Intraoperative electrophysiological monitoring for C1-2 spinal cord stimulation.

OBJECTIVE This study is a retrospective case series involving C1-2 spinal cord stimulation in patients with complex regional pain syndrome (CRPS) under general endotracheal anesthesia. Currently, C1-2 paddle lead placement is an accepted practice, which provides effective cervical stimulation to ameliorate upper-extremity and sometimes lower-extremity symptoms experienced by patients with CRPS. However, this technique must be performed under general endotracheal anesthesia rather than in an awake or semiconscious state due to intraoperative safety concerns and patient comfort. The authors aim to provide additional data to support the following novel technique: the use of somatosensory evoked potential (SSEP) diminution data to assist with proper midline placement of C1-2 leads under general anesthesia. METHODS SSEP median nerve (MN) and posterior tibial nerve (PTN) data were collected from 6 patients undergoing placement of C1-2 leads under general anesthesia. Fluoroscopy was used as an initial guide for proper anatomical midline placement. This was followed by the activation of the spinal cord stimulator and simultaneous collection of primarily MN SSEPs as well as PTN SSEPs for physiological midline placement. Unilateral and bilateral reductions in SSEPs assisted with the correct lateralization of the lead to ensure effective postoperative coverage according to the patient's individual preoperative symptoms. RESULTS Six patients were monitored using SSEPs and repeatable, reliable MN and PTN baseline responses were obtained from all. A reduction in amplitude ranging from 5% to 87% was observed, confirming inhibition of dorsal column conduction, and an average pain relief of 63% at short-term and 64% at long-term follow-up was recorded with 6 of 6 and 5 of 6 patients responding, respectively. CONCLUSIONS Intraoperative SSEP collision study testing appears to be a safe technique to monitor placement of C1-2 paddle leads intraoperatively under general anesthesia.

Is impedance a parameter to be taken into account in spinal cord stimulation?

BACKGROUND: Over the last few decades, spinal cord stimulation (SCS) has become one of the main treatments in the therapeutic arsenal available to pain treatment units. New stimulation systems have been developed and the indications of neurostimulation have been expanded. The premises for a successful technique remain the same; good patient selection, good surgical technique, and good management of electrical parameters when programming. DESIGN: An observational report. OBJECTIVES: The primary objective of the study was to determine the relationship between changes in impedance (R) and energy requirement (E) elicited by changes in patients posture. The postures analyzed were supine (S), sitting (SI), standing (ST), and walking (W). As a second objective, the difference produced in the energy requirement when changing posture was analyzed. METHODS: A study was carried out in 70 patients with chronic intractable pain implanted with a neurostimulation system between January 2000 and March 2006. We define the perception threshold (Tp); the discomfort threshold (Td); and the therapeutic threshold (Tt). The amplitude of perception was measured in mA. With the resulting data, the therapeutic range (TR) was determined. After performing all measurements with the patient in the ST position, the neurostimulation system was shut off and the patient maintained in the other position for 5 minutes before performing the measurements. The variables R and E were compared by age groups, sex, implant duration, and the time since implant placement. Patients were divided into groups according to whether the location of the implanted electrodes was cervical or thoracic. The full analysis by age, sex, and implant duration was performed in the cervical and thoracic implant groups. RESULTS: No correlation was found between impedance and posture. When the results for R and E were analyzed by sex and age, no statistical differences were found in any of the values in any position. The analysis of time since implant greater than or less than 6 months did not find differences in the energy requirement, although there was a significant difference in the impedance value when patients were in the S position. No significant differences were observed in the analysis by age groups.

Evidence-based practice guidelines for interventional techniques in the management of chronic spinal pain.

