Subcutaneous trigeminal nerve field stimulation for refractory trigeminal pain: a cohort analysis

Trigeminal Postherpetic Neuralgia: From Pathophysiology to Treatment

PURPOSE OF REVIEW

Trigeminal postherpetic neuralgia (TG-PHN) is a neuropathic pain condition complicating herpes zoster (HZ) attributed to the trigeminal nerve. It poses significant challenges due to its persistent and debilitating nature. This review explores the clinical characteristics of TG-PHN, analyzes its pathophysiological underpinnings, and addresses existent and potential therapies.

RECENT FINDINGS

TG-PHN is one of the most common and complex PHN locations. It has distinguishing clinical and pathophysiological characteristics, starting with viral triggered injuries to the trigeminal ganglion (TG) and peripheral tissue and involving the ascending and descending brain modulation pathways. Current therapies include vaccines, oral and topical medications, and interventional approaches, like nerve blocks and neurostimulation. This review covers TG-PHN's clinical and physiological components, treatment options, and potential future targets for improved management. By exploring the complexities of this condition, we aim to contribute to developing more effective and targeted therapies for patients suffering from trigeminal PHN.

Dual-neuromodulation strategy in pain management of herpes zoster ophthalmicus: retrospective cohort study and literature review

BACKGROUND

Effective pain control of herpes zoster ophthalmicus (HZO) is not only essential to attenuate the clinical symptoms but to reduce the risk of postherpetic neuralgia development. Recently, neuromodulation therapy has been one promising option for neuropathic pain and increasingly applied in management of zoster-related pain. One key factor of neuromodulation treatment is the therapeutic site for the impaired nerves. In this study we aim to investigate one novel dual-neuromodulation strategy, targeting the level of the peripheral branch and trigeminal ganglion, in the pain management of HZO.

METHODS

Dual neuromodulation strategy combining short-term peripheral nerve stimulation (PNS) with pulsed radiofrequency (PRF) of trigeminal ganglion was compared with single PNS treatment for HZO-related pain. Clinical recordings of patients were retrospectively reviewed. The primary outcome was the pain severity, assessed by the visual analogue scale (VAS) before and after neuromodulation therapy.

RESULTS

PNS achieved significant relief of pain with or without PRF treatment before discharge, which provided enduring therapeutic effect up to 12-month follow-up. The mean reduction of VAS was 6.7 ± 1.4 in dual modulation therapy (n = 13) at last follow-up and 5.4 ± 1.5 in PNS subgroup (n = 20), respectively. Moreover, dual modulation strategy provided better control of pain compared with PNS therapy alone at each time point.

CONCLUSION

It is feasible and effective to combine the PNS and PRF in pain management of HZO. This novel dual modulation strategy of trigeminal pathway may provide additional therapeutic effects of pain symptoms in HZO population.

Clinical outcomes and complications of peripheral nerve field stimulation in the management of refractory trigeminal pain: a systematic review and meta-analysis

OBJECTIVE

Peripheral nerve field stimulation (PNFS) is a tool in the armamentarium of treatment options for trigeminal pain. The efficacy of this modality in mitigating trigeminal pain remains unclear. The aim of this study was to examine the existing literature on PNFS and elucidate pain score outcomes associated with its use in patients with trigeminal pain.

METHODS

A systematic review and meta-analysis was performed in accordance with the PRISMA framework. The PubMed, Web of Science, and Scopus databases were queried on June 10, 2020. Studies reporting pain outcomes in more than 5 adult patients treated with PNFS for facial pain were included. The primary outcome of the study was the mean difference in the visual analog scale (VAS) score from the last follow-up to baseline, and it was analyzed by an inverse-variance, random-effect model. The risk of bias was assessed using the Newcastle-Ottawa Scale and a funnel plot.

RESULTS

Of the 4597 studies screened for inclusion, 46 relevant full-text articles were assessed for eligibility. Eleven observational cohort studies from the 46 articles were found to be eligible, and reported on a total of 109 patients. In 86% (94/109) of cases, trial stimulation was successful and followed by a permanent system implantation. VAS scores improved by 75% (mean difference 6.32/10 points, 95% CI 5.38-7.27 points) compared to baseline. Seventy-six percent (42/55) of patients became medication free or required lower doses of medications. The complication rate necessitating surgical revision was estimated at 32% per procedure.

CONCLUSIONS

These findings support the belief that PNFS provides effective, long-term pain control for trigeminal pain. Statistical heterogeneity was considerable across all studies. Future work should be aimed at conducting double-blind randomized controlled trials to determine the utility of PNFS for treating various forms of trigeminal pain for which limited therapeutic options exist.

