Aetiology and pathogenesis of trigeminal neuralgia: a comprehensive review

Trigeminal neuralgia

Trigeminal neuralgia (TN) is a facial pain disorder characterized by intense and paroxysmal pain that profoundly affects quality of life and presents complex challenges in diagnosis and treatment. TN can be categorized as classical, secondary and idiopathic. Epidemiological studies show variable incidence rates and an increased prevalence in women and in the elderly, with familial cases suggesting genetic factors. The pathophysiology of TN is multifactorial and involves genetic predisposition, anatomical changes, and neurophysiological factors, leading to hyperexcitable neuronal states, central sensitization and widespread neural plasticity changes. Neurovascular compression of the trigeminal root, which undergoes major morphological changes, and focal demyelination of primary trigeminal afferents are key aetiological factors in TN. Structural and functional brain imaging studies in patients with TN demonstrated abnormalities in brain regions responsible for pain modulation and emotional processing of pain. Treatment of TN involves a multifaceted approach that considers patient-specific factors, including the type of TN, with initial pharmacotherapy followed by surgical options if necessary. First-line pharmacological treatments include carbamazepine and oxcarbazepine. Surgical interventions, including microvascular decompression and percutaneous neuroablative procedures, can be considered at an early stage if pharmacotherapy is not sufficient for pain control or has intolerable adverse effects or contraindications.

Trigeminal Neuralgia as a Primary Demyelinating Disease: Potential Multimodal Evidence and Remaining Controversies

Trigeminal neuralgia is a heterogeneous disorder with likely multifactorial and complex etiology; however, trigeminal nerve demyelination and injury are observed in almost all patients with trigeminal neuralgia. The current management strategies for trigeminal neuralgia primarily involve anticonvulsants and surgical interventions, neither of which directly address demyelination, the pathological hallmark of trigeminal neuralgia, and treatments targeting demyelination are not available. Demyelination of the trigeminal nerve has been historically considered a secondary effect of vascular compression, and as a result, trigeminal neuralgia is not recognized nor treated as a primary demyelinating disorder. In this article, we review the evolution of our understanding of trigeminal neuralgia and provide evidence to propose its potential categorization, at least in some cases, as a primary demyelinating disease by discussing its course and similarities to multiple sclerosis, the most prevalent central nervous system demyelinating disorder. This proposed categorization may provide a basis in investigating novel treatment modalities beyond the current medical and surgical interventions, emphasizing the need for further research into demyelination of the trigeminal sensory pathway in trigeminal neuralgia. PERSPECTIVE: This article proposes trigeminal neuralgia as a demyelinating disease, supported by histological, clinical, and radiological evidence. Such categorization offers a plausible explanation for controversies surrounding trigeminal neuralgia. This perspective holds potential for future research and developing therapeutics targeting demyelination in the condition.

Diabetes Mellitus and Its Influence on Oral Health: Review

Diabetes mellitus (DM) is one of the most common diseases all over the world. The effect of this endocrine disease on body systems cannot be ignored, where its oral side effects are well distinguished. As this disease incident is increasing dramatically, it is essential for the health care providers to be fully aware of the disease diagnosis, management and to deal with it in a full confident. This review discusses the disease itself, its complications, methods of diagnosis as well as its management. Furthermore, oral manifestations and dental considerations that should be followed when treating patients with diabetes mellitus have been discussed in this review.

Locus coeruleus-noradrenergic modulation of trigeminal pain: Implications for trigeminal neuralgia and psychiatric comorbidities

Trigeminal neuralgia is the most common neuropathic pain involving the craniofacial region. Due to the complex pathophysiology, it is therapeutically difficult to manage. Noradrenaline plays an essential role in the modulation of arousal, attention, cognitive function, stress, and pain. The locus coeruleus, the largest source of noradrenaline in the brain, is involved in the sensory and emotional processing of pain. This review summarizes the knowledge about the involvement of noradrenaline in acute and chronic trigeminal pain conditions and how the activity of the locus coeruleus noradrenergic neurons changes in response to acute and chronic pain conditions and how these changes might be involved in pain-related comorbidities including anxiety, depression, and sleep disturbance.

Blood-nerve barrier disruption and coagulation system activation induced by mechanical compression injury participate in the peripheral sensitization of trigeminal neuralgia

Introduction

The aim of this study was to investigate the effect and possible mechanisms of the blood-nerve barrier (BNB) and the coagulation-anticoagulation system in modulating the mechanical allodynia in a trigeminal neuralgia (TN) rat model induced by chronic compression of the trigeminal root entry zone (TREZ).

