Advances in diagnosis and treatment of trigeminal neuralgia

A Comparison Between the Efficacy of Trigeminal Ganglion Radiofrequency Thermocoagulation and Ultrasound-Guided Maxillary-Mandibular Nerve Pulsed Radiofrequency in the Treatment of Trigeminal Neuralgia: A Randomized Clinical Trial

Background and objective Trigeminal neuralgia (TN) is a debilitating disorder characterized by acute episodic attacks of pain that significantly impair patients' quality of life and overall functioning. Initial therapeutic strategies to treat this condition include pharmacological options, particularly carbamazepine. In cases with resistance to dose escalation and polypharmacy, interventional procedures may be warranted. The primary aim of this study was to compare the efficacy of trigeminal ganglion (TG) radiofrequency thermocoagulation (RFT) and ultrasound (US)-guided maxillary/mandibular (max/mand) nerve pulsed radiofrequency (PRF) for treating TN, based on the findings at six months post-treatment. The secondary aims were to assess the impact of these interventions on drug consumption and interventional safety based on adverse events. Methods This prospective, randomized, single-blind study was conducted at a single pain clinic. Forty-four patients were randomized into two groups. Group RFT received TG RFT at 60 °C, 65 °C, and 70 °C for 60 seconds each, whereas Group PRF received max/mand PRF for 240 seconds. Pain relief was assessed by using the numeric rating scale (NRS) and intervention effectiveness on medication consumption was evaluated by using the Medication Quantification Scale III (MQS III). The rates of intervention-related adverse events were also compared. Results Both RFT and PRF significantly alleviated pain at one and six months post-treatment compared to baseline (p<0.05). No statistical differences were found in the NRS and MQS III scores between the groups. At six months, 77.3% of RFT patients and 63.9% of PRF patients experienced at least 50% pain relief, with no statistically significant difference. Hypoesthesia occurred in two RFT patients, and masseter weakness was observed in one patient, while no adverse events were reported in the PRF group. Conclusions TG RFT and max/mand PRF are effective treatments for TN. US-guided max/mand PRF, which avoids RFT-associated complications and radiation exposure, may be the superior and preferable option. In this study, the potential space between the coronoid process and maxilla was used to access the maxillary nerve during the maxillary block and PRF procedures, in contrast to the classical approach through the mandibular notch. Further large-scale randomized controlled trials are required to gain deeper insights into the topic.

Deciphering the functional role of insular cortex stratification in trigeminal neuropathic pain

Trigeminal neuropathic pain (TNP) is a major concern in both dentistry and medicine. The progression from normal to chronic TNP through activation of the insular cortex (IC) is thought to involve several neuroplastic changes in multiple brain regions, resulting in distorted pain perception and associated comorbidities. While the functional changes in the insula are recognized contributors to TNP, the intricate mechanisms underlying the involvement of the insula in TNP processing remain subjects of ongoing investigation. Here, we have overviewed the most recent advancements regarding the functional role of IC in regulating TNP alongside insights into the IC's connectivity with other brain regions implicated in trigeminal pain pathways. In addition, the review examines diverse modulation strategies that target the different parts of the IC, thereby suggesting novel diagnostic and therapeutic management of chronic TNP in the future.

Trigeminal neuralgia with enlarged suprameatal tubercle: A case report

According to the International Classification of Orofacial Pain (ICOP), secondary trigeminal neuralgia can result from various conditions such as tumors in the cerebellopontine angle, arteriovenous malformation, and multiple sclerosis. This case report describes a 41-year-old woman with trigeminal neuralgia caused by narrowing of the cerebellopontine cistern due to an enlarged suprameatal tubercle. Carbamazepine treatment was initially effective, but became inadequate within a few months. Magnetic resonance imaging revealed compression of the trigeminal nerve by the superior cerebellar artery and an enlarged suprameatal tubercle. Microvascular decompression surgery was done to alleviate the neurovascular compression. Dentists should be aware of such anatomical factors contributing to trigeminal neuralgia, particularly in younger patients. Key words:Trigeminal neuralgia, enlarged suprameatal tubercle, microvascular decompression.

Systematic review on the frequency of occurrence in nerve branches and the side of the face involved in trigeminal neuralgia and its clinical implication

Purpose

The purpose of this systematic review is to answer the focused question, "What is the commonly affected nerve branch and the side of the face involved in trigeminal neuralgia?"

Types of studies reviewed

This systematic review included studies reporting commonly affected trigeminal nerve branches and the side of the face involved in trigeminal neuralgia. To find the potential studies published, the authors utilized specific search databases such as PubMed, and Google scholar.

Results

Among 132 published studies, the authors selected only 11 to be included for this systematic review. The sample size ranged from 50 to 43,518 study subjects. This review identified that the mandibular branches of the trigeminal nerve were the most affected, followed by the maxillary branch. The review also identified that the right side of the face was predominantly affected.

Conclusion and practical implications

The authors of this review identified a higher occurrence of trigeminal neuralgia in the mandibular division of the nerve, commonly affected on the right side of the face. Further prospective-based research and meta-analysis are required to validate the commonly occurring trigeminal nerve branch and sidedness of the face involved with its clinical implications in trigeminal neuralgia.

The CSF1-CSF1R pathway in the trigeminal ganglion mediates trigeminal neuralgia via inflammatory responses in mice

BACKGROUND

Trigeminal neuralgia (TN) is the most severe type of neuropathic pain. The trigeminal ganglion (TG) is a crucial target for the pathogenesis and treatment of TN. The colony-stimulating factor 1 (CSF1) - colony-stimulating factor 1 receptor (CSF1R) pathway regulates lower limb pain development. However, the effect and mechanism of the CSF1-CSF1R pathway in TG on TN are unclear.

METHODS

Partial transection of the infraorbital nerve (pT-ION) model was used to generate a mouse TN model. Mechanical and cold allodynia were used to measure pain behaviors. Pro-inflammatory factors (IL-6, TNF-a) were used to measure inflammatory responses in TG. PLX3397, an inhibitor of CSF1R, was applied to inhibit the CSF1-CSF1R pathway in TG. This pathway was activated in naïve mice by stereotactic injection of CSF1 into the TG.

RESULTS

The TN model activated the CSF1-CSF1R pathway in the TG, leading to exacerbated mechanical and cold allodynia. TN activated inflammatory responses in the TG manifested as a significant increase in IL-6 and TNF-a levels. After using PLX3397 to inhibit CSF1R, CSF1R expression in the TG declined significantly. Inhibiting the CSF1-CSF1R pathway in the TG downregulated the expression of IL-6 and TNF-α to reduce allodynia-related behaviors. Finally, mechanical allodynia behaviors were exacerbated in naïve mice after activating the CSF1-CSF1R pathway in the TG.

CONCLUSIONS

The CSF1-CSF1R pathway in the TG modulates TN by regulating neuroimmune responses. Our findings provide a theoretical basis for the development of treatments for TN in the TG.

When the nerve keeps firing: an institutional experience and systematic review on delayed response after microvascular decompression for trigeminal neuralgia

BACKGROUND

This study aimed to investigate the occurrence of delayed response following microvascular decompression (MVD) in patients with trigeminal neuralgia (TN) and identify potential contributing factors. Additionally, we present two cases with delayed relief observed at our institution.

METHOD

Two TN patients with delayed response and clear intra-operative arterial findings are presented in this study. Furthermore, we conducted a systematic review by searching electronic bibliographic databases, including MEDLINE (PubMed), Web of Science, Scopus, and Embase, from inception to 2022.

RESULTS

We identified a total of 28 full-text articles involving 322 TN patients who experienced delayed pain relief. Out of these, only 11 studies provided sufficient evidence and were included in the final analysis. Among the patients, 73.46% were female. The mean incidence rate of delayed response after MVD treatment for TN was 10.5%, with a range of 0.95 to 57.14% across different studies. The mean age of these patients was 59.86 years. The reported time to pain relief in the existing reports was at least 4 days post-surgery. In 72.88% of the reported cases, right-side dominance was observed. The majority of delayed cases experienced pain relief within 3 months, with a median time of 1 month.

CONCLUSIONS

A thorough examination of the probability of delayed pain relief after MVD for TN and understanding the characteristics of this phenomenon can offer surgeons valuable post-operative guidance and aid in decision-making regarding potential immediate reoperation.

Effectiveness of gamma knife radiosurgery in the management of trigeminal neuralgia associated with multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Trigeminal neuralgia (TN) is a chronic condition characterized by intense facial pain akin to electric shocks, often associated with the trigeminal nerve. It can be either idiopathic or secondary, with multiple sclerosis (Ms) being a significant contributing factor. Non-responsive patients may opt for minimally invasive procedures, such as gamma knife radiosurgery (GKRS), which offers precise, non-invasive treatment and is frequently chosen as a primary approach. This meta-analysis evaluates the long-term efficacy of GKRS in TN management in Ms patients.

