Trigeminal Ganglionopathy on Brain Magnetic Resonance Imaging-A Rare Etiology

This case report describes a 56-year-old man with periorbital swelling and hyperpigmentation on the right side of the face and a hypopigmented patch on the anterior chest.

Glia-derived adenosine in the ventral hippocampus drives pain-related anxiodepression in a mouse model resembling trigeminal neuralgia

Glial activation and dysregulation of adenosine triphosphate (ATP)/adenosine are involved in the neuropathology of several neuropsychiatric illnesses. The ventral hippocampus (vHPC) has attracted considerable attention in relation to its role in emotional regulation. However, it is not yet clear how vHPC glia and their derived adenosine regulate the anxiodepressive-like consequences of chronic pain. Here, we report that chronic cheek pain elevates vHPC extracellular ATP/adenosine in a mouse model resembling trigeminal neuralgia (rTN), which mediates pain-related anxiodepression, through a mechanism that involves synergistic effects of astrocytes and microglia. We found that rTN resulted in robust activation of astrocytes and microglia in the CA1 area of the vHPC (vCA1). Genetic or pharmacological inhibition of astrocytes and connexin 43, a hemichannel mainly distributed in astrocytes, completely attenuated rTN-induced extracellular ATP/adenosine elevation and anxiodepressive-like behaviors. Moreover, inhibiting microglia and CD39, an enzyme primarily expressed in microglia that degrades ATP into adenosine, significantly suppressed the increase in extracellular adenosine and anxiodepressive-like behaviors. Blockade of the adenosine A2A receptor (A2AR) alleviated rTN-induced anxiodepressive-like behaviors. Furthermore, interleukin (IL)-17A, a pro-inflammatory cytokine probably released by activated microglia, markedly increased intracellular calcium in vCA1 astrocytes and triggered ATP/adenosine release. The astrocytic metabolic inhibitor fluorocitrate and the CD39 inhibitor ARL 67156, attenuated IL-17A-induced increases in extracellular ATP and adenosine, respectively. In addition, astrocytes, microglia, CD39, and A2AR inhibitors all reversed rTN-induced hyperexcitability of pyramidal neurons in the vCA1. Taken together, these findings suggest that activation of astrocytes and microglia in the vCA1 increases extracellular adenosine, which leads to pain-related anxiodepression via A2AR activation. Approaches targeting astrocytes, microglia, and adenosine signaling may serve as novel therapies for pain-related anxiety and depression.

Daily olive oil intake is feasible to reduce trigeminal neuralgia facial pain: A pilot study

Extra virgin olive oil (EVOO) is thought to contribute to neuroprotection and, thus, may influence pain symptoms experienced by adults with demyelination-related trigeminal neuralgia (TN). This study aimed to determine the feasibility of daily intake of EVOO and its potential to alleviate facial pain of TN. Adults, self-reporting as female and affected by TN, were enrolled in a 16-week nonblinded, parallel study. After a 4-week baseline, participants were randomized to 60 mL/day EVOO or control (usual diet and no supplemental EVOO) for 12 weeks. Participants completed a daily questionnaire on pain intensity and compliance, the Penn Facial Pain Scale weekly, the 36-Item Short Form Survey monthly, and dietary assessment during baseline and intervention. Participants (n = 52; 53.3 ± 12.9 years) were recruited nationally; 42 completed the study. The EVOO group, with 90% intake compliance, showed significant decreases in the Penn Facial Pain Scale items of interference with general function, interference with orofacial function, and severity of pain from baseline, whereas the control group showed no improvements. EVOO benefit, compared with control, trended for the interference with orofacial function (P = .05). The 36-Item Short Form Survey items of role limitations resulting from emotional problems and role limitations from physical health favored EVOO. The EVOO group significantly improved their Healthy Eating Index 2015 component scores of fatty acids (primarily from increased oleic acid), sodium, and refined grains. EVOO intake of 60 mL/day was feasible for participants experiencing TN and may mitigate pain and improve quality of life. This trial was registered at clinicaltrials.gov (NCT05032573).

FOXD3-mediated transactivation of ALKBH5 promotes neuropathic pain via m6A-dependent stabilization of 5-HT3A mRNA in sensory neurons

The N6-methyladenosine (m6A) modification of RNA is an emerging epigenetic regulatory mechanism that has been shown to participate in various pathophysiological processes. However, its involvement in modulating neuropathic pain is still poorly understood. In this study, we elucidate a functional role of the m6A demethylase alkylation repair homolog 5 (ALKBH5) in modulating trigeminal-mediated neuropathic pain. Peripheral nerve injury selectively upregulated the expression level of ALKBH5 in the injured trigeminal ganglion (TG) of rats. Blocking this upregulation in injured TGs alleviated trigeminal neuropathic pain, while mimicking the upregulation of ALKBH5 in intact TG neurons sufficiently induced pain-related behaviors. Mechanistically, histone deacetylase 11 downregulation induced by nerve injury increases histone H3 lysine 27 acetylation (H3K27ac), facilitating the binding of the transcription factor forkhead box protein D3 (FOXD3) to the Alkbh5 promoter and promoting Alkbh5 transcription. The increased ALKBH5 erases m6A sites in Htr3a messenger RNA (mRNA), resulting in an inability of YT521-B homology domain 2 (YTHDF2) to bind to Htr3a mRNA, thus causing an increase in 5-HT3A protein expression and 5-HT3 channel currents. Conversely, blocking the increased expression of ALKBH5 in the injured TG destabilizes nerve injury-induced 5-HT3A upregulation and reverses mechanical allodynia, and the effect can be blocked by 5-HT3A knockdown. Together, FOXD3-mediated transactivation of ALKBH5 promotes neuropathic pain through m6A-dependent stabilization of Htr3a mRNA in TG neurons. This mechanistic understanding may advance the discovery of new therapeutic targets for neuropathic pain management.

Peculiar CADASIL phenotype in monozygotic twins carrying a novel NOTCH3 pathogenetic variant

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominantly inherited cerebral small vessel disease caused by Neurogenic locus notch homolog protein 3 (NOTCH3) gene mutations. The main clinical features include migraine with aura, recurrent ischemic strokes and dementia. Brain MRI typically shows multiple small lacunar infarcts and severe, diffuse, symmetrical white matter hyperintensities (WMHs), with characteristic involvement of the anterior temporal pole, external capsule, and superior frontal gyrus. Reports of twins with CADASIL are scarce. Herein we describe a pair of monozygotic twins with peculiar CADASIL phenotype, carrying a new NOTCH3 variant.

CASE PRESENTATION

Twin A was a 45-year-old male suffering from migraine, obesity, arterial hypertension, and polycythemia (with negative genetic analysis), who complained of a transient, short-lasting (~ 5 minutes) episode of speech difficulties. Brain MRI showed diffuse, symmetrical, confluent periventricular WMHs involving frontal, parietal, and temporal lobes and external capsules, with sparing of anterior temporal poles. Genetic analysis of NOTCH3 gene demonstrated the presence of missense c.3329G>A, p.(Cys1110Tyr) variant, confirming CADASIL diagnosis. Twin B, affected by migraine and polycythemia, as well as his monozygotic twin, presented with a 2-month history of trigeminal neuralgia. Brain MRI demonstrated diffuse WMHs with a pattern of distribution like his twin. Genetic analysis revealed the same NOTCH3 pathogenic variant.

CONCLUSIONS

Our monozygotic twins have a strikingly similar neuroimaging picture with sparing of anterior temporal poles. They also have a peculiar phenotype, both presenting polycythemia without genetically confirmed cause. Twin B had trigeminal neuralgia, that is unusual in CADASIL. The possible association of the peculiar findings with the newly reported NOTCH3 variant needs to be confirmed with further observations.

