying different electrode combinations and polaritiesTest by trying different electrode combinations and polarities Goal of matching stimulation to pain patternGoal of matching stimulation to pain pattern

CURRENT STEERING Longitudinal Steering Lateral Steering

CASE STUDY 45 year-old male with bilateral leg and lower back pain (red indicates pain pattern) Implanted with dual Octrode leads and an Eon rechargeable IPG T-8

- + Stim-set 1 uses a bipole and 5.1 mA current to cover the right leg pain (light blue indicates paresthesia) 5.1 mA

4.6 mA Stim-set 1 remains running Stim-set 2 uses a guarded cathode and 4.6 mA current to capture the left calf Current needs to be steered cephalad to capture the left leg pain mA

4.6 mA mA 6.0 mA - + Stim-set 1 remains running Stim-set 2 steers current up one electrode to capture the entire left leg at 6.0 mA Patient does not like stimulation in the left calf

5.1 mA Stim-set 1 remains running Stim-set 2 focuses the 6.0 mA current by using a guarded cathode to pull stimulation out of the left calf 6.0 mA

5.1 mA 7.1 mA Stim-sets 1 and 2 remain running Stim-set 3 covers the lower back pain Now, the current levels to each stim- set need to be optimized with Active Balancing™ 6.0 mA

30 Test Stimulation Lead secured to skinLead secured to skin Allows for test stimulation of several daysAllows for test stimulation of several days Success is defined if more than 50% pain reliefSuccess is defined if more than 50% pain relief 30

Goals of the Trial Evaluation The goals of the trial evaluation period (several days) are to evaluate the effect that SCS therapy has on –pain –opioid use –function and activity levels determine the patient’s –electrical energy requirements –optimal parameter settings The goal is at least a 50% reduction in pain without intolerable side effects

32 Permanent Percutaneous Implantation 1.Successful trial 2.Percutaneous lead placement Lead anchored to supraspinous ligamentLead anchored to supraspinous ligament Retest the patientRetest the patient Extension externalizedExtension externalized 32

33 Employ local anesthetic for tunneling path Create stab wound on flank Tunneling to flank Pass extension through stab wound 33 Permanent Percutaneous Implantation

34 Permanent Percutaneous Implantation Pocket site identified and created Extension connected with lead Pocket creation for connector and excess lead 34

35 Permanent Percutaneous Implantation 35 Neurostimulator/extension connectionNeurostimulator/extension connection Implant neurostimulator in pocketImplant neurostimulator in pocket X-rays for system visualizationX-rays for system visualization Incisions closedIncisions closed Settings optimized with external programmerSettings optimized with external programmer

SCS in the IR: Things You Will Need Surgical Instruments Scalpel Bovey Suction Scissors Grabbers Retractors Suture/Closures

Sutures Non absorbable Tichron (0. 2-0) Silk Absorbable Dexon (3-0) Moncril (4-0)

SCS in the IR: Things You Will Need Programmer

Post Procedural Antibiotics Ancef 1 gm 7-10 days Post procedural pain Resume prior pain meds # to call for problems Appt. for f/u programming, wound recheck

41 Complications –Infection –Lead dislodgment –Loss of functionality –Lead fracture –Surgical revision for reduction or loss of pain relief –Interference may be caused by MRIs and other radio frequency devices 41

SCS and Interventional Radiology Can I do it ? Training –Medtronic, ANS, Advanced Bionics Reimbursement Privileges SCS clinical Service

Peripheral SCS

SCS Service Consultation Trial Remove lead Assess trial and check wound Permanent placement Check would Follow up Office, nurse (PA), support staff