A 12-month prospective study of gasserian ganglion stimulation for trigeminal neuropathic pain

Gasserian ganglion stimulation for refractory trigeminal neuropathic pain

BACKGROUND AND OBJECTIVE

Painful trigeminal neuropathy is a complex clinical entity due to its severity and refractoriness to pharmacological and interventional management. We describe our experience in treating refractory painful trigeminal neuropathy (RPTN) with gasserian ganglion stimulation (GGS).

MATERIALS AND METHODS

Six patients with RPTN were treated with GGS in our Unit between 2019 and 2022. The following data were collected: socio-demographic characteristics, triggering event, duration of the disease and treatment received prior to surgery, pre- and post-intervention visual analogue scale (VAS) score, follow-up time, and pre- and post-intervention functionality and quality of life.

RESULTS

All patients were women who had received aggressive first-, second-, and third-line pharmacological, non-pharmacological, and interventional management before being referred for GGS. Patients reported a 50%-72% decrease in pain on VAS and improved functionality during follow-up.

CONCLUSIONS

GGS is a promising therapeutic alternative for patients with RPTN. Although the initial outcomes and experience are encouraging, RPTN is recommended on the basis of safety, reproducibility, and trends observed in clinical practice.

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.

An Anatomical Study of the Foramen Ovale for Neuromodulation of Trigeminal Neuropathic Pain

OBJECTIVE

Neuromodulation for trigeminal pain syndromes such as trigeminal neuropathic pain (TNP) necessitates accurate localization of foramen ovale (FO). The Härtel-type approach is very well-established and safe, ideal for temporary cannulation of the FO for ablative procedures such as balloon microcompression. A key shortcoming of the Hartel approach for placement of neuromodulation leads is the limited opportunity for secure anchoring. The aim of this study is to introduce a novel surgical approach for the treatment of TNP by investigating key osseous landmarks and their spatial relationships to the FO.

MATERIALS AND METHODS

Sixteen sides of cadaver heads were dissected to investigate a surgical route of the FO via transoral gingival buccal approach. Alveolar arch of the maxilla and zygomaticomaxillary suture were selected to serve as an osseous landmark for the surgical guidance to the FO. Through the intraoral route, a needle simulating electrode was traversed to aim the FO from the inferior lateral to the superior medial direction to target specific fibers of the aimed division of the nerve.

RESULTS

Visual identification and access to the trigeminal nerve at the external opening of FO was successful in all 16 hemifacial cadavers. A needle successfully targeted different regions of the trigeminal nerve by changing the angle of the trajectory allowing the needle to reach a specific division of the trigeminal nerve.

CONCLUSIONS

This study provides a novel means of approaching the FO via transoral gingival buccal access.

Design and manufacturing challenges of optogenetic neural interfaces: a review

Optogenetics is a relatively new technology to achieve cell-type specific neuromodulation with millisecond-scale temporal precision. Optogenetic tools are being developed to address neuroscience challenges, and to improve the knowledge about brain networks, with the ultimate aim of catalyzing new treatments for brain disorders and diseases. To reach this ambitious goal the implementation of mature and reliable engineered tools is required. The success of optogenetics relies on optical tools that can deliver light into the neural tissue. Objective/Approach: Here, the design and manufacturing approaches available to the scientific community are reviewed, and current challenges to accomplish appropriate scalable, multimodal and wireless optical devices are discussed.

SIGNIFICANCE

Overall, this review aims at presenting a helpful guidance to the engineering and design of optical microsystems for optogenetic applications.

Successful Management of Corneal Neuropathic Pain with Intrathecal Targeted Drug Delivery

OBJECTIVE

To describe the successful treatment of refractory corneal neuropathic pain with neuromodulation techniques.

DESIGN

Single case report.

SETTING

Academic tertiary care center in the United States of America.

SUBJECT AND METHODS

A 30-year-old woman presented with a 7-year history of refractory bilateral keratoneuralgia following laser-assisted in-situ keratomileusis (LASIK) procedure on both eyes. Having failed all conservative measures, the patient initially underwent trigeminal nerve stimulation and subsequently was implanted with an intrathecal drug delivery system (IDDS) with the catheter placed at the level C1.

RESULTS

Following an initial favorable response to the trigeminal nerve stimulator, the pain became refractory to neurostimulation after a few months and the system was explanted. The patient was successfully trialed with an intrathecal catheter placed at the level of C1 delivering a combination of bupivacaine and low dose fentanyl. The patient was then implanted with an IDDS equipped with a patient-activated bolus system. The patient was very satisfied with the treatment and has had greater than 50% pain relief for over a year.

