Pain anticipatory phenomena in patients with central poststroke pain: a magnetoencephalography study

Contact Heat in Magnetoencephalography: A Systematic Review

BACKGROUND

Contact heat is commonly used in experimental research to evoke brain activity, most frequently acquired with electroencephalography (EEG). Although magnetoencephalography (MEG) improves spatial resolution, using some contact heat stimulators with MEG can present methodological challenges. This systematic review assesses studies that utilise contact heat in MEG, their findings and possible directions for further research.

METHODS

Eight electronic databases were searched for relevant studies, in addition to the selected papers' reference lists, citations and ConnectedPapers maps. Best practice recommendations for systematic reviews were followed. Papers met inclusion criteria if they used MEG to record brain activity in conjunction with contact heat, regardless of stimulator equipment or paradigm.

RESULTS

Of 646 search results, seven studies met the inclusion criteria. Studies demonstrated effective electromagnetic artefact removal from MEG data, the ability to elicit affective anticipation and differences in deep brain stimulation responders. We identify contact heat stimulus parameters that should be reported in publications to ensure comparisons between data outcomes are consistent.

CONCLUSIONS

Contact heat is a viable alternative to laser or electrical stimulation in experimental research, and methods exist to successfully mitigate any electromagnetic noise generated by PATHWAY CHEPS equipment - though there is a dearth of literature exploring the post-stimulus time window.

The Wisdom and Vision From the ACMEGS Inaugural Decade

Concise history of fascinating magnetoencephalography (MEG) technology and catalog of very selected milestone preclinical and clinical MEG studies are provided as the background. The focus is the societal context defining a journey of MEG to and through clinical practice and formation of the American Clinical MEG Society (ACMEGS). We aspired to provide an objective historic perspective and document contributions of many professionals while focusing on the role of ACMEGS in the growth and maturation of clinical MEG field. The ACMEGS was born (2006) out of inevitability to address two vital issues-fair reimbursement and proper clinical acceptance. A beacon of accountable MEG practice and utilization is now an expanding professional organization with the highest level of competence in practice of clinical MEG and clinical credibility. The ACMEGS facilitated a favorable disposition of insurances toward MEG in the United States by combining the national replication of the grassroots efforts and teaming up with the strategic partners-particularly the American Academy of Neurology (AAN), published two Position Statements (2009 and 2017), the world's only set of MEG Clinical Practice Guidelines (CPGs; 2011) and surveys of clinical MEG practice (2011 and 2020) and use (2020). In addition to the annual ACMEGS Course (2012), we directly engaged MEG practitioners through an Invitational Summit (2019). The Society remains focused on the improvements and expansion of clinical practice, education, clinical training, and constructive engagement of vendors in these issues and pivotal studies toward additional MEG indications. The ACMEGS not only had the critical role in the progress of Clinical MEG in the United States and beyond since 2006 but positioned itself as the field leader in the future.

Functional Magnetic Resonance Imaging Correlates of Ventral Striatal Deep Brain Stimulation for Poststroke Pain

OBJECTIVE

Deep brain stimulation (DBS) for pain has largely been implemented in an uncontrolled manner to target the somatosensory component of pain, with research leading to mixed results. We have previously shown that patients with poststroke pain syndrome who were treated with DBS targeting the ventral striatum/anterior limb of the internal capsule (VS/ALIC) demonstrated a significant improvement in measures related to the affective sphere of pain. In this study, we sought to determine how DBS targeting the VS/ALIC modifies brain activation in response to pain.

MATERIALS AND METHODS

Five patients with poststroke pain syndrome who were blinded to DBS status (ON/OFF) and six age- and sex-matched healthy controls underwent functional magnetic resonance imaging (fMRI) measuring blood oxygen level-dependent activation in a block design. In this design, each participant received heat stimuli to the affected or unaffected wrist area. Statistical comparisons were performed using fMRI z-maps.

RESULTS

In response to pain, patients in the DBS OFF state showed significant activation (p < 0.001) in the same regions as healthy controls (thalamus, insula, and operculum) and in additional regions (orbitofrontal and superior convexity cortical areas). DBS significantly reduced activation of these additional regions and introduced foci of significant inhibitory activation (p < 0.001) in the hippocampi when painful stimulation was applied to the affected side.

CONCLUSIONS

These findings suggest that DBS of the VS/ALIC modulates affective neural networks.

