A database is presented of sensory responses to electrical stimulation of the dorsal neural structures at various spine levels in 106 subjects subjected to epidural spinal cord stimulation. All patients were implanted for chronic pain management and were able to perceive stimulation in the area of pain. All patients entered in this study were able to reliably report their stimulation pattern. Several patients were implanted with more than one electrode array. The electrode arrays were placed in the dorsal epidural space at levels between C-1 and L-1. The structures that were likely involved include the dorsal roots, dorsal root entry zone, dorsal horn, and dorsal columns. At the present time, exact characterization of the structure being stimulated is possible only in limited instances. Various body areas are presented with the correspondent spine levels where implanted electrodes generate paresthesias. Areas that are relatively easy targets for stimulation are the median aspect of the hand, the abdominal wall, the anterior aspect of the thigh, and the foot. Some areas are particularly difficult to cover with stimulation-induced paresthesias; these include the C-2 distribution, the neck, the low back, and the perineum.

No abstract

Vagus nerve stimulation (VNS) significantly reduces the frequency of partial seizures in refractory epilepsy patients. We examined the serious adverse events, side effects, and tolerability as they relate to the surgical implant procedure and the stimulating device. We also reviewed potential drug interactions, device output complications, and impact of the therapy on overall health status. We analyzed the first 67 patients to exist the acute phase of the EO3 VNS trial comparing high (therapeutic) VNS to low (less or noneffective) VNS. Data were collected from case report forms used at each of the four visits during the 12-week baseline and at each of the four visits during the 14-week randomized phase of the trial. No significant complications were reported as a result of the implant procedure. Serious adverse events included 1 patient who experienced direct current to the vagus nerve owing to generator malfunction resulting in left vocal cord paralysis and withdrawal of the patient from the study. No clinically significant effects on vital signs, cardiac function, or gastric function were detected. Side effects associated with VNS in the high group were hoarseness (35.5%), coughing (13.9%), and throat pain (12.9%). In the low group, only hoarseness (13.9%) and throat pain (13.9%) were associated with VNS. These effects generally wrre not considered clinically significant and occurred primarily during the stimulation pulses. No patients discontinued VNS therapy during the acute phase because of side effects associated with normal stimulation. Except for the one instance of a short circuit in the system resulting in a direct current, stimulating system complications were minor, limited to programming, unscheduled stimulation, and high lead impedance. Patients, investigators, and patient companions rated patients receiving high stimulation as more "improved" than those receiving low stimulation in regards to overall health status. Antiepileptic drug (AED) plasma concentrations were not affected by VNS. The implant procedure, stimulating system, and therapy proved safe and tolerable during the study. The high percentage (67 of 68) of patients completing the study reflects patient acceptance and tolerability of this mode of therapy.

No abstract

The potential distributions produced in the spinal cord and surrounding tissues by dorsal epidural stimulation at the midcervical, midthoracic, and low thoracic levels were calculated with the use of a volume conductor model. Stimulus thresholds of myelinated dorsal column fibers and dorsal root fibers were calculated at each level in models in which the thickness of the dorsal csf layer was varied. Calculated stimulus thresholds were compared with paresthesia thresholds obtained from measurements at the corresponding spinal levels in patients. The influences of the csf layer thickness, the contact separation in bipolar stimulation and the laterality of the electrodes on the calculated thresholds were in general agreement with the clinical data.

In order to provide a data bank to allow a more precise and effective Implementation of spinal cord stimulation, a computerized analysis of 1,375 combinations obtained from electrode arrays located in the thoracic and cervical epidural area was performed. 67 electrode arrays implanted in 34 subjects were subjected to analysis. During the Stimulation trial, all the available combinations were systematically tested and the results entered into a computerized database. The study was not meant to analyze the clinical results or the indications of epidural spinal cord stimulation. Parameters studied include position of each electrical contact as related to midline, vertebral level of each contact, distribution of stimulation-induced paresthesiae, and electrical parameters (voltage, rate, pulse width, perception threshold, discomfort threshold, usage range). Analysis of the data allow the surgeon (1) to define the characteristics of the stimulation-induced paresthesiae; (2) to define the spectrum of the electrical parameters used to stimulate the spinal cord; (3) to define the population of implanted electrode arrays/contacts; (4) to study objectively how the position of the electrodes within the spinal canal, their vertebral level and the interelectrode distance affect the electrical parameters and the stimulation-induced responses. The multifactorial systematic analysis of such a large number of combinations provides the basis for further developments in the area of electrical stimulation of the nervous system.

Objective For many medical professionals dealing with patients with persistent pain following spine surgery, the term failed back surgery syndrome (FBSS) as a diagnostic label is inadequate, misleading and potentially troublesome. It misrepresents causation. Alternative terms have been suggested but none has replaced FBSS. The International Association for the Study of Pain (IASP) published a revised classification of chronic pain, as part of the new International Classification of Diseases (ICD-11), which has been accepted by the World Health Organization (WHO). This includes the term Chronic pain after spinal surgery (CPSS), which is suggested as a replacement for FBSS. Methods This article provides arguments and rationale for a replacement definition. In order to propose a broadly applicable yet more precise and clinically informative term, an international group of experts was established. Results 14 candidate replacement terms were considered and ranked. The application of agreed criteria reduced this to a shortlist of four. A preferred option – Persistent spinal pain syndrome – was selected by a structured workshop and Delphi process. We provide rationale for using Persistent spinal pain syndrome and a schema for its incorporation into ICD-11. We propose the adoption of this term would strengthen the new ICD-11 classification. Conclusions This project is important to those in the fields of pain management, spine surgery and neuromodulation, as well as patients labelled with FBSS. Through a shift in perspective it could facilitate the application of the new ICD-11 classification and allow clearer discussion amongst medical professionals, industry, funding organisations, academia, and the legal profession.

No abstract