METHODS

We conducted a focused search across various databases. Inclusion criteria encompassed studies with ≥ 30 patients using GKRS for TN in Ms, reporting pertinent clinical outcomes. Primary outcomes assessed GKRS efficacy through Barrow Neurological Institute Pain scores. Secondary outcomes encompassed bothersome numbness, facial numbness, and recurrence. Data analysis employed OpenMeta, random effect models, and odds ratios with 95% confidence intervals. Heterogeneity was assessed using I2 statistics.

RESULTS

Fourteen studies with 752 cases of GKRS for TN were included. Regarding the outcomes, 83% of patients experienced a positive initial pain response, while the overall treatment success rate was 51%. Additionally, 19.6% of patients reported facial numbness, 4.1% experienced bothersome numbness, and 40% faced recurrence. The odds ratio for positive initial pain response was 0.83 (95% CI, 0.76-0.89), while for treatment success, it was 0.51 (95% CI, 0.379-0.639). Facial numbness had an odds ratio of 0.196 (95% CI, 0.130-0.262), bothersome numbness had an odds ratio of 0.041 (95% CI, 0.013-0.069), and recurrence had an odds ratio of 0.403 (95% CI, 0.254-0.551).

CONCLUSIONS

In conclusion, treating trigeminal neuralgia in multiple sclerosis patients remains challenging. GKRS shows promise, but customized treatment approaches tailored to individual patient characteristics are urgently needed to address the unique challenges of this condition.

Occipital Nerve Stimulation for Recurrent Trigeminal Neuralgia Without Occipital Pain

OBJECTIVES

Trigeminal neuralgia (TN) is a severe, debilitating pain condition causing physical and emotional distress. Although the management of TN is well codified with medical and then surgical treatments, 15% to 30% of patients will experience intractable pain. Neuromodulation techniques have been scarcely used for refractory TN, with only small case series and short-term follow-up.

MATERIALS AND METHODS

We conducted a retrospective study of patients treated with occipital nerve stimulation (ONS) for medically and surgically resistant TN without painful trigeminal neuropathy. The effectiveness of the ONS was evaluated using the Barrow Neurological Institute (BNI) pain score and the pain relief (0%-100%) at best and at last follow-up.

RESULTS

Seven patients who have refractory TN were included. The mean age at ONS was 49 years. The mean pain duration was 8.6 years. The mean number of medical and surgical treatments before ONS was six and five, respectively. A percutaneous trial was performed in five of seven patients; all responded (pain relief > 40%), and four of five patients experienced pain recurrence after explantation. Eventually, six patients had a permanent ONS implantation. The average BNI pain score before implantation was V. The mean follow-up after implantation was 59 months. All patients reported an improvement after implantation. The average BNI score and mean pain relief at best were IIIa and 86.7%, respectively. At last follow-up, the average BNI score and mean pain relief were IIIa and 58.0%, respectively, with three patients experiencing pain recurrence. Adverse events were reported for four patients who required surgical revision for lead breakage (1), erosion (1), migration (1), or hardware-related discomfort (1). One patient finally underwent explantation because of infection.

CONCLUSIONS

Although ONS is not validated in this indication, these results suggest that it can induce an improvement in TN recurring after several surgical treatments, and the benefit of the stimulation can be sustained in the long term.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT01842763.

The role of artificial intelligence in the management of trigeminal neuralgia

Trigeminal neuralgia (TN) is the most frequent facial pain. It is difficult to treat pharmacologically and a significant amount of patients can become drug-resistant requiring surgical intervention. From an etiologically point of view TN can be distinguished in a classic form, usually due to a neurovascular conflict, a secondary form (for example related to multiple sclerosis or a cerebello-pontine angle tumor) and an idiopathic form in which no anatomical cause is identifiable. Despite numerous efforts to treat TN, many patients experience recurrence after multiple operations. This fact reflects our incomplete understanding of TN pathogenesis. Artificial intelligence (AI) uses computer technology to develop systems for extension of human intelligence. In the last few years, it has been a widespread of AI in different areas of medicine to implement diagnostic accuracy, treatment selection and even drug production. The aim of this mini-review is to provide an up to date of the state-of-art of AI applications in TN diagnosis and management.

Therapeutic Approach for Trigeminal Neuralgia: A Systematic Review

This umbrella review aimed to determine the various drugs used to treat trigeminal neuralgia (TN) and to evaluate their efficacies as well as side effects by surveying previously published reviews. An online search was conducted using PubMed, CRD, EBSCO, Web of Science, Scopus, and the Cochrane Library with no limits on publication date or patients' gender, age, and ethnicity. Reviews and meta-analyses of randomized controlled trials pertaining to drug therapy for TN, and other relevant review articles added from their reference lists, were evaluated. Rapid reviews, reviews published in languages other than English, and reviews of laboratory studies, case reports, and series were excluded. A total of 588 articles were initially collected; 127 full-text articles were evaluated after removing the duplicates and screening the titles and abstracts, and 11 articles were finally included in this study. Except for carbamazepine, most of the drugs had been inadequately studied. Carbamazepine and oxcarbazepine continue to be the first choice for medication for classical TN. Lamotrigine and baclofen can be regarded as second-line drugs to treat patients not responding to first-line medication or for patients having intolerable side effects from carbamazepine. Drug combinations using carbamazepine, baclofen, gabapentin, ropivacaine, tizanidine, and pimozide can yield satisfactory results and improve the tolerance to the treatment. Intravenous lidocaine can be used to treat acute exaggerations and botulinum toxin-A can be used in refractory cases. Proparacaine, dextromethorphan, and tocainide were reported to be inappropriate for treating TN. Anticonvulsants are successful in managing trigeminal neuralgia; nevertheless, there have been few studies with high levels of proof, making it challenging to compare or even combine their results in a statistically useful way. New research on other drugs, combination therapies, and newer formulations, such as vixotrigine, is awaited. There is conclusive evidence for the efficacy of pharmacological drugs in the treatment of TN.

Trigeminal Neuralgia Due to Unilateral Early Bifurcated Superior Cerebellar Artery: Case Report and Literature Review

Trigeminal neuralgia (TN) is considered a debilitating pain syndrome resulting from a neurovascular conflict in the prepontine cistern, usually through compression of the trigeminal nerve by the superior cerebellar artery (SCA), resulting in neural pathology at the root entry zone. This is a case report of a patient whose TN symptoms were attributed to an anatomical variant of the SCA, managed successfully through conservative treatment. Anatomical variants of the SCA have been related to TN. However, this is the first reported case in the PubMed literature of primary TN due to an unilateral early bifurcated SCA treated conservatively with first-line sodium channel blockers with a good outcome.

Sex differences in patient journeys to diagnosis, referral, and surgical treatment of trigeminal neuralgia: implications for equitable care

OBJECTIVE

Trigeminal neuralgia (TN) is an orofacial pain disorder that is more prevalent in females than males. Although an increasing number of studies point to sex differences in chronic pain, how sex impacts TN patients' journeys to care has not been previously addressed. This study sought to investigate sex differences in patients' journeys to diagnosis, referral, and treatment of TN within a large national context.

METHODS

Patients with classic TN (n = 100; 50 females and 50 males) were randomly selected through chart reviews at the largest surgical treatment center for TN in Canada for a cross-sectional study. Statistical tests, including Welch's t-test, the chi-square test, Pearson's correlations, and analyses of covariance, were conducted with Python.

RESULTS

Key discrepancies between sexes in access to care were identified. Females had a significantly longer referral time interval (average 53.2 months vs 20.4 months, median 27.5 months vs 11.0 months, p = 0.018) and total time interval (average 121.1 months vs 67.8 months, median 78.0 months vs 45.2 months, p = 0.018) than males, despite reporting higher pain intensity at referral. Although medically intolerant patients had a significantly shorter referral time interval than medically tolerant patients (average 13.0 months vs 41.0 months, median 6.0 months vs 17.0 months, p < 0.001), medically tolerant females had a significantly longer referral time interval than medically tolerant males (average 59.9 months vs 21.7 months, median 30.0 months vs 12.0 months, p = 0.017). No statistically significant differences were detected between the sexes for diagnostic time interval (average 63.3 months vs 43.0 months, median 24.0 months vs 24.0 months, p = 0.263) or treatment time interval (average 4.6 months vs 4.7 months, median 4.0 months vs 3.0 months, p = 0.986).

