Claudio Feler

Lumbar and Sacral Nerve Root Stimulation (NRS) in the Treatment of Chronic Pain: A Novel Anatomic Approach and Neuro Stimulation Technique

Objective. The conventional technique used to stimulate the lumbar dermatomes is by stimulation of the dorsal columns of the spinal cord. Until recently, stimulation of nerve roots had not been successfully accomplished. We had performed selective nerve root cannulations for the placement of temporary catheters at cervical, thoracic, lumbar, and sacral levels in chronic pain patients using a caudad rather than craniad approach. We hypothesized that by stimulating the nerve roots we could improve paresthesia coverage in areas which cannot be covered effectively by spinal cord stimulation (SCS). To test this hypothesis, we have performed trials of nerve root stimulation (NRS) in patients who had failed SCS, or who were not candidates for SCS because their pain was otherwise inaccessible to stimulation.

Spinal Cord Stimulation for Complex Regional Pain Syndrome I [RSD]: a Retrospective Multicenter Experience from 1995 to 1998 of 101 Patients.

Objective. To evaluate effectiveness of spinal cord stimulation (SCS) applied to complex regional pain syndrome I (CRPS I). To analyze trends to focus the design of a multicenter prospective study.

Sacral neuromodulation for chronic pain conditions.

Some of the pelvic pain syndromes seem to have features of neurogenic inflammation and neuropathic pain in common. As opposed to being separate disease entities, they may represent a spectrum of clinical presentations of CRPS I of the pelvis. Sacral nerve root stimulation provides good symptomatic relief of pain and voiding dysfunction. The techniques of retrograde root stimulation may offer superior results with fewer complications and lead migrations when compared with other methods. Perhaps neuromodulation should be used earlier in the treatment paradigm for these disorders, before the potentially injurious procedures of hydrodistention, bladder installations, and cystectomies.

Application of spinal ablative techniques for the treatment of benign chronic painful conditions: history, methods, and outcomes.

Study Design. The literature on current neuroablative techniques for treating benign chronic painful conditions is comprehensively reviewed. Objective. To provide the reader with an understanding of the indications, techniques, and outcomes for the various ablative procedures used to treat chronic pain syndromes. Summary of Background Data. Neuromodulatory techniques are rapidly supplanting the traditional neuroablative procedures used to treat many types of pain. Methods. A MEDLINE search was conducted for each of the following procedures: radiofrequency facet denervation, cordotomy, myelotomy, sympathectomy, DREZotomy, rhizotomy, and ganglionectomy. In the review of each article, special attention given to the outcome, length of follow-up, complications, and number of patients. Summaries of this data were compiled to provided historical perspective, current techniques, indications, and outcomes for each of the aforementioned procedures. The outcomes cited for each procedure generally represent the data from the three or four largest series with adequate follow-up length. Results. The aforementioned procedures have 30% to 90% success rates, with success defined as at least a 50% reduction in perceived pain. These results tend to diminish with time. However, most are associated with a significant degree of morbidity and relatively high complication rates. In addition, many of the techniques lead to deafferentation pain syndromes. Conclusions. Ablative spinal techniques offer pain relief for many patients, but the use of these methods should be considered carefully in the light of available nondestructive procedures that may achieve similar goals with potentially lower morbidities.

The Appropriate Use of Neurostimulation: Avoidance and Treatment of Complications of Neurostimulation Therapies for the Treatment of Chronic Pain

The International Neuromodulation Society (INS) has determined that there is a need for guidance regarding safety and risk reduction for implantable neurostimulation devices. The INS convened an international committee of experts in the field to explore the evidence and clinical experience regarding safety, risks, and steps to risk reduction to improve outcomes.

Neurologic complications including paralysis after a medication error involving implanted intrathecal catheters

PURPOSE Long-term continuous intrathecal infusion of medications for chronic medical problems is common. We investigated the cause of a cluster of severe neurologic complications in patients with intrathecal catheters. METHODS We performed an epidemiologic cohort study of patients who had intrathecal catheters in place in one neurosurgical practice, to assess the presence of new neurologic complications and associated risk factors. RESULTS The practice included 61 patients who received pain medication through implanted intrathecal catheter pumps, 19 of whom were treated with morphine, either alone or in combination with other medications. None of the 42 patients whose drug regimen did not include morphine developed a complication, whereas 8 of 13 patients who received morphine in refills of their pumps during one 4-week period experienced neurologic complications. Three persons underwent laminectomy for sterile abscesses and were left with new paralysis or leg weakness. Testing of two stock bottles from the involved pharmacy, both labeled as containing pure morphine, revealed the presence of methadone in addition to morphine. One of these bottles also contained trace ethanol. A sample of medication aspirated from the pump of a patient prescribed morphine from the same pharmacy was also found to have contained methadone and methanol. CONCLUSIONS A variety of severe neurologic complications was associated with inadvertent administration of methadone, and perhaps other unintended substances, by means of implanted intrathecal catheters to a group of patients. Medical errors in an outpatient pharmacy led to this outbreak.

