Spinal Cord Stimulation in Visceral Pathologies: Table 1

Peripheral and Spinal Mechanisms Involved in Electro-Acupuncture Therapy for Visceral Hypersensitivity

One of the important characteristic features of clinically significant gastrointestinal disorders is visceral hypersensitivity (VH). Pain sensitization or VH is a big challenge for clinicians and becomes a very thorny work in clinical practices; the therapeutic efficacy for VH results in limited success. A popular second therapy that is being approved for the induction of analgesia and attenuates VH with fewer side effects includes electro-acupuncture (EA). Different peripheral and spinal neurological chemicals, including neurotransmitters, neuropeptides, and cytokines, and different signaling pathways were associated with EA treatment in VH. Despite the higher acceptance of EA, the underlying mechanism still needs to be further explored. In this paper, we review the available literature to find the peripheral and spinal mechanisms involved in EA to relieve VH.

Acute recurrent bradycardia with evoked potential loss during transforaminal lumbar interbody fusion

During a transforaminal lumbar interbody fusion a patient experienced acute intermittent bradycardia with manipulation of the intervertebral body space, followed by loss of somatosensory evoked potentials that did not recover. Postoperative evaluation revealed new bilateral lower extremity sensory and motor deficits. We postulate an afferent reflex arc to explain this and other reported instances of bradycardia and asystole during transforaminal lumbar interbody fusion surgery. Awareness of the association between bradycardia during lumbar spine surgery may alert anaesthetists, surgeons and neuromonitoring teams to impending neurological harm.

Interventional options for the management of refractory cancer pain--what is the evidence?

PURPOSE

Pain is the most common symptom in cancer patients. Standard pain treatment according to the WHO three-step analgesic ladder provides effective pain management in approximately 70-90% of cancer patients. Refractory pain is defined as not responding to "standard" treatments. Interventional analgesic techniques can be used in an attempt to control refractory pain in patients in whom conventional analgesic strategies fail to provide effective pain relief or are intolerable due to severe adverse effects. This systematic review aims to provide the latest evidence on interventional refractory pain management in cancer patients.

METHODS

Systematic literature search in Cochrane, EMBASE and PubMed including reviews and randomised controlled trials (RCTs) and non-randomised controlled trials in the absence of reviews.

RESULTS

Neuraxial analgesia may play a role in refractory cancer pain management. Paravertebral blocks decrease the incidence of persistent post-surgical pain after breast cancer. Coeliac plexus blocks improve pain scores in refractory pancreatic cancer pain for up to 4 weeks after the intervention with fewer burdensome side effects as compared to opioids. Cordotomy has mainly been studied in mesothelioma, and the case series suggest possible benefit for pain at the expense of a relatively high risk of side effects.

CONCLUSIONS

Overall, very few RCTs have been conducted on interventional pain techniques. In reality, it is very difficult to undertake large controlled trials for a number of reasons. Therefore, today's best evidence for practice may be from large case series of comparable patients with careful response and toxicity evaluation and follow-up.

Treatment-Limiting Complications of Percutaneous Spinal Cord Stimulator Implants: A Review of Eight Years of Experience From an Academic Center Database

OBJECTIVE

The study aims to evaluate the long-term implant survival and complications of spinal cord stimulation (SCS) leading to surgical revision or explant in patients treated for chronic noncancer pain.

MATERIALS AND METHODS

This is a retrospective study of all patients who underwent a percutaneous spinal cord stimulation trial followed by implant in an academic Pain Medicine division by four practitioners from 2007 to 2013, with follow-up data through April 2014.

RESULTS

A total of 345 patients were considered candidates for dorsal column stimulation and underwent a trial. Two hundred thirty-four patients were implanted with an implant-to-trial ratio of 67-86% across various chronic pain entities (postlaminectomy syndrome, complex regional pain syndrome, small-fiber peripheral neuropathy, abdominal/pelvic pain, nonsurgical candidates with lumbosacral neuropathy, and neuropathic pain not otherwise specified), with the exception of nonsurgical candidates with lumbosacral neuropathy who had an implant ratio of 43%. The complication rate was 34.6%, with the hardware related being the most common reason, comprising 74.1% of all complications. The revision and explant rates were 23.9% each. The most common reason for explant was loss of therapeutic effect (41.1%).