Progress in study on animal models of trigeminal neuralgia

Trigeminal neuralgia is a manifestation of orofacial neuropathic pain disorder, always deemed to be an insurmountable peak in the field of pain research and treatment. The pain is recurrent, abrupt in onset and termination similar to an electric shock or described as shooting. A poor quality of life has been attributed to trigeminal neuralgia, as the paroxysms of pain may be triggered by innocuous stimuli on the face or inside the oral cavity, such as talking, washing face, chewing and brushing teeth in daily life. The pathogenesis of trigeminal neuralgia has not been fully elucidated, although the microvascular compression in the trigeminal root entry zone is generally considered to be involved in the emergence and progression of the pain disorder. In addition, orofacial neuropathic pain restricted to one or more divisions of the trigeminal nerve might be secondary to peripheral nerve injury. Based on current hypotheses regarding the potential causes, a variety of animal models have been designed to simulate the pathogenesis of trigeminal neuralgia, including models of compression applied to the trigeminal nerve root or trigeminal ganglion, chronic peripheral nerve injury, peripheral inflammatory pain and center-induced pain. However, it has not yet been possible to determine which model can be perfectly employed to explain the mechanisms. The selection of appropriate animal models is of great significance for the study of trigeminal neuralgia. Therefore, it is necessary to discuss the characteristics of the animal models in terms of animal strains, materials, operation methods and behavior observation, in order to gain insight into the research progress in animal models of trigeminal neuralgia. In the future, animal models that closely resemble the features of human trigeminal neuralgia pathogenesis need to be developed, with the aim of making valuable contributions to the relevant basic and translational medical research.

Activation of A1 reactive astrocytes in the medullary dorsal horn of rats participates in the chronification of trigeminal neuralgia

OBJECTIVES

The activation of astrocytes is an important process in the formation of chronic pain. This study aims to observe the activation of A1 reactive astrocytes in the medullary dorsal horn in the rat model of trigeminal neuralgia, and to explore the mechanism of central sensitization caused by A1 reactive astrocyte.

METHODS

The adult male rats were randomly divided into a sham group and a chronic constriction injury of infraorbital nerve (ION-CCI) group. The facial mechanical pain threshold and thermal withdrawal latency were measured before the operation and on the 1st, 3rd, 7th, 10th, and 14th day after the operation. After pain behavior observation, the expression of glial fibrillary acidic protein (GFAP) in the medullary dorsal horn was observed by immunohistochemistry and immunofluorescence colocalization of GFAP, complement 3 (C3)/S100A10, and 4', 6-diamidino-2-phenylindole (DAPI) was analyzed. Primary astrocytes were cultured and randomly divided into a naive group and a DHK group. The DHK group was treated with 1 mmol/L of astrocyte activation inhibitor dihydrokainic acid (DHK). Fura-2/AM was used to stain the astrocytes and the calcium wave of the 2 groups under the stimulation of high potassium was recorded and compared. The expression of C3 was detected by Western blotting.

RESULTS

The facial mechanical pain threshold and thermal withdrawal latency of the ION-CCI group were significantly lower than those of the sham group (both P<0.05). There were a large number of GFAP positive astrocytes in the medullary dorsal horn of the ION-CCI group. The fluorescence intensity of GFAP in the ION-CCI group was higher than that in the sham group (P<0.05). GFAP and C3/S100A10 were co-expressed in astrocytes. Compared with the sham group, the fluorescence intensity of C3 and the protein expression of C3 in the ION-CCI group were increased (both P<0.05). The expression of C3 in ION-CCI group was significantly increased (P<0.05). Compared with the naive group, the C3 protein expression was significantly decreased in the DHK group (P<0.05). The intensity of calcium fluorescence was increased after high potassium stimulation in both groups. Furthermore, the peak and increase amplitude of calcium fluorescence in the naive group were much higher than those in the DHK group (both P<0.05).

CONCLUSIONS

A1 reactive astrocytes in the medullary dorsal horn of trigeminal neuralgia model rats are increased significantly, which may participate in central sensitization of trigeminal neuralgia by impacting astrocyte calcium wave.

Altered brain function in classical trigeminal neuralgia patients: ALFF, ReHo, and DC static- and dynamic-frequency study

The present study aimed to clarify the brain function of classical trigeminal neuralgia (CTN) by analyzing 77 CTN patients and age- and gender-matched 73 healthy controls (HCs) based on three frequency bands of the static and dynamic amplitude of low-frequency fluctuation, regional homogeneity, and degree centrality (sALFF, sReHo, sDC, dALFF, dReHo, and dDC). Compared to HCs, the number of altered brain regions was different in three frequency bands, and the classical frequency band was most followed by slow-4 in CTN patients. Cerrelellum_8_L (sReHo), Cerrelellum_8_R (sDC), Calcarine_R (sDC), and Caudate_R (sDC) were found only in classical frequency band, while Precuneus_L (sALFF) and Frontal_Inf_Tri_L (sReHo) were found only in slow-4 frequency band. Except for the above six brain regions, the others overlapped in the classical and slow-4 frequency bands. CTN seriously affects the mental health of patients, and some different brain regions are correlated with clinical parameters. The static and dynamic indicators of brain function were complementary in CTN patients, and the changing brain regions showed frequency specificity. Compared to slow-5 frequency band, slow-4 is more consistent with the classical frequency band, which could be valuable in exploring the pathophysiology of CTN.

Evaluation of the serum level of estrogen, progesterone, prolactin, and testosterone in patients with trigeminal neuralgia compared to a healthy population

OBJECTIVES

The goal of this study is to measure and compare the hormonal serum levels (estrogen, progesterone, testosterone, prolactin, dihydrotestosterone [DHT]) in trigeminal neuroglia (TN) menopausal women and healthy women.

MATERIALS AND METHODS

This cross-sectional and case-control study was performed in 2018 and 2019. For this study, menopausal women with confirmed TN were enrolled. Twenty-two healthy women in the control group and 19 in the case group participated. Blood samples were taken from participants for assessment of hormonal serum levels (estrogen, progesterone, testosterone, prolactin, DHT). Data were analyzed by SPSS version 18. Mann-Whitney, T-test, kormography test, nonmetric, χ2  test, and odds ratios have been used.

RESULTS

In patients with TN, the serum level of testosterone was significantly higher (p = .036), and the serum level of prolactin (p = .016) was significantly lower. Other evaluated hormones' serum level was identical in the two groups. Patients with abnormal estrogen levels were more in the TN group in comparison with the healthy group. The abnormality of progesterone in TN patients was more in comparison to the healthy control group.

CONCLUSIONS

Estrogen and progesterone serum levels in TN patients are higher in comparison with the healthy group, while prolactin and testosterone serum levels are lower in the control group. Moreover, the DHE serum level is similar in both groups.

Attenuates reactive oxygen species: induced pyroptosis via activation of the Nrf2/HO-1 signal pathway in models of trigeminal neuralgia

In this study, we examined the impact of demyelinating and neuroinflammation on trigeminal neuralgia (TN) by utilizing models of chronic constriction injury to the infraorbital nerve (CCI). The CCI rats were treated with either VX-765 (an inhibitor of caspase-1) or a control solution of PBS/DMSO to observe the effects on neurobehavioral and neuropathological outcomes. The histochemical changes, pyroptosis-related proteins were assessed using immunohistochemistry, Elisa, and western blotting. RSC96 cells were pretreated with belnacasan (VX-765, an inhibitor of caspase-1), Gasdermin D(GSDMD)-targeting siRNAs, cobalt protoporphyrin (CoPP) or zinc protoporphyrin (Znpp) before being exposed to H2O2. Following these treatments, the Reactive oxygen species (ROS) level, cell viability, percentage of pyroptosis, pyroptosis-related proteins, nuclear factor erythroid 2-related factor 2 (Nrf2) and HO-1 level was measured. The scanning electron microscopy revealed increased ball-like bulge and membrane pore formation in the CCI group. In the CCI and CCI+ Vehicle groups, we found ROS level and expression of pyroptosis-related proteins increased. While, treatment with VX-765resulted in a decreased expression of GSDMD, IL-1, IL-18, and caspase-1 decreased. In the in-vitro study, RSC96 cells showed mild pyroptosis and overall mild edema after being exposed to H2O2. The ROS level, percentage of pyroptosis, pyroptosis-related proteins, Nrf2 and HO-1 level increased significantly in the H2O2 group. While, the percentage of pyroptosis and pyroptosis-related proteins decreased significantly in the H2O2 + VX-765 group, H2O2 + siRNA group, and H2O2 + VX-765 + siRNA group. After treatment with HO-1-inhibitor Znpp and HO-1-activator Copp, the percentage of pyroptosis and pyroptosis-related proteins increased and decreased significantly respectively. In conclusions, the pyroptosis of Schwann cell in the CCI model generated the demyelination of TN nerve. The ROS is an upstream event of NLRP3 inflammasome activation which induced eventual pyroptosis. The Nrf2/HO-1 signaling pathway could protect the H2O2-induced pyroptosis in RSC96 cells.