Methods

Von Frey filaments were applied to determine the orofacial mechanical allodynia threshold. The BNB permeability was evaluated by Evans blue extravasation test. Immunohistochemical staining and laser confocal microscopy were used to measure the length of the depletion zones of the nodes of Ranvier in the TREZ, the diameter of nerve fibers and the length of the nodal gap. The transcriptional levels of prothrombin and endogenous thrombin inhibitor protease nexin-1 (PN-1) in the TREZ of TN rats were assessed by RT-qPCR. A Western blotting assay was performed to detect the expression of paranodal proteins neurofascin-155 (NF155) and neurofascin-125 (NF125) in the TREZ. The spatiotemporal expression pattern of thrombin activated receptor (i.e. protease activated receptor 1, PAR1) in TREZ were defined by immunostaining and immunoblotting assays. PAR1 receptor inhibitors SCH79797 were administrated to TN rats to analyze the effect of thrombin-PAR1 on orofacial hyperalgesia.

Results

A compression injury of a rat's TREZ successfully induced TN-like behavior and was accompanied by the destruction of the permeability of the BNB and the promotion of prothrombin and thrombin inhibitor protease nexin-1 (PN-1) expression. The expression of the paranodal proteins neurofascin-155 (NF155) and neurofascin-125 (NF125) was increased, while the nodal gap length of the nodes of Ranvier was widened and the length of node-depleted zones was shortened. Moreover, the expression of PAR1 within the TREZ was upregulated at an early stage of TN, and administration of the PAR1 antagonist SCH79797 effectively ameliorated orofacial mechanical allodynia.

Conclusion

A compression injury of the TREZ increased the permeability of the BNB and induced disturbances in the local coagulation-anticoagulation system, concomitant with the structural changes in the nodes of Ranvier, thrombin-PAR1 may play a critical role in modulating orofacial mechanical hyperalgesia in a TN rat model.

Rich-club reorganization and related network disruptions are associated with the symptoms and severity in classic trigeminal neuralgia patients

BACKGROUND

Alterations in white matter microstructure and functional activity have been demonstrated to be involved in the central nervous system mechanism of classic trigeminal neuralgia (CTN). However, the rich-club organization and related topological alterations in the CTN brain networks remain unclear.

METHODS

We simultaneously collected diffusion-tensor imaging (DTI) and resting state functional magnetic resonance imaging (rs-fMRI) data from 29 patients with CTN (9 males, mean age = 54.59 years) and 34 matched healthy controls (HCs) (12 males, mean age = 54.97 years) to construct structural networks (SNs) and functional networks (FNs). Rich-club organization was determined separately based on each group's SN and different kinds of connections. For both network types, we calculated the basic connectivity properties (network density and strength) and topological properties (global/local/nodal efficiency and small worldness). Moreover, SN-FN coupling was obtained. The relationships between all those properties and clinical measures were evaluated.

RESULTS

Compared to their FN, the SN of CTN patients was disrupted more severely, including its topological properties (reduced network efficiency and small-worldness), and a decrease in network density and strength was observed. Patients showed reorganization of the rich-club architecture, wherein the nodes with decreased nodal efficiency in the SN were mainly non-hub regions, and the local connections were closely related to altered global efficiency and whole brain coupling. While the cortical-subcortical connections of feeder were found to be strengthened in the SN of patients, the coupling between networks increased in all types of connections. Finally, disease severity (duration, pain intensity, and affective alterations) was negatively correlated with coupling (rich-club, feeder, and whole brain) and network strength (the rich-club of the SN and local connections of the FN). A positive correlation was only found between pain intensity and the coupling of local connections.

CONCLUSIONS

The SN of patients with CTN may be more vulnerable. Accompanied by the reorganization of the rich-club, the less efficient network communication and the impaired functional dynamics were largely attributable to the dysfunction of non-hub regions. As compensation, the pain transmission pathway of feeder connections involving in pain processing and emotional regulation may strengthen. The local and feeder sub-networks may serve as potential biomarkers for diagnosis or prognosis.

Trigeminal Neuralgia Is a Dementia Risk Factor: A Retrospective Cohort Study

Background: Dementia, a worldwide public-health issue, is regarded as a disorder rather than a normal aging process. Trigeminal neuralgia (TN) is a chronic debilitating pain disorder that impairs daily activities. Both are most prevalent in females and in patients older than 50 years. Recent studies reveal that pain and dementia may have a reciprocal interaction with each other. Objective: In response, we estimated whether adults with TN have an increased dementia risk. Methodology: By means of Taiwan's National Health Insurance Research Database, between 1996 and 2010, 762 patients aged over 50 years in the TN group were matched with 3048 patients in the non-TN group at a ratio of 1:4. Kaplan-Meier method and Cox proportional hazard regression models were also used to determine the cumulative incidence and compare the hazard ratios of dementia in each group. Results: The incidence of dementia was higher in the TN group compared to the non-TN group. After adjusting for covariates, the TN group had a 4.47-fold higher risk of dementia compared to the non-TN group. Additionally, the impact of TN on dementia risk was larger in young-aged patients than in old-aged patients. As well, the age at the time of dementia diagnosis was younger in the TN group compared to the non-TN group. Conclusions: TN is a dementia risk factor. Given the lack of a curative therapy for dementia, early identification of TN patients may help to prevent dementia sequelae.

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.

