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Biomedical subjects

Richard B North

Publications and source records attributed to Richard B North.

14 recordsLinked to original sources
PubMed2006

Prevention of percutaneous electrode migration in spinal cord stimulation by a modification of the standard implantation technique.

OBJECT: Percutaneous spinal cord stimulation (SCS) electrodes are prone to migration even after scar tissue encapsulation. The authors devised a simple technique to eliminate longitudinal migration. METHODS: In 99 patients who received implanted percutaneous electrodes, less than 0.1 cm3 of silicone elastomer adhesive was injected between the anchoring sleeve and the electrode. As a result, no patient required revision surgery due to longitudinal electrode migration over a mean follow-up period of 20.2 +/- 12.3 months (range 1.8-39.7 months). Postimplant SCS-related surgical procedures were required in 15 patients (15%) for the following indications: infection in three patients, expanded area of pain in four patients, lateral migration after the sutures eroded through the supraspinous ligament in one patient, postural changes in stimulation in one patient, receiver-site pain in two patients, technical failure in three patients, and inadequate pain relief in one patient. CONCLUSIONS: With modification of the standard technique for implantation of percutaneous SCS electrodes, no longitudinal migration of electrodes was noted in this series of 99 patients.

Chronic Disease↗
PubMed2005

Spinal cord stimulation for axial low back pain: a prospective, controlled trial comparing dual with single percutaneous electrodes.

STUDY DESIGN: A prospective, controlled, clinical trial comparing single and dual percutaneous electrodes in the treatment of axial low back pain from failed back surgery syndrome. OBJECTIVES: To clarify technical requirements and test the hypothesis that placing two linear arrays in parallel, thereby doubling the number of contacts, improves outcome. SUMMARY OF BACKGROUND DATA: Technical improvements have enhanced outcomes of spinal cord stimulation for chronic axial low back pain. Dual, parallel electrodes reportedly improve these outcomes. METHODS: Acting as their own controls, 20 patients who passed screening with single, 4-contact electrodes received permanent dual, 4-contact electrodes with 7- or 10-mm intercontact distances at the same vertebral level(s). We quantified and compared the technical and clinical results of the single and dual electrodes, adjusting stimulation parameters to specific psychophysical thresholds. RESULTS: Single electrodes provided significant (P < 0.01) advantages in patient- and computer-calculated ratings of pain coverage by paresthesias and in the scaled amplitude necessary to cover the low back, compared with dual 7-mm electrodes. Slight advantages without statistical significance were observed for the single over the dual 10-mm electrodes. Amplitude requirements were significantly lower for the single electrode than for either dual electrode. At long-term follow-up, 53% of patients met the criteria for clinical success. CONCLUSIONS: While we observed disadvantages for dual electrodes in treating axial low back pain, we achieved technical success with single or dual electrodes in most patients and maintained this success clinically with dual electrodes in 53%.

Adult↗
PubMed2005

Spinal cord stimulation versus repeated lumbosacral spine surgery for chronic pain: a randomized, controlled trial.

OBJECTIVE: Persistent or recurrent radicular pain after lumbosacral spine surgery is often associated with nerve root compression and is treated by repeated operation or, as a last resort, by spinal cord stimulation (SCS). We conducted a prospective, randomized, controlled trial to test our hypothesis that SCS is more likely than reoperation to result in a successful outcome by standard measures of pain relief and treatment outcome, including subsequent use of health care resources. METHODS: For an average of 3 years postoperatively, disinterested third-party interviewers followed 50 patients selected for reoperation by standard criteria and randomized to SCS or reoperation. If the results of the randomized treatment were unsatisfactory, patients could cross over to the alternative. Success was based on self-reported pain relief and patient satisfaction. Crossover to the alternative procedure was an outcome measure. Use of analgesics, activities of daily living, and work status were self-reported. RESULTS: Among 45 patients (90%) available for follow-up, SCS was more successful than reoperation (9 of 19 patients versus 3 of 26 patients, P <0.01). Patients initially randomized to SCS were significantly less likely to cross over than were those randomized to reoperation (5 of 24 patients versus 14 of 26 patients, P=0.02). Patients randomized to reoperation required increased opiate analgesics significantly more often than those randomized to SCS (P <0.025). Other measures of activities of daily living and work status did not differ significantly. CONCLUSION: SCS is more effective than reoperation as a treatment for persistent radicular pain after lumbosacral spine surgery, and in the great majority of patients, it obviates the need for reoperation.

