Neurostimulation with the SynergyT System

Who can benefit from Neurostimulation ?

Spinal Cord Stimulation with SynergyT

Proven benefits

Patient selection

SynergyT System

Important safety information

FAQ

1. What is the appropriate clinical role of neurostimulation therapies in the management of chronic intractable pain?

Neurostimulation therapies (spinal cord stimulation and peripheral nerve stimulation) can be effective for managing pain in patients with intractable neuropathic pain. Most commonly, these patients have chronic back or leg pain associated with failed back syndrome. Other types of pain that may be managed by neurostimulation include pain associated with arachnoiditis, complex regional pain syndromes (causalgia and reflex sympathetic dystrophy [RSD]), radiculopathies and epidural fibrosis. Appropriate candidates should have failed treatment
with more conservative therapies and must meet established selection criteria for implantation of a neurostimulation system.

2. Is neurostimulation an appropriate alternative to reoperation? If so, what are the general guidelines to consider when selecting appropriate patients?

Neurostimulation has been demonstrated to provide an acceptable alternative to re-operation for patients with chronic back or leg pain.[1] Of course, there are multiple factors to consider. Appropriate candidates should meet general selection criteria for neurostimulation-there should be confirmation that the pain is of physiological origin and the patient is a surgical candidate. If neurostimulation is considered for symptomatic treatment of a patient with a surgically treatable lesion (e.g., intervertebral disc herniation), the patient should not have significant or progressive neurological deficit or dysfunction (e.g., weakness, bladder or bowel dysfunction) related to the structural lesion, nor should the spinal canal be compromised substantially by a structural abnormality (e.g., large central intervertebral disc herniation).
The patient and physician should carefully compare the relative benefits, risks, and expected outcomes of re-operation for correction of structural abnormality and implantation of a neurostimulation system for symptomatic treatment. It is important to note that placement of
a neurostimulation system does not preclude a future operation should neurological deficits develop.

[1] North, RB, et al: Spinal cord stimulation versus reoperation for the failed back surgery syndrome. A prospective, randomized study design. Stereotact Funct Neurosurg.1994;62(1-4):267-72.

3. Is a psychological evaluation a requirement for patient selection?

Psychological factors have a significant influence on many chronic pain disorders. Psychological evaluation serves several purposes. It can identify psychological "risk" factors; facilitate treatment of these risk factors; facilitate patient selection to the extent to which there
is a physiological origin of pain; and provide insight into a patient's response to a screening test or treatment. The need for psychological evaluation will vary according to the nature of the patient and the nature of the pain being treated. Psychological evaluation may be invaluable in an individual with non-cancer pain, especially if the patient's history suggests the presence of psychological factors that might complicate a good outcome.

Psychological factors that are considered exclusions for implantation include active psychosis, major uncontrolled depression or anxiety, active suicidal or homicidal behaviour, serious drug or alcohol addiction problems, and serious cognitive deficits. Other factors that may be cause for exclusion or caution include unusual pain ratings, certain personality disorders (e.g., borderline or antisocial), somatisation, litigation related to the pain disorder, lack of social support, and unrealistic outcomes expectations. In some cases, these factors can be viewed as risk factors, rather than exclusionary criteria, and might be modified through psychological intervention to promote a good outcome.

The role of the psychological evaluation is not to "rule in" or "rule out" a patient, but to identify patients in whom overall quality of life is likely to be significantly improved by a treatment plan that includes neurostimulation. The frequency with which a psychologist identifies previously unrecognised risk factors varies with the experience and expertise of the referring physician and the psychologist, but is sufficiently common to warrant psychological evaluation of most,
if not all, candidates for neuromodulation therapies.

4. Given that the psychosocial aspects of chronic pain can be the predominant factor in a patient's dysfunction, how frequently does the psychological evaluation identify a patient that is not appropriate for Medtronic Pain Therapies?