Hypoxia Induces Apoptosis of Microglia BV2 by Upregulating Kir2.1 to Activate Mitochondrial-Related Apoptotic Pathways

Aim

To explore the role of Kir2.1 in hypoxia-induced microglial apoptosis.

Methods

BV2 microglial cell lines were cultured and treated with ML133 hydrochloride, a Kir2.1 channel blocker, for 23 h and with 500 μmol/L of CoCl₂ for 8 h. Cells were divided into the control, CoCl₂ (hypoxia-induced model), and CoCl₂+ML133 (hypoxia-induced model established after ML133 pretreatment) groups. Cell activity was assessed using the CCK-8 technique. The membrane potential and Kir2.1 current of BV2 were evaluated with the whole-cell patch-clamp technique. The protein levels and mRNA levels of Kir2.1, apoptotic proteins Bax and caspase-3, and antiapoptotic protein Bcl-2 in BV2 cells were evaluated via immunofluorescence, Western blot analysis, and real-time quantitative reverse transcription. The apoptosis rate of BV2 cells was detected via flow cytometry.

Results

CCK-8 analysis showed that the cell activity of each group increased initially and then decreased. The 2 h intervention group had the highest cell activity, and that of the 8 h group was >90%. Hence, there was a significant difference in the results (P < 0.05). Western blot analysis revealed that the expression of cleaved caspase-3 significantly increased in the 8 h group compared with the 0 h group. Compared with the control group, the expression of Kir2.1 and mRNA in the CoCl₂ group increased. Thus, hypoxia could upregulate the expression of Kir2.1. The whole-cell patch-clamp results showed that the Kir2.1 channel current amplitude of the CoCl₂ group increased compared with that of the control group. Therefore, hypoxia could enhance Kir2.1 function. The apoptosis rate of the CoCl₂ group was significantly higher than that of the control group. Further, the ML133 group had a significantly lower apoptosis rate than the CoCl₂ group. The expression of apoptotic proteins Bax and cleaved caspase-3 increased in the CoCl₂ group, and that of the antiapoptotic protein Bcl-2 decreased. The expression of apoptotic proteins Bax and cleaved caspase-3 reduced in the CoCl₂+ML133 group, whereas that of the antiapoptotic protein Bcl-2 increased.

Conclusion

Hypoxia can induce microglia BV2 apoptosis accompanied by the upregulation of Kir2.1 and mRNA expression levels and an increase in the Kir2.1 current. Moreover, ML133 can inhibit hypoxia-induced BV2 cell apoptosis. Hence, Kir2.1 may be involved in the process of hypoxia-induced BV2 cell apoptosis.

Percutaneous Radiofrequency Thermocoagulation in Trigeminal Neuralgia : Analysis of Early and Late Outcomes of 156 Cases and 209 Interventions

Objective

Trigeminal neuralgia is one of the most common causes of facial pain. Our aim is to investigate the efficacy and borders of percutaneous radiofrequency thermocoagulation in the treatment of trigeminal neuralgia.

Methods

Between May 2007 and April 2017, 156 patients with trigeminal neuralgia were treated with radiofrequency thermocoagulation. These 156 patients underwent 209 procedures. In our study, we investigated the early and late results of percutaneous radiofrequency thermocoagulation under guiding fluoroscopic imaging in the treatment of trigeminal neuralgia. Barrow Neurological Institute (BNI) pain scale was used for grading the early results. In addition, Kaplan-Meier survival analysis was used to assess long-term outcomes. Of the 156 patients who underwent radiofrequency thermocoagulation for trigeminal neuralgia, 45 had additional disease. Patients with this condition were evaluated with their comorbidities. Early and late results were compared with those without comorbidity.

Results

In 193 of 209 interventions BNI pain scale I to III results were obtained. Out of the 193 successful operation 136 patients (65.07%) were discharged as BNI I, 14 (6.70%) as BNI II, 43 (20.58%) as BNI III. Sixteen patients (7.65%) remained uncontrolled (BNI IV and V). While the treatment results of trigeminal neuralgia patients with comorbidity seem more successful in the early period, this difference was not observed in follow-up examinations.

Conclusion

Finally, we concluded that percutaneous radiofrequency thermocoagulation of the Gasserian ganglion is a safe and effective method in the treatment of trigeminal neuralgia. However, over time, the effectiveness of the treatment decreases. Neverthless, the reapprability of this intervention gives it a distinct advantage.

Retrogasserian radiofrequency thermocoagulation: A repeatable treatment in trigeminal neuralgia unresponsive to drug therapy

Background:

Trigeminal neuralgia present an incidence rates ranging between 5.9 and 12.6 per 100.000 persons; although not frequent, it is a pathology often characterized by intense pain, an extremely significant reduction in quality of life and medical therapy is not always effective or tolerated. In these cases, the patient can undergo interventional treatments including radiofrequency thermocoagulation. There are still doubts regarding the effectiveness over time, the injury parameters and the repeatability of the procedure.