Adult↗
PubMed2005

Spinal cord stimulation electrode design: a prospective, randomized, controlled trial comparing percutaneous with laminectomy electrodes: part II-clinical outcomes.

OBJECTIVE: Spinal cord stimulation, in use for more than 30 years, has evolved into an easily implemented technique involving percutaneous or laminectomy electrode placement. In a randomized comparison of four-contact percutaneous and four-contact insulated laminectomy electrodes placed at the same level in the dorsal, epidural midline, quantitative measures of stimulator performance revealed significant technical advantages for the laminectomy electrodes. Our prospective, randomized, controlled trial compares clinical results in these same patients. METHODS: Impartial third parties followed our series of 24 patients with failed back surgery syndrome to gather clinical outcome data. We defined "success" as at least 50% sustained relief of pain and patient satisfaction with the result of treatment. RESULTS: At a mean follow-up of 1.9 years, 10 of 12 patients receiving the laminectomy electrode and 5 of 12 patients receiving the percutaneous electrode reported a successful outcome (P < 0.05). Follow-up at a mean of 2.9 years showed that this result was maintained in 5 of 12 patients with the laminectomy electrode and 3 of 12 with the percutaneous electrode (not statistically significant). Many patients reported improvements in most activities of daily living, and loss of function was rare. In addition, 9 patients with laminectomy electrodes and 4 with percutaneous electrodes reducted or eliminated analgesic intake (P < 0.05), and 2 returned to work. No electrode migration was observed. CONCLUSION: Laminectomy electrode placement, although more invasive than percutaneous placement, yields significantly better clinical results in patients with failed back surgery syndrome at mean 1.9 years follow-up. In our small sample, however, the statistical significance of this advantage disappeared at mean 2.9 years follow-up.

Adult↗
PubMed2005

Surgical management of spinal metastases: analysis of prognostic factors during a 10-year experience.

OBJECT: Refinement of surgical techniques, especially anterior approaches, for the management of spinal metastases has improved patient outcomes, despite the fact that a complete analysis of the prognostic factors that would inform patient selection has not been undertaken. The authors sought to identify such prognostic factors for neurological outcome and life expectancy in patients with spinal metastases. METHODS: The authors used Kaplan-Meier techniques, log-rank comparisons, and a multivariate model stratified by tumor type to identify prognostic factors for duration of ability to walk and survival in patients who underwent surgical treatment for spinal metastases during a decade when all current treatment options were available. Preoperatively, 53 (87%) of the 61 patients in the study population suffered neurological symptoms (for example, weakness) and 52 (85%) were ambulatory. Postoperatively, 59 (97%) were ambulatory. Most patients who survived 6 months (81%) remained ambulatory, as did 66% of those alive at 1.6 years. The median postoperative survival was 10 months. The risk factors for loss of ambulation were preoperative loss of ambulatory ability, recurrent or persistent disease after primary radiotherapy of the operative site, a procedure other than corpectomy, and tumor type other than breast cancer. Prognostic factors for reduced survival were surgical intervention extending over two or more spinal segments, recurrent or persistent disease after primary radiotherapy involving the operative site, diagnosis other than breast cancer, and a cervical spinal procedure. CONCLUSIONS: The results of this analysis allowed the authors to create a simple prognostic factor scoring system that can be applied to individual patients. The positive experience derived from this study supports an expanded role for the surgical treatment of metastatic spinal disease.

Adolescent↗
PubMed2003

Automated, patient-interactive, spinal cord stimulator adjustment: a randomized controlled trial.

