An update on noninvasive neuromodulation in the treatment of patients with prolonged disorders of consciousness

BACKGROUND

With the improvement of emergency techniques, the survival rate of patients with severe brain injury has increased. However, this has also led to an annual increase in the number of patients with prolonged disorders of consciousness (pDoC). Hence, recovery of consciousness is an important part of treatment. With advancing techniques, noninvasive neuromodulation seems a promising intervention. The objective of this review was to summarize the latest techniques and provide the basis for protocols of noninvasive neuromodulations in pDoC.

METHODS

This review summarized the advances in noninvasive neuromodulation in the treatment of pDoC in the last 5 years.

RESULTS

Variable techniques of neuromodulation are used in pDoC. Transcranial ultrasonic stimulation (TUS) and transcutaneous auricular vagus nerve stimulation (taVNS) are very new techniques, while transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are still the hotspots in pDoC. Median nerve electrical stimulation (MNS) has received little attention in the last 5 years.

CONCLUSIONS

Noninvasive neuromodulation is a valuable and promising technique to treat pDoC. Further studies are needed to determine a unified stimulus protocol to achieve optimal effects as well as safety.

Interventional procedures and future drug therapy for hypertension

Hypertension management poses a major challenge to clinicians globally once non-drug (lifestyle) measures have failed to control blood pressure (BP). Although drug treatment strategies to lower BP are well described, poor control rates of hypertension, even in the first world, suggest that more needs to be done to surmount the problem. A major issue is non-adherence to antihypertensive drugs, which is caused in part by drug intolerance due to side effects. More effective antihypertensive drugs are therefore required which have excellent tolerability and safety profiles in addition to being efficacious. For those patients who either do not tolerate or wish to take medication for hypertension or in whom BP control is not attained despite multiple antihypertensives, a novel class of interventional procedures to manage hypertension has emerged. While most of these target various aspects of the sympathetic nervous system regulation of BP, an additional procedure is now available, which addresses mechanical aspects of the circulation. Most of these new devices are supported by early and encouraging evidence for both safety and efficacy, although it is clear that more rigorous randomized controlled trial data will be essential before any of the technologies can be adopted as a standard of care.

Technology for Peripheral Nerve Stimulation

Peripheral nerve stimulation (PNS) has been in use for over 50 years to treat patients suffering from chronic pain who have failed conservative treatments. Despite this long history, the devices being used have changed very little. In fact, current PNS technology was developed specifically for spinal cord stimulation. The use of technology developed for other applications in PNS has led to an unnecessary number of device complications and the limited adoption of this promising therapy. The following chapter provides an overview of PNS technology throughout the years, outlining both the benefits and limitations. We will briefly explore the electrophysiology of PNS stimulation, with an emphasis on technology and indication-specific devices. Finally, design and technical requirements of an ideal PNS device will be discussed.

The future of peripheral nerve stimulation

The field of peripheral nerve stimulation (PNS) is now experiencing a phase of rapid growth in number of patients, number of implanters, number of indications, and procedure types. This, however, appears to be only a beginning of major developments that could revolutionize the field of PNS. It is expected that the progress in PNS will continue simultaneously in several directions as new indications, new stimulation targets and new device designs evolve in the foreseeable future. Responding to a major need for safe and effective pain treatments and following a general trend toward less-invasive and nondestructive interventions, PNS has the potential of becoming a premier pain-relieving modality that will be used instead of or in combination with existing more established approaches such as spinal cord stimulation and pharmacological pain control. Recent technological advancements are cause for considerable optimism regarding the development of PNS and are likely to be a beginning of a major overhaul in our perception of PNS approaches. Expanding the number of applications will without question strengthen the field of PNS. The turning point, however, will not occur until sufficient scientific evidence is gathered to unequivocally prove its safety, clinical efficacy and cost-effectiveness, and when PNS applications become officially endorsed through regulatory approval of each indication. Such changes will allow implanters to use approved devices for approved indications--instead of the contemporary 'off-label' use--and at the same time give device manufacturers a chance to market these devices and support education on their appropriate use.

Peripheral nerve stimulation for fibromyalgia

Fibromyalgia is a condition marked by widespread chronic pain, accompanied by a variety of other symptoms, including sleep and fatigue disorders, headaches, disorders of the autonomic nervous system, as well as cognitive and psychiatric symptoms. It occurs predominantly in women and is often associated with other systemic or autoimmune diseases. Despite its serious socio economical burden, the treatment options remain poor. In this chapter, the authors discuss the possibilities of using greater occipital nerve stimulation as a treatment for fibromyalgia, based on available clinical studies. Greater occipital nerve stimulation has already been used successfully to treat occipital neuralgia and various primary headache syndromes. Testable hypothetical working mechanisms are proposed to explain the surprising effect of this treatment on widespread bodily pain.