Evidence-based practice guidelines for interventional techniques in the management of chronic spinal pain are systematically developed and professionally derived statements and recommendations that assist both physicians and patients in making decisions about appropriate health care in the diagnosis and treatment of chronic or persistent pain. The guidelines were developed utilizing an evidence-based approach to increase patient access to treatment, to improve outcomes and appropriateness of care, and to optimize cost-effectiveness. All types of relevant and published evidence and consensus were utilized. The guidelines include a discussion of their purpose, rationale, and importance, including descriptions of the patient population served, the methodology, and the pathophysiologic basis for intervention. Multiple diagnostic and therapeutic interventional techniques are included in this document. Strong evidence was shown for diagnostic facet joint blocks for the diagnosis of facet joint pain, and lumbar provocative discography for discogenic pain. Moderate evidence was shown for sacroiliac joint blocks in the diagnosis of sacroiliac joint pain, and for transforaminal epidural injections in the preoperative evaluation of patients with negative or inconclusive imaging studies, but with clinical findings of nerve root irritation. Moderate to strong evidence was shown for multiple therapeutic interventional techniques including medial branch blocks and medial branch neurotomy; caudal epidural steroid injections and transforaminal epidural steroid injections; lumbar percutaneous adhesiolysis; and implantable therapies. These guidelines do not constitute inflexible treatment recommendations. It is expected that a provider will establish a plan of care on a case-by-case basis, taking into account an individual patient's medical condition, personal needs, and preferences, and the physician's experience. Based on an individual patient's needs, treatment different from that outlined here could be warranted. These guidelines do not represent "standard of care."

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.

Catheter tip granuloma associated with sacral region intrathecal drug administration.

Spinal cord compression from catheter tip granulomatous masses following intrathecal drug administration may produce devastating permanent neurologic deficits. Some authors have advocated intrathecal catheter placement below the conus medullaris to avoid the possibility of spinal cord involvement. Multiple cases of catheter tip granulomas in the thoracolumbar region have been reported. We present a unique case of a sacral region catheter tip inflammatory mass producing permanent neurologic deficits. A 71-year-old white male with a diagnosis of failed back surgery syndrome was referred to the senior author for evaluation. After more extensive conservative therapy, including spinal cord stimulation, failed to yield adequate pain relief, he was offered implantation of an intrathecal pump for opioid administration. Excellent pain relief was achieved in the postoperative period; however, three years after implantation, he presented with progressive saddle anesthesia and bowel/bladder incontinence. Magnetic resonance imaging demonstrated a space occupying lesion associated with the catheter tip. The patient underwent emergent second level complete sacral laminectomy with partial resection of an intradural extra-axial mass and removal of intrathecal catheter. At discharge, the patient had no restoration of neurologic function. Histologic examination of the mass confirmed a sterile inflammatory mass. It has been suggested that intrathecal catheters be placed below the conus medullaris to avoid the possibility of spinal cord involvement. We present an unusual case documenting devastating permanent neurologic deficits from a catheter tip granuloma in the sacral region.

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.

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.

Spina bifida occulta as a relative contraindication for percutaneous retrograde lead insertion for sacral nerve root stimulation.

Percutaneous retrograde lead insertion for sacral nerve root stimulation is a newly described technique being applied to a variety of pain disorders. The success of the procedure rests in a defined epidural space such that there is unimpeded progression of the lead into the desired location. It is hypothesized that any condition that results in anatomic compromise of the epidural space would prevent the success of the procedure. Two patients with biopsy-proven interstitial cystitis and intractable pain were referred to the senior author for evaluation. Percutaneous retrograde lead insertion for sacral nerve root stimulation was performed on these patients in a standard fashion (1,2). Intraoperative fluoroscopy verified the diagnosis of spina bifida occulta. In one patient, implantation was completed percutaneously, but later two of the leads were found to have been placed intradurally. In another patient, repeated attempts at passing the epidural lead distal to the congenital defect were unsuccessful, and the percutaneous procedure was aborted. In conclusion, we have found that the diagnosis of spina bifida occulta, or any other condition in which the epidural space is anatomically disrupted, is a relative contraindication for this procedure. Preoperative roentograms of the lumbar spine may be helpful in avoiding technical difficulties due to this diagnosis.