OBJECTIVE: Programmable, multicontact, implanted stimulation devices represent an important advance in spinal cord stimulation for the management of pain. They facilitate the technical goal of covering areas of pain by stimulation-evoked paresthesiae. Adjustment after implantation requires major investments of time and effort, however, if the capabilities of these devices are to be used to full advantage. The objective of maximizing coverage should be met while using practitioners' time efficiently. METHODS: We have developed a patient-interactive, computerized system designed for greater ease and safety of operation, compared with the standard external devices used to control and adjust implanted pulse generators. The system automatically and rapidly presents to the patient the contact combinations and pulse parameters specified by the practitioner. The patient adjusts the amplitude of stimulation and then records drawings of stimulation paresthesiae (for comparison with pain drawings), followed by visual analog scale ratings for each setting. Test results are analyzed and sorted to determine the optimal settings. We compared the automated, patient-interactive system with traditional, practitioner-operated, manual programming methods in a randomized controlled trial at two study centers, with 44 patients. RESULTS: The automated, patient-interactive system yielded significantly (P < 0.0001) better technical results than did traditional manual methods, in achieving coverage of pain by stimulation paresthesiae (mean 100-point visual analog scale ratings of 70 and 46, respectively). The visual analog scale ratings were higher for automated testing for 38 patients, higher for manual testing for 0 patients, and equal (tied) for 6 patients. Multivariate analysis demonstrated that the advantage of automated testing occurred independently of practitioner experience; the advantage was significantly greater, however, for experienced patients. The rate of testing (number of settings tested per unit time) was significantly (P < 0.0001) greater for the automated system, in comparison with the rate with a human operator using traditional, manual, programming methods (mean of 0.73 settings/min versus 0.49 settings/min). The automated system also identified settings with improved estimated battery life (and corresponding anticipated cost savings). No complications were observed with automated testing; one complication (transient discomfort attributable to excessive stimulation) occurred with manual testing. CONCLUSION: Automated, patient-interactive adjustment of implanted spinal cord stimulators is significantly more effective and more efficient than traditional manual methods of adjustment. It offers not only improved clinical efficacy but also potential cost savings in extending implanted battery life. It has the additional potential advantages of standardization, quality control, and record keeping, to facilitate clinical research and patient care. It should enhance the clinical application of spinal cord stimulation for the treatment of chronic intractable pain.

Adult↗
PubMed2003

Attenuation of cerebellar tremor with implantation of an intrathecal baclofen pump: the role of gamma-aminobutyric acidergic pathways. Case report.

The authors present the case of a 49-year-old woman with disabling bilateral upper-extremity cerebellar tremor that resolved unexpectedly after placement of an intrathecal baclofen pump for lower-extremity spasticity. The tremor amplitude decreased nearly linearly with increasing intrathecal baclofen dosage, and disappeared completely at a dose of 250 microg/day. In this report the authors demonstrate the role of the gamma-aminobutyric acidergic system in the pathogenesis of cerebellar tremor, and these findings may lead to a new treatment modality for patients disabled by this manifestation of their disease.

Baclofen↗
PubMed2002

Spinal cord stimulation for chronic pain of spinal origin: a valuable long-term solution.

STUDY DESIGN: A literature review was conducted. OBJECTIVE: To review the indications and efficacy of spinal cord stimulation, particularly in reference to chronic pain of spinal origin. SUMMARY OF BACKGROUND DATA: The first spinal cord stimulation was implanted by Shealy in 1967 via a subarachnoid route. Early systems were plagued with a high rate of complications and technical problems. With the evolving technology, especially the advent of multichannel programmable systems and more precise epidural placement, the ability of spinal cord stimulation to treat various pain syndromes improved. This article reviews the literature on spinal cord stimulation from 1967 to the present. METHODS: The literature is reviewed, with a particular focus on recent studies investigating the efficacy of spinal cord stimulation for low back pain. RESULTS: Most studies are limited by the same flaws, namely, retrospective study design. At this writing, the few published randomized prospective studies have suggested that spinal cord stimulation may be superior to repeat surgery. Complication rates have declined to approximately 8%, and reoperation is necessary in approximately 4% of patients. When current percutaneous techniques are used, a lead migration rate lower than 3% may be achieved. For certain topographies, laminotomy leads may be superior, particularly with regard to low back pain. CONCLUSIONS: The ultimate efficacy of spinal cord stimulation remains to be determined, primarily because of limitations associated with the published literature. However, on the basis of the current evidence, it may represent a valuable treatment option, particularly for patients with chronic pain of predominantly neuropathic origin and topographical distribution involving the extremities. The potential treatment of other pain topographies and etiologies by spinal cord stimulation continues to be studied.

Animals↗
PubMed2002

Spinal cord stimulation electrode design: prospective, randomized, controlled trial comparing percutaneous and laminectomy electrodes-part I: technical outcomes.