Orofacial Migraine and Other Idiopathic Non-Dental Facial Pain Syndromes: A Clinical Survey of a Social Orofacial Patient Group

Background: Orofacial pain syndromes (OFPs) are a heterogeneous group of syndromes mainly characterized by painful attacks localized in facial and oral structures. According to the International Classification of Orofacial Pain (ICOP), the last three groups (non-dental facial pain, NDFP) are cranial neuralgias, facial pain syndromes resembling primary headache syndromes, and idiopathic orofacial pain. These are often clinical challenges because the symptoms may be similar or common among different disorders. The diagnostic efforts often induce a complex diagnostic algorithm and lead to several imaging studies or specialized tests, which are not always necessary. The aim of this study was to describe the encountered difficulties by these patients during the diagnostic-therapeutic course. Methods: This study was based on the responses to a survey questionnaire, administered to an Italian Facebook Orofacial Patient Group, searching for pain characteristics and diagnostic-therapeutic care courses. The questionnaire was filled out by patients affected by orofacial pain, who were 18 years and older, using a free online tool available on tablets, smartphones, and computers. Results: The sample was composed of 320 subjects (244F/76M), subdivided by age range (18-35 ys: 17.2%; 36-55 ys: 55.0%; >55 ys 27.8%). Most of the patients were affected by OFP for more than 3 years The sample presented one OFP diagnosis in 60% of cases, more than one in 36.2% of cases, and 3.8% not classified. Trigeminal neuralgia is more represented, followed by cluster headaches and migraines. About 70% had no pain remission, showing persisting background pain (VAS median = 7); autonomic cranial signs during a pain attack ranged between 45 and 65%. About 70% of the subjects consulted at least two different specialists. Almost all received drug treatment, about 25% received four to nine drug treatments, 40% remained unsatisfied, and almost 50% received no pharmacological treatment, together with drug therapy. Conclusion: To the authors' knowledge, this is the first study on an OFP population not selected by a third-level specialized center. The authors believe this represents a realistic perspective of what orofacial pain subjects suffer during their diagnostic-therapeutic course and the medical approach often results in unsatisfactory outcomes.

Mental nerve shielding from possible injury during mandibular surgical procedures: technical note

Injuries to the mental nerve are not an uncommon complication in maxillofacial surgeries. Manipulation close to the mental nerve poses a great risk of nerve injury from drills, bone cutting and trimming burs, and oscillating/reciprocating saws. Nerve injuries can be painful and affect the patient's quality of life. The accompanying complication of the nerve injury depends on the severity of the damage inflicted and can range from transient hypoesthesia to neuropathic pain or trigeminal neuralgia. It is considered that direct injury to the nerve may lead to permanent damage and more severe postoperative clinical symptoms than indirect injuries caused by nerve stretching or during endosteal implant fixation. This technical note describes a technique for shielding the mental nerve and protecting it from rotary drill injury during mandibular inferior border recontouring, orthognathic surgeries, and mandibular body fracture fixation.

Curcumin alleviates orofacial allodynia and improves cognitive impairment via regulating hippocampal synaptic plasticity in a mouse model of trigeminal neuralgia

OBJECTIVE

Cognitive impairment, one of the most prevalent complications of trigeminal neuralgia, is troubling for patients and clinicians due to limited therapeutic options. Curcumin shows antinociception and neuroprotection pharmacologically, suggesting that it may have therapeutic effect on this complication. This study aimed to investigate whether curcumin alleviates orofacial allodynia and improves cognitive impairment by regulating hippocampal CA1 region synaptic plasticity in trigeminal neuralgia.

METHODS

A mouse model of trigeminal neuralgia was established by partially transecting the infraorbital nerve (pT-ION). Curcumin was administered by gavage twice daily for 14 days. Nociceptive thresholds were measured using the von Frey and acetone test, and the cognitive functions were evaluated using the Morris water maze test. Dendritic spines and synaptic ultrastructures in the hippocampal CA1 area were observed by Golgi staining and transmission electron microscopy.

RESULTS

Curcumin intervention increased the mechanical and cold pain thresholds of models. It decreased the escape latency and distance to the platform and increased the number of platform crossings and dwell time in the target quadrant of models, and improved spatial learning and memory deficits. Furthermore, it partially restored the disorder of the density and proportion of dendritic spines and the abnormal density and structure of synapses in the hippocampal CA1 region of models.

CONCLUSION

Curcumin alleviates abnormal orofacial pain and cognitive impairment in pT-ION mice by a mechanism that may be related to the synaptic plasticity of hippocampal CA1, suggesting that curcumin is a potential strategy for repairing cognitive dysfunction under long-term neuropathic pain conditions.

Joint European Academy of Neurology-European Pain Federation-Neuropathic Pain Special Interest Group of the International Association for the Study of Pain guidelines on neuropathic pain assessment

BACKGROUND AND PURPOSE

In these guidelines, we aimed to develop evidence-based recommendations for the use of screening questionnaires and diagnostic tests in patients with neuropathic pain (NeP).

METHODS

We systematically reviewed studies providing information on the sensitivity and specificity of screening questionnaires, and quantitative sensory testing, neurophysiology, skin biopsy, and corneal confocal microscopy. We also analysed how functional neuroimaging, peripheral nerve blocks, and genetic testing might provide useful information in diagnosing NeP.

RESULTS

Of the screening questionnaires, Douleur Neuropathique en 4 Questions (DN4), I-DN4 (self-administered DN4), and Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) received a strong recommendation, and S-LANSS (self-administered LANSS) and PainDETECT weak recommendations for their use in the diagnostic pathway for patients with possible NeP. We devised a strong recommendation for the use of skin biopsy and a weak recommendation for quantitative sensory testing and nociceptive evoked potentials in the NeP diagnosis. Trigeminal reflex testing received a strong recommendation in diagnosing secondary trigeminal neuralgia. Although many studies support the usefulness of corneal confocal microscopy in diagnosing peripheral neuropathy, no study specifically investigated the diagnostic accuracy of this technique in patients with NeP. Functional neuroimaging and peripheral nerve blocks are helpful in disclosing pathophysiology and/or predicting outcomes, but current literature does not support their use for diagnosing NeP. Genetic testing may be considered at specialist centres, in selected cases.

CONCLUSIONS

These recommendations provide evidence-based clinical practice guidelines for NeP diagnosis. Due to the poor-to-moderate quality of evidence identified by this review, future large-scale, well-designed, multicentre studies assessing the accuracy of diagnostic tests for NeP are needed.

Successful percutaneous cannulation of foramen ovale obstructed by completely ossified pterygoalar ligament using the Hartel approach: Two case reports

RATIONALE

Ossification of the pterygoalar ligament, which lies inferolateral to the exocranial opening of the foramen ovale, is traditionally considered to be a bony bar that could obstruct percutaneous needle access to the foramen ovale using the Hartel approach. We herein present two case reports of successfully penetrating the foramen ovale by a needle across the pterygoalar bar. Lack of knowledge of this type of presentation might lead to a change in the surgical approach.