CONCLUSIONS

Critical sex differences in patients' journeys to TN surgical treatment were identified, with females enduring considerably longer referral timelines and expressing significantly greater pain intensity than males at referral. Taken together, our findings suggest the presence of unconscious bias and discrimination against females and highlight the need for expediting TN treatment referral for female TN patients.

Percutaneous high cervical spinal cord stimulation for refractory trigeminal neuralgia

Background

Trigeminal neuralgia (TN) is a debilitating pain that affects the dermatomes associated with the trigeminal nerve (V1, V2, and V3). Unfortunately, many medical treatments and surgical procedures fail to sufficiently modulate the pain associated with this condition.

Case Description

This study presents two extreme cases of refractory TN (RTN) that progressed to atypical facial pain and describes successful mitigation of the neuralgia of said cases by percutaneous implantation of upper cervical spinal cord stimulation (SCS). The SCS was designed to target the descending spinal trigeminal tract.

Conclusion

Together, these cases collaborate with the limited literature and further delineate the use and potential advantages of SCS in the treatment of RTN.

Trigeminal neuralgia secondary to vascular compression and neurocysticercosis: illustrative case

BACKGROUND

Trigeminal neuralgia (TN) is a frequent neurosurgical problem negatively influencing the quality of life of patients. The standard surgical treatment is microvascular decompression for primary cases and decompression of the mass effect, mainly tumors, for secondary cases. Neurocysticercosis (NCC) in the cerebellopontine angle is a rare etiology of TN. The authors report a case in which NCC cysts around the trigeminal nerve coexisted with a vascular loop, which compressed the exit of the trigeminal nerve from the pons.

OBSERVATIONS

A 78-year-old woman presented with a 3-year history of persistent severe pain in the left side of her face, refractory to medical treatment. On gadolinium-enhanced magnetic resonance imaging, cystic lesions were observed around the left trigeminal nerve and a vascular loop was also present and in contact with the nerve. A retrosigmoid approach for cyst excision plus microvascular decompression of the trigeminal nerve was successfully performed. There were no complications. The patient was discharged without facial pain.

LESSONS

Albeit rare, TN secondary to NCC cysts should be considered in the differential diagnosis in NCC-endemic regions. In this case, the cause of the neuralgia was probably both problems, because when both were treated, the patient improved.

Open surgery vs. stereotactic radiosurgery for tumour-related trigeminal neuralgia: A systematic review

BACKGROUND

Secondary trigeminal neuralgia is a facial pain in trigeminal nerve dermatome caused by an underlying disease, such as cerebellopontine angle tumours. Treatment options to relieve the pains were surgical tumour resection and stereotactic radiosurgery of the tumour or trigeminal nerve. This study aims to review the efficacy of open surgery and stereotactic radiosurgery and recommend the treatment of choice for secondary trigeminal neuralgia due to cerebellopontine angle tumours.

METHOD

The inclusion criteria were studies covering patients with trigeminal neuralgia associated with cerebellopontine angle tumours that were treated with either open surgery or stereotactic radiosurgery and reported pain outcomes after treatment. Non-English articles or studies with a population of less than five were excluded. We systematically searched studies from PubMed, Ebscohost, and Cochrane Library from inception until December 20, 2021. Several works of literature from manual search were also added. Selected articles were appraised using a critical appraisal tool for prognostic studies.

RESULT

Included articles were 26 retrospective studies and one prospective study comprising 517 patients. Of 127 schwannomas, 226 epidermoids, 154 meningiomas, and ten other tumours, 320 cases received surgical tumour excision with or without MVD, 196 had tumour-targeted radiosurgery, and 22 underwent nerve-targeted radiosurgery. In surgical series, 92.2 % gained pain improvement, 2.8 % were unchanged, and 4.5 % had recurrence; none of the patients had worsened outcomes. In cases treated with tumour-targeted radiosurgery, the improvement rate was 79.1 %, unchanged at 14.3 %, recurrence at 26.5 %, and worse symptoms rate after the intervention was 6.6 %. Six patients with recurrent pain after tumour-targeted radiosurgery received secondary nerve-targeted radiosurgery with improved outcomes. Only one patient in our review underwent primary nerve-targeted radiosurgery, and the result was satisfactory. One study treated 15 patients with a single session of tumour-targeted and nerve-targeted radiosurgery, with an improvement rate of 93.3 % and a recurrence rate of 21.4 %.

CONCLUSION

Open surgery releasing the nerve root from compressive lesions is advocated to be the first-line treatment to gain satisfactory outcomes. Total removal surgery is recommended if possible. Nerve-targeted radiosurgery should be reserved as a secondary treatment for recurrent cases.

CSF neuron-specific enolase as a biomarker of neurovascular conflict severity in drug-resistant trigeminal neuralgia: a prospective study in patients submitted to microvascular decompression

BACKGROUND

Although neurovascular conflict (NVC) is the most widely accepted cause of trigeminal neuralgia (TN), few articles have analyzed molecular and biochemical mechanisms underlying TN. In the present study, we dosed neuron-specific enolase (NSE) on serum and CSF samples of 20 patients submitted to microvascular decompression (MVD) and correlated these findings with the type of NVC.

METHODS

Blood samples were obtained preoperatively and 48 h after MVD. CSF from trigeminal cistern was intraoperatively obtained. NSE levels were measured using the Diasorin kit (LIAISON®NSE). NVC was classified as "contact" or "trigeminal nerve distortion/indentation" or "trigeminal root atrophy" based on MRI and intraoperative findings. Clinical outcome was measured by acute pain relief (APR) and Barrow Neurological Institute (BNI) scale at last available follow-up (FU; 6.40 ± 5.38 months).

RESULTS

APR was obtained in all patients. A statistically significant BNI reduction was obtained at latest FU (p < 0.0001). Serum NSE levels significantly decreased following MVD (from 12.15 ± 3.02 ng/mL to 8.95 ± 2.83 ng/mL, p = 0.001). The mean CSF NSE value was 48.94 ng/mL, and the mean CSF/serum NSE rate was 4.18 with a strong correlation between these two variables (p = 0.0008). CSF NSE level in "trigeminal root atrophy" group was significantly higher compared to "contact" (p = 0.0045) and "distortion/indentation" (p = 0.010) groups.

CONCLUSION

NSE levels seem to be related to the etiopathology and severity of NVC. A significant reduction of serum NSE levels could be related to the resolution of the NVC and clinical TN improvement.

Different MRI-based methods for the diagnosis of neurovascular compression in trigeminal neuralgia or hemifacial spasm: A network meta-analysis

BACKGROUND

Accurate preoperative diagnosis of neurovascular compression (NVC) is crucial in the treatment of trigeminal neuralgia (TN) or hemifacial spasm (HFS). At present, there are many magnetic resonance imaging (MRI)-based methods for diagnosing NVC in clinical practice. This network meta-analysis (NMA) aimed to evaluate the diagnostic performance of different MRI-based imaging methods for NVC in patients with TN and HFS.

MATERIALS AND METHODS

Related studies based on a search of PubMed, Embase, Web of Science and the Cochrane Library were retrieved. A two-way analysis of variance model was constructed for the Bayesian NMA to compare the performance of different diagnostic imaging methods.

RESULTS

Our search identified 595 articles, of which 26 studies (including 2085 patients) related to 4 diagnostic imaging methods (3D time-of-flight magnetic resonance angiography (3D TOF MRA), high resolution T2-weighted imaging (HR T2WI), 3D TOF MRA combined with HR T2WI, and 3D multimodal image fusion (MIF) based on 3D TOF MRA combined with HR T2WI) were included in this NMA. The results showed that 3D MIF based on 3D TOF MRA combined with HR T2WI had the highest related sensitivity, the highest superiority index and the largest area under the receiver operating characteristic curve among all the methods.

CONCLUSIONS

3D MIF based on 3D TOF MRA combined with HR T2WI had better diagnostic performance for detecting NVC in patients with TN or HSF than other MRI-based imaging methods. This method can be used as an effective tool for preoperative evaluation of MVD.