CONCLUSIONS

SCS is an effective treatment for chronic noncancer pain. It is a minimally invasive procedure, safe, and with good long-term outcomes. However, the surgical revision and explant rates are relatively high. As the use of SCS continues to grow, research into the causes of and risk factors for SCS-related complications is paramount to decrease complication rates in the future.

Is the introduction of another variable to the strength-duration curve necessary in neurostimulation?

INTRODUCTION

Neurostimulation is the process and technology derived from the application of electricity with different parameters to activate or inhibit nerve pathways. Pulse width (Pw) is the duration of each electrical impulse and, along with amplitude (I), determines the total energy charge of the stimulation.

OBJECTIVES

The aim of the study was to test Pw values to find the most adequate pulse widths in rechargeable systems to obtain the largest coverage of the painful area, the most comfortable paresthesia, and the greatest patient satisfaction.

MATERIAL AND METHODS

A study of the parameters was performed, varying Pw while maintaining a fixed frequency at 50 Hz. Data on perception threshold (Tp ), discomfort threshold (Td ), and therapeutic threshold (Tt ) were recorded, applying 14 increasing Pw values ranging from 50 µsec to 1000 µsec. Lastly, the behavior of the therapeutic range (TR), the coverage of the painful area, the subjective patient perception of paresthesia, and the degree of patient satisfaction were assessed.

RESULTS

The findings after analyzing the different thresholds were as follows: When varying the Pw, the differences obtained at each threshold (Tp , Tt , and Td ) were statistically significant (p < 0.05). The differences among the resulting Tp values and among the resulting Tt values were statistically significant when varying Pw from 50 up to 600 µsec (p < 0.05). For Pw levels 600 µsec and up, no differences were observed in these thresholds. In the case of Td , significant differences existed as Pw increased from 50 to 700 µsec (p ≤ 0.05). The coverage increased in a statistically significant way (p < 0.05) from Pw values of 50 µsec to 300 µsec. Good or very good subjective perception was shown at about Pw 300 µsec.

CONCLUSIONS

The patient paresthesia coverage was introduced as an extra variable in the chronaxie-rheobase curve, allowing the adjustment of Pw values for optimal programming. The coverage of the patient against the current chronaxie-rheobase formula will be represented on three axes; an extra axis (z) will appear, multiplying each combination of Pw value and amplitude by the percentage of coverage corresponding to those values. Using this new comparison of chronaxie-rheobase curve vs. coverage, maximum Pw values will be obtained different from those obtained by classic methods.

Peripheral neuromodulation and headaches: history, clinical approach, and considerations on underlying mechanisms

Implantable peripheral neurostimulation was introduced in 1969 as a potential treatment for certain neuropathic pain syndromes, primarily involving the limbs. While a few early studies included implants for occipital neuralgia, serious interest in its potential as a treatment for head pain came only after our 1999 report of positive findings in a series of patients with occipital neuralgia. Subsequent investigators confirmed these initial findings, and then extended the application to patients with various primary headache disorders, including migraine. While most found a therapeutic response, the degree of that response varied significantly, and analysis suggests that the issue of paresthesia concordancy may be central, both in explaining the data, as well as providing direction for future endeavors. Therefore, while at present peripheral neurostimulation is gaining increasing acceptance as a treatment for chronic headaches, the precise clinical indications and procedures, as well as the underlying neurophysiological mechanisms, are still being worked out.