PATIENT CONCERNS

A 27-year-old woman had an 11-year history of facial pain because of a space-occupying lesion in the left cerebellopontine angle. Neither open surgery nor drug therapy resolved her facial pain. Another 67-year-old woman developed episodic facial pain because of herpes zoster infection 20 days earlier, and she could not achieve pain relief from drug therapy.

DIAGNOSES

Both patients were diagnosed with secondary trigeminal neuralgia.

INTERVENTIONS

The patients underwent radiofrequency thermocoagulation of the semilunar ganglion via the foramen ovale.

OUTCOMES

The three-dimensional computed tomography scan showed that the ipsilateral foramen ovale was obstructed by the pterygoalar bar. However, percutaneous needle cannulation of the foramen ovale was successful using the anterior approach. The facial pain was immediately and completely resolved without complications except for facial numbness.

LESSONS

During percutaneous radiofrequency thermocoagulation for the treatment of trigeminal neuralgia, the Hartel approach can still be used when the foramen ovale is blocked by a pterygoalar bar. To our knowledge, this is the first report of such a treatment. Moreover, we herein provide specific technical recommendations to assist surgeons who may encounter such cases in the future.

Foramen lacerum impingement of trigeminal nerve root as a rodent model for trigeminal neuralgia

Trigeminal neuralgia (TN) is a classic neuralgic pain condition with distinct clinical characteristics. Modeling TN in rodents is challenging. Recently, we found that a foramen in the rodent skull base, the foramen lacerum, provides direct access to the trigeminal nerve root. Using this access, we developed a foramen lacerum impingement of trigeminal nerve root (FLIT) model and observed distinct pain-like behaviors in rodents, including paroxysmal asymmetric facial grimaces, head tilt when eating, avoidance of solid chow, and lack of wood chewing. The FLIT model recapitulated key clinical features of TN, including lancinating pain-like behavior and dental pain-like behavior. Importantly, when compared with a trigeminal neuropathic pain model (infraorbital nerve chronic constriction injury [IoN-CCI]), the FLIT model was associated with significantly higher numbers of c-Fos-positive cells in the primary somatosensory cortex (S1), unraveling robust cortical activation in the FLIT model. On intravital 2-photon calcium imaging, synchronized S1 neural dynamics were present in the FLIT but not the IoN-CCI model, revealing differential implication of cortical activation in different pain models. Taken together, our results indicate that FLIT is a clinically relevant rodent model of TN that could facilitate pain research and therapeutics development.

Capsaicin-induced depolymerization of axonal microtubules mediates analgesia for trigeminal neuropathic pain

ABSTRACT

Capsaicin is a specific agonist of transient receptor potential vanilloid 1 (TRPV1), which is enriched in nociceptors. Capsaicin not only produces acute pain but also leads to long-lasting analgesia in patients with chronic pain. Although capsaicin-induced TRPV1 and Ca 2+ /calpain-dependent ablation of axonal terminals is necessary for long-lasting analgesia, the mechanisms underlying capsaicin-induced ablation of axonal terminals and its association with analgesia are not fully understood. Microtubules are composed of tubulin polymers and serve as a main axonal cytoskeleton maintaining axonal integrity. In this study, we hypothesized that capsaicin would increase the depolymerization of microtubules and lead to axonal ablation and analgesia for trigeminal neuropathic pain. Paclitaxel, a microtubule stabilizer, decreased capsaicin-induced ablation of axonal terminals in time-lapsed imaging in vitro. Capsaicin increases free tubulin in dissociated sensory neurons, which was inhibited by paclitaxel. Consistently, subcutaneous injection of paclitaxel prevented capsaicin-induced axonal ablation in the hind paw skin. Capsaicin administration to the facial skin produced analgesia for mechanical hyperalgesia in mice with chronic constriction injury of the infraorbital nerve, which was prevented by the coadministration of paclitaxel and capsaicin. Whole-mount staining of facial skin showed that paclitaxel reduced capsaicin-induced ablation of peptidergic afferent terminals. Despite the suggested involvement of TRPV1 Ser801 phosphorylation on microtubule integrity, capsaicin-induced analgesia was not affected in TRPV1 S801A knock-in mice. In conclusion, capsaicin-induced depolymerization of axonal microtubules determined capsaicin-induced ablation of nociceptive terminals and the extent of analgesia. Further understanding of TRPV1/Ca 2+ -dependent mechanisms of capsaicin-induced ablation and analgesia may help to improve the management of chronic pain.

Comorbidity between hypothyroidism and headache disorders in a Mexican population

INTRODUCTION

Headache and hypothyroidism are common comorbidities. This is a cross-sectional study of the prevalence of hypothyroidism in headache patients in the largest Mexican headache registry.

PATIENTS AND METHODS

PREMECEF is an e-database for patients with headaches. Data was recollected from July 2017-April 2019 in three centers of Monterrey, Mexico.

RESULTS

Of 869 patients, 35 (4%) had hypothyroidism. Four had two different headache diagnoses; of the 39 individual diagnoses, 23 were primary, 1 secondary, 13 cranial neuralgias, and 2 unspecified headaches. Hypothyroidism prevalence: 8.3% in unspecified, 6.5% in cranial neuralgias, 3.4% in primary, and 1.9% in secondary headaches; in tension-type headache (TTH) was 3.9%, in migraines 3.2%, in trigeminal neuralgia 6.1%, and in occipital neuralgia 6.3%.

CONCLUSION

This is the first report on the prevalence of hypothyroidism in occipital and trigeminal neuralgia. The prevalence of hypothyroidism in migraine and TTH is higher than the general population.

Microanatomy of the central myelin portion and transitional zone of the oculomotor and abducens nerves

BACKGROUND

The microanatomy of the central myelin portion and transitional zone of several cranial nerves including trigeminal, facial, vestibulocochlear, glossopharyngeal, and vagus nerves have been clearly demonstrated to provide information for neurovascular compression syndrome such as trigeminal neuralgia and hemifacial spasm. However, the study of oculomotor and abducens nerve is limited.

MATERIALS AND METHODS

Oculomotor and abducens nerves were harvested with a portion of brainstem and embedded in paraffin. Longitudinal and serial sections from ten of each cranial nerve were stained and a photomicrograph was taken to make the following observations and measurements: 1) patterns of central myelin portion, 2) length of central myelin portion, and 3) depth of central myelin- peripheral myelin transitional zone.

RESULTS

For oculomotor nerve, the longest central myelin bundle was always seen on the first nerve bundle and that the length of central myelin decreased gradually. For abducens nerve, morphological patterns were classified into four types based on number of nerve rootlets emerging from the brainstem and number of nerve bundles in each rootlet. Length of central myelin portion was between 0.36-6.10 mm (2.75 ± 0.83 mm) and 0.13-5.01 mm (1.66 ± 1.39 mm) for oculomotor and abducens nerves, respectively. The oculomotor nerve transitional zone depth was 0.07-058 mm (0.23 ± 0.07 mm), while for abducens nerve, depth was 0.05-0.40 mm (0.16 ± 0.07 mm). Positive weak correlations between central myelin and depth of TZ were found in oculomotor nerve (r +0.310, p < 0.05) and abducens nerves (r +0.413, p < 0.05).

CONCLUSIONS

Detailed microanatomy of the central myelin and transitional zone might be beneficial for locating the site of compression in neurovascular conflicts at oculomotor and abducens nerves.

