Neuropathic pain and deep brain stimulation

Reduced GABAergic neuronal activity in zona incerta causes neuropathic pain in a rat sciatic nerve chronic constriction injury model

PURPOSE

The zona incerta (ZI) is below the ventral tier of the thalamus and has a strong influence selectively in higher-order thalamic relays. Although neuropathic pain has been suggested to result from reduced gamma-aminobutyric acid (GABA) and GABAergic signaling in the ZI, the mechanisms remain unclear. Here, the role of GABA and GABAergic signaling was investigated in the ZI in neuropathic pain using sciatic nerve chronic constriction injury (CCI) rats.

MATERIALS AND METHODS

Single-unit neuronal activity was recorded, and microdialysis was performed in the ZI of CCI rats and sham-treated rats in vivo. This study also compared ZI neuronal activity after treatment with saline, the GABAA receptor agonist (muscimol), or the GABAA receptor antagonist (bicuculline).

RESULTS AND CONCLUSION

CCI rats exhibited hypersensitivity to pain as evidenced by decreased hind paw withdrawal threshold and latency. CCI rats also showed reduced GABA level and decreased neuronal activity in the ZI compared with sham-treated rats. Treatment with GABAA receptor agonist, but not GABAA receptor antagonist, ameliorated pain hypersensitivity and increased the firing rate (spikes/s) of ZI neurons in CCI rats.

Deep Brain Stimulation Improves the Symptoms and Sensory Signs of Persistent Central Neuropathic Pain from Spinal Cord Injury: A Case Report

Central neuropathic pain (CNP) is a significant problem after spinal cord injury (SCI). Pharmacological and non-pharmacological approaches may reduce the severity, but relief is rarely substantial. While deep brain stimulation (DBS) has been used to treat various chronic pain types, the technique has rarely been used to attenuate CNP after SCI. Here we present the case of a 54-year-old female with incomplete paraplegia who had severe CNP in the lower limbs and buttock areas since her injury 30 years prior. She was treated with bilateral DBS of the midbrain periaqueductal gray (PAG). The effects of this stimulation on CNP characteristics, severity and pain-related sensory function were evaluated using the International SCI Pain Basic Data Set (ISCIPBDS), Neuropathic Pain Symptom Inventory (NPSI), Multidimensional Pain Inventory and Quantitative Sensory Testing before and periodically after initiation of DBS. After starting DBS treatment, weekly CNP severity ratings rapidly decreased from severe to minimal, paralleled by a substantial reduction in size of the painful area, reduced pain impact and reversal of pain-related neurological abnormalities, i.e., dynamic-mechanical and cold allodynia. She discontinued pain medication on study week 24. The improvement has been consistent. The present study expands on previous findings by providing in-depth assessments of symptoms and signs associated with CNP. The results of this study suggest that activation of endogenous pain inhibitory systems linked to the PAG can eliminate CNP in some people with SCI. More research is needed to better-select appropriate candidates for this type of therapy. We discuss the implications of these findings for understanding the brainstem's control of chronic pain and for future progress in using analgesic DBS in the central gray.

Innovations in Functional Neurosurgery and Anesthetic Implications

Functional neurosurgery has undergone rapid growth over the last few years fueled by advances in imaging technology and novel treatment modalities. These advances have led to new surgical treatments using minimally invasive and precise techniques for conditions such as Parkinson's disease, essential tremor, epilepsy, and psychiatric disorders. Understanding the goals and technological issues of these procedures is imperative for the anesthesiologist to ensure safe management of patients presenting for functional neurosurgical procedures. In this review, we discuss the advances in neurosurgical techniques for deep brain stimulation, focused ultrasound and minimally invasive laser-based treatment of refractory epilepsy and provide a guideline for anesthesiologists caring for patients undergoing these procedures.

EAN guidelines on central neurostimulation therapy in chronic pain conditions

BACKGROUND AND PURPOSE

Our aim was to update previous European Federation of Neurological Societies guidelines on neurostimulation for neuropathic pain, expanding the search to new techniques and to chronic pain conditions other than neuropathic pain, and assessing the evidence with the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

METHODS

A systematic review and meta-analysis of trials published between 2006 and December 2014 was conducted. Pain conditions included neuropathic pain, fibromyalgia, complex regional pain syndrome (CRPS) type I and post-surgical chronic back and leg pain (CBLP). Spinal cord stimulation (SCS), deep brain stimulation (DBS), epidural motor cortex stimulation (MCS), repetitive transcranial magnetic stimulation (rTMS) and transcranial direct electrical stimulation (tDCS) of the primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC) were assessed. The GRADE system was used to assess quality of evidence and propose recommendations.