A thorough psychological evaluation will rarely reveal that an individual is not a good candidate for Medtronic Pain Therapies because of overt psychological dysfunction and distress (e.g., major depression, homicidal behaviour). Typically, such gross psychological dysfunction
is apparent to the physician who first evaluates the patient for an implantable therapy,
and psychological evaluation serves to confirm the finding.

More commonly, a psychologist may elicit from the patient information that was never volunteered to the physician (or about which the physician never inquired), revealing the presence of "risk factors." These risk factors (e.g., personality disorders, somatisation, unrealistic outcomes expectations) may complicate a good outcome and should be identified before initiating Medtronic Pain Therapies. In some instances, these factors will exclude the patient from candidacy. In other cases, risk factors can be viewed as caution signs-efforts to modify risk factors can be incorporated into the overall treatment program to make the individual a better candidate for the therapy.

The role of the psychological evaluation is not to "rule in" or "rule out" a patient, but to identify patients in whom overall quality of life is likely to be significantly improved by a treatment plan that includes Medtronic Pain Therapies. The frequency with which a psychologist identifies previously unrecognized risk factors varies with the experience and expertise of the referring physician and the psychologist, but is sufficiently common to warrant psychological evaluation of most, if not all, candidates for neurostimulation and intrathecal drug delivery.

1. Is there a limit to the spinal canal diameter below which epidural leads should not be placed? If so, what is it? How should it be determined?

There are no established guidelines regarding minimum canal diameters that permit safe implantation of a spinal catheter or electrode. Any patient being considered for implantation of
a spinal cord stimulation system should be assessed for patency of the spinal canal. This may be accomplished via the patient's history and physical examinations (e.g., a young person with no history or physical signs of spinal abnormality probably has a patent canal) or with radiographic imaging. Magnetic resonance imaging (MRI) provides a simple, non-invasive means of assessing spinal canal patency before implant.

In general, if radiographic imaging shows significant effacement of the epidural and subarachnoid space by bone, ligament, or other structure (e.g. tumor), and certainly if the spinal cord or cauda equina are compressed, then the physician's medical judgement must
be used to determine if implantation of a stimulation electrode is appropriate. In such cases, the patient may be a candidate for decompressive laminectomy with placement of a laminotomy-type spinal cord stimulation electrode. Even in the absence of frank compression of spinal cord or cauda equina, abnormalities such as spinal stenosis from degenerative spine disease can render percutaneous placement of an epidural stimulation electrode more difficult. An implanting physician should be aware of the presence of canal compromise and recognize the potential difficulty in implanting an electrode in the setting of such compromise.

2. When inserting a percutaneous or laminotomy lead into the cervical region, what is the recommended patient position-prone or lateral?

Patient positioning for placement of cervical stimulation leads varies according to the preference of the implanting physician and patient. Either prone or lateral positioning is acceptable, but percutaneous and open surgical procedures are easier, in general, when the patient is in the prone position. With either approach, care should be taken to assure that a good fluoroscopic image can be obtained (e.g., check for radio-opaque components of the operating room table), and the patient should be sufficiently comfortable to tolerate the procedure.

3. What fluoroscopy techniques should be used to avoid the incidence of undesirable paresthesia during lead implantation and test stimulation?

Fluoroscopy itself does not prevent the occurrence of undesirable paresthesia during lead implantation and test stimulation, but it facilitates good lead placement to minimise the occurrence of such problems. Most uncomfortable paresthesia locations are due to being
in the ventral epidural space, lateral in the posterior epidural space, or sub-dural. Appropriate fluoroscopic technique, contrast, and anatomic knowledge can help avoid such placement.

A key to effective use of fluoroscopy is to minimize parallax error, which causes misrepresentation of locations of the stimulation lead and anatomic landmarks. Keep the fluoroscopy machine centered over the patient and the stimulation electrode. When viewing
the AP fluoroscopy image, be sure the spinous processes are centered as close as possible between the pedicles on each side, and be sure the fluoroscopy unit is centered over the contacts of the lead. Proper centering of the fluoroscopy unit over the lead and patient facilitates placement of the lead in the proper rostro-caudal and medio-lateral location, and lessens
the likelihood of undesired stimulation results.