Orofacial Pain: Molecular Mechanisms, Diagnosis, and Treatment 2021

The Special Issue “Orofacial Pain: Molecular Mechanisms, Diagnosis, and Treatment 2021” contains 6 articles published by 41 authors from different countries focusing on nucleus accumbens core GABAergic neurons, receptor-interacting serine/threonine-protein kinase 1, pannexin 1-mediated ATP signaling, ultra-low-frequency transcutaneous electrical nerve stimulation, and triamcinolone acetonide. The content covers several pain models, including neuropathic pain caused by peripheral nerve constriction or malpositioned dental implants, tongue cancer, myogenous temporomandibular dysfunction, and oral ulcerative mucositis. In addition, a review paper on trigeminal neuralgia is included.

Use of Radiofrequency Ablation for the Management of Headache: A Systematic Review

BACKGROUND

Headache is a very common condition that affects 5-9% of men and 12-25% of women in North America and Europe. Globally, the prevalence of active headaches among adults is 47%. The most common type of headache is tension headaches (38% of adults), followed by migraines (10%), and chronic headaches (3%). While the majority of headaches are benign, the disorder can severely negatively influence a patients' quality of life, which is directly reflected in societal costs.

OBJECTIVE

The objective of this review was to summarize available evidence behind radiofrequency ablation (RFA) for headache, including pain outcome measures, secondary outcomes, and complications.

STUDY DESIGN

Systematic review.

SETTING

This systematic review examined studies that applied the use of RFA for management of headache.

METHODS

This systematic review was reported following the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). Two reviewers independently scored the methodological quality of the selected studies. Due to heterogeneity of studies, a best-evidence synthesis of the available prognostic factors was provided.

RESULTS

In the present investigation, we evaluated 18 studies composed of 6 randomized controlled trials (RCTs), 6 prospective studies, and 6 retrospective studies. All the studies assessed pain improvement with RFA in patients with headache. Most studies targeted the occipital nerve for treatment. Complications were mostly mild and self-limiting, including eyelid swelling, rash, superficial infection of the procedural site, and worsening of headache.

LIMITATIONS

A large variability in definitions of trigeminal neuralgia, radiofrequency technique, and patient selection bias was observed in our selected cohort of studies. In addition, there is a paucity of strong longitudinal RCTs and prospective studies.

CONCLUSION

Our review discusses several studies that suggest the efficacy of RFA in the treatment of headaches. Outcomes varied based on the difference in approaches regarding continuous radiofrequency versus pulsed radiofrequency, temperature, and duration of administration. The majority of the studies discussed in this review indicate a therapeutic benefit of RFA for headaches over a short-term period. Pain outcomes beyond one year are understudied and further studies are needed to determine the long-term effects of RFA for headaches.

Using RNA-Seq to Explore the Hub Genes in the Trigeminal Root Entry Zone of Rats by Compression Injury

BACKGROUND

Mechanical compression on the trigeminal root entry zone (TREZ) by microvascular is the main etiology of primary trigeminal neuralgia (TN).

OBJECTIVES

To study the pathogenesis of TN, hub genes screening in the TREZ of TN in an animal model was performed.

STUDY DESIGN

A double blind, randomized study was designed in a controlled animal trial.

SETTING

The research took place in the Laboratory of Clinical Applied Anatomy at the School of Basic Medical Science of Fujian Medical University.

METHODS

Twelve male rats were randomly divided into a sham operation group and a TN animal model group. TN animal model was induced by chronic compression of trigeminal nerve root (CCT) operation. Gene expression in the TREZ were analyzed by RNA sequencing (RNA-Seq) technique. KEGG analysis, GO analysis, and PPI analysis were performed in the DEGs. Key signaling pathways analyzing by GSEA and the hub genes in the DEGs were also studied. Reverse transcription real-time polymerase chain reaction (RT-qPCR) was used to verify the RNA-Seq results.

RESULTS

Transcriptome data showed that 352 genes up-regulated and 59 genes down-regulated in DEGs on post-operation day 21, after CCT operation in the TN group. KEGG analysis revealed that, "neuroactive ligand receptor interaction" and "cytokine cytokine receptor interaction" may be related to the pathogenesis of TN. GO analysis showed "regulation of signing receptor activity", "chemokine activity", and "carbohydrate binging" may be related to TN. The RT-qPCR results were consistent with the test results, indicating that the transcriptome sequencing results were reliable.

LIMITATIONS

Although the incidence of TN in female rats was higher than in male rats, we only used male SD rats to establish the TN animal model, to avoid the effect of estrogen on experimental results. This study only presents some respects of RNA-Seq technique and, therefore, did not identify the DEGs at the protein level. The relationship between the DEGs at different levels shoud be done in the future.

CONCLUSIONS

Based on the results of RNA-seq, this study discovered 6 hub genes in the TREZ that are closely related to the TN animal model, which provide a potential breakthrough point to explore the pathogenesis of TN.

Altered somatosensory processing in secondary trigeminal neuralgia: A case report

Secondary trigeminal neuralgia might be very rarely preceded by trigeminal neuropathic pain. The patient, in this case, presented with paroxysmal pain in the left mandible and numbness of the lower lip and tongue. Sensory testing of these areas revealed cold and heat hyperalgesia and mechanical hyposensitivity in the mandibular region. Magnetic resonance imaging showed a mass in the left cerebellopontine angle. The patient was prescribed systemic mirogabalin (2.5 mg/day), which provided some relief until the tumor was removed. The histopathological diagnosis was an epidermoid tumor. This article discusses the clinical characteristics and sensory testing findings that distinguish secondary trigeminal neuralgia from trigeminal neuropathic pain based on the International Classification of Orofacial Pain.

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.

Idiopathic Facial Pain Syndromes–An Overview and Clinical Implications

BACKGROUND

Idiopathic facial pain syndromes are relatively rare. A uniform classification system for facial pain became available only recently, and many physicians and dentists are still unfamiliar with these conditions. As a result, patients frequently do not receive appropriate treatment.

METHODS

This article is based on pertinent publications retrieved by a selective search in PubMed, focusing on current international guidelines and the International Classification of Orofacial Pain (ICOP).

RESULTS

The ICOP subdivides orofacial pain syndromes into six major groups, the first three of which consist of diseases of the teeth, the periodontium, and the temporomandibular joint. The remaining three groups (non-dental facial pain) are discussed in the present review. Attack-like facial pain syndromes most closely resemble the well-known primary headache syndromes, such as migraine, but with pain located below the orbitomeatal line. These syndromes are treated in accordance with the guidelines for the corresponding types of headache. Persistent idiopathic facial pain (PIFP) is a chronic pain disorder with persistent, undulating pain in the face and/or teeth, without any structural correlate. Since this type of pain tends to become chronified after invasive procedures, no dental procedures should be performed to treat it if the teeth are healthy; rather, the treatmentis similar to that of neuropathic pain, e.g., with antidepressant and anticonvulsive drugs. Neuropathic facial pain is also undulating and persistent. It is often described as a burning sensation, and neuralgiform attacks may additionally be present. Trigeminal neuralgia is a distinct condition involving short-lasting, lancinating pain of high intensity with a maximum duration of two minutes. The first line of treatment is with medications; invasive treatment options should be considered only if pharmacotherapy is ineffective or poorly tolerated.

CONCLUSION

With the aid of this pragmatic classification system, the clinician can distinguish persistent and attack-like primary facial pain syndromes rather easily and treat each syndrome appropriately.

Novel fluoroscopic landmark to significantly facilitate the visualization of foramen ovale in treating idiopathic trigeminal neuralgia

BACKGROUND AND OBJECTIVES

Access through the foramen ovale (FO) is essential in performing trigeminal ganglion injection, glycerol rhizolysis, balloon compression, and radiofrequency thermocoagulation (RFT) to treat idiopathic trigeminal neuralgia (ITN). However, identification of the FO under fluoroscopy can be difficult and time-consuming, and thus exposes patients to increased radiation and procedure risks. Here we present the 'H-figure' as a novel fluoroscopic landmark to quickly visualize the FO.

