Spinal cord stimulation and intrathecal baclofen therapy: combined neuromodulation for treatment of advanced complex regional pain syndrome

Transcutaneous spinal stimulation in patients with intrathecal baclofen pump delivery system: A preliminary safety study

Objective

To determine the effect of transcutaneous spinal stimulation (TSS) on an implanted intrathecal baclofen (ITB) pump in persons with traumatic spinal cord injury (SCI).

Design

Prospective clinical trial.

Participants

Five individuals with chronic traumatic SCI, >18 years of age, and an anteriorly implanted Medtronic SynchroMed™ II ITB pump delivery system.

Intervention

Transcutaneous spinal stimulation trials with cathode at T11/12, with pump interrogation before, during and after stimulation.

Results

There was no evidence of any effect of the TSS in regards to disruption of the ITB pump delivery mechanism. Communication interference with the interrogator to the pump occurred often during stimulation for log transmission most likely secondary to the electromagnetic interference from the stimulation. One individual had elevated blood pressure at the end of the trial, suspected to be unrelated to the spinal stimulation.

Conclusion

Based upon this pilot study, further TSS studies including persons with an implanted Medtronic SynchroMed™ II ITB pump can be considered when stimulating at the low thoracic spine, although communication with the programmer during the stimulation may be affected.

GABAB Receptors and Pain

A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABA_B receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABA_B receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.

Enhancing analgesic spinal cord stimulation for chronic pain with personalized immersive virtual reality

ABSTRACT

Spinal cord stimulation (SCS) is an approved treatment for truncal and limb neuropathic pain. However, pain relief is often suboptimal and SCS efficacy may reduce over time, requiring sometimes the addition of other pain therapies, stimulator revision, or even explantation. We designed and tested a new procedure by combining SCS with immersive virtual reality (VR) to enable analgesia in patients with chronic leg pain. We coupled SCS and VR by linking SCS-induced paresthesia with personalized visual bodily feedback that was provided by VR and matched to the spatiotemporal patterns of SCS-induced paresthesia. In this cross-sectional prospective interventional study, 15 patients with severe chronic pain and an SCS implant underwent congruent SCS-VR (personalized visual feedback of the perceived SCS-induced paresthesia displayed on the patient's virtual body) and 2 control conditions (incongruent SCS-VR and VR alone). We demonstrate the efficacy of neuromodulation-enhanced VR for the treatment of chronic pain by showing that congruent SCS-VR reduced pain ratings on average by 44%. Spinal cord stimulation-VR analgesia was stronger than that in both control conditions (enabling stronger analgesic effects than incongruent SCS-VR analgesia or VR alone) and kept increasing over successive stimulations, revealing the selectivity and consistency of the observed effects. We also show that analgesia persists after congruent SCS-VR had stopped, indicating carry over effects and underlining its therapeutic potential. Linking latest VR technology with recent insights from the neuroscience of body perception and SCS neuromodulation, our personalized new SCS-VR platform highlights the impact of immersive digiceutical therapies for chronic pain.Registration: clinicaltrials.gov, Identifier: NCT02970006.

Pharmacological disinhibition enhances paced breathing following complete spinal cord injury in rats

Respiratory dysfunction is one of the most devastating and life-threatening deficits that occurs following cervical spinal cord injury (SCI). Assisted breathing with mechanical ventilators is a necessary part of care for many cervical injured individuals, but it is also associated with increased risk of secondary complications such as infection, muscle atrophy and maladaptive plasticity. Pre-clinical studies with epidural stimulation (EDS) have identified it as an alternative/additional method to support adequate lung ventilation without mechanical assistance. The full potential of EDS, however, may be limited by spinal inhibitory mechanisms within the injured spinal cord. The goal of the present work is to assess the potential improvement for EDS in combination with pharmacological disinhibition of spinal circuits following complete high cervical SCI. All experiments were performed in decerebrate, unanesthetized, non-paralyzed (n = 13) and paralyzed (n = 8) adult Sprague-Dawley rats 6 h following a complete C1 transection. The combination of high-frequency EDS (HF-EDS) at the C4 spinal segment with intrathecal delivery of GABA and glycine receptors antagonists (GABAzine and strychnine, respectively) resulted in significantly increased phrenic motor output, tidal volume and amplitude of diaphragm electrical activity compared to HF-EDS alone. Thus, it appears that spinal fast inhibitory mechanisms limit phrenic motor output and present a new neuropharmacological target to improve paced breathing in individuals with cervical SCI.

A medical mystery of complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a condition of neuropathic pain, which is characterized by significant autonomic and inflammatory features. CRPS occurs in patients who have limb surgery, limb fractures, or trauma. Many patients may have pain resolve within twelve months of the inciting incident; however, a small subset progresses to the chronic form. This transitional process often happens by changing from warm CRPS with dominant inflammatory phase to cold CRPS, in which autonomic characteristics or manifestations dominate. Several peripheral and central mechanisms are involved, which might vary among individuals over a period of time. Other contributors include peripheral and central sensitization, autonomic alterations, inflammatory and immune changes, neurochemical changes, and psychological and genetic factors. Although effective management of the chronic CRPS form is often challenging, there are a few high quality randomized controlled trials that support the efficacy of the most commonly used therapeutic approaches.