Sacral nerve modulation in overactive bladder

This article represents a general overview of therapies for urinary urgency, frequency, and overactive bladder, with specific emphasis on sacral neuromodulation. The history of sacral neuromodulation is discussed along with an update of the current literature. Future directions for neuromodulation of the pelvic floor also are discussed.

Outcome of transcutaneous electrical nerve stimulation in chronic pain: short-term results of a double-blind, randomised, placebo-controlled trial

The aim of this study was to test the efficacy of shortterm transcutaneous electrical nerve stimulation (TENS) treatment in chronic pain with respect to pain intensity and patients’ satisfaction with treatment results. We therefore performed a randomised controlled trial comparing TENS and sham TENS. Patients, researchers and therapists were blinded for treatment allocation. One hundred and sixty-three patients with chronic pain referred to the Pain Centre entered the study. Conventional TENS and sham TENS were applied in the segments of pain, for a period of ten days. Outcome measures were pain intensity (visual analogue scale) and patients’ satisfaction with treatment result (yes or no). The proportions of patients satisfied with treatment result differed significantly for TENS compared to sham TENS (58 and 42.7% respectively, x²=3.8, p=0.05). However, no differences in pain intensity were found for patients treated with TENS or sham TENS. Only for patients satisfied with treatment results pain intensity gradually decrease equally both for TENS and sham TENS with repeated treatment application.

Intraoperative Motor Evoked Potential Monitoring: Overview and Update

Amidst controversy about methodology and safety, intraoperative neurophysiology has entered a new era of increasingly routine transcranial and direct electrical brain stimulation for motor evoked potential (MEP) monitoring. Based on literature review and illustrative clinical experience, this tutorial aims to present a balanced overview for experienced practitioners, surgeons and anesthesiologists as well as those new to the field. It details the physiologic basis, indications and methodology of current MEP monitoring techniques, evaluates their safety, explores interpretive controversies and outlines some applications and results, including aortic aneurysm, intramedullary spinal cord tumor, spinal deformity, posterior fossa tumor, intracranial aneurysm and peri-rolandic brain surgeries. The many advances in motor system assessment achieved in the last two decades undoubtedly improve monitoring efficacy without unduly compromising safety. Future studies and experience will likely clarify existing controversies and bring further advances.

Transcutaneous electrical nerve stimulation for the treatment of chronic low back pain: a systematic review

STUDY DESIGN

Systematic review.

OBJECTIVE

To determine the effectiveness of transcutaneous electrical nerve stimulation (TENS) in the management of chronic LBP.

SUMMARY OF BACKGROUND DATA

Chronic low back pain (LBP) affects a significant proportion of the population. TENS was introduced more than 30 years ago as an adjunct to pharmacologic pain management. However, despite its widespread use, the usefulness of TENS in chronic LBP is still controversial.

METHODS

We searched MEDLINE, EMBASE, PEDro, and the Cochrane Central Register of Controlled Trials (Issue 2, 2005), up to April 1, 2005. Only randomized controlled clinical trials (RCTs) evaluating the effect of TENS on chronic LBP were included. Two reviewers independently selected trials and extracted data using predetermined forms. Heterogeneity was tested with Cochrane's Q test. A fixed effect model was used throughout for calculating continuous variables, except where heterogeneity existed, in which case a random effects model was used. Results are presented as weighted mean differences with 95% confidence intervals (95% CI), where the difference between the treated and control groups was weighted by the inverse of the variance. Standardized mean differences were calculated by dividing the difference between the treated and control by the baseline variance. Standardized mean differences were used when different scales were used to measure the same concept. Dichotomous outcomes were analyzed with odds ratios.

RESULTS

Two RCTs (175 patients) were included. They differed with respect to study design, methodologic quality, inclusion and exclusion criteria, characteristics of TENS application, treatment schedule, cointerventions, and measured outcomes. In one RCT, TENS produced significantly greater pain relief than the placebo control. However, in the other RCT, no statistically significant differences between treatment and control groups were shown for multiple outcome measures. Preplanned subgroup analyses, intended to examine the impact of different stimulation parameters, sites of TENS application, treatment durations, and baseline patient characteristics were not possible because of the small number of included trials.