METHODS

The H-figure landmark can be recognized as the medial border of the mandible and the lateral edge of the maxilla as the two vertical lines, and the superior line of petrous ridge of temporal bone (S-P-T line) as the horizontal line, and the FO fluoroscopic view is then optimized at the center of the H-figure immediately above the S-P-T line. We applied this landmark in a clinical cohort of 136 patients with ITN who underwent fluoroscopy-guided RFT of the trigeminal ganglion. We also compared the H-figure method with the traditional method. The primary outcome was the total number of fluoroscopic images required to visualize the FO (as a proxy of radiation exposure). Secondary measures included the procedure time required to finalize the FO view and the sensory testing voltage for paresthesia.

RESULTS

With the H-figure approach we were able to view the FO with an average of 4.2 fluoroscopic shots at an average time of 6.8 min. When compared with the non-H-figure traditional technique, the H-figure method required almost half the fluoroscopic shots in nearly half the procedure duration time, and paresthesia was evoked with half of the voltage.

CONCLUSION

The H-figure is an easy fluoroscopic landmark that can help to view the FO with less radiation and procedure time, and the needles placed with this approach can be closer to the target for the RFT treatment of patients with ITN.

Structural and Functional Brain Abnormalities in Trigeminal Neuralgia: A Systematic Review

AIMS

To evaluate the available literature on structural and functional brain abnormalities in trigeminal neuralgia (TN) using several brain magnetic resonance imaging (MRI) techniques to further understand the central mechanisms of TN.

METHODS

PubMed and Web of Science databases and the reference lists of identified studies were searched to identify potentially eligible studies through January 2019. Eligible articles were assessed for risk of bias and reviewed by two independent researchers.

RESULTS

A total of 17 articles meeting the inclusion criteria were included in this study. The methodologic quality of the included studies was moderate. A total of 10 studies evaluated structural gray matter (GM) changes, and there was reasonable evidence that the GM of some specific brain regions changed in TN patients. In addition, there was a significant change in the root entry zone of the trigeminal nerve and in several regions of white matter. Functional changes in resting state were assessed in 9 studies. TN patients showed increased activation of resting state, and this activation was reduced in specific brain regions. There were several studies that focused on the correlation between functional parameters or strength of functional connectivity and clinical features (eg, visual analog score and pain duration), but each study focused on different brain areas or different functional connectivities within the brain.

CONCLUSION

There is moderate evidence that TN patients show structural brain differences in specific cortical and subcortical regions. In addition, TN patients show changes in pain-related functional connections in the resting state. Future research should focus on longitudinal designs and integration of different brain-imaging techniques.

Painful Post-traumatic Trigeminal Neuropathy Occurs After Third Molar Extraction

Painful post-traumatic trigeminal neuropathy (PTTN), or anesthesia dolorosa, is a condition on the same continuum as trigeminal neuralgia. Unlike trigeminal neuralgia, trigeminal neuropathy is a more significant state of neural pathology resulting in constant pain opposed to the episodic nature of trigeminal neuralgia. This typically occurs after facial trauma or as a complication from some treatments for trigeminal neuralgia. Useful diagnostic features that can help distinguish PTTN are an identified trauma to the nerve and other clinical features such as facial swelling. The presented case describes a classic presentation after third molar (wisdom tooth) removal and a review of pertinent literature.

Idiopathic Trigeminal Neuralgia (ITN): Facts and Fiction

In this paper the authors present neuroanatomical and neurophysiological arguments against the microvascular compression in the root entry zone of trigeminal nerve nerve as an ethiopathogenetic factor of ITN. Clinical experience has proven that compression of mixed sensorymotor nerve (peripheral or central one), cannot provoke paroxysmal neuralgic pain. The authors conclude that the well known fact that dental pulp has only pain sensory modality brings up the question what might be consequence of tooth extraction where neural fibers are broken in the innervation areas of maxillar and mandibular nerve. The answer could be only one. If exclusive algophoric deafferentation hypersensitivity after tooth extraction exceeds a certain threshold, patients will experience paroxysmal neuralgic pain. Broken neural fibers develop pathological ephaptic communication with other trigeminal sensory modalities through supraspinal central structures responsible for the transmision of dental pulp pain. This can explain trigger phenomena and latency between the touching of circumoral areas and onset of neuralgic paroxysm, which is a central epileptic phenomenon. In conclusion, the so-called idiopathic trigeminal neuralgia (ITN) is the expression of algophoric deafferentation hypersensitivity after tooth extraction.

Comparison of the Neuropathic Pain Symptoms and Psychosocial Impacts of Trigeminal Neuralgia and Painful Posttraumatic Trigeminal Neuropathy

AIMS

To compare the impacts of trigeminal neuralgia (TN) and painful posttraumatic trigeminal neuropathy (PPTTN) on psychologic function and health-related quality of life (HRQoL) using a comprehensive quantitative assessment.

METHODS

This was a comparative cross-sectional study. A total of 97 patients diagnosed with PPTTN and 40 patients diagnosed with TN who sought treatment at an orofacial pain clinic completed standardized self-report measures of pain intensity, neuropathic symptoms, pain self-efficacy, mood, and indicators of general and oral HRQoL. Differences between the PPTTN and TN groups were tested, and associations of each condition with pain severity, psychologic function, and HRQoL were examined.

RESULTS

The majority of PPTTN (66%) and TN patients (80%) were affected by orofacial pain. Pain attacks were more frequent in TN (71%) than PPTTN (28%) patients, while numbness was more common in PPTTN (51%) than TN (12%) patients. Pain intensity was higher in TN for intermittent and affective pain dimensions. Both PPTTN and TN had a significant, but comparable, impact on patients' oral HRQoL. The burden of condition on overall health was significantly more pronounced in patients with TN than PPTTN, with evident differences in the mobility and self-care domains. There was a trend showing that more TN (54%) than PPTTN (36%) patients reported signs of depression, but clinically significant anxiety was comparably high in both groups (34% to 39%). Anxiety and pain self-efficacy were closely related to oral and general health statuses in both groups.

CONCLUSIONS

Both TN and PPTTN are associated with significant psychosocial burden and reduced HRQoL, indicating a need to develop effective treatments for neuropathic orofacial pain that target functional restoration.

Endoscopic Infraorbital Microdissection for Localized V2 Trigeminal Neuralgia

Trigeminal neuralgia is a chronic and debilitating syndrome characterized by short paroxysms of lancinating facial pain. Patients may be medically managed; however, in cases of medically refractory trigeminal neuralgia, surgical management is often required. Our objective was to present and describe a technique for endoscopic microdissection of the infraorbital nerve, a peripheral method of management for refractory V2 trigeminal neuralgia in patients without evidence of neurovascular compression. The technique is designed to spare sensation in unaffected portions of the V2 distribution. We present 2 patients with medically refractory V2 trigeminal neuralgia localized to the lateral midface who underwent infraorbital microdissection. After first confirming that there was no neurovascular compression on imaging in these patients, we administered infraorbital bupivacaine injections to localize the symptomatic nerve. The nerve was then accessed via a 1.5-cm buccogingival incision, and the connective tissue sheath was incised. The nerve fascicles were bluntly separated, and the symptomatic branches were cauterized with fine-tipped monopolar cautery. Both patients reported complete resolution of their pain postoperatively and were pain free at last follow-up. They reported some hypoesthesia in the lateral face; however, they retained some sensation in the medial upper lip, midface, and nose. Infraorbital microdissection is a safe and effective technique for symptomatic management of V2 trigeminal neuralgia while sparing sensation in asymptomatic portions of the dermatome.

Sphenopalatine Ganglion Block with Botulinum Neurotoxin for Treating Trigeminal Neuralgia Using CAD/CAM-Derived Injection Guide

AIMS

To examine the effectiveness and safety of using a CAD/CAM-derived injection guide for botulinum neurotoxin block of the sphenopalatine ganglion for trigeminal neuralgia treatment.