Modulation of trigeminal neuropathic pain by optogenetic inhibition of posterior hypothalamus in CCI-ION rat

Posterior hypothalamus (PH), an important part of the descending pain processing pathway, has been found to be activated in trigeminal autonomic cephalalgias. However, there are very few studies conducted and information regarding its implications in trigeminal neuropathic pain (TNP). Therefore, we aimed to ascertain whether optogenetic inhibition of PH could affect the outcomes of a chronic constriction injury in the infraorbital nerve (CCI-ION) rat model. Animals were divided into the TNP animal, sham, and naive-control groups. CCI-ION surgery was performed to mimic TNP symptoms, and the optogenetic or null virus was injected into the ipsilateral PH. In vivo single-unit extracellular recordings were obtained from both the ipsilateral ventrolateral periaqueductal gray (vlPAG) and contralateral ventral posteromedial (VPM) thalamus in stimulation "OFF" and "ON" conditions. Alterations in behavioral responses during the stimulation-OFF and stimulation-ON states were examined. We observed that optogenetic inhibition of the PH considerably improved behavioral responses in TNP animals. We found increased and decreased firing activity in the vlPAG and VPM thalamus, respectively, during optogenetic inhibition of the PH. Inhibiting PH attenuates trigeminal pain signal transmission by modulating the vlPAG and trigeminal nucleus caudalis, thereby providing evidence of the therapeutic potential of PH in TNP management.

Functional MRI-Guided Motor Cortex and Deep Brain Stimulation for Intractable Facial Pain: A Novel, Personalized Approach in 1 Patient

BACKGROUND

Facial neuropathic pain syndromes such as trigeminal neuralgia are debilitating disorders commonly managed by medications, vascular decompression, and/or ablative procedures. In trigeminal neuralgia cases unresponsive to these interventions, trigeminal deafferentation pain syndrome (TDPS) can emerge and remain refractory to any further attempts at these conventional therapies. Deep brain stimulation (DBS) and motor cortex stimulation are 2 neuromodulatory treatments that have demonstrated efficacy in small case series of TDPS yet remain largely underutilized. In addition, functional MRI (fMRI) is a tool that can help localize central processing of evoked stimuli such as mechanically triggered facial pain. In this study, we present a case report and operative technique in a patient with TDPS who underwent fMRI to guide the operative management and placement of dual targets in the sensory thalamus and motor cortex.

OBJECTIVE

To evaluate the safety, efficacy, and outcome of a novel surgical approach for TDPS in a single patient.

METHODS

The fMRI and operative technique of unilateral DBS targeting the ventroposteromedial nucleus of the thalamus and facial motor cortex stimulator placement through a single burr hole is illustrated as well as the patient's clinical outcome.

RESULTS

In less than 1 year, the patient had near complete resolution of his facial pain with no postoperative complications.

CONCLUSION

We present the first published case of successful treatment of TDPS using simultaneous DBS of the ventroposteromedial and motor cortex stimulation. fMRI can be used as an effective imaging modality to guide neuromodulation in this complex disorder.

The efficacy and safety of gabapentin vs. carbamazepine in patients with primary trigeminal neuralgia: A systematic review and meta-analysis

Background

Drug therapy is the most commonly used treatment for primary trigeminal neuralgia (PTN), in which carbamazepine is the first-line drug. Recently, the anti-epileptic drug gabapentin has also been widely used in patients with PTN, but whether it can be used as a substitute for carbamazepine still needs to be verified. Our study aimed to assess the safety and efficacy of gabapentin vs. carbamazepine as a treatment for PTN.

Methods

We searched seven electronic databases for studies published as of 31 July 2022. All randomized controlled trials (RCTs) of gabapentin vs. carbamazepine on patients with PTN that met the inclusion criteria were included. Meta-analysis was conducted using Revman 5.4 and Stata 14.0, in which forest plots, funnel plots, and sensitivity analysis were performed. Mean difference (MD) and odds ratio (OR) with 95% confidence intervals (CIs) were used for the measurement indicators of continuous and categorical variables, respectively.

Results

A total of 18 RCTs with 1,604 patients were eventually identified. The meta-analysis showed that compared with the carbamazepine group, the gabapentin group significantly improved the effective rate (OR = 2.02, 95% CI 1.56 to 2.62, P < 0.001), reduced the adverse event rate (OR = 0.28, 95% CI 0.21 to 0.37, P < 0.001), and improved the visual analog scale (VAS) score (MD = -0.46, 95% CI -0.86 to -0.06, P = 0.03). Although the funnel plot showed evidence of publication bias, the sensitivity analysis revealed the stability of the results.

Conclusion

The current evidence showed that gabapentin may be superior to carbamazepine in relation to efficacy and safety in patients with PTN. It is crucial that more RCTs are conducted to confirm the conclusion in the future.

Morphologic and Morphometric Measurements of the Foramen Ovale: Comparing Digitized Measurements Performed on Dried Human Crania With Computed Tomographic Imaging. An Observational Anatomic Study

The foramen ovale (FO) of the sphenoid bone is clinically important for the interventional treatment of trigeminal neuralgia. Percutaneous procedures applied to treat the chronic pain condition typically involve the cannulation of this oval-like foramen located at the base of the skull. Anatomic variations of the FO have been reported to contribute to difficulties in the cannulation of this structure. Computed tomography (CT) can help the surgeon improve the accuracy and safety of the intervention. However, even with navigation technology, unsuccessful cannulation of the FO has been reported. The aim of this observational anatomic study was to define morphometric and morphologic data of the FO and to investigate for potential differences between measurements taken on dried human crania and digitized measurements of the FO measured on CT images. One hundred eighteen FOs were evaluated. Twenty FOs underwent CT scanning. The mean length of the foramen was 7.41±1.3 mm on the left side and 7.57±1.07 mm on the right. The mean width of the foramen was 4.63±0.86 mm on the left side and 4.33±0.99 on the right. The mean area on the left side was 27.11±7.58 and 25.73±6.64 mm 2 on the right. No significant left-right differences were found for any of these dimensions. The most important conclusion that we can draw is that the measurements can indeed be performed on CT images to obtain an accurate picture of the morphology. Considering the surgical importance of the FO and taking into consideration the limitations this study added to scientific knowledge, this study was constructive as far as neurosurgeons and anatomists are concerned.

Neurovascular Structures at Risk During Surgical Access to Trigeminal Ganglion and Meckel's Cave - An Anatomical Study

Background

It is difficult to approach the Trigeminal Ganglion (TG) and Meckel's cave (MC) during surgeries. Therefore, the exact knowledge of the relationship of surgical landmarks to related anatomical structures is vital to reduce the associated postoperative morbidity. The aim of the present study was to enhance the knowledge of the surgical anatomy of structures that are present in the conduit of all surgical approaches to TG and MC, their distances from surrounding neurovascular structures, and their variations.

Material and Methods

The study was carried out on 40 embalmed cadavers (Eight Female) of the anatomy department of a teaching hospital in Central India. Meticulous dissection of cranial fossae was done to locate TG, MC, and related anatomical structures. All distances from TG and MC were measured using an electronic digital calliper.

Results

Length, width, and thickness of TG were 15.39 mm, 4.39 mm, and 2.54 mm, respectively. The distance from zygomatic arch, the lateral end of the petrous ridge, arcuate eminence, foramen ovale, and foramen spinosum to MC was 26.10 mm and 37.94 mm, 16.46 mm, 4.54 mm, and 11.23 mm, respectively. The sixth, fourth, and third cranial nerves were 6.26 mm, 4.94 mm, and 2.53 mm from MC, respectively. The MC was 42.72 mm and 33.87 mm anteromedial from posterior and anterior limits of the sigmoid sinus.

Conclusion

Findings of the present study will aid surgical planning and decide the approach to TG and MC and avoid surgical complications.

Three-dimensional time-of-flight magnetic resonance angiography combined with high resolution T2-weighted imaging in preoperative evaluation of microvascular decompression

BACKGROUND

Neurovascular compression (NVC) is the main cause of primary trigeminal neuralgia (TN) and hemifacial spasm (HFS). Microvascular decompression (MVD) is an effective surgical method for the treatment of TN and HFS caused by NVC. The judgement of NVC is a critical step in the preoperative evaluation of MVD, which is related to the effect of MVD treatment. Magnetic resonance imaging (MRI) technology has been used to detect NVC prior to MVD for several years. Among many MRI sequences, three-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA) is the most widely used. However, 3D TOF MRA has some shortcomings in detecting NVC. Therefore, 3D TOF MRA combined with high resolution T2-weighted imaging (HR T2WI) is considered to be a more effective method to detect NVC.

AIM

To determine the value of 3D TOF MRA combined with HR T2WI in the judgment of NVC, and thus to assess its value in the preoperative evaluation of MVD.

METHODS

Related studies published from inception to September 2022 based on PubMed, Embase, Web of Science, and the Cochrane Library were retrieved. Studies that investigated 3D TOF MRA combined with HR T2WI to judge NVC in patients with TN or HFS were included according to the inclusion criteria. Studies without complete data or not relevant to the research topics were excluded. The Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. The publication bias of the included literature was examined by Deeks’ test. An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize data. Data analysis was performed using the MIDAS module of statistical software Stata 16.0. Two independent investigators extracted patient and study characteristics, and discrepancies were resolved by consensus. Individual and pooled sensitivities and specificities were calculated. The I² statistic and Q test were used to test heterogeneity. The study was registered on the website of PROSERO (registration No. CRD42022357158).