Materials and Methods:

We analyze patients with trigeminal pain undergo retrogasserian radiofrequency in a single center over a period of 8 years. The procedure was performed with the following parameters: Lesion time 60 sec, lesion temperature 70°C for first thermolesion 72°C for subsequent thermolesions. Duration of benefit, number of repetitions of the maneuver, and incidence of adverse events were assessed.

Results:

Totally, 122 patients with essential trigeminal neuralgia and 20 patients with trigeminal neuralgia secondary to multiple sclerosis were analyzed; almost all patients (96.5%) showed a significant reduction in pain after one or more procedures over time; 96.5 of the patients showed excellent pain relief after 1 (40%) or more procedures (60%). The average time between one procedure and the next was 26 months.

Conclusion:

The use of time and temperature parameters chosen shows excellent efficacy, in line with the literature, with very low incidence of adverse events. The pain-free time between one procedure and the next does not seem to be a significant prognostic criterion which may or may not indicate the repetition of the procedure.

Long-Term Retrospective Analysis of Microvascular Decompression in Patients With Recurrent Trigeminal Neuralgia

Objective: To explore the clinical characteristics of patients with recurrent trigeminal neuralgia (TN) and the experience of microvascular decompression (MVD) in the treatment of such patients. Methods: We retrospectively analyzed clinical data, imaging examination results, surgical methods, and treatment efficacies in 127 patients with recurrent typical TN from January 2005 to December 2014. Results: The age of the recurrent group was higher than that of the non-recurrent group (p < 0.05). The duration of pain before the first MVD procedure was longer in the recurrent group than in the non-recurrent group (p < 0.05). Patients in the recurrent group were more likely to have compression of the trigeminal nerve by the vertebrobasilar artery (VBA) or multiple vessels than patients in the non-recurrent group (p < 0.05). A Kaplan-Meier curve showed a median pain-free survival of 12 months after the first MVD procedure. The severity of pain (preoperative visual analog scale [VAS] score) in patients with recurrence was lower than that in patients with first-onset TN (p < 0.05). Vessel compression, Teflon compression or granuloma and arachnoid adhesion were considered the main causes of recurrence. Postoperative Barrow Neurological Institute (BNI) scores in the redo MVD group were excellent (T = 2) for 69 patients (53.33%) and good (T = 3) for 46 patients (36.22%). The postoperative follow-up was 63-167 months (105.92 ± 25.66). During the follow-up, no recurrence was noted. All complications were cured or improved. Conclusions: Microvascular decompression (MVD) is an effective surgical method for the treatment of TN. For recurrent patients, reoperation can achieve good results.

Novel theory about radiosurgery's action mechanisms on trigeminal ganglion for idiopathic trigeminal neuralgia: Role of the satellite glial cells

BACKGROUND

There are many theories about the cause of trigeminal neuralgia (TN). None of them satisfactorily explains how demyelination alone through the ephaptic mechanism can contribute to the development of the TN crisis. The main characteristic of TN pain is its dynamic nature, which is difficult to explain based only on anatomical findings. With these antecedents, the exact mechanism by which radiosurgery produces pain relief in TN is unknown.

METHODS

It is based on the trigeminal ganglion (TG) cytoarchitecture and the pathophysiological findings observed after an injury to a trigeminal branch. TG seems to have a predominant role given its cellular structure. The neuronal component in sensory ganglia is generally surrounded by a single layer of satellite glial cells (SGC), which forms a sheath around each body cell. There is increasing evidence that SGCs play a key role in nociception. This depends on their ability to influence the neuronal excitability that occurs in conditions of neuropathic and inflammatory pain; contributing to both the generation and maintenance of pain.

RESULTS

We have already published the beneficial effects of radiosurgery on the TG for the treatment of idiopathic TN and secondary to vertebrobasilar ectasia. Now, we are investigating the functioning of the TG and how radiosurgery could act on the SGC, deactivating them, and contributing to the decrease or disappearance of the painful condition.

CONCLUSION

We are postulating a theory on how radiosurgery in TG produces changes in the SGC, with implications in the pathological mechanisms initiated by the alteration caused in the neuron after a nerve injury.

Trigeminal Neuralgia: Basic and Clinical Aspects

The trigeminal nerve is the largest of all cranial nerves. It has three branches that provide the main sensory innervation of the anterior two-thirds of the head and face. Trigeminal neuralgia (TN) is characterized by sudden, severe, brief, and stabbing recurrent episodes of facial pain in one or more branches of the trigeminal nerve. Pain attacks can occur spontaneously or can be triggered by non-noxious stimuli, such as talking, eating, washing the face, brushing teeth, shaving, a light touch or even a cool breeze. In addition to pain attacks, a proportion of the patients also experience persistent background pain, which along with autonomic signs and prolonged disease duration, represent predictors of worse treatment outcomes. It is now widely accepted that the presence of a neurovascular compression at the trigeminal root entry zone is an anatomic abnormality with a high correlation with classical TN. However, TN may be related to other etiologies, thus presenting different and/or additional features. Since the 1960s, the anticonvulsant carbamazepine is the drug of choice for TN treatment. Although anti-epileptic drugs are commonly used to treat neuropathic pain in general, the efficacy of carbamazepine has been largely limited to TN. Carbamazepine, however, is associated with dose-limiting side-effects, particularly with prolonged usage. Thus, a better understanding and new treatment options are urgently warranted for this rare, but excruciating disease.