The safety, tolerability, and pharmacokinetics of fosphenytoin after intramuscular and intravenous administration in neurosurgery patients.

Study Objective. To evaluate the safety, tolerability, and pharmacokinetic profile of fosphenytoin, a water‐soluble phenytoin prodrug, after intramuscular and intravenous administration.

The appropriate use of neurostimulation: New and evolving neurostimulation therapies and applicable treatment for chronic pain and selected disease states

The International Neuromodulation Society (INS) has determined that there is a need to provide an expert consensus that defines the appropriate use of neuromodulation technologies for appropriate patients. The Neuromodulation Appropriateness Consensus Committee (NACC) was formed to give guidance to current practice and insight into future developments.

C1‐C2 Sublaminar Insertion of Paddle Leads for the Management of Chronic Painful Conditions of the Upper Extremity

While spinal cord stimulation has commonly been carried out using percutaneous leads, these devices have limitations in cervical implants due to problems with positional stimulation and lead migration. Paddle leads, by virtue of their design, are more stable in their apposition to the neural elements; however, mid and lower cervical insertions have been associated with both acute and subacute spinal cord injuries. These complications are likely related to limitations in canal diameter, as paddle leads occupy a greater volume than percutaneous leads. At C1‐C2, the space around the spinal cord is more generous, and thus allows greater room for insertion of leads. We report a series of patients treated with a technique for the implantation of a C1‐C2 paddle electrode that capitalizes on this anatomy while still meeting the need for paresthetic overlap in patients with upper extremity pain syndromes. While the technique is not novel, it has not yet been popularized ( 1 ). This paper is presented to increase implanters’ awareness of the method, its safety and utility. Twenty consecutive patients with neuropathic pain syndromes of the upper extremity were implanted using this technique. Surgical implantation of leads was done under a general anesthetic. An upper cervical incision was used, and after performing minimal laminotomies at C1 and C2, the lead was passed rostro‐caudally under direct visualization beneath the lamina. Paresthetic overlap of pain segments was achieved in all but one patient. Pre and postoperative VAS scores were compared to evaluate effectiveness of treatment. Eighteen of 20 patients reported a significant benefit from stimulation, with an average of 63 percent reduction in pain scores. The only complication was a malpositioned lead that required reoperation to adjust placement. No patient suffered neurologic sequelae as a result of this procedure. We have found C1‐C2 sublaminar insertions of paddle leads to be a safe and effective way of treating neuropathic pain phenomenon involving the upper extremity. To further assess the relative benefit over percutaneous leads, a prospective trial would be required.

Effect of Acute Phase Response on Phenytoin Metabolism in Neurotrauma Patients

The purpose of this prospective study was to correlate measures of the acute phase response, associated therapeutic interventions, and other clinical variables with the process of altered drug metabolism previously observed in patients with severe neurotrauma. Nine patients with severe head injury (Glasgow Coma Scale ≤ 8) requiring intravenous phenytoin were included in the study. A loading dose of phenytoin was followed by daily maintenance doses. Serial blood samples were taken after the loading dose and every even‐numbered study day for 10 to 14 days for measurement of total and unbound concentrations of phenytoin, interleukin‐1 β, interleukin‐6 (IL‐6), tumor necrosis factor α, α1‐acid‐glycoprotein, C‐reactive protein, and albumin. Time‐invariant and time‐variant Michaelis‐Menten models were fit to the phenytoin concentration—time data. Protein intake was closely monitored. The mean (± SEM) unbound fraction of phenytoin increased from 0.17 ± 0.02 on day 1 to 0.24 ± 0.04 on day 10 (P < 0.05). The time‐variant model was superior in describing the concentration—time data of unbound phenytoin in eight of nine patients. Mean (± SEM) pharmacokinetic parameter estimates for unbound phenytoin were: VmaxΔ = 605 ± 92 mg/day, VmaxB = 149 ± 26.3 mg/day, kind = 0.013 ± 0.004 hr−1. Interleukin‐6 was the only cytokine with significant concentration changes over time; it was inversely correlated with Vmax,t. Peak concentrations of interleukin‐6 also proved to be inversely correlated with VmaxB. The daily amount of protein administered was significantly correlated with Vmax,t. Significant alterations in the metabolism of phenytoin occur after severe neurotrauma. The etiology of these changes is probably multifaceted. These results suggest that low initial phenytoin Vmax may be explained by the presence of interleukin‐6. An increase in oxidative metabolism that correlated with nutritional protein administration was observed later in these patients.