Anchoring of a mental nerve stimulator for treatment of facial neuropathic pain: a case illustration

INTRODUCTION

Mental nerve stimulation is recognised as a treatment option for neuropathic facial pain. Historically however, lead migration across the mobile temporomandibular joint has prevented this procedures utility.

METHODS

We describe a new method of insertion and anchoring of a mental nerve stimulator for the management of refractory neuropathic pain in the distribution of the mental nerve. We anchored the stimulator lead to the mandibular body.

RESULTS

Significant analgesic effect was achieved and no lead migration had occurred at 1 year post-operatively.

CONCLUSIONS

This report describes in detail the procedure of mental nerve stimulator insertion, with a novel technique of mandibular anchoring of the lead.

Trigeminal Traumatic Neuroma: a Comprehensive Review of the Literature Based On a Rare Case

PURPOSE OF REVIEW

Traumatic neuromas in general, and trigeminal traumatic neuromas in particular, are relatively rare entities originating from a damage to a corresponding nerve or its branches. This manuscript is a comprehensive review of the literature on trigeminal traumatic neuromas based on an interesting and challenging case of bilateral intraoral lesions.

RECENT FINDINGS

The diagnosis for this patient was bilateral trigeminal traumatic neuromas. It is possible that these patients have a genetic predisposition to the development of these lesions. It is a neuropathic pain condition and may mimic dental and other trigeminal pain entities. Topical treatment with lidocaine gel, utilizing a custom-made neurosensory stent, rendered the patient significant and sustained pain relief. Trigeminal traumatic neuromas present a diagnostic challenge even to a seasoned clinician, due to the complex clinical features that may mimic other entities. Topical medications such as local anesthetics may be a good viable alternative to systemic medications to manage the pain associated with the condition. Early identification of the lesion and the associated pain helps in the succinct management of symptomatic trigeminal traumatic neuromas.

Wireless Subcutaneous Trigeminal Nerve Field Stimulation for Refractory Trigeminal Pain: A Single Center Experience

INTRODUCTION

Subcutaneous trigeminal nerve field stimulation (sTNFS) is a neuromodulatory treatment for neuropathic trigeminal pain with the ability to reduce the intensity and frequency of pain attacks. However, hardware issues including lead migration, skin erosion, infection, so-called pocket pain at the site of the implanted neurostimulator are reported. Implantable wireless neurostimulation technology promises not only an even less invasive sTNFS treatment and thinner and more flexible electrodes better suited for facial implants, but also provides further advantages such as lack of an implantable neurostimulator and 3T magnetic resonance imaging compatibility.

MATERIAL AND METHODS

All patients who had received trial stimulation with a partially implantable sTNFS system were analyzed for ICHD-3 (3rd edition of the International Classification of Headache Disorders) diagnosis, success of trial stimulation, pre- and postoperative pain intensity, frequency of attacks, complications, and side-effects of sTNFS.

RESULTS

All patients (N = 3) responded to sTNFS (≥50% pain reduction) during the trial period. According to ICHD-3, N = 2 of the patients were classified with trigeminal neuralgia (TN) with concomitant persistent facial pain and N = 1 patient with multiple sclerosis associated TN. The time of the test period was 44 ± 31.24 days (mean ± SD). The average daily duration of stimulation per patient amounted 2.5 ± 2.2 hours (range 1-5). The pain intensity (defined on a visual analog scale) was reduced by 80% ± 17% (mean ± SD). Reduction or cessation in pain medication was observed in all patients. No surgical complications occurred in the long-term follow-up period of 18.84 ± 6 (mean ± SD) months.

CONCLUSION

The partially implantable sTNFS device seems to be safe, effective, and reliable. Compared to conventional devices, the equipment is not limited to the length of trial stimulation. Furthermore, the daily stimulation duration was much shorter compared to previous reports.

Implantable Peripheral Nerve Stimulation for Trigeminal Neuropathic Pain: A Systematic Review and Meta-Analysis

OBJECTIVES

Implantable peripheral nerve stimulation has been increasingly used to treat neuropathic pain. This neuromodulation strategy may be an alternative option for intractable trigeminal neuropathic pain; however, evidence for this treatment approach remains limited. A systematic review was conducted to identify studies of patients that underwent peripheral nerve stimulation implantation for trigeminal neuropathic pain.