Optogenetic Activation of Dopamine Receptor D1 and D2 Neurons in Anterior Cingulate Cortex Differentially Modulates Trigeminal Neuropathic Pain

Background:

Anterior cingulate cortex (ACC) is a critical brain center for chronic pain processing. Dopamine signaling in the brain has been demonstrated to contribute to descending pain modulation. However, the role of ACC dopamine receptors in chronic neuropathic pain remains unclear.

Objective:

In this study, we investigated the effect of optogenetic activation of ACC dopamine receptors D1- and D2-expressing neurons on trigeminal neuropathic pain.

Methods:

Chronic constriction injury of infraorbital nerve (CCI-ION) was carried out to induce trigeminal neuropathic pain in mice. We conducted optogenetic stimulation to specifically activate D1- and D2-expressing neurons in the ACC. Western blotting and immunofluorescence staining were used to examine ACC D1 and D2 expression and localization. The von Frey and real-time place preference tests were performed to measure evoked mechanical pain and nonreflexive emotional pain behaviors, respectively.

Results:

We observed that dopamine receptors D1 and D2 in the ACC are primarily expressed in excitatory neurons and that the D2 receptor is differentially regulated in the early and late phases of trigeminal neuropathic pain. Optogenetic activation of D1-expressing neurons in the ACC markedly exacerbates CCI-ION-induced trigeminal neuropathic pain in both early and late phases, but optogenetic activation of D2-expressing neurons in the ACC robustly ameliorates such pain in its late phase.

Conclusion:

Our results suggest that dopamine receptors D1 and D2 in the ACC play different roles in the modulation of trigeminal neuropathic pain.

TRESK alleviates trigeminal neuralgia induced by infraorbital nerve chronic constriction injury in rats

Trigeminal neuralgia commonly results in pain behaviors and cognitive impairment. Convincing evidence suggests that TWIK-related spinal cord K⁺ (TRESK) exerts antinociceptive and neuroprotective effects. However, its possible potentials in trigeminal neuralgia remain unclear. Trigeminal neuralgia model was established in rats by generating an infraorbital nerve chronic constriction injury, and rats received intrathecal injections of TRESK-overexpressing lentivirus and siRNA expression vector-targeted against TRESK (si-TRESK) into the trigeminal ganglions. Mechanical allodynia was evaluated by mechanical withdrawal threshold. Cognitive capacity was tested using Morris water maze. The TRESK expression was determined by quantitative real-time polymerase chain reaction and Western blotting. Results showed that the mRNA and protein levels of TRESK were significantly downregulated in trigeminal ganglions in injured rats. Intrathecal treatment with TRESK reduced mechanical allodynia and relieved learning and memory deficits in trigeminal neuralgia rats, while si-TRESK injection caused neuropathic pain and cognitive deficits. In summary, the present study concluded that TRESK ameliorated pain-associated behaviors and cognitive deficits, which was useful as an alternative approach in management of trigeminal neuralgia.

Foramen ovale cannulation guided by intraoperative computed tomography with magnetic resonance image fusion plays a role in improving the long-term outcome of percutaneous radiofrequency trigeminal rhizotomy

Background

Percutaneous radiofrequency trigeminal rhizotomy (RF-TR) is a well-established treatment for patients suffering from trigeminal neuralgia (TN) as a primary modality or for those refractory to medical treatment. However, few existing studies have identified intraoperative parameter or navigation technique that can be used to predict the rates of short-term or long-term pain relief. In this study, we analyzed patient characteristics, intraoperative parameters and technical factors, and postoperative changes in relation to immediate and long-term pain relief.

Method

This study included a total 252 patients in which 340 RF-TR were performed under the guidance of intraoperative computed tomography (iCT) alone or with magnetic resonance image (MRI) and iCT fusion imaging.

Result

The immediate pain relief of RF-TR with iCT alone and iCT with MR image guidance with or without cerebrospinal fluid (CSF) outflow were all above 90.4%. The 2-year pain relief rate of RF-TR using iCT alone and iCT with MR images guidance with or without CSF outflow were 47.8%, 39.8%, 71.7%, and 53.9% respectively. Significant factors for 2-year pain relief were CSF outflow, iCT with MR image fusion, non-recurrent TN, and presence of postoperative facial numbness.

Conclusion

This preliminary study demonstrated foramen ovale cannulation under the aid of iCT with MR image guidance could improve 2-year pain relief.

Gamma knife radiosurgery on the trigeminal ganglion for idiopathic trigeminal neuralgia: Results and review of the literature

Background

In the present study, we evaluate the results of gamma knife surgery (GKS) for the treatment of trigeminal neuralgia (TN) using the trigeminal ganglion (TG') and the adjacent fibers of trigeminal nerve as a target.