RESULTS

Our search identified 595 articles, of which 12 (including 855 patients) fulfilled the inclusion criteria. Bivariate analysis showed that the pooled sensitivity and specificity of 3D TOF MRA combined with HR T2WI for detecting NVC were 0.96 [95% confidence interval (CI): 0.92-0.98] and 0.92 (95%CI: 0.74-0.98), respectively. The pooled positive likelihood ratio was 12.4 (95%CI: 3.2-47.8), pooled negative likelihood ratio was 0.04 (95%CI: 0.02-0.09), and pooled diagnostic odds ratio was 283 (95%CI: 50-1620). The area under the receiver operating characteristic curve was 0.98 (95%CI: 0.97-0.99). The studies showed no substantial heterogeneity (I²= 0, Q = 0.001 P = 0.50).

CONCLUSION

Our results suggest that 3D TOF MRA combined with HR T2WI has excellent sensitivity and specificity for judging NVC in patients with TN or HFS. This method can be used as an effective tool for preoperative evaluation of MVD.

Surgical and Clinical Outcomes of Microvascular Decompression: A Comparative Study between Young and Elderly Patients

Microvascular decompression (MVD) is the only etiological technique for the treatment of trigeminal neuralgia (TN). Whilst there is a consensus MVD is likely effective regardless of age, the elderly population is thought to be more prone to have a higher rate of surgical complication, morbidity, and mortality. The main objective of our single-center, retrospective study was to analyze the surgical and clinical outcomes of MVD in TN elderly patients. From a surgical series of patients with TN who had undergone MVD from April 2018 to April 2022, 76 patients who matched the inclusion criteria were divided into two groups: twenty-five (32.9%) patients were older than 65 years and included in the elderly group, while the remaining fifty-one (61.1%) patients were below 65 years included in the non-elderly one. There were no differences between the groups in terms of acute pain relief (APR), Barrow Neurological Index (BNI) at follow-up, complications, and recurrence rate. In multivariate analysis (Cox proportional hazards regression analysis) the presence of an offending artery with nerve root distortion/indentation emerged as the only independent prognostic factor for pain-free survival (p = 0.0001). Our data endorse MVD as a safe and effective surgical procedure also for elderly patients with TN.

The role of biomarkers in drug-resistant trigeminal neuralgia: a prospective study in patients submitted to surgical treatment

BACKGROUND

Molecular mechanisms underlying trigeminal neuralgia (TN) have been poorly understood. Recently, different biomarkers have been studied in several chronic neuropathic diseases or in neuronal damage, but their role in TN has not yet been investigated. Here, we firstly analyzed the serum levels of the neuron-specific enolase (NSE) (as an index of neuronal tissue damage) in TN patients submitted to surgical treatment. Different cytokines and interleukins related to inflammation were also studied.

METHODS

Blood samples from 40 patients were prospectively collected preoperatively and after the surgical procedure, namely microvascular decompression (MVD) and percutaneous balloon compression (PBC). Serum levels of uric acid, NSE, ferritin, CRP, IL-2R, and IL-6 were studied. The acute pain relief (APR) and the pre- and postoperative BNI were used to evaluate the clinical outcome.

RESULTS

Overall, we obtained an APR in 87.5% of patients and a significant reduction of BNI after surgery (p < 0.0001). We observed a significant reduction of postoperative NSE values in the group of patients undergoing MVD (p = 0.0055) and a significant increase of postoperative NSE values in patients undergoing PBC (p < 0.05). Furthermore, in the group of patients undergoing MVD, we found a significant postoperative increase of CRP (p < 0.0001), ferritin (p = 0.001), and IL-6 (p = 0.01) values. The only patient who did not respond to MVD had NSE levels unchanged.

CONCLUSION

Our results suggest the hypothesis that TN would be related to the neural damage instead of the systemic inflammatory status and indicate NSE as a possible biomarker of response in patients submitted to MVD.

BmK DKK13, A Scorpion Toxin, Alleviates Pain Behavior in a Rat Model of Trigeminal Neuralgia by Modulating Voltage-Gated Sodium Channels and MAPKs/CREB Pathway

BmK DKK13 (DKK13) is a mutated recombinant peptide, which has a significant antinociception in a rat model of the inflammatory pain. The purpose of this study was to evaluate the antinociceptive effect of DKK13 on trigeminal neuralgia (TN) in rats. Male Sprague-Dawley (SD) rats were treated with the chronic constriction injury of the infraorbital nerve (IoN-CCI) model to induce stable symptoms of TN. DKK13 (1.0 mg/kg, 2.0 mg/kg and 4.0 mg/kg, i.v.) or morphine (4.0 mg/kg, i.v.) was administered by tail vein once on day 14 after IoN-CCI injury. Behavioral tests, electrophysiology and western blotting were performed to investigate the role and underlying mechanisms of DKK13 on IoN-CCI model. Behavioral test results showed that DKK13 could significantly increase the mechanical pain and thermal radiation pain thresholds of IoN-CCI rats and inhibit the asymmetric spontaneous pain scratching behavior. Electrophysiological results showed that DKK13 could significantly reduce the current density of Nav1.8 in the ipsilateral side of trigeminal ganglion (TG) neurons in IoN-CCI rats, and the steady-state activation and inactivation curves of Nav1.8 shifted, respectively, to the direction of hyperpolarization and depolarization. Western blotting results showed that DKK13 significantly reduced the expression of Nav1.8 and the phosphorylation levels of key proteins of MAPKs/CREB pathway in TG tissues of IoN-CCI rats. In brief, DKK13 has a significant antinociceptive effect on IoN-CCI rats, which may be achieved by changing the dynamic characteristics of Nav1.8 channel and regulating the protein phosphorylation in MAPKs/CREB pathway.

Global Trends and Hotspots in Trigeminal Neuralgia Research From 2001 to 2021: A Bibliometric Analysis

Background

In recent years, there have been an increasing number of studies on trigeminal neuralgia (TN). However, a scientific and comprehensive study of the current situation and trends in the field of TN research is lacking. The purpose of this study is to summarize and visualize the development, research hotspots, and future trends in TN based on a bibliometric approach.

Methods

Studies on TN published from 2001 to 2021 were obtained from the Web of Science Core Collection (WoSCC). Bibliometrics, CiteSpace, and VOSviewer tools were used for bibliometric analysis and visualization.

Results

In total, 4,112 documents were searched. The number of research articles in the field is generally on an upward trend, with the fastest growth in the number of articles from 2017 to 2020. Shanghai Jiao Tong University, Pittsburgh University, and Mayo Clinic are the three institutions with the most publications. Shiting Li and Zakrzewska JM are the most prolific author and top co-cited authors, respectively. The Journal of Neurosurgery is the most influential journal. The top 5 keywords in that time frame are TN, microvascular decompression, facial pain, stereotactic radiosurgery, and neuropathic pain.

Conclusion

This is the first comprehensive scientific bibliometric analysis of the global research field on TN over the past 21 years, providing a meaningful reference for further exploration of topical issues and research trends in the field.

Suspected Recurrence of Cranial Neuralgia Following Infection With SARS-CoV-2: A Case Report

It is understood that patients infected with the COVID-19 virus can present with headache as an initial symptom, but it is unclear if those with a history of cranial neuralgias may have a different initial COVID-19 presentation, or if infections from SARS-CoV-2 virus may cause a recurrence of previous cranial neuralgias. In this review, we report a case of cranial neuralgia recurrence that was preceded by a SARS-CoV-2 exposure. There is currently a lack of literature describing COVID-19 patients with a recurrence of a previous cranial neuralgia, and this case draws attention to potential reactivation of cranial neuralgia symptoms in COVID-19 patients, highlights key components of the pathophysiology of cranial neuralgias, and underscores the potential need to identify previous history of cranial neuralgia to more appropriately navigate management and treatment of neuralgia causing head pain as a consequence of COVID-19 infection.