MATERIALS AND METHODS

Databases including, PubMed, EMBASE, and Cochrane Library were searched up to October 5, 2020. The primary outcomes were changes in pain scores and response rates of neuromodulation therapy. A random effects model was used for meta-analysis. Subgroup analysis was performed to examine the source of heterogeneity.

RESULTS

Thirteen studies including 221 participants were evaluated. The estimated response rate of neuromodulation treatment was 61.3% (95% CI: 44.4-75.9%, I²  = 70.733%, p < 0.0001) at the last follow-up. The overall reduction in pain scores was 2.363 (95% CI: 1.408-3.319, I²  = 85.723%, p < 0.0001). Subgroup analysis further confirmed that stimulation target (peripheral branch vs. trigeminal ganglion vs. trigeminal nerve root) contributed the heterogeneity across enrolled studies. Better clinical outcome was associated with stimulation of the trigeminal peripheral branch (p < 0.0001).

CONCLUSION

Peripheral nerve stimulation may be a promising approach in the management of trigeminal neuropathic pain, especially for patients intractable to conventional therapy.

Peripheral nerve field stimulation in medically refractory trigeminal neuralgia attributed to multiple sclerosis

OBJECTIVE

Case reports and small patient series have suggested peripheral nerve field stimulation (PNFS) as a treatment for refractory trigeminal neuralgia attributed to multiple sclerosis (MS). Here, the authors aimed to assess the effects of this technique on long-term pain severity.

METHODS

Data were prospectively collected on patients with refractory trigeminal neuralgia attributed to MS who underwent PNFS between July 2013 and August 2017 at the authors' neurosurgical department. Patients were evaluated before and after the first treatment as well as at follow-up at least twice a year. Patients underwent assessment of their pain severity using the Barrow Neurological Institute (BNI) Scale before treatment and at follow-up and were questioned about adverse events following cranial MRI performed after implantation of a permanent PNFS system.

RESULTS

Eight patients (3 women) underwent PNFS trials and their median age was 61 years (IQR 73.75 - 46.5 years). Seven patients proceeded to permanent implantation of the stimulation system. At a median follow-up of 33 months (IQR 42 - 24 months), pain severity decreased from baseline to the last follow-up (BNI score decrease from V [IQR V - V] to III [IQR V - III], p = 0.054). Four patients experienced long-lasting benefit (at 48, 33, 24, and 15 months' follow-up, respectively), while in 3 patients the treatment eventually failed after an initially successful period. One patient had an infection, requiring system removal and subsequent reimplantation. No other complications occurred. No adverse events were noted in the patients undergoing MRI postimplantation.

CONCLUSIONS

This analysis indicates a possibly beneficial long-term effect of PNFS on refractory trigeminal neuralgia attributed to MS in some patients.

Electrical stimulation of cranial nerves in cognition and disease

The cranial nerves are the pathways through which environmental information (sensation) is directly communicated to the brain, leading to perception, and giving rise to higher cognition. Because cranial nerves determine and modulate brain function, invasive and non-invasive cranial nerve electrical stimulation methods have applications in the clinical, behavioral, and cognitive domains. Among other neuromodulation approaches such as peripheral, transcranial and deep brain stimulation, cranial nerve stimulation is unique in allowing axon pathway-specific engagement of brain circuits, including thalamo-cortical networks. In this review we amalgamate relevant knowledge of 1) cranial nerve anatomy and biophysics; 2) evidence of the modulatory effects of cranial nerves on cognition; 3) clinical and behavioral outcomes of cranial nerve stimulation; and 4) biomarkers of nerve target engagement including physiology, electroencephalography, neuroimaging, and behavioral metrics. Existing non-invasive stimulation methods cannot feasibly activate the axons of only individual cranial nerves. Even with invasive stimulation methods, selective targeting of one nerve fiber type requires nuance since each nerve is composed of functionally distinct axon-types that differentially branch and can anastomose onto other nerves. None-the-less, precisely controlling stimulation parameters can aid in affecting distinct sets of axons, thus supporting specific actions on cognition and behavior. To this end, a rubric for reproducible dose-response stimulation parameters is defined here. Given that afferent cranial nerve axons project directly to the brain, targeting structures (e.g. thalamus, cortex) that are critical nodes in higher order brain networks, potent effects on cognition are plausible. We propose an intervention design framework based on driving cranial nerve pathways in targeted brain circuits, which are in turn linked to specific higher cognitive processes. State-of-the-art current flow models that are used to explain and design cranial-nerve-activating stimulation technology require multi-scale detail that includes: gross anatomy; skull foramina and superficial tissue layers; and precise nerve morphology. Detailed simulations also predict that some non-invasive electrical or magnetic stimulation approaches that do not intend to modulate cranial nerves per se, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), may also modulate activity of specific cranial nerves. Much prior cranial nerve stimulation work was conceptually limited to the production of sensory perception, with individual titration of intensity based on the level of perception and tolerability. However, disregarding sensory emulation allows consideration of temporal stimulation patterns (axon recruitment) that modulate the tone of cortical networks independent of sensory cortices, without necessarily titrating perception. For example, leveraging the role of the thalamus as a gatekeeper for information to the cerebral cortex, preventing or enhancing the passage of specific information depending on the behavioral state. We show that properly parameterized computational models at multiple scales are needed to rationally optimize neuromodulation that target sets of cranial nerves, determining which and how specific brain circuitries are modulated, which can in turn influence cognition in a designed manner.