CONCLUSIONS

Intrathecal delivery of bupivacaine and low dose fentanyl in the upper cervical spine can be effective in controlling refractory eye pain in properly selected patients and treatment centers.

Neuromodulation for cephalgias

Headaches (cephalgias) are a common reason for patients to seek medical care. There are groups of patients with recurrent headache and craniofacial pain presenting with malignant course of their disease that becomes refractory to pharmacotherapy and other medical management options. Neuromodulation can be a viable treatment modality for at least some of these patients. We review the available evidence related to the use of neuromodulation modalities for the treatment of medically refractory craniofacial pain of different nosology based on the International Classification of Headache Disorders, 2(nd) edition (ICHD-II) classification. This article also reviews the scientific rationale of neuromodulation application in management of cephalgias.

Optogenetics: a novel optical manipulation tool for medical investigation

Optogenetics is a new and rapidly evolving gene and neuroengineering technology that allows optical control of specific populations of neurons without affecting other neurons in the brain at high temporal and spatial resolution. By heterologous expression of the light-sensitive membrane proteins, cell type-specific depolarization or hyperpolarization can be optically induced on a millisecond time scale. Optogenetics has the higher selectivity and specificity compared to traditional electrophysiological techniques and pharmaceutical methods. It has been a novel promising tool for medical research. Because of easy handling, high temporal and spatial precision, optogenetics has been applied to many aspects of nervous system research, such as tactual neural circuit, visual neural circuit, auditory neural circuit and olfactory neural circuit, as well as research of some neurological diseases. The review highlights the recent advances of optogenetics in medical study.

Optical control after transfection of channelrhodopsin-2 recombinant adenovirus in visual cortical cells

Channelrhodopsin-2 ectopically expressed in the retina can recover the response to blue light in genetically blind mice and rats, but is unable to restore visual function due to optic nerve or optic tract lesions. Long Evans rats at postnatal day 1 were used for primary culture of visual cortical cells, and 24 hours later, cells were transfected with recombinant adenovirus carrying channelrhodopsin-2 and green fluorescent protein genes. After 2-4 days of transfection, green fluorescence was visible in the cultured cells. Cells were stimulated with blue light (470 nm), and light-induced action potentials were recorded in patch-clamp experiments. Our findings indicate that channelrhodopsin-2-recombinant adenovirus transfection of primary cultured visual cortical cells can control the production of action potentials via blue light stimulation.

1. Trigeminal neuralgia

Trigeminal neuralgia is a common cause of facial pain. It has a significant impact on the quality of life and the socioeconomic functioning of the patient. The aim of this review is to provide recommendations for medical management of trigeminal neuralgia based on current evidence. Based upon the analyses of the literature combined with experience in pain management, symptoms, assessment, differential diagnosis, and treatment possibilities of trigeminal neuralgia are described and discussed. Recommendations for pain management are given and are displayed in a clinical practice algorithm. Treatment should be multidisciplinary. Various treatment options and their risks should be discussed with the patient. The first treatment of choice is carbamazepine or oxcarbazepine. In younger patients, the first choice of invasive treatment is probably microvascular decompression. For elderly patients, radiofrequency treatment of Gasserian ganglion is recommended and the technique is described in detail.

Peripheral nerve stimulation for neuropathic pain

Peripheral nerve stimulation (PNS) has been used for treatment of neuropathic pain for more than 40 years. Recent resurgence of interest to this elegant surgical modality came from the introduction of less invasive implantation techniques and the wider acceptance of neuromodulation as a treatment of medically refractory cases. This article reviews the literature on the use of PNS for neuropathic pain and describes current indications and hardware choices in frequent use. Published experience indicates that neuropathic pain responds to PNS in many patients. PNS works well in both established indications, such as post-traumatic and postsurgical neuropathy, occipital neuralgia, and complex regional pain syndromes, and in relatively new indications for neuromodulation, such as migraines and daily headaches, cluster headaches, and fibromyalgia. Future research and growing clinical experience will help in identifying the best candidates for PNS, choosing the best procedure and best hardware for each individual patient, and defining adequate expectations for patients and pain specialists.

Circuit-breakers: optical technologies for probing neural signals and systems

Neuropsychiatric disorders, which arise from a combination of genetic, epigenetic and environmental influences, epitomize the challenges faced in understanding the mammalian brain. Elucidation and treatment of these diseases will benefit from understanding how specific brain cell types are interconnected and signal in neural circuits. Newly developed neuroengineering tools based on two microbial opsins, channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR), enable the investigation of neural circuit function with cell-type-specific, temporally accurate and reversible neuromodulation. These tools could lead to the development of precise neuromodulation technologies for animal models of disease and clinical neuropsychiatry.