RESULTS

The following recommendations were reached: 'weak' for SCS added to conventional medical management in diabetic painful neuropathy, CBLP and CRPS, for SCS versus reoperation in CBLP, for MCS in neuropathic pain, for rTMS of M1 in neuropathic pain and fibromyalgia and for tDCS of M1 in neuropathic pain; 'inconclusive' for DBS in neuropathic pain, rTMS and tDCS of the DLPFC, and for motor cortex tDCS in fibromyalgia and spinal cord injury pain.

CONCLUSIONS

Given the poor to moderate quality of evidence identified by this review, future large-scale multicentre studies of non-invasive and invasive neurostimulation are encouraged. The collection of higher quality evidence of the predictive factors for the efficacy of these techniques, such as the duration, quality and severity of pain, is also recommended.

Brainjacking: Implant Security Issues in Invasive Neuromodulation

The security of medical devices is critical to good patient care, especially when the devices are implanted. In light of recent developments in information security, there is reason to be concerned that medical implants are vulnerable to attack. The ability of attackers to exert malicious control over brain implants ("brainjacking") has unique challenges that we address in this review, with particular focus on deep brain stimulation implants. To illustrate the potential severity of this risk, we identify several mechanisms through which attackers could manipulate patients if unauthorized access to an implant can be achieved. These include blind attacks in which the attacker requires no patient-specific knowledge and targeted attacks that require patient-specific information. Blind attacks include cessation of stimulation, draining implant batteries, inducing tissue damage, and information theft. Targeted attacks include impairment of motor function, alteration of impulse control, modification of emotions or affect, induction of pain, and modulation of the reward system. We also discuss the limitations inherent in designing implants and the trade-offs that must be made to balance device security with battery life and practicality. We conclude that researchers, clinicians, manufacturers, and regulatory bodies should cooperate to minimize the risk posed by brainjacking.

Characteristics of local field potentials correlate with pain relief by deep brain stimulation

OBJECTIVE

To investigate the link between neuronal activity recorded from the sensory thalamus and periventricular gray/periaqueductal gray (PVAG) and pain relief by deep brain stimulation (DBS).

METHODS

Local field potentials (LFPs) were recorded from the sensory thalamus and PVAG post-operatively from ten patients with neuropathic pain. The LFPs were quantified using spectral and time-frequency analysis, the relationship between the LFPs and pain relief was quantified with nonlinear correlation analysis.

RESULTS

The theta oscillations of both sensory thalamus and PVAG correlated inversely with pain relief. The high beta oscillations in the sensory thalamus and the alpha oscillations in the PVAG correlated positively with pain relief. Moreover, the ratio of high-power duration to low-power duration of theta band activity in the sensory thalamus and PVAG correlated inversely with pain relief. The duration ratio at the high beta band in the sensory thalamus correlated positively with pain relief.

CONCLUSIONS

Our results reveal distinct neuronal oscillations at the theta, alpha, and beta frequencies correlating with pain relief by DBS.

SIGNIFICANCE

The study provides quantitative measures for predicting the outcomes of neuropathic pain relief by DBS as well as potential biomarkers for developing adaptive stimulation strategies.

Deep brain stimulation of the dorsal anterior cingulate cortex for the treatment of chronic neuropathic pain

Chronic neuropathic pain is estimated to affect 3%-4.5% of the worldwide population. It is associated with significant loss of productive time, withdrawal from the workforce, development of mood disorders such as depression and anxiety, and disruption of family and social life. Current medical therapeutics often fail to adequately treat chronic neuropathic pain. Deep brain stimulation (DBS) targeting subcortical structures such as the periaqueductal gray, the ventral posterior lateral and medial thalamic nuclei, and the internal capsule has been investigated for the relief of refractory neuropathic pain over the past 3 decades. Recent work has identified the dorsal anterior cingulate cortex (dACC) as a new potential neuromodulation target given its central role in cognitive and affective processing. In this review, the authors briefly discuss the history of DBS for chronic neuropathic pain in the United States and present evidence supporting dACC DBS for this indication. They review existent literature on dACC DBS and summarize important findings from imaging and neurophysiological studies supporting a central role for the dACC in the processing of chronic neuropathic pain. The available neurophysiological and empirical clinical evidence suggests that dACC DBS is a viable therapeutic option for the treatment of chronic neuropathic pain and warrants further investigation.