Recurrent Trigeminal Neuralgia: A Case Series and a Review of the Literature

Trigeminal neuralgia is a peripheral neuropathy characterized by intermittent episodes of severe facial pain originating in the sensory nucleus of the trigeminal nerve. The most commonly involved area is the mandibular division with a higher prevalence on the right side. Advances in the field of MRI have played an important role in its diagnosis, especially in presurgical assessment, to probe into any secondary causes of nerve compression and/or neurovascular conflict. The condition is primarily managed medically, although many patients may require surgical or radiotherapeutic intervention. A recurrence rate ranging from 6 to 41% has been postulated. Reasons for recurrence are mainly attributed to improper operative techniques, dislocation of the Teflon implant, or granuloma formation. MRI serves as a powerful tool in the segmental evaluation of the trigeminal nerve. A proper diagnosis with a structured treatment protocol is critical for managing such cases of trigeminal neuralgia. In this report, we present a series of two cases of recurrent trigeminal neuralgia.

The Molecular Basis and Pathophysiology of Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a complex orofacial pain syndrome characterized by the paroxysmal onset of pain attacks in the trigeminal distribution. The underlying mechanism for this debilitating condition is still not clearly understood. Decades of basic and clinical evidence support the demyelination hypothesis, where demyelination along the trigeminal afferent pathway is a major driver for TN pathogenesis and pathophysiology. Such pathological demyelination can be triggered by physical compression of the trigeminal ganglion or another primary demyelinating disease, such as multiple sclerosis. Further examination of TN patients and animal models has revealed significant molecular changes, channelopathies, and electrophysiological abnormalities in the affected trigeminal nerve. Interestingly, recent electrophysiological recordings and advanced functional neuroimaging data have shed new light on the global structural changes and the altered connectivity in the central pain-related circuits in TN patients. The current article aims to review the latest findings on the pathophysiology of TN and cross-examining them with the current surgical and pharmacologic management for TN patients. Understanding the underlying biology of TN could help scientists and clinicians to identify novel targets and improve treatments for this complex, debilitating disease.

Predictive and prognostic factors for outcome of microvascular decompression in trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia (TN) is a disease characterized by recurring, short-lived, electric shock-like pain experienced on one side of the face. Microvascular decompression (MVD) is one of the most effective surgical interventions for resolving TN caused by neurovascular compression. This study aimed to determine the predictive and prognostic factors of surgical outcomes.

METHODS

This retrospective cohort study enrolled patients diagnosed with TN who underwent MVD at our hospital during 2013-2019. The demographic information, pain character, peri-operative Barrow Neurological Institute (BNI) scale, medication, operative finding were recorded. And the outcome was Outcomes were divided into drug-free and drug-dependent group. Predisposing factors for each outcome were analyzed by one-way analysis of variance, followed by a Mann-Whitney U test or Kruskal-Wallis test.

RESULTS

A total of 104 consecutive patients received MVD to treat TN, and 88 patients were enrolled in this study. The overall postoperative drug-free outcome was 72.7%. A significant difference in drug-free outcomes was observed for patients with typical TN (80.8%) compared with patients with atypical TN (33.33%, p = 0001). When severe venous compression was encountered during MVD, the drug-free outcome fell to 50% (10/20, p = 0.009). The Mann-Whitney U test indicated typical TN as a positive predictive factor of a drug-free outcome, whereas severe venous compression was a negative predictive factor. The patients with preoperative BNI score of 4 had better improvement than others (p = 0.045). Age, onset duration, and arterial loop had no specific difference in this study.

CONCLUSION

In our study, atypical TN and severe venous compression were associated with poor outcomes. Regrouping atypical TN into precise diagnosis represents an immediate priority according to our result. The preoperative BNI score could be used as an effective predictive tool for the outcome of MVD surgery.

Animal models - Mimicking the pain of trigeminal neuralgia

Trigeminal neuralgia (TN) is an episodic facial pain which feels like an electric shock of unilateral origin. This neuropathic disorder is an intensely stressful to bear for patient and impacts the quality of life. Most of the cases of TN arise when the root of fifth cranial nerve, i.e., trigeminal nerve is compressed after a few millimeters of its entry into the pons. This article describes various animal models and the role of biomarkers to study the underlying mechanisms of neuropathic pain in animal models as well as different modes of management of TN.

Unilateral Approach to Primary Bilateral Trigeminal Neuralgia Via Bilateral Microvascular Decompression

Primary bilateral trigeminal neuralgia is a rare disease characterized by paroxysmal bilateral facial pain confined to the somatosensory distribution of the trigeminal nerve. Nonetheless, while treatment of bilateral trigeminal neuralgia with microvascular decompression (MVD) has been reported, there have been no trials of a unilateral approach for bilateral MVD.

The Up-regulation of TNF-α Maintains Trigeminal Neuralgia by Modulating MAPKs Phosphorylation and BKCa Channels in Trigeminal Nucleus Caudalis

Trigeminal neuralgia (TN) is a severe chronic neuropathic pain. Despite numerous available medical interventions, the therapeutic effects are not ideal. To control the pain attacks, the need for more contemporary drugs continues to be a real challenge. Our previous study reported that Ca²⁺-activated K⁺ channels (BK_Ca) channels modulated by mitogen-activated protein kinases (MAPKs) in the trigeminal ganglia (TG) neurons play crucial roles in regulating TN, and some research studies demonstrated that inflammatory cytokine tumor necrosis factor alpha (TNF-α) could promote neuropathic pain. Meanwhile, the trigeminal nucleus caudalis (TNC), the first central site of the trigeminal nociceptive pathway, is responsible for processing sensory and pain signals from the peripheral orofacial area. Thus, this study is aimed to further investigate whether TNF-α and MAPKs phosphorylation in the TNC could mediate the pathogenesis of TN by modulating BK_Ca channels. The results showed that TNF-α of the TNC region is upregulated significantly in the chronic constriction injury of infraorbital nerve (ION-CCI) rats model, which displayed persistent facial mechanical allodynia. The normal rats with target injection of exogenous TNF-α to the fourth brain ventricle behaved just like the ION-CCI model rats, the orofacial mechanical pain threshold decreased clearly. Meanwhile, the exogenous TNF-α increased the action potential frequency and reduced the BK_Ca currents of TNC neurons significantly, which could be reversed by U0126 and SB203580, the inhibitors of MAPK. In addition, U0126, SB203580, and another MAPK inhibitor SP600125 could relieve the facial mechanical allodynia by being injected into the fourth brain ventricle of ION-CCI model rats, respectively. Taken together, our work suggests that the upregulation of TNF-α in the TNC region would cause the increase of MAPKs phosphorylation and then the negative regulation of BK_Ca channels, resulting in the TN.

Internal Neurolysis for the Treatment of Trigeminal Neuralgia: A Systematic Review

INTRODUCTION

Trigeminal neuralgia (TN) remains a challenging disease with debilitating symptoms and variable efficacy in terms of treatment options. Microvascular decompression (MVD) with internal neurolysis (IN) is an alternative treatment that might benefit patients but has limited understanding. We performed a systematic review of IN for the treatment of TN.

METHODS

Studies from 2000 to 2021 that had assessed IN for TN were aggregated and independently reviewed.

RESULTS

A total of 520 patients in 12 studies were identified, with 384 who had undergone IN (mean age, 53.8 years; range, 46-61.4 years; mean follow-up, 36.5 months). Preoperative symptoms had been present for ∼55.0 months before treatment, and pain was predominantly in V2 and V3 (26.8%), followed by other distributions. Of the patients, 83.7% (range, 72%-93.8%) had had an excellent to good outcome (Barrow Neurological Institute pain scale score [BNI-PS], I-II). The pain outcomes at 1 year were excellent for 58%-78.4%, good or better for 77%-93.75%, and fair or better for 80%-93.75% of the patients. On average, facial numbness after IN was experienced by 96% of the patients. However, at follow-up, facial numbness remained in only 1.75%-10%. Most of the remaining numbness was not significantly distressing to the patients. Subgroup comparisons of IN versus recurrent MVD, IN versus radiofrequency ablation, the effects of IN in the absence of vascular compression, and IN with and without MVD were also evaluated.

CONCLUSIONS

IN represents a promising surgical intervention for TN in the absence of vascular compression and for potential cases of recurrence. Complications were limited in general but require further study.

Trigeminal Neuralgia: Current Approaches and Emerging Interventions

Trigeminal neuralgia (TN) has been described in the literature as one of the most debilitating presentations of orofacial pain. This review summarizes over 150 years of collective clinical experience in the medical and surgical treatment of TN. Fundamentally, TN remains a clinical diagnosis that must be distinguished from other types of trigeminal neuropathic pain and/or facial pain associated with other neuralgias or headache syndromes. What is increasingly clear is that there is no catch-all medical or surgical intervention that is effective for all patients with trigeminal neuralgia, likely reflective of the fact that TN is likely a heterogenous group of disorders that jointly manifests in facial pain. The first-line treatment for TN remains anticonvulsant medical therapy. Patients who fail this have a range of surgical options available to them. In general, microvascular decompression is a safe and effective procedure with immediate and durable outcomes. Patients who are unable to tolerate general anesthesia or whose medical comorbidities preclude a suboccipital craniectomy may benefit from percutaneous methodologies including glycerol or radiofrequency ablation, or both. For patients with bleeding diathesis due to blood thinning medications who are ineligible for invasive procedures, or for those who are unwilling to undergo open surgical procedures, radiosurgery may be an excellent option-provided the patient understands that maximum pain relief will take on the order of months to achieve. Finally, peripheral neurectomies continue to provide an inexpensive and resource-sparing alternative to pain relief for patients in locations with limited economic and medical resources. Ultimately, elucidation of the molecular mechanisms underlying trigeminal neuralgia will pave the way for novel, more effective and less invasive therapies.