Use of Oral Prednisolone and a 3-Phase Bone Scintigraphy in Patients with Complex Regional Pain Syndrome Type I

To compare the treatment effects of a high-dose and low-dose oral steroid regimen based on changes in the radioisotope uptake ratio (RUR) observed from three-phase bone scintigraphy (TPBS) in patients with complex regional pain syndrome type I (CRPS I), we retrospectively analyzed data of 34 patients with CRPS I from traumatic brain injury and stroke. Depending on the dose of steroid administered, patients were divided into high-dose (n = 14) and low-dose steroid groups (n = 20). We compared the severity scores, Kozin's classification scores, and RUR observed from TPBS between the two groups. There were significant changes in the severity scores and Kozin's classification between the baseline and 2 weeks from baseline (p < 0.05), however, there were no significant differences in terms of changes in the scores, classification, or the RUR observed from TPBS at 2 weeks from baseline (p > 0.05). There were no treatment-emergent adverse events (TEAEs) such as blood pressure elevation, impaired glycemic control, or gastrointestinal disturbances. Our results indicate that the efficacy profile of a low-dose oral steroid regimen is comparable to that of a high-dose regimen in alleviating symptoms in CRPS I patients. However, additional prospective, large-scale, multi-center studies are warranted to confirm our results.

Spinal Cord Stimulation

Spinal cord stimulation (SCS) has been well established as a safe and effective treatment of pain derived from a wide variety of etiologies. Careful patient selection including a rigorous trial period and psychological evaluation are essential. When patients proceed to permanent implantation, various considerations should be made, such as the type of lead, type of anesthesia, and waveform patterns for SCS. This article discusses the common indications for SCS, patient selection criteria, and pertinent outcomes from randomized clinical trials related to common indications treated with SCS. Technical considerations, such as type of implant, anesthesia, and programming, are also discussed.

Complex Regional Pain Syndrome, Current Concepts and Treatment Options

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) refers to a chronic pain condition that is characterized by progressively worsening spontaneous regional pain without dermatomal distribution. The symptomatology includes pain out of proportion in time and severity to the inciting event. The purpose of this review is to present the most current information concerning epidemiology, diagnosis, pathophysiology, and therapy for CRPS.

RECENT FINDINGS

In recent years, discovery of pathophysiologic mechanisms of CRPS has led to significant strides in the understanding of the disease process. Continued elucidation of the underlying pathophysiological mechanisms will allow for the development of more targeted and effective evidence-based therapy protocols. Further large clinical trials are needed to investigate mechanisms and treatment of the disorder.

Complex regional pain syndrome: a recent update

Complex regional pain syndrome (CRPS) is a debilitating condition affecting the limbs that can be induced by surgery or trauma. This condition can complicate recovery and impair one’s functional and psychological well-being. The wide variety of terminology loosely used to describe CRPS in the past has led to misdiagnosis of this condition, resulting in poor evidence-base regarding the treatment modalities available and their impact. The aim of this review is to report on the recent progress in the understanding of the epidemiology, pathophysiology and treatment of CRPS and to discuss novel approaches in treating this condition.

The positive allosteric GABAB receptor modulator rac-BHFF enhances baclofen-mediated analgesia in neuropathic mice

Neuropathic pain is associated with impaired inhibitory control of spinal dorsal horn neurons, which are involved in processing pain signals. The metabotropic GABAB receptor is an important component of the inhibitory system and is highly expressed in primary nociceptors and intrinsic dorsal horn neurons to control their excitability. Activation of GABAB receptors with the orthosteric agonist baclofen effectively reliefs neuropathic pain but is associated with severe side effects that prevent its widespread application. The recently developed positive allosteric GABAB receptor modulators lack most of these side effects and are therefore promising drugs for the treatment of pain. Here we tested the high affinity positive allosteric modulator rac-BHFF for its ability to relief neuropathic pain induced by chronic constriction of the sciatic nerve in mice. rac-BHFF significantly increased the paw withdrawal threshold to mechanical stimulation in healthy mice, indicating an endogenous GABABergic tone regulating the sensitivity to mechanical stimuli. Surprisingly, rac-BHFF displayed no analgesic activity in neuropathic mice although GABAB receptor expression was not affected in the dorsal horn as shown by quantitative receptor autoradiography. However, activation of spinal GABAB receptors by intrathecal injection of baclofen reduced hyperalgesia and its analgesic effect was considerably potentiated by co-application of rac-BHFF. These results indicate that under conditions of neuropathic pain the GABAergic tone is too low to provide a basis for allosteric modulation of GABAB receptors. However, allosteric modulators would be well suited as an add-on to reduce the dose of baclofen required to achieve analgesia.

Functional dystonia

Although currently lacking a sensitive and specific electrophysiologic battery test, functional (psychogenic) dystonia can sometimes be diagnosed with clinically definite certainty using available criteria. Certain regional phenotypes have been recognized as distinctive, such as unilateral lip and jaw deviation, laterocollis with ipsilateral shoulder elevation and contralateral shoulder depression, fixed wrist and finger flexion with relative sparing of the thumb and index fingers, and fixed foot plantar flexion and inversion. The pathophysiologic abnormalities in functional dystonia overlap substantially with those of organic dystonia, with similar impairments in cortical and spinal inhibition and somatosensory processing, but with emerging data suggesting abnormalities in regional blood flow and activation patterns on positron emission tomography and functional magnetic resonance imaging, respectively. Management of functional dystonia begins with compassionate and assertive debriefing of the diagnosis to ensure full acceptance by the patient, a critical step in enhancing the likelihood of success with physical rehabilitation, and psychodynamic or cognitive therapy. Physical therapy, with or without cognitive behavioral therapy, appears to be of benefit but has not yet been examined in a controlled fashion. While the prognosis remains grim for a substantial majority of patients, partly stemming from restricted mobility, delayed diagnosis, and inappropriate pharmacotherapy, early recognition and initiation of therapy stand to minimize iatrogenic harm and unnecessary laboratory investigations, and potentially reduce the long-term neurologic disability.