Deep brain stimulation for obesity: past, present, and future targets

The authors review the history of deep brain stimulation (DBS) in patients for treating obesity, describe current DBS targets in the brain, and discuss potential DBS targets and nontraditional stimulation parameters that may improve the effectiveness of DBS for ameliorating obesity. Deep brain stimulation for treating obesity has been performed both in animals and in humans with intriguing preliminary results. The brain is an attractive target for addressing obesity because modulating brain activity may permit influencing both sides of the energy equation--caloric intake and energy expenditure.

A decade of emerging indications: deep brain stimulation in the United States

OBJECTIVE Deep brain stimulation (DBS) is an emerging treatment option for an expanding set of neurological and psychiatric diseases. Despite growing enthusiasm, the patterns and implications of this rapid adoption are largely unknown. National trends in DBS surgery performed for all indications between 2002 and 2011 are reported. METHODS Using a national database of hospital discharges, admissions for DBS for 14 indications were identified and categorized as either FDA approved, humanitarian device exempt (HDE), or emerging. Trends over time were examined, differences were analyzed by univariate analyses, and outcomes were analyzed by hierarchical regression analyses. RESULTS Between 2002 and 2011, there were an estimated 30,490 discharges following DBS for approved indications, 1647 for HDE indications, and 2014 for emerging indications. The volume for HDE and emerging indications grew at 36.1% annually in comparison with 7.0% for approved indications. DBS for emerging indications occurred at hospitals with more neurosurgeons and neurologists locally, but not necessarily at those with the highest DBS caseloads. Patients treated for HDE and emerging indications were younger with lower comorbidity scores. HDE and emerging indications were associated with greater rates of reported complications, longer lengths of stay, and greater total costs. CONCLUSIONS DBS for HDE and emerging indications underwent rapid growth in the last decade, and it is not exclusively the most experienced DBS practitioners leading the charge to treat the newest indications. Surgeons may be selecting younger and healthier patients for their early experiences. Differences in reported complication rates warrant further attention and additional costs should be anticipated as surgeons gain experience with new patient populations and targets.

Cerebral Perfusion and Gray Matter Changes Associated With Chemotherapy-Induced Peripheral Neuropathy

PURPOSE

To investigate the longitudinal relationship between chemotherapy-induced peripheral neuropathy (CIPN) symptoms (sx) and brain perfusion changes in patients with breast cancer. Interaction of CIPN-sx perfusion effects with known chemotherapy-associated gray matter density decrease was also assessed to elucidate the relationship between CIPN and previously reported cancer treatment-related brain structural changes.

METHODS

Patients with breast cancer treated with (n = 24) or without (n = 23) chemotherapy underwent clinical examination and brain magnetic resonance imaging at the following three time points: before treatment (baseline), 1 month after treatment completion, and 1 year after the 1-month assessment. CIPN-sx were evaluated with the self-reported Functional Assessment of Cancer Therapy/Gynecologic Oncology Group-Neurotoxicity four-item sensory-specific scale. Perfusion and gray matter density were assessed using voxel-based pulsed arterial spin labeling and morphometric analyses and tested for association with CIPN-sx in the patients who received chemotherapy.

RESULTS

Patients who received chemotherapy reported significantly increased CIPN-sx from baseline to 1 month, with partial recovery by 1 year (P < .001). CIPN-sx increase from baseline to 1 month was significantly greater for patients who received chemotherapy compared with those who did not (P = .001). At 1 month, neuroimaging showed that for the group that received chemotherapy, CIPN-sx were positively associated with cerebral perfusion in the right superior frontal gyrus and cingulate gyrus, regions associated with pain processing (P < .001). Longitudinal magnetic resonance imaging analysis in the group receiving chemotherapy indicated that CIPN-sx and associated perfusion changes from baseline to 1 month were also positively correlated with gray matter density change (P < .005).

CONCLUSION

Peripheral neuropathy symptoms after systemic chemotherapy for breast cancer are associated with changes in cerebral perfusion and gray matter. The specific mechanisms warrant further investigation given the potential diagnostic and therapeutic implications.

A single thalamic target for deep brain stimulation to treat hemi-body pain syndrome

BACKGROUND

Patients experiencing hemi-body pain represent a difficult problem when using the thalamus as a DBS target given its anatomical topology.