A Segmentation Method of Foramen Ovale Based on Multiatlas

Trigeminal neuralgia is a neurological disease. It is often treated by puncturing the trigeminal nerve through the skin and the oval foramen of the skull to selectively destroy the pain nerve. The process of puncture operation is difficult because the morphology of the foramen ovale in the skull base is varied and the surrounding anatomical structure is complex. Computer-aided puncture guidance technology is extremely valuable for the treatment of trigeminal neuralgia. Computer-aided guidance can help doctors determine the puncture target by accurately locating the foramen ovale in the skull base. Foramen ovale segmentation is a prerequisite for locating but is a tedious and error-prone task if done manually. In this paper, we present an image segmentation solution based on the multiatlas method that automatically segments the foramen ovale. We developed a data set of 30 CT scans containing 20 foramen ovale atlas and 10 CT scans for testing. Our approach can perform foramen ovale segmentation in puncture operation scenarios based solely on limited data. We propose to utilize this method as an enabler in clinical work.

Leveraging high-resolution 7-tesla MRI to derive quantitative metrics for the trigeminal nerve and subnuclei of limbic structures in trigeminal neuralgia

BACKGROUND

Trigeminal Neuralgia (TN) is a chronic neurological disease that is strongly associated with neurovascular compression (NVC) of the trigeminal nerve near its root entry zone. The trigeminal nerve at the site of NVC has been extensively studied but limbic structures that are potentially involved in TN have not been adequately characterized. Specifically, the hippocampus is a stress-sensitive region which may be structurally impacted by chronic TN pain. As the center of the emotion-related network, the amygdala is closely related to stress regulation and may be associated with TN pain as well. The thalamus, which is involved in the trigeminal sensory pathway and nociception, may play a role in pain processing of TN. The objective of this study was to assess structural alterations in the trigeminal nerve and subregions of the hippocampus, amygdala, and thalamus in TN patients using ultra-high field MRI and examine quantitative differences in these structures compared with healthy controls.

METHODS

Thirteen TN patients and 13 matched controls were scanned at 7-Tesla MRI with high resolution, T1-weighted imaging. Nerve cross sectional area (CSA) was measured and an automated algorithm was used to segment hippocampal, amygdaloid, and thalamic subregions. Nerve CSA and limbic structure subnuclei volumes were compared between TN patients and controls.

RESULTS

CSA of the posterior cisternal nerve on the symptomatic side was smaller in patients (3.75 mm2) compared with side-matched controls (5.77 mm2, p = 0.006). In TN patients, basal subnucleus amygdala volume (0.347 mm3) was reduced on the symptomatic side compared with controls (0.401 mm3, p = 0.025) and the paralaminar subnucleus volume (0.04 mm3) was also reduced on the symptomatic side compared with controls (0.05 mm3, p = 0.009). The central lateral thalamic subnucleus was larger in TN patients on both the symptomatic side (0.033 mm3) and asymptomatic side (0.035 mm3), compared with the corresponding sides in controls (0.025 mm3 on both sides, p = 0.048 and p = 0.003 respectively). The inferior and lateral pulvinar thalamic subnuclei were both reduced in TN patients on the symptomatic side (0.2 mm3 and 0.17 mm3 respectively) compared to controls (0.23 mm3, p = 0.04 and 0.18 mm3, p = 0.04 respectively). No significant findings were found in the hippocampal subfields analyzed.

CONCLUSIONS

These findings, generated through a highly sensitive 7 T MRI protocol, provide compelling support for the theory that TN neurobiology is a complex amalgamation of local structural changes within the trigeminal nerve and structural alterations in subnuclei of limbic structures directly and indirectly involved in nociception and pain processing.

Puerarin Attenuates Complete Freund's Adjuvant-Induced Trigeminal Neuralgia and Inflammation in a Mouse Model via Sirt1-Mediated TGF-β1/Smad3 Inhibition

Background

Puerarin, an active compound of radix puerariae, is a major compound used in Chinese herbal medicines and it has been well known for its pharmacological effects, including antioxidant, anti‑inflammatory, neuroprotective and cardioprotective properties. The aim of the present study was to determine the role of puerarin (Pue) in complete Freund’s adjuvant (CFA)-induced trigeminal neuralgia (TN) and the effects of this compound on Sirt1 activity and on the progression of CFA-induced TN.

Methods

Mice were injected with CFA on the unilateral face to induce TN. A cell model of inflammation-associated TN was established by interleukin-1β (IL-1β; 10 ng/mL) and tumor necrosis factor-α (TNF-α; 50 ng/mL) stimulation of neurons. Reverse transcription-quantitative PCR and Western blot analyses were performed to analyze mRNA and protein expression levels in trigeminal ganglion and nerve cells. Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) staining was used to determine nerve cell apoptosis following IL-1β/TNF-α or Pue treatment.

Results

Pue is a conceivable Sirtuin1 (Sirt1) activator used for the prevention of trigeminal nerve injury that attenuates CFA-induced TN and inflammatory cytokine-evoked overactivation of neuronal inflammation and apoptosis. Treatment of mice with inflammatory cytokines induced upregulation of cleaved caspase-3 protein expression, which was neutralized by Pue supplementation. Both in vivo and in vitro experiments led to the conclusion that Pue modulated Sirt1 activation and repressed transforming growth factor-β1 (TGF-β1) protein expression and drosophila mothers against decapentaplegic homolog3 (Smad3) phosphorylation in order to exert neuroprotection.

Conclusion

The findings suggested that Pue functioned as a potential Sirt1 activator to improve neuroinflammation-induced TN and neuronal apoptosis via the suppression of TGF-β1/Smad3 activity. The pharmacological activity of Pue provides a new perspective for the effective prevention and treatment of TN.

Polymorphisms of Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 genes in trigeminal neuralgia

SUBJECTS

Trigeminal neuralgia is a neuropathic pain characterized by episodes of severe shock-like pain within the distribution of one or more divisions of the trigeminal nerve. Pain can be influenced by ethnicity, environment, gender, psychological traits, and genetics. Molecules Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 have been involved in mechanisms that underlie pain and neurological conditions.

OBJECTIVE

The aim of this case-control study was to investigate the occurrence of genetic polymorphisms in Nav1.6 sodium channel (SCN8A/rs303810), Brain-derived Neurotrophic Factor (BDNF/rs6265/Val66Met), Catechol-O-methyltransferase (COMT/rs4680/Val158Met), and Guanosine Triphosphate Cyclohydrolase 1 (GCH1/rs8007267) genes in trigeminal neuralgia patients.

METHODS

Ninety-six subjects were divided into two groups: 48 with trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated by visual analog scale and genomic DNA was obtained from oral swabs and analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed among SCN8A, BDNF, COMT or GCH1 polymorphisms and the presence of trigeminal neuralgia. Genotype distribution and allele frequencies did not correlate to pain severity.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia or pain was observed, our data contributes to the knowledge of genetic susceptibility to trigeminal neuralgia, which is very scarce. Further studies may focus on other polymorphisms and mutations, as well as on epigenetics and transcriptional regulation of these genes, in order to clarify or definitively exclude the role of Nav1.6, BDNF, COMT or GCH1 in trigeminal neuralgia susceptibility and pathophysiology.

Efficacy and Safety of Awake CT-guided Percutaneous Balloon Compression of Trigeminal Ganglion for Trigeminal Neuralgia

OBJECTIVES

To describe the method and clinical efficacy of awake CT-guided percutaneous balloon compression (PBC) as a treatment for trigeminal neuralgia (TN).

DESIGN

In this case-series, TN patients were treated with awake CT-guided PBC and followed for treatment efficacy and complications for 12 months.

SETTING

A single-center study.

SUBJECTS

66 patients with medical treatment-refractory TN were recruited for the study.