Combined occipital and supraorbital neurostimulation for the treatment of chronic migraine headaches: Initial experience

A novel approach to the treatment of chronic migraine headaches based on neurostimulation of both occipital and supraorbital nerves was developed and reduced to clinical practice in a series of patients with headaches unresponsive to currently available therapies. Following positive trials, seven patients with chronic migraine and refractory chronic migraine headaches had permanent combined occipital nerve–supraorbital nerve neurostimulation systems implanted. The relative responses to two stimulation programs were evaluated: one that stimulated only the occipital leads and one that stimulated both the occipital and supraorbital leads together. With follow-up ranging from 1 to 35 months all patients reported a full therapeutic response but only to combined supraorbital–occipital neurostimulation. Occipital nerve stimulation alone provided a markedly inferior and inadequate response. Combined occipital nerve–supraorbital nerve neurostimulation systems may provide effective treatment for patients with chronic migraine and refractory chronic migraine headaches. For patients with chronic migraine headaches the response to combined systems appears to be substantially better than occipital nerve stimulation alone.

Neuromodulation of thoracic intraspinal visceroreceptive transmission by electrical stimulation of spinal dorsal column and somatic afferents in rats

Clinical studies have shown that neuromodulation therapies, such as spinal cord stimulation (SCS) and transcutaneous electrical nerve stimulation (TENS), reduce symptoms of chronic neuropathic and visceral pain. The neural mechanisms underlying SCS and TENS therapy are poorly understood. The present study was designed to compare the effects of SCS and TENS on spinal neuronal responses to noxious stimuli applied to the heart and esophagus. Direct stimulation of an intercostal nerve (ICNS) was used to simulate the effects of TENS. Extracellular potentials of left thoracic (T3) spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated male rats. SCS (50 Hz, 0.2 ms, 3-5 minutes) at a clinical relevant intensity (90% of motor threshold) was applied on the C1-C2 or C8-T1 ipsilateral spinal segments. Intercostal nerve stimulation (ICNS) at T3 spinal level was performed using the same parameters as SCS. Intrapericardial injection of bradykinin (IB, 10 microg/mL, 0.2 mL, 1 minute) was used as the noxious cardiac stimulus. Noxious thoracic esophageal distension (ED, 0.4 mL, 20 seconds) was produced by water inflation of a latex balloon. C1-C2 SCS suppressed excitatory responses of 16/22 T3 spinal neurons to IB and 25/30 neurons to ED. C8-T1 SCS suppressed excitatory responses of 10/15 spinal neurons to IB and 17/23 neurons to ED. ICNS suppressed excitatory responses of 9/12 spinal neurons to IB and 17/22 neurons to ED. These data showed that SCS and ICNS modulated excitatory responses of T3 spinal neurons to noxious stimulation of the heart and esophagus.

PERSPECTIVE

Neuromodulation of noxious cardiac and esophageal inputs onto thoracic spinal neurons by spinal cord and intercostal nerves stimulation observed in the present study may help account for therapeutic effects on thoracic visceral pain by activating the spinal dorsal column or somatic afferents.

Pain in chronic pancreatitis and pancreatic cancer

Chronic, debilitating abdominal pain is arguably the most important component of chronic pancreatitis, leading to significant morbidity and disability. Attempting to treat this pain, which is too often unsuccessful, is a frustrating experience for physician and patient. Multiple studies to improve understanding of the pathophysiology that causes pain in some patients but not in others have been performed since the most recent reviews on this topic. In addition, new treatment modalities have been developed and evaluated in this population. This review discusses new advances in neuroscience and the study of visceral pain mechanisms, as well as genetic factors that may play a role. Updates of established therapies, as well as new techniques used in addressing pain from chronic pancreatitis, are reviewed. Lastly, outcome measures, which have been highly variable in this field over the years, are addressed.

Spinal cord stimulation for relief of abdominal pain in two patients with familial Mediterranean fever

Familial Mediterranean fever is a hereditary disease characterized by recurrent attacks of fever and serosal inflammation that commonly presents as severe abdominal pain. Though colchicine remains the mainstay of treatment, a significant proportion of patients are partially responsive, unresponsive or intolerant to it. We present two such cases where spinal cord stimulation (SCS) was used to manage the paroxysmal abdominal pain associated with this disease. Abdominal visceral pain pathways and the application of SCS techniques in its management are discussed.