Placement and Anchoring of Trigeminal Neurostimulation Electrodes: Technical Report

BACKGROUND

Peripheral neurostimulation (PNS) for medically refractory trigeminal and craniofacial pain is an emerging alternative to traditional surgical approaches. Technical problems with craniofacial PNS have included electrode migration and erosion, limiting the utility and cost-effectiveness of this procedure.

OBJECTIVE

To review our institutional surgical technique for trigeminal PNS implantation, focusing on a novel technique for electrode anchoring.

METHODS

Consecutive cases of permanent craniofacial PNS placement by a single surgeon over 36 months were reviewed for surgical technique and technical outcomes. Electrodes were placed percutaneously with open anchoring to the pericranium at a separate parietal incision.

RESULTS

Sixteen systems (53 electrodes) were implanted in 14 patients. Median follow-up was 13 months (range, 5-29 months). Electrode placement was successful in all cases with no intraoperative complications. There was 1 lead migration (6.3% per patient; 1.8% per lead) and no cases of erosion. Two patients (14.3%) required explant for infection, 1 of whom was successfully reimplanted. Three patients (21.4%) underwent surgical revision other than for infection.

CONCLUSIONS

We present an improved method for craniofacial PNS surgery which introduces a separate incision for electrode anchoring at the parietal boss. This technique simplifies the procedure and greatly reduces rates of erosion and migration, improving patient comfort and satisfaction.

Recent advances in understanding/managing trigeminal neuralgia

Despite recent advances in understanding and treating trigeminal neuralgia, its management remains a considerable challenge. Better classification of different types of facial pain and the identification of prognostic factors for different treatment options lead the way toward better quality of life for the individual patient. Although the principles of treating trigeminal neuralgia remain basically the same, antiepileptic drugs, muscle relaxants, and neuroleptic agents are widely used medical treatment options. They were not originally developed for treating trigeminal neuralgia. Carbamazepine was studied in adequate placebo-controlled clinical trials in the 1960s and is still considered the most effective drug. Among emerging treatment options currently under clinical investigation are local botulinum neurotoxin type A injections and a novel sodium channel blocker (CNV1014802) that selectively blocks the Na _v1.7 sodium channel. Non-pharmacological treatment options are non-invasive electrical stimulation with either transcranial direct-current stimulation or repetitive transcranial magnetic stimulation which both require further evaluation in regard to applicability. Surgical options remain a valid choice for patients not responding to medical treatment and include Gasserian ganglion percutaneous techniques, gamma knife surgery, and microvascular decompression. There is continual effort to improve these techniques and predict the outcome for better patient selection.

Double Blinded Randomized Trial of Subcutaneous Trigeminal Nerve Stimulation as Adjuvant Treatment for Major Unipolar Depressive Disorder

BACKGROUND

More than 30% of major depressive disorder patients fail to respond to adequate trials of medications and psychotherapy. While modern neuromodulation approaches (ie, vagal nerve stimulation, deep brain stimulation) are yet to prove their efficacy for such cases in large randomized controlled trials, trigeminal nerve stimulation (TNS) has emerged as an alternative with promising effects on mood disorders.

OBJECTIVE

To assess efficacy, safety, tolerability, and placebo effect duration of continuous subcutaneous TNS (sTNS) in treatment-resistant depression (TRD).

METHODS

The TREND study is a single-center, double-blind, randomized, controlled, phase II clinical trial. Twenty unipolar TRD patients will receive V1 sTNS as adjuvant to medical therapy and randomized to active vs sham stimulation throughout a 24-wk period. An additional 24-wk open-label phase will follow. Data concerning efficacy, placebo response, relapse, and side effects related to surgery or electrical stimulation will be recorded. We will use the HDRS-17, BDI-SR, IDS_SR30, and UKU scales.