METHODS

The procedure was performed under moderate sedation. A balloon catheter was inserted through a trocar needle to reach Meckel's cavity under CT-guidance. The position and optimal shape of the contrast-filled balloon was confirmed with CT 3-dimension reconstruction. Compression of the TG was considered completed when the patient notified operators about facial hypoesthesia or the resolution of TN symptoms. All patients were followed up monthly for 12 months to monitor treatment efficacy and complications.

RESULTS

The average TG compression time was 272±81 seconds, at which point the patients reported significant facial hypoesthesia comparing to the contralateral side or resolution of triggered pain in the affected area. All patients had resolution of TN symptoms for 6 months, with a 1-year recurrent rate of 13%. Overall safety profile is improved with the current technique. Side effects, such as hypoesthesia, and mastication weakness, were overall mild, and did not impact patients' quality-of-life. Some complications that were historically associated with PBC, such as diplopia and keratitis, were not present.

CONCLUSIONS

This new awake CT-guided PBC technique produces better outcomes than the traditional PBC under fluoroscopy-guidance and general anesthesia.

Percutaneous Radiofrequency Rhizotomy Is Equally Effective for Trigeminal Neuralgia Patients with or without Neurovascular Compression

BACKGROUND

Neurovascular compression (NVC) in patients with trigeminal neuralgia (TN) can be a factor of treatment outcome especially in microvascular decompression and stereotactic radiosurgery. No such effect has been reported in percutaneous radiofrequency rhizotomy (RF). This study is to investigate if NVC affects the efficacy of RF in patients with TN.

METHODS

We retrospectively reviewed patients with TN who received RF in our institution. Pre-treatment MRI was performed in every patient, and the presence of NVC was reviewed independently by two physicians. The patients were followed up at least for a year after the treatment. Pain severity was assessed with numerical rating scale (NRS).

RESULTS

Sixty-two patients were included in the study. All the patients had single-sided lesion, and 35 patients had NVC. There was no significant difference between these two groups of patients in terms of gender distribution, age, and pre-treatment pain severity. Comparable pain severity improvement was found in one-year follow-up between these two groups (NRS 7.93 ± 0.492 without compression vs. 7.57 ± 0.451 with compression, p = 0.600). No significant difference in post-treatment pain severity at one year between these two patient groups (NRS 1.37 ± 0.466 without compression vs. 1.66 ± 0.458 with compression, p = 0.667) was found.

CONCLUSIONS

For patients with TN treated by RF, the presence of NVC or not is not likely to affect the one-year pain control rate.

Comparison of Effectiveness and Safety between Intraoperative 3D-CT-Guided and C-Arm-Guided Percutaneous Balloon Compression for Idiopathic Trigeminal Neuralgia: A Multi-Center Retrospective Study

Objectives

To compare 3D-CT-guided and C-arm-guided percutaneous balloon compression (PBC) in terms of effectiveness and safety.

Methods

The medical records and follow-up data of patients with idiopathic trigeminal neuralgia who underwent 3D-CT-guided or C-arm-guided PBCs in Beijing Tiantan Hospital and the Characteristic Medical Center of the Chinese People's Armed Police Force between February 2018 and March 2020 were retrospectively reviewed and analysed.

Results

A total of 291 patients were included. Among them, 212 patients underwent PBC treatment with 3D-CT and others with C-arm. One (0.5%) patient in 3D-CT group and 4 (5.1%) patients in C-arm group failed to receive PBC treatment because of failure of foramen ovale (FO) puncture (P=0.020). Among patients with successful attempts, 5 (2.4%) patients in the 3D-CT group and 11 (14.7%) patients in the C-arm group received more than one needle pass during the procedure (P < 0.001). The 3D-CT group required less time than the C-arm group for puncture (P < 0.001) and for the whole operation (P < 0.001). The groups shared similar initial relief rates (P=0.749) and similar recurrence-free survival during follow-ups for a median of 22 months (P=0.839). No puncture-related complications occurred in either group and the two groups had similar incidences of compression-related complications.

Conclusion

3D-CT facilitated FO puncture and improved success rate of PBC. The overall time efficiency of PBC was also increased with 3D-CT. Thus, 3D-CT is a potentially useful image guidance technology for treating idiopathic trigeminal neuralgia by PBC.

c-Abl-p38 signaling pathway mediates dopamine neuron loss in trigeminal neuralgia

Trigeminal neuralgia is a common neuropathic pain in the head and face. The pathogenesis of trigeminal neuralgia is complex, and so far, the pathogenesis of trigeminal neuralgia involving peripheral and central nervous inflammation theory has not been explained clearly. The loss of dopamine neurons in striatum may play an important role in the development of trigeminal nerve, but the reason is not clear. C-Abl is a nonreceptor tyrosine kinase, which can be activated abnormally in the environment of neuroinflammation and cause neuron death. We found that in the rat model of infraorbital nerve ligation trigeminal neuralgia, the pain threshold decreased, the expression of c-Abl increased significantly, the downstream activation product p38 was also activated abnormally and the loss of dopamine neurons in striatum increased. When treated with imatinib mesylate (STI571), a specific c-Abl family kinase inhibitor, the p38 expression was decreased and the loss of dopaminergic neurons was reduced. The mechanical pain threshold of rats was also improved. In conclusion, c-abl-p38 signaling pathway may play an important role in the pathogenesis of trigeminal neuralgia, and it is one of the potential targets for the treatment of trigeminal neuralgia.

Recent Advances in Trigeminal Neuralgia and Its Management: A Narrative Review

Trigeminal neuralgia (TN) is a chronic facial pain condition that affects one or more divisions of the trigeminal nerve (5th cranial nerve). It can be idiopathic, primary, or secondary. The cornerstone of the therapy has been antiepileptic medications, peripheral nerve blocks with various neurolytic agents, and surgical procedures. With the advent of newer technologies, minimally invasive neurolytic techniques like low-level laser therapy and ozone injection have revolutionized the management of TN. Novel drugs like vixotrigine and eslicarbazepine have been promising in reducing the frequency and severity of attacks. Inhaled carbon dioxide too has shown promising results in initial trials. Neuromodulation has given robust data in controlling neuralgic pain especially refractory to medical management. Pulsed radiofrequency has been used with increasing success and the side effects like dysesthesia and paresthesia are less. Cryotherapy, neural prolotherapy, and fiber knife techniques have helped us believe that TN can be controlled and cured. The need of the hour is to develop and explore newer modalities for trigeminal neuralgia treatment with minimum side effects. In this narrative review, we have tried to shed light into the newer modalities of treatment of TN along with new clinical classification for better disease recognition and management.

Efficacy and safety of radiofrequency in the treatment of trigeminal neuralgia: a systematic review and meta-analysis

To assess the effectiveness of radiofrequency (RF) versus other percutaneous strategies (balloon compression, glycerol rhizotomy [GR], and microvascular decompression [MVD]) in patients with trigeminal neuralgia. We systematically searched the electronic databases of PubMed, Embase, and the Cochrane Library to identify eligible studies throughout October 2020. The odds ratio (OR) with 95% confidence interval (CI) was applied to assess effect estimates using the random-effects model. Eighteen retrospective cohort studies that enrolled 6391 patients with trigeminal neuralgia were included. We noted that RF was associated with an increased incidence of immediate pain relief compared with GR (OR 2.65; 95% CI 1.29-5.44; P = 0.008). Moreover, RF was associated with an increased risk of pain recurrence compared with MVD (OR 3.80; 95% CI 2.00-7.20; P < 0.001). Furthermore, RF was associated with an increased incidence of postoperative anesthesia compared with GR (OR 3.01; 95% CI 1.11-8.13; P = 0.030) or MVD (OR 4.62; 95% CI 2.15-9.93; P < 0.001). This study found that RF was superior to GR for the improvement in immediate pain relief; whereas, RF yielded an excess risk of pain recurrence compared with MVD. Moreover, the incidence of postoperative anesthesia in patients treated with RF significantly increased compared with the incidence after treatment with GR and MVD.

The role of the P2X4 receptor in trigeminal neuralgia, a common neurological disorder

Neurological disorders, which include various types of diseases with complex pathological mechanisms, are more common in the elderly and have shown increased prevalence, morbidity and mortality worldwide. Unfortunately, current therapies for these diseases are usually suboptimal or have undesirable side effects. This necessitates the development of new potential targets for disease-modifying therapies. P2X4R, a type of purinergic receptor, has multiple roles in neurological disorders. In this review, we briefly introduce a neurological disorder, trigeminal neuralgia and its' symptoms, etiology and pathology. Moreover, we focused on the role of P2X4R in neurological disorders and their related pathophysiologic mechanisms. Further studies of P2X4R are required to determine potential therapeutic effects for these pathophysiologies.