Methods

From February 2013 to July 2017, we treated 30 cases of TN with GKS. In this group, all patients had an idiopathic typical TN. The radiosurgical target was conformed through two isocenters, 8 and 4 mm at the cavum de Meckel. The maximum dose was 86 Gy using the isodose line of 50%. The median age of the patients was 58.5 (range 28-94) years old, and the median time from diagnosis to GKS was 94 months (range 13-480 months). The median follow-up was 28.5 (range 12-49) months. Clinical outcomes were analyzed. Univariate and multivariate analyses were performed to evaluate factors that correlated with a favorable, pain-free outcome.

Results

The mean time to relief of pain was 7 (range 1-40) days. The percentage of patients with significant pain relief was 93.3%. Relapse in pain was noted in four patients at 3, 16, 19, and 36 months. Nine patients were treated in acute status. Fourteen patients had intense pain between 1 and 7 days before the procedure. Among those with the recurrence of their symptoms, one patient had a microvascular decompression. Multivariate regression adjusted for age and sex suggests that, by 40 months, 70% of the patients treated with radiosurgery will remain pain free. At the last follow-up, GKS resulted in pain relief in 86.6% of patients. Our analysis suggests that, using this technique, we can expect that approximately 70% of patients with TN will have some degree of pain improvement at 3 years' post radiosurgery.

Conclusions

GKS on TG appears to be a reasonable treatment option with short latency period, minor collateral effects, and high percentage of pain control. The mechanism of action of radiosurgery could be related to the inactivation of the satellite glial cells in the TG.

Histopathological Evaluation of Inferior Alveolar Neurovascular Bundle in Cases of Trigeminal Neuralgia

Background

Trigeminal neuralgia is a painful disease that has been afflicting mankind since time immemorial. The etiology and pathophysiology have been widely studied but poorly understood. There are well-documented researches analyzing ultrastructural changes in trigeminal root specimens obtained following microvascular decompression surgery. However, there are no studies evaluating microscopic changes following peripheral neurectomy.

Purpose

The present study examined microscopic changes in inferior alveolar neurovascular bundle in trigeminal neuralgia patients of mandibular division with no underlying cause.

Materials and Methods

The biopsy specimens were obtained from peripheral neurectomy of 11 trigeminal neuralgia patients' refractory to anti-neuralgic medications. The autopsy specimens from 10 cadavers were used as control. The specimens were subjected to histopathological examination by hematoxylin and eosin, Masson trichrome and Luxol fast blue stains.

Results

All biopsy specimens reported luminal occlusion of small vessels, medial degeneration and intense mononuclear inflammatory infiltrate. Focal myelin digestion chambers were observed in large and small axons. No pathological alterations of either blood vessel or nerve fibers were reported in autopsy specimens.

Conclusion

The demyelination of inferior alveolar nerve due to pathologic vascular changes in peripheral vasculature may have a role in initiation and precipitation of trigeminal neuralgia, and hence, peripheral neurectomy has a significant role in alleviating pain.

Altered Spontaneous Brain Activity in Patients with Classical Trigeminal Neuralgia Using Regional Homogeneity: A Resting-State Functional MRI Study

OBJECTIVE

Neuroimaging studies have shown that patients with pain-related conditions have altered neuronal activity and structural functions. The purpose of this study was to investigate whether patients with classical trigeminal neuralgia (CTN) exhibit changes in corresponding neuronal activity via analysis of neuronal activity regional homogeneity (ReHo).

METHODS

A total of 28 patients presenting with sore eyes (12 men and 16 women) were matched with 28 healthy controls (12 men and 16 women). All participants underwent functional magnetic resonance imaging (fMRI). This ReHo method was used to assess the consistency of changes in neural activity in various brain regions. The receiver operating characteristic (ROC) curve was applied to differentiate ReHo values of patients with CTN from ReHo values of healthy controls. Pearson's correlation analysis was applied to evaluate the correlation between ReHo values of different brain regions of patients with CTN and clinical manifestations.

RESULTS

Compared with healthy controls, patients with CTN were found to have increased ReHo values in the inferior cerebellum bilaterally, right inferior temporal gyrus, right middle occipital gyrus, right fusiform gyrus, right superior frontal gyrus, and right precentral gyrus. ROC curve analysis of each brain region revealed near-perfect accuracy regarding the area under the curve. However, no correlation between ReHo values and clinical manifestations in patients with CTN was found.

CONCLUSIONS

CTN is associated with altered neuronal networks in different areas of the brain. ReHo values all possess different degrees of change, implying that CTN has a certain impact on cerebral function.