OBJECTIVE: The clinical use of spinal cord stimulation for treatment of chronic intractable pain has been increasingly successful because of recent technical improvements, particularly the development of multiple-contact electrodes supported by programmable implanted pulse generators. Contemporary electrodes can be placed percutaneously in some cases and require a limited laminectomy in other cases. METHODS: We performed a prospective, randomized, controlled trial comparing two prototypical electrode designs, using a computerized system that allows direct patient interaction and quantitative measurements. A series of 24 patients with chronic lumbosacral pain syndromes first underwent testing with percutaneous four-contact electrodes and then underwent implantation, at the same spinal level, of one of two different electrode configurations; 12 patients received a new percutaneous four-contact electrode of the same design and 12 received an insulated four-contact array, which was implanted via laminectomy. RESULTS: The insulated array performed significantly (P = 0.0005-0.0047) better than the temporary percutaneous electrode for the same patients, according to all three measures tested (ratings of paresthesia coverage of pain, coverage calculated from patient drawings, and amplitudes), at the "usage" amplitude for the three standard bipoles examined. The insulated array also performed significantly (P = 0.0000-0.026) better than the permanent percutaneous electrode in terms of coverage ratings and amplitude requirements. Low back coverage ratings were significantly better for the insulated array than for the temporary percutaneous electrode, and scaled amplitudes necessary for low back coverage were significantly better for the permanent percutaneous electrode than for the temporary electrode. In comparison with the percutaneous temporary electrode, at subjectively identical stimulation intensities, the permanent insulated array required significantly lower amplitude. CONCLUSION: We can immediately infer from these technical data that the use of an insulated array, in comparison with a percutaneous electrode, would double battery life. Extended follow-up monitoring will be required to assess the extent to which the technical advantages we observed for the insulated array might be associated with improved clinical outcomes.

Electric Stimulation Therapy↗
PubMed1996

Specificity of diagnostic nerve blocks: a prospective, randomized study of sciatica due to lumbosacral spine disease.

Temporary nerve blocks using local anesthetic are employed extensively in the evaluation of pain problems, particularly lumbosacral spine disease. Their specificity and sensitivity in localizing anatomic sources of pain have never been studied formally, however, and so their diagnostic and prognostic value is questionable. There have been anecdotal reports of relief of pain by temporary blocks directed to areas of pain referral, as opposed to areas of documented underlying pathology; but there has been no study to define the frequency or magnitude of this effect. We have examined the specificity and sensitivity of a battery of local anesthetic blocks in a series of 33 patients with a chief complaint of sciatica, attributable in all cases to spinal disease (radiculopathy, with some clinical features of arthropathy). As determined by blinded patient analog ratings in randomized sequence, three different nerve blocks were significantly more effective than control lumbar subcutaneous injection of an identical volume of 3 ml of 0.5% bupivacaine (P < 0.05). Not only paraspinal lumbosacral root blocks and medial branch posterior primary ramus blocks (at or proximal to the pathology), but also sciatic nerve blocks (distal or collateral to the pathology) produced temporary relief in a majority of patients. This confirmed the study hypothesis that false positive results are common, and specificity is low. For sciatic nerve blocks, specificity was between 24% and 36%. Patterns of responses specific to the established diagnosis of radiculopathy (i.e., root block most effective) had sensitivities between 9% and 42%. Statistical analysis of clinical and technical prognostic factors revealed that the only association with pain relief by any block were the effects of other blocks. The strongest association was between relief by sciatic nerve block and relief by medial branch posterior primary ramus (facet) block (P = 0.001, odds ratio 16.0). There were no associations between the results of blocks and clinical findings (history, physical examination, diagnostic imaging) in these patients, chosen for their homogeneous clinical presentation and absence of functional signs. Our findings indicate a limited role for uncontrolled local anesthetic blocks in the diagnostic evaluation of sciatica and referred pain syndromes in general. Negative blocks or a pattern of responses may have some predictive value, but isolated, positive blocks are non-specific. This lack of specificity may, however, be advantageous in therapeutic applications.

Adult↗
PubMed1994

Radiofrequency lumbar facet denervation: analysis of prognostic factors.