EXPECTED OUTCOMES

The main outcome measure is improvement in depression scores using HAM-17 under continuous sTNS as adjuvant to antidepressants. Active stimulation is expected to significantly impact response and remission rates. Minor side effects are expected due to the surgical procedure and electrical stimulation. The open-label phase should further confirm efficacy and tolerability.

DISCUSSION

This study protocol is designed to define efficacy of a novel adjuvant therapy for TRD. We must strive to develop safe, reproducible, predictable, and well-tolerated neuromodulation approaches for TRD patients impaired to manage their lives and contribute with society.

After microvascular decompression to treat trigeminal neuralgia, both immediate pain relief and recurrence rates are higher in patients with arterial compression than with venous compression

We explored differences in postoperative pain relief achieved through decompression of the trigeminal nerve compressed by arteries and veins. Clinical characteristics, intraoperative findings, and postoperative curative effects were analyzed in 72 patients with trigeminal neuralgia who were treated by microvascular decompression. The patients were divided into arterial and venous compression groups based on intraoperative findings. Surgical curative effects included immediate relief, delayed relief, obvious reduction, and invalid result. Among the 40 patients in the arterial compression group, 32 had immediate pain relief of pain (80.0%), 5 cases had delayed relief (12.5%), and 3 cases had an obvious reduction (7.5%). In the venous compression group, 12 patients had immediate relief of pain (37.5%), 13 cases had delayed relief (40.6%), and 7 cases had an obvious reduction (21.9%). During 2-year follow-up period, 6 patients in the arterial compression group experienced recurrence of trigeminal neuralgia, but there were no recurrences in the venous compression group. Simple artery compression was followed by early relief of trigeminal neuralgia more often than simple venous compression. However, the trigeminal neuralgia recurrence rate was higher in the artery compression group than in the venous compression group.

Neuromodulation and Devices in Trigeminal Neuralgia

PREMISE

Trigeminal neuralgia is a severe facial pain disorder that has been studied for decades. Classical trigeminal neuralgia (CTN) is either idiopathic or caused by neurovascular compression. The related painful trigeminal neuropathies are often secondary to other causes, such as multiple sclerosis or trauma.

PROBLEM

Therapies for trigeminal neuralgia and neuropathy have often been pharmacologic or surgical. Pharmacologic therapies are not effective in some cases and often cause side effects, some substantial. Surgery can have comorbidity (such as anesthesia dolorosa, or painful differentiation of the affected nerve distribution) and also is not always effective. There is a desire, as in all chronic conditions, to find effective treatments with minimal morbidity and side effects.

POTENTIAL SOLUTIONS

We review several devices including neuromodulation, ranging in invasiveness, for treatment of trigeminal neuralgia and neuropathy. We review existing data on sphenopalatine ganglion blocks, transcranial magnetic stimulation, transcortical direct stimulation, deep brain stimulation, spinal cord stimulation, peripheral nerve stimulation, and transcutaneous electrical stimulation for CTN and pain trigeminal neuropathies. We also offer hope for further research in this area with the goal of discovering a device that can provide treatment for many with few side effects and minimal morbidity.

Subcutaneous Trigeminal Nerve Field Stimulation for Refractory Facial Pain

Chronic or neuropathic trigeminal facial pain can be challenging to treat. Neurosurgical procedures should be applied when conservative treatment fails. Neuromodulation techniques for chronic facial pain include deep brain stimulation and motor cortex stimulation, which are complex to perform. Subcutaneous nerve field stimulation is certified for chronic back pain and is the least invasive form of neuromodulation. We applied this technique to treat chronic and neuropathic trigeminal pain as an individual therapy concept. First, trial stimulation is performed. Subcutaneous leads are placed in the painful trigeminal dermatome under local anesthesia. The leads are connected to an external neurostimulator that applies constant stimulation. Patients undergo a 12 day outpatient trial to assess the effect of the stimulation. Electrodes are removed after the trial. If the patient reports pain reduction of at least 50% in intensity and/or attack frequency, a reduction in medication or increase in quality of life, permanent implantation is scheduled. New electrodes are implanted under general anesthesia and are subcutaneously tunneled to an infraclavicular internal pulse generator. Patients are able to turn stimulation on and off and to increase or decrease the stimulation amplitude as needed. This technique represents a minimal invasive alternative to other more invasive means of neuromodulation for trigeminal pain such as motor cortex stimulation or deep brain stimulation.