Surgical treatment of trigeminal neuralgia with no neurovascular compression: A retrospective study and literature review

The objective of the current study is to summarize the experiences of 360-degree circumferential arachnoid dissection for TN in patients without NVC. Clinical data from 19 TN patients without NVC who underwent 360-degree circumferential arachnoid dissection were retrospectively analyzed. All patients underwent preoperative examinations of three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) and three-dimensional nuclear magnetic resonance of constructive interference in steady state (3D-CISS) to identify the neurovascular structures around the trigeminal nerve. Surgical outcomes were evaluated based on the Barrow Neurological Institute (BNI) Pain Intensity Scale, and severity of pain was determined using the visual analogue scale (VAS) score. Preoperative imaging showed that no patients had NVC compression. The preoperative BNI pain score was IV among 9 patients and V among other 10 patients. The preoperative VAS score was 7.89 ± 0.658. After the operation, pain disappeared in all 19 patients, and transient facial numbness occurred in 3 patients. During follow-up, pain in 2 of 19 patients (10.5%) recurred at postoperative 20 and 23 months. This study demonstrated that 360-degree circumferential arachnoid dissection is an alternative treatment for trigeminal neuralgia in patients with no neurovascular compression, especially when a thickened arachnoid, angulation, or torsion of the trigeminal nerve root was found during the operation. However, further study is needed to compare the outcomes of different surgical strategies and prove the efficacy of 360-degree circumferential arachnoid dissection in cases without neurovascular compression (NVC).

Establishing rarity in the context of orphan medicinal product designation in the European Union

In the European Union (EU) legislative framework for orphan medicinal product designation, establishing that a condition affects not more than five in 10,000 people is a prerequisite for applications based on rarity. Demonstrating this requirement to the Committee of Orphan Medicinal Products (COMP) can be a particularly challenging task for sponsors. Here, we identify and examine three common issues with the estimation of prevalence in orphan drug applications in the EU (the discernment between diagnosed and undiagnosed cases; the duration of the disease; and the need for an explicit contemporary conclusion) as critical factors for acceptable prevalence estimation. These concerns are discussed in detail based on recent examples of applications, which are reflected in published European Medicines Agency (EMA) documents.

Brain white matter plasticity and functional reorganization underlying the central pathogenesis of trigeminal neuralgia

Peripheral nerve damage does not fully explain the pathogenesis of trigeminal neuralgia (TN). Central nervous system changes can follow trigeminal nerve dysfunction. We hypothesized that brain white matter and functional connectivity changes in TN patients were involved in pain perception, modulation, the cognitive-affective system, and motor function; moreover, changes in functional reorganization were correlated with white matter alterations. Twenty left TN patients and twenty-two healthy controls were studied. Diffusion kurtosis imaging was analyzed to extract diffusion and kurtosis parameters, and functional connectivity density (FCD) mapping was used to explore the functional reorganization in the brain. In the patient group, we found lower axial kurtosis and higher axial diffusivity in tracts participated in sensory, cognitive-affective, and modulatory aspects of pain, such as the corticospinal tract, superior longitudinal fasciculus, anterior thalamic radiation, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, cingulated gyrus, forceps major and uncinate fasciculus. Patients exhibited complex FCD reorganization of hippocampus, striatum, thalamus, precentral gyrus, precuneus, prefrontal cortex and inferior parietal lobule in multiple modulatory networks that played crucial roles in pain perception, modulation, cognitive-affective system, and motor function. Further, the correlated structural-functional changes may be responsible for the persistence of long-term recurrent pain and sensory-related dysfunction in TN.

Severe Radiation Necrosis Successfully Treated With Bevacizumab in an Infant with Low-Grade Glioma and Tumor-Associated Intractable Trigeminal Neuralgia

We present a unique case of radiation necrosis in a child with brain stem low-grade glioma (LGG) presenting with trigeminal neuralgia. Despite extensive therapies, severe pain persisted. She received proton beam radiation with significant improvement. However, she developed radiation necrosis and hydrocephalus. Despite surgical correction of hydrocephalus, the patient remained critically ill. She was treated with dexamethasone and bevacizumab with rapid clinical improvement. Subsequent MRIs revealed almost complete resolution of the necrosis. This case illustrates the successful treatment of trigeminal neuralgia with radiation and a rare case of radiation necrosis in an LGG successfully treated with bevacizumab and dexamethasone.

Neurovascular Compression at the Root Entry Zone Correlates with Trigeminal Neuralgia and Early Microvascular Decompression Outcome

BACKGROUND

Trigeminal neurovascular contact (NVC) is hypothesized to be the etiology of classical trigeminal neuralgia (TGN). We aimed to seek a correlation between types of NVCs and the presence of TGN as well as early surgical outcome in patients with TGN treated with trigeminal microvascular decompression (MVD).

METHODS

We blindly analyzed preoperative high-resolution magnetic resonance images with respect to the degree (none, "touch," or compression) and location of bilateral NVC in 57 retrospectively identified Burchiel Type 1 TGN patients treated by MVD. Location of NVC was noted as either at the root entry zone or distal to it. Using a logistic regression model, we assessed the degree and location of trigeminal NVC for correlation with the symptomatic side. Furthermore, the NVC characteristics on the symptomatic side were correlated with early postoperative pain relief.