METHODS

Ten patients with second-division trigeminal neuralgia who did not respond to submucosal administration of botulinum neurotoxin were enrolled in this study. The target point around the sphenopalatine fossa was determined after fusion of computed tomography data with a scan of a maxillary model using a software program for dental implant surgery. A CAD/CAM-derived injection guide was fabricated. The guide was affixed to the patient's maxilla, and a needle was inserted to an exactly analyzed depth. Subsequently, 50 units of botulinum neurotoxin were injected. Pain intensity evaluated using a visual analog scale and pain frequency were measured.

RESULTS

By using the guides, sphenopalatine ganglion block with botulinum toxin was performed 18 times without any complications. The visual analog scale score (8.1 ± 1.0) and pain frequency (19.4 ± 8.8 times/day) decreased (to 1.9 ± 1.4 and 4.9 ± 5.4 times/day, respectively) significantly (P < .001). After 4 weeks, the mean subjective improvement achieved was 77.5% ± 13.8%, and all patients responded to treatment.

CONCLUSION

Even without prior experience of sphenopalatine ganglion block, the CAD/CAM-derived guide enabled the accurate and safe administration of botulinum neurotoxin to the sphenopalatine ganglion for the treatment of trigeminal neuralgia.

Minimally Invasive Trigeminal Ablation: Long Buccal Nerve

AIMS

To describe a technique of minimally invasive trigeminal nerve ablation of the long buccal nerve that was performed at a tertiary care academic medical center.

METHODS

This case describes a 44-year-old woman with refractory left long buccal nerve neuropathy following a dental procedure. After failing medical management, she was taken for nerve exploration, which revealed no nerve discontinuity or neuroma formation. She was therefore counseled regarding the risks and possible benefits of a novel minimally invasive trigeminal nerve thermoablation of the long buccal nerve technique.

RESULTS

Postoperatively, the patient experienced mild anesthesia along the long buccal nerve division and no longer experiences any allodynia or hypersensitivity. Additionally, she no longer requires any additional medical therapy or interventions.

CONCLUSION

Minimally invasive trigeminal nerve ablation of the long buccal nerve may be effective surgical intervention in treating refractory neuropathic pain in cases of no structural nerve defects. However, long-term well-designed studies are required to fully define its role.

Effects of surgical treatment for classical trigeminal neuralgia with concomitant persistent facial pain

PURPOSE

Classical trigeminal neuralgia with concomitant persistent facial pain responds poorly to conservative treatment. The authors describe the effects of microvascular decompression and radiofrequency thermocoagulation for patients with classical trigeminal neuralgia and concomitant persistent facial pain.

CASE REPORT

Case 1 was a 61-year-old man with dull, continuous, aching pain in the left maxillary and mandibular molar area. Case 2 was a 68-year-old woman with aching pain in the maxillary right molar. Case 3 was a 67-year-old woman with severe pain in the right upper lip and maxillary right second premolar. Case 4 was a 42-year-old man with orofacial pain of 14 months' duration. Cases 1 and 2 underwent radiofrequency thermocoagulation and reported good relief of symptoms. Cases 3 and 4 underwent microvascular decompression and attained excellent relief.

CONCLUSION

Microvascular decompression may be more effective than radiofrequency thermocoagulation for patients with classical trigeminal neuralgia with concomitant persistent facial pain.

[Anatomical rationale for surgical treatment of trigeminal neuralgia combined with cerebellopontine angle tumors]

Trigeminal neuralgia (TN) can be combined with tumors of the cerebellopontine angle (CPA). The optimal surgical management in these cases depends on the anatomical relationship of the trigeminal nerve root (TNR) with tumors and vessels. The purpose of this study is to evaluate variants of the anatomical relationship between the TNR and the surrounding structures as well as to analyze the results of using various surgical techniques for treatment of TN in CPA tumors.

MATERIAL AND METHODS

We performed a retrospective analysis of 51 patients (38 females and 13 males aged 22 to 77 years) with TN and ipsilateral CPA tumors. Space-occupying lesions were represented by 29 meningiomas of the petrous apex, 11 epidermoids, 9 vestibular schwannomas, 1 hemangioma, and 1 cavernoma.

RESULTS

Intraoperatively, we identified 6 types of the anatomical relationships among the TNR, tumors, and CPA vessels: type I - the TNR is completely surrounded by the tumor (4 epidermoids); type II - the tumor compresses and displaces the TNR (21 meningiomas, 4 schwannomas, and 6 epidermoids); type III - the tumor occurs inside the TNR (1 cavernoma); type IV - the tumor together with the vessel compresses the TNR (3 meningiomas and 1 epidermoid); type V - the tumor displaces the TNR towards the vessel (5 meningiomas and 5 schwannomas); type VI - the tumor does not contact the TNR that is compressed by the vessel (1 hemangioma). Preoperative MRI and intraoperative findings revealed compression and deformity of the brain stem at the TNR entry level in all but two patients. Vascular compression of the TNR (usually by the superior cerebellar artery) was found in 15 of 51 patients. Microvascular decompression (MVD) was performed using various techniques: interposition of implants between vessels and the TNR, transposition of the compressing vessels from the TNR, or transposition of the nerve root. In all patients, except 1, pain syndrome regressed immediately after tumor removal and MVD. In 1 case, the pain syndrome did not regress after total removal of epidermoid and MVD, and TN was resolved by percutaneous radiofrequency rhizotomy. Long-term postoperative follow-up results showed complete elimination of TN in all cases; there were no persistent neurological complications and postoperative mortality.

CONCLUSION

TN may result from direct compression and deformation of the TNR and brain stem by CPA tumors. In some cases, the cause of TN is combined compression of the TNR by the tumor and vessels. Assessment of the neurovascular relationships requires detailed examination of the entire TNR after tumor removal. In the case of vascular compression of the TNR, various MVD techniques can be used for treatment of TN.

[Experimental study of a new animal model with trigeminal neuralgia produced by administration of talc to peripheral infraobital nerve in rats]

PURPOSE

To establish a new animal model of trigeminal neuralgia（TN） produced by administration of talc to peripheral infraobital nerve in rats.

METHODS

Thirty male Wistar rats were randomly divided into 2 groups. Talcum powder (30％,0.3 mL) was injected into the peripheral infraorbital foramen in one group, the same dose of normal saline was injected by the same method in another group. On 3 day before surgery and 3 days, 1 week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 and 12 weeks postoperatively, mechanical pain behavior was determined. Statistical analysis of the threshold of pain response was performed and the behavior of pain was observed in the area of infraorbital nerve innervation in rats. Histopathological changes of the peripheral infraorbital nerve tissue in the rats were observed 3 days, 4 weeks, 8 weeks and 12 weeks postoperatively. The expression of inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin -1β (IL-1β) in the territory of the infraorbital nerve was detected by immunohistochemistry. SPSS16.0 software package was used to analyze the data.

RESULTS

The mechanical pain threshold of rats in the infraorbital innervation area 3 days postoperatively in the experimental group was significantly decreased compared with that in the preoperative group and the control group (P<0.01). The rats in the experimental group 3 days postoperatively experienced symptoms of irritability, scratching the face or aggressive behavior. Twelve weeks after operation, the mechanical pain threshold was still significantly decreased. Histopathological examination in the experimental group 3 days postoperatively mainly showed inflammation with a few inflammatory factors（IL-1β and TNF-α）expression. Inflammation in the experimental group 1week postoperatively was more intense and more inflammatory factors were expressed. Four weeks postoperatively, there was more proliferation of granulation tissue in the area of peripheral infraorbital nerve tissue and expression of inflammatory factors was highest. Four to twelve weeks, the inflammatory response in the experimental group was gradually reduced, increased scar and infraorbital nerve compressing by scar were observed, and the expression of inflammatory factors decreased gradually.