4. What do you do if the patient reports uncomfortable paresthesia during test stimulation?

Patients may report undesirable stimulation-induced paresthesia during test stimulation for two reasons: the stimulation is in the wrong location or the sensation itself is unpleasant.
If the paresthesia does not cover the patient's area of pain, different electrode combinations should be tested and/or different stimulation parameters (pulse width, frequency and amplitude) should be tried. If this does not correct the problem, the lead should be repositioned to achieve better coverage of the painful area. If the stimulation-induced paresthesia is in the proper location but the patient perceives the stimulation as unpleasant, different stimulation parameters (frequency, pulse width, and/or amplitude) should be tested.

1. How often does a patient need to come in to the clinic to have a neurostimulation system reprogrammed?

Therapy maintenance varies widely from patient to patient. It is important to see the patient the day following surgery because this is the most common time when changes must be made.
A week to 10 days following surgery (usually at the time of suture removal), it is important to see the patient again and reprogramme the device if necessary. During the first 2 or 3 months after implantation, fine-tuning of the system may be required as tissues heal around the stimulation lead and the patient's understanding of the nature of the stimulation matures (i.e., what it can and cannot do, how it feels). A typical programming strategy might include re-programming 2 or 3 weeks after implantation, at 6 weeks, and at 12 weeks after implantation. After 12 weeks, the patient should come into the clinic on a periodic basis.
While reprogramming may not be needed, the battery (implantable neurostimulator) should
be checked.

2. Under what conditions would it be necessary to explant a neurostimulation system?

A neurostimulation system should be removed if it presents an infection that does not respond to medical therapy (e.g., pocket infection, meningitis, epidural abscess). It may need to be explanted if the patient requests that it be removed, for example, if an acceptable therapeutic response cannot be achieved after thorough efforts to maximize the effectiveness of the pain relief. Other causes that have resulted in the explantation of a neurostimulation system include loss of pain relief, and persistent pain. A system may be replaced versus explanted in the case of tissue erosion, lead fracture, or battery depletion.

If a patient requests removal, ensure that the neurostimulator is off for at least a month before agreeing to explant the neurostimulation system. It may be possible, especially in young reflex sympathetic dystrophy (RSD) patients, that after time the symptoms have subsided to the point the neurostimulator is no longer necessary. It may be prudent, however, to leave the device in situ and turned off for up to six months before explanting, to make sure the patient's symptoms do not reappear.

1. What is the appropriate corrective action for lead migration?

Lead migration is one of the most common complications affecting spinal cord stimulation systems. It presents as a change in the topographical distribution of stimulation-induced paresthesia. Lead migration occurs more frequently in the first six weeks following placement before tissues heal around the lead. Many instances of lead migration are related to medial-lateral movement, but inadequate anchoring may allow the electrode to migrate rostro-caudally. Solid anchoring of the lead to fascia is therefore recommended. In some cases of lead migration (especially dual lead systems), re-programming the stimulation system may recapture good coverage of the painful area. If this cannot be accomplished, the leads need to be repositioned (replaced). Consideration may be given to implantation of a laminotomy-type lead, which may reduce the likelihood of recurrent migration.[1]

Limiting certain patient activities such as reaching overhead, or twisting and bending at the waist. may help minimize early migration. Post-operative anteroposterior (AP) and lateral
X-rays are useful baselines to compare with films that should be taken following the suspicion of a migrating lead.

[1] Villavicencio AT, Leveque JC, Rubin L, Bulsara K, Gorecki JP. Laminectomy versus percutaneous electrode placement for spinal cord stimulation. Neurosurgery. 2000 Feb;46(2):399-405; discussion 405-6.