METHODS

A 50-year-old HIV positive male underwent a right unilateral thalamic DBS to treat his severe left hemi-body central post-stroke pain following years of unsuccessful medication therapy.

RESULTS

The final active contact of the electrode corresponded to stimulation of the nucleus ventrocaudalis parvocellularis internis, which has provided prolonged pain relief.

CONCLUSION

To our knowledge this was the first time this pattern of pain was treated by a single thalamic DBS electrode, suggesting stimulation in this region may be a feasible target for achieving relief from chronic severe hemi-body pain.

Network effects of deep brain stimulation

The ability to differentially alter specific brain functions via deep brain stimulation (DBS) represents a monumental advance in clinical neuroscience, as well as within medicine as a whole. Despite the efficacy of DBS in the treatment of movement disorders, for which it is often the gold-standard therapy when medical management becomes inadequate, the mechanisms through which DBS in various brain targets produces therapeutic effects is still not well understood. This limited knowledge is a barrier to improving efficacy and reducing side effects in clinical brain stimulation. A field of study related to assessing the network effects of DBS is gradually emerging that promises to reveal aspects of the underlying pathophysiology of various brain disorders and their response to DBS that will be critical to advancing the field. This review summarizes the nascent literature related to network effects of DBS measured by cerebral blood flow and metabolic imaging, functional imaging, and electrophysiology (scalp and intracranial electroencephalography and magnetoencephalography) in order to establish a framework for future studies.

Deep brain stimulation for chronic pain

Deep brain stimulation (DBS) is a neurosurgical intervention popularised in movement disorders such as Parkinson's disease, and also reported to improve symptoms of epilepsy, Tourette's syndrome, obsessive compulsive disorders and cluster headache. Since the 1950s, DBS has been used as a treatment to relieve intractable pain of several aetiologies including post stroke pain, phantom limb pain, facial pain and brachial plexus avulsion. Several patient series have shown benefits in stimulating various brain areas, including the sensory thalamus (ventral posterior lateral and medial), the periaqueductal and periventricular grey, or, more recently, the anterior cingulate cortex. However, this technique remains "off label" in the USA as it does not have Federal Drug Administration approval. Consequently, only a small number of surgeons report DBS for pain using current technology and techniques and few regions approve it. Randomised, blinded and controlled clinical trials that may use novel trial methodologies are desirable to evaluate the efficacy of DBS in patients who are refractory to other therapies. New imaging techniques, including tractography, may help optimise electrode placement and clinical outcome.

Deep brain stimulation for movement disorders: update on recent discoveries and outlook on future developments

Modern deep brain stimulation (DBS) has become a routine therapy for patients with movement disorders such as Parkinson's disease, generalized or segmental dystonia and for multiple forms of tremor. Growing numbers of publications also report beneficial effects in other movement disorders such as Tourette's syndrome, various forms of chorea and DBS is even being studied for Parkinson's-related dementia. While exerting remarkable effects on many motor symptoms, DBS does not restore normal neurophysiology and therefore may also have undesirable side effects including speech and gait deterioration. Furthermore, its efficacy might be compromised in the long term, due to progression of the underlying disease. Various programming strategies have been studied to try and address these issues, e.g., the use of low-frequency rather than high-frequency stimulation or the targeting of alternative brain structures such as the pedunculopontine nucleus. In addition, further technical developments will soon provide clinicians with an expanded choice of hardware such as segmented electrodes allowing for a steering of the current to optimize beneficial effects and reduce side effects as well as the possibility of adaptive stimulation systems based on closed-loop concepts with or without accompanying advances in programming and imaging software. In the present article, we will provide an update on the most recent achievements and discoveries relevant to the application of DBS in the treatment of movement disorder patients and give an outlook on future clinical and technical developments.

Role of radiology in central nervous system stimulation

Central nervous system (CNS) stimulation is becoming increasingly prevalent. Deep brain stimulation (DBS) has been proven to be an invaluable treatment for movement disorders and is also useful in many other neurological conditions refractory to medical treatment, such as chronic pain and epilepsy. Neuroimaging plays an important role in operative planning, target localization and post-operative follow-up. The use of imaging in determining the underlying mechanisms of DBS is increasing, and the dependence on imaging is likely to expand as deep brain targeting becomes more refined. This article will address the expanding role of radiology and highlight issues, including MRI safety concerns, that radiologists may encounter when confronted with a patient with CNS stimulation equipment in situ.