Diagnosis, Treatment, and Management of Dejerine-Roussy Syndrome: a Comprehensive Review

PURPOSE OF REVIEW

Post-stroke pain represents a complex condition with few standardized diagnostic criteria. As such, the array of symptoms is often difficult to categorize and diagnose. Central post-stroke pain (CPSP), also known as Dejerine-Roussy syndrome, presents as painful paresthesia in any part of the body that is usually coupled with sensory abnormalities.

RECENT FINDINGS

In patients who had experienced a cerebrovascular accident, CPSP typically affects the same areas of the body that are also impacted by the general motor and sensory deficits that result from stroke. Though it is generally debated, CPSP is thought to result from a lesion in any part of the central nervous system. Pain usually presents in the range of 3-6 months after the occurrence of stroke, manifesting contralaterally to the lesion, and most commonly involving the upper extremities. For the most accurate diagnosis of CPSP, a thorough history and clinical examination should be supplemented with imaging. Infarcted areas of the brain can be visualized using either CT or MRI. First-line treatment of CPSP is pharmacologic and consists of a three-drug regimen. Despite this, CPSP is often refractory to medical management producing only modest pain reduction in a limited subset of patients. Adverse effects associated with pharmacologic management of CPSP and frequent recalcitrance to treatment have driven alternative minimally invasive methods of pain control which include transcranial stimulation, deep brain stimulation, and neuromodulation. The aim of this review is to provide a comprehensive update to recent advances in the understanding of the treatment and management of CPSP.

Deep brain stimulation of the ventral striatal area for poststroke pain syndrome: a magnetoencephalography study

Poststroke pain syndrome (PSPS) is an often intractable disorder characterized by hemiparesis associated with unrelenting chronic pain. Although traditional analgesics have largely failed, integrative approaches targeting affective-cognitive spheres have started to show promise. Recently, we demonstrated that deep brain stimulation (DBS) of the ventral striatal area significantly improved the affective sphere of pain in patients with PSPS. In the present study, we examined whether electrophysiological correlates of pain anticipation were modulated by DBS that could serve as signatures of treatment effects. We recorded event-related fields (ERFs) of pain anticipation using magnetoencephalography (MEG) in 10 patients with PSPS preoperatively and postoperatively in DBS OFF and ON states. Simple visual cues evoked anticipation as patients awaited a painful (PS) or nonpainful stimulus (NPS) to the nonaffected or affected extremity. Preoperatively, ERFs showed no difference between PS and NPS anticipation to the affected extremity, possibly due to loss of salience in a network saturated by pain experience. DBS significantly modulated the early N1, consistent with improvements in affective networks involving restoration of salience and discrimination capacity. Additionally, DBS suppressed the posterior P2 (aberrant anticipatory anxiety) while enhancing the anterior N1 (cognitive and emotional regulation) in responders. DBS-induced changes in ERFs could potentially serve as signatures for clinical outcomes. NEW & NOTEWORTHY We examined the electrophysiological correlates of pain affect in poststroke pain patients who underwent deep brain stimulation (DBS) targeting the ventral striatal area under a randomized, controlled trial. DBS significantly modulated early event-related components, particularly N1 and P2, measured with magnetoencephalography during a pain anticipatory task, compared with baseline and the DBS-OFF condition, pointing to possible mechanisms of action. DBS-induced changes in event-related fields could potentially serve as biomarkers for clinical outcomes.

Deep Brain Stimulation for the Treatment of Dejerine-Roussy Syndrome

BACKGROUND/AIMS

Patients who suffer from Dejerine-Roussy syndrome commonly experience severe poststroke hemibody pain which has historically been attributed to thalamic lesions. Despite pharmacological treatment, a significant proportion of the population is resistant to traditional therapy. Deep brain stimulation is often appropriate for the treatment of resistant populations. In this review we aim to summarize the targets that are used to treat Dejerine-Roussy syndrome and provide insight into their clinical efficacy.

METHODS

In reviewing the literature, we defined stimulation success as achievement of a minimum of 50% pain relief.

RESULTS

Contemporary targets for deep brain stimulation are the ventral posterior medial/ventral posterior lateral thalamic nuclei, periaqueductal/periventricular gray matter, the ventral striatum/anterior limb of the internal capsule, left centromedian thalamic nuclei, the nucleus ventrocaudalis parvocellularis internis, and the posterior limb of the internal capsule.

CONCLUSIONS

Due to technological advancements in deep brain stimulation, its therapeutic effects must be reevaluated. Despite a lack of controlled evidence, deep brain stimulation has been effectively used as a therapeutic in clinical pain management. Further clinical investigation is needed to definitively evaluate the therapeutic efficacy of deep brain stimulation in treating the drug-resistant patient population.