CONCLUSIONS

Injection of talc to the peripheral infraorbital foramen can establish a reliable and stable animal model for research of etiology and treatment of TN.

Subtle Sensory Abnormalities Detected by Quantitative Sensory Testing in Patients with Trigeminal Neuralgia

BACKGROUND

Trigeminal neuralgia (TN) is characterized by paroxysmal pain attacks affecting the somatosensory distributions of the trigeminal nerve. It is thought to be associated with a neurovascular conflict most frequently, but pathomechanisms have not been fully elucidated. In general, no sensory deficit is found in routine clinical examination. There is limited data available, however, showing subtle subclinical sensory deficits upon extensive testing.

OBJECTIVE

We used quantitative sensory testing (QST) to detect abnormalities in sensory processing in patients with TN by comparing the affected and non-affected nerve branches with their contralateral counterparts and by comparing the results of the patients with those of controls.

STUDY DESIGN

Observational study.

SETTING

University Hospital, Departments of Neurosurgery, Institute for Cognitive and Clinical Neuroscience.

METHODS

QST was conducted on 48 patients with idiopathic TN and 27 controls matched for age and gender using the standardized protocol of the German Neuropathic Pain Network. Stimulations were performed bilaterally in the distribution of the trigeminal branches. The patients had no prior invasive treatment, and medications at the time of examination were noted.

RESULTS

In patients with TN deficits in warm and cold sensory detection thresholds in the affected and also the non-affected nerve branches were found. Tactile sensation thresholds were elevated in the involved nerve branches compared to the contralateral side.

LIMITATIONS

More data are needed on the correlation of such findings with the length of history of TN and with changes of the morphology of the trigeminal nerve.

CONCLUSIONS

QST shows subtle sensory abnormalities in patients with TN despite not being detected in routine clinical examination. Our data may provide a basis for further research on the development of TN and also on improvement after treatment.

KEY WORDS

Quantitative sensory testing, trigeminal neuralgia, facial pain, neuropathic pain, microvascular decompression, cranial nerve.

[Evaluation of therapeutic effectiveness and safety of botulinum toxin type A in the treatment of idiopathic trigeminal neuralgia in patients older than 70 years]

OBJECTIVE

To evaluate therapeutic effectiveness and safety of botulinum toxin type A in the treatment of idiopathic trigeminal neuralgia in patients older than 70 years.

METHODS

The total 64 patents were involved from neurology clinic and inpatient department from Aug 2008 to Sep 2013. They were divided into two groups according to the age (older than 70 years versus younger than 60 years. The therapeutic dose, safety, effectiveness were compared between two groups. Visual analog scores were employed to measure the degree of pain.

RESULTS

The mean dosage was (88 ± 30) U in the group aged above 70 years old, and (72 ± 33) U in the group aged below 60 years old respectively. There was no significant difference of dosage between the two groups. The average visual analog score of all patients was (7.7 ± 2.2) before the treatment and decreased to (4.4 ± 2.9) one month after the treatment. To be precise, the average visual analog score of the group aged above 70 years old was (8.2 ± 1.9) before and (4.5 ± 3.2) after the treatment, and the visual analog score of the group aged below 60 years old was (7.2 ± 2.4) before and (4.4 ± 2.5) after the treatment. The effect of botulinum toxin type A in the treatment of idiopathic trigeminal neuralgia was considered statistically significant. The D-value of visual analog score in the elderly group was (3.5 ± 3.6), and (2.8 ± 3.5) in the younger group. There was no significant difference in the D-value between the two groups. Five patients had transient minor side effects in the former group and two patients had transient minor side effects in latter group. There was no significant difference in the incidence rate of side effects between the two groups (P > 0.05).

CONCLUSIONS

Botulinum toxin type A is safe and effective in the treatment of idiopathic trigeminal neuralgia for the patients older than 70 years and the dosages of it are approximate to the patients under 60 years old.

[Alarming effect of intraoperative neuroelectrophysiological monitoring in microvascular decompression for primary trigeminal neuralgia]

OBJECTIVE

To explore the alarming effect of intraoperative neuroelectrophysiological monitoring in microvascular decompression (MVD) for primary trigeminal neuralgia.

METHODS

In 2014, a total of 44 patients with an initial diagnosis of primary trigeminal neuralgia were consecutively recruited for surgery. And 41 of them with an intraoperative confirmation of primary trigeminal neuralgia underwent MVD. Intraoperative neuroelectrophysiological monitoring was employed for brainstem auditory evoked potentials (BAEPs), spontaneous electromyogram for obicularis oculi, obicularisoris and masseter muscles. The real-time alarming report was offered to the operator who adjusted operations accordingly.

RESULTS

There were abnormal changes in 23 cases (56.10%) with a total of 77 instances (BAEPs 27, trigeminal nerve 32, facial nerve 18). The outcomes were no facial pain (n=26), pain relief (n=15) and facial numbness (n=6, two with concurrent hearing disturbance). And the rates of facial pain disappearance and sequela occurrence were much better than those in controls without monitoring.

CONCLUSION

Intraoperative neuroelectrophysiological monitoring helps enhance the MVD effect and decrease operative squela through alarming reporting.

[Changes in pain threshold and glial cell line-derived neurotrophic factor in rat model of trigeminal neuralgia]

OBJECTIVE

This research aims to study the changes in pain threshold and glial cell line-derived neurotrophic factor (GDNF) in a Sprague Dawley (SD) rat model oftrigeminal neuralgia.

METHODS

A total of 36 male SD rats were randomly divided into three groups: operative, sham-operative, and control. In the operative group, a chronic constriction injury (CCI) was caused by placing loose chromic gut ligatures around the right infraorbital nerve (ION). In the sham-operative group, the right ION was subjected to the same procedure, but without ligation. In the control group, the right ION was not subjected to any treatment. The pain thresholds of the three groups were recorded at different times after the operation. The GDNF expression in each group was analyzed via immunohistochemical staining.

RESULTS

An allodynia to mechanical stimulation in the region of the ligated ION was observed starting on the 2nd week after operation. Pain thresholds started to increase gradually from the 6th week and returned to the original level at the 10th to 12th week after operation. Cells that expressed the GDNF markedly increased in number in the operative group with changes observed at different times.

CONCLUSION

We use chronic constriction injury to the infraorbital nerve (CCI-ION) to establish a trigeminal neuralgia-like animal model in SD rats. GDNF may play a role in regulating pain by promoting the restoration and regeneration of nerve fibers.

[Controlled clinical study of trigeminal ganglion puncture guided by CT/MRI image fusion interface navigation]

OBJECTIVE

To build the radio-frequency thermocoagulation (RFT) interface under navigation including foramen ovale and trigeminal ganglion based on CT/MRI image fusion technology, to visualize the relationship between the trigeminal ganglion and the puncture needle, and to observe clinical effects of this method.

METHODS

CT and MRI data of 20 trigeminal neuralgia patients which were input into BrainLAB-iPlan navigation planning system, were aligned and merged, so that the 3-dimentional image fusion interface of CT and MRI for puncture was built. According to the image fusion interface, the pathways targeting the trigeminal ganglion were planned to assist trigeminal ganglion puncture and RFT. The treatment consequences were observed and compared with 20 patients under the RFT only with the direction of pre- and intra-operative CT.

RESULTS

In the group of CT/MRI image fusion cases, 3 cases had been predicted to be difficult because of unreachable ganglion through the foramen ovale pathway. The postoperative clinical examination proved that the ganglions of these 3 cases were only insufficiently damaged or undamaged. The other 17 cases proved better results, except 2 cases whose treatment was changed in operation. The valid rates for both image fusion navigation group and CT group were all above 95%.

CONCLUSION

Navigation interface including both foramen ovale and trigeminal ganglion based on CT/MRI image fusion made visualization of the pathway targeting ganglion come true, which made the treatment more accurate and individual. Whether the pathway could reach the ganglion might distinguish the trouble cases from others.