RESULTS

Although the degree and location of NVC were not statistically correlative independently, a combined interaction analysis of both statistically correlated with the symptomatic side and with early postoperative pain relief.

CONCLUSIONS

We conclude that in TGN patients treated with MVD, magnetic resonance imaging identified neurovascular compression at the root entry zone (correlates with the affected side and early postoperative pain relief.

Dental pulp stem cells as a multifaceted tool for bioengineering and the regeneration of craniomaxillofacial tissues

Dental pulp stem cells, or DPSC, are neural crest-derived cells with an outstanding capacity to differentiate along multiple cell lineages of interest for cell therapy. In particular, highly efficient osteo/dentinogenic differentiation of DPSC can be achieved using simple in vitro protocols, making these cells a very attractive and promising tool for the future treatment of dental and periodontal diseases. Among craniomaxillofacial organs, the tooth and salivary gland are two such cases in which complete regeneration by tissue engineering using DPSC appears to be possible, as research over the last decade has made substantial progress in experimental models of partial or total regeneration of both organs, by cell recombination technology. Moreover, DPSC seem to be a particularly good choice for the regeneration of nerve tissues, including injured or transected cranial nerves. In this context, the oral cavity appears to be an excellent testing ground for new regenerative therapies using DPSC. However, many issues and challenges need yet to be addressed before these cells can be employed in clinical therapy. In this review, we point out some important aspects on the biology of DPSC with regard to their use for the reconstruction of different craniomaxillofacial tissues and organs, with special emphasis on cranial bones, nerves, teeth, and salivary glands. We suggest new ideas and strategies to fully exploit the capacities of DPSC for bioengineering of the aforementioned tissues.

Risk of psychiatric disorders following trigeminal neuralgia: a nationwide population-based retrospective cohort study

Background

TN is one of the most common causes of facial pain. A higher prevalence of psychiatric co-morbidities, especially depressive disorder, has been proven in patients with TN; however, a clear temporal-causal relationship between TN and specific psychiatric disorders has not been well established. We performed a nationwide population-based retrospective cohort study to explore the relationship between TN and the subsequent development of psychiatric disorders, including schizophrenia, bipolar disorder, depressive disorder, anxiety disorder, and sleep disorder.

Methods

We identified subjects who were newly diagnosed with TN between January 1, 2000 and December 31, 2010 in the Taiwan National Health Insurance Research Database. A comparison cohort was constructed for patients without TN who were matched according to age and sex. All TN and control patients were observed until diagnosed with psychiatric disorders, death, withdrawal from the National Health Institute system, or until December 31, 2010.

Results

The TN cohort consisted of 3273 patients, and the comparison cohort consisted of 13,092 matched control patients without TN. The adjusted hazard ratio (aHR) of depressive disorder, anxiety disorder and sleep disorder in subjects with TN was higher than that of the controls during the follow-up [aHR: 2.85 (95 % confidence interval: 2.11–3.85), aHR: 2.98 (95 % confidence interval: 2.12–4.18) and aHR: 2.17 (95 % confidence interval: 1.48–3.19), respectively].

Conclusions

TN might increase the risk of subsequent newly diagnosed depressive disorder, anxiety disorder, and sleep disorder, but not schizophrenia or bipolar disorder. Additional prospective studies are required to confirm these findings.

Trigeminal neuralgia: pain, pricks, and anxiety

Trigeminal neuralgia (TN) is one of the most common forms of neuralgia experienced by older adults. Early in the course of the illness, individuals may be misdiagnosed, with associated delays in treatment. The current article uses an individual example to provide a framework for assessment and clinical management. Because pain associated with TN may be chronic, specific quality of life issues and related management approaches are presented, as well as guidelines for monitoring response to treatment. Targeted strategies to prevent pain triggers and suggestions for supportive coaching provide direction for health providers caring for older adults with TN.

Differential diagnostics of pain in the course of trigeminal neuralgia and temporomandibular joint dysfunction

Chronic oral and facial pain syndromes are an indication for intervention of physicians of numerous medical specialties, while the complex nature of these complaints warrants interdisciplinary diagnostic and therapeutic approach. Oftentimes, lack of proper differentiation of pain associated with pathological changes of the surrounding tissues, neurogenic pain, vascular pain, or radiating pain from idiopathic facial pain leads to improper treatment. The objective of the paper is to provide detailed characterization of pain developing in the natural history of trigeminal neuralgia and temporomandibular joint dysfunction, with particular focus on similarities accounting for the difficulties in diagnosis and treatment as well as on differences between both types of pain. It might seem that trigeminal neuralgia can be easily differentiated from temporomandibular joint dysfunction due to the acute, piercing, and stabbing nature of neuralgic pain occurring at a single facial location to spread along the course of the nerve on one side, sometimes a dozen or so times a day, without forewarning periods. Both forms differ significantly in the character and intensity of pain. The exact analysis of the nature, intensity, and duration of pain may be crucial for the differential diagnostics of the disorders of our interest.