CONCLUSIONS

Evidence for the efficacy of TENS as an isolated intervention in the management of chronic LBP is limited and inconsistent. Larger, multicenter, RCTs are needed to better resolve its role in this condition. Increased attention should be given to the risks and benefits of long-term use, which more appropriately addresses the realities of managing chronic low back pain.

Devices in the treatment of epilepsy

The goal of the treatment of epilepsy is to eliminate seizures while causing no side effects. For persons whose seizures are refractory, epilepsy surgery may be an option. In addition, these patients may benefit from the vagus nerve stimulator (VNS), the first device approved for the treatment of refractory epilepsy. Although VNS was the first to be approved, investigators have been interested in the effectiveness of stimulating other brain regions: the cerebellum, thalamus, subthalamic nucleus, and locus coeruleus are a few examples. These studies have produced mixed results. As our understanding of the underlying mechanisms of epilepsy grows, it is likely that we will design better and more effective devices for the treatment of epilepsy.

Neuroprostheses for grasping

In recent years a number of neuroprostheses have been developed and used to assist stroke and spinal cord injured subjects to restore or improve grasping function. These neuroprostheses clearly demonstrated that the targeted group of subjects can significantly benefit from this technology and that functional electrical stimulation (FES) is a viable method for restoring or improving grasping function. In this article the FES technology is briefly explained and some of the better known neuroprostheses for grasping are discussed. Furthermore, a typical population of subjects that can benefit from this technology is indicated as well as the methodology to select and train these subjects to apply the neuroprosthesis in daily living activities. This article also provides a brief summary of the achieved results with the existing neuroprostheses for grasping and discusses some of the challenges this technology is currently facing.

An overview of the state of the art of noninvasive FES for independent ambulation by thoracic level paraplegics

This paper is an overview of the status of transcutaneous noninvasive (unbraced) functional electrical stimulation (FES) for independent standing and for independent ambulation by traumatic spinal-cord injured (SCI) paraplegics with complete spinal cord lesions at the thoracic level. The paper discusses aspects of patient selection, patient training, system performance, ambulation range, medical benefits and psychological benefits. It also considers problems relating to system adoption and long term system use. Furthermore, the paper discusses the various aspects of transcutaneous noninvasive FES as compared with implanted FES systems for ambulation by thoracic level SCI patients.

[Permanent percutaneous electric connection. General principles]

The Swedes for more than twenty years, and the Germans for over five years have been able to maintain inert or active prostheses with permanent percutaneous connections, thanks to the dependable and proven material and techniques of extraoral implants. The significant improvement extra-oral implants have brought about is not only in a new therapeutic approach to the treatment of important facial defects or transmission deafness; it is also because for some twenty old years now, the few millimeter wide cylinders of Titanium, the <<abutment cylinders>> affixed on the implants, have crossed the cutaneous barrier for extended periods without complications. The percutaneous abutment thus creates a permanent communication between the interior and the exterior of the organism. If the abutment, instead of simply carrying a Maxillo-Facial Prosthesis or an auditive prosthesis, is modified by placing an electric conductor inside it, the simple "percutaneous peg" will turn out to be, in a way, a "percutaneous electric plug". By adapting classic "mechanical" abutments and implants, authors have created a Permanent Percutaneous Electric Connection (PPEC) which has been successfully experimented on rabbits to record EEG. Clinical applications on humans would make it possible either to receive "bio-electrical information" coming from within the organism, or to send electrical energy into the organism. This last application opens vast perspectives of improvement both in diagnosis and therapy in many fields.

Transcutaneous electrical nerve stimulation and pain relief: an overview

Pain serves a very useful purpose. It is an important symptom for the physician when diagnosing disease. Pain is often thought of as a secondary phenomenon for some sort of bodily dysfunction. However, pain can become the principal problem and very often the only problem. Its persistence over many months ultimately leads to personal, familial and social deterioration. Chronic pain costs industry a minimum of 50 billion dollars a year. One in every 10 Americans will sooner or later suffer from chronic pain. Pain and headaches together account for 30 million yearly visits to health practitioners. Drugs have always been used as the primary source of relief from pain. These may range from aceteminophen and aspirin, to strong narcotics, such as morphine. Drugs, however, are not the final answer to pain relief. In addition to other side effects, 25 percent of patients with chronic pain become addicted, and many go through withdrawal upon discontinuing the pain relieving drugs. Transcutaneous electrical nerve stimulation (TENS) works by providing sensation which interferes with the perception of pain, sometimes providing periods of relief after the electrical sensation has stopped.