Percutaneous radiofrequency lumbar facet denervation has been in use as a treatment for intractable, mechanical low back pain for over 2 decades. A number of case series have been reported with high rates of success in selected patients; however, there has been limited objective outcome assessment, long-term follow-up, and analysis of prognostic factors. We have reviewed our experience with diagnostic lumbar facet blocks and percutaneous radiofrequency denervation at a mean follow-up interval of 3.2 years. Long-term outcome has been assessed by disinterested third party interview. Of 82 patients selected for these procedures, 56 had undergone prior low back surgery. Following diagnostic medial branch posterior primary ramus blocks, 42 reported at least 50% relief of pain and proceeded to radiofrequency denervation. Forty-five percent of patients undergoing denervation reported at least 50% relief of pain at long-term follow-up. Among the 40 patients who only underwent temporary blocks, 13% reported relief (i.e., spontaneous improvement or placebo effect) by at least 50% at long-term follow-up). By multivariate statistical analysis, patients undergoing bilateral blocks for bilateral or axial symptoms were significantly more likely to achieve temporary relief, and to proceed to permanent denervation. There was no difference, however, between the long-term results of bilateral denervation for bilateral or axial pain and those of unilateral denervation for unilateral pain. There was no significant difference in the rate of response between the 56 patients who had undergone prior lumbosacral spine surgery and the 26 who had not. There were no complications from the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Automated 'pain drawing' analysis by computer-controlled, patient-interactive neurological stimulation system.

We have developed a new method for the collection and analysis of pain drawings, as part of a computer-controlled, patient-interactive system for use with implanted neurological stimulators. The system has been tested in 44 patients with permanently implanted spinal cord stimulators for the relief of chronic, intractable pain. Patients interact directly with the system, using a graphics tablet, to enter pain drawings and corresponding outlines of their perceptions of stimulation paresthesias, for different stimulating pulse parameters and electrode geometries. Image analysis software has been developed to examine these data quantitatively. This precludes the inter-rater inconsistencies reported for manual pain drawing scoring techniques. A highly significant correlation has been observed between patients' analog ratings of the overlap of pain by paresthesias and the results of our automated analysis of graphic data. This in turn has been found to correlate with clinical observations of pain relief. The contemporary implantable stimulation devices supported by our system permit non-invasive selection of stimulating anodes and cathodes from a linear array of 4 electrodes. The 50 possible electrode combinations have certain geometric features, which we have entered into a multivariate statistical analysis, to determine their relationship with the overlap of pain by paresthesias. One particular configuration (cathode(s) flanked by anode(s) above and below) is significantly better, by this measure, than all the alternatives. This is consistent with prior clinical observations that this configuration is favored by patients whose systems have been adjusted by conventional, manual methods. Pain drawing' entry and analysis by a computerized, patient-interactive system has been useful in this specialized setting and may have broader applications.

Adult↗
PubMed1991

Spinal cord stimulation for chronic, intractable pain: superiority of "multi-channel" devices.

Spinal cord stimulation has evolved over the past 20 years into an easily implemented technique, with low morbidity, for the treatment of intractable, chronic pain in properly selected patients. We report our experience with a series of 62 patients implanted between 1983 and 1987, with percutaneous and laminectomy electrodes, and with single- and "multi-channel" (programmable, multi-contact) devices. Fifty had chronic, intractable low back and leg pain ("failed back surgery syndrome," lumbar arachnoid fibrosis), five had spinal cord injuries, and seven "peripheral" pathology or stump pain. Statistical analysis of these and other patient characteristics and technical factors was undertaken to identify predictors of outcome. All patients were interviewed by a disinterested third party at a mean of 2.14 years following implantation. A majority of patients reported at least 50% sustained relief of pain and indicated that they would go through the procedure again for the same result. There was corresponding improvement in ability to perform various everyday activities, and decrease in use of analgesics. Ten of 40 failed back patients who were disabled before the procedure returned to work postoperatively. Superposition of stimulation paresthesias upon a patient's topography of pain was found to be a statistically significant predictor of successful relief of pain, by linear regression methods. Univariate and multivariate analysis of patient characteristics and technical factors as predictors of outcome demonstrated significant advantages for female patients, and for patients implanted with "multi-channel" devices. With these devices, electrode geometries with central cathode(s) flanked by rostral and caudal anode(s) were favored disproportionately. Technical improvements in implanted spinal cord stimulation devices, in particular the development of multi-contact percutaneous electrode arrays and supporting programmable electronics, have significantly improved clinical results.

Adult↗