Flow cytometry analysis of immune and glial cells in a trigeminal neuralgia rat model

Microvascular compression of the trigeminal root entry zone (TREZ) is the main cause of most primary trigeminal neuralgia (TN), change of glial plasticity was previously studied in the TREZ of TN rat model induced by chronic compression. To better understand the role of astrocytes and immune cells in the TREZ, different cell markers including glial fibrillary acidic protein (GFAP), complement C3, S100A10, CD45, CD11b, glutamate-aspartate transporter (GLAST), Iba-1 and TMEM119 were used in the TN rat model by immunohistochemistry and flow cytometry. On the post operation day 28, GFAP/C3-positive A1 astrocytes and GFAP/S100A10-positive A2 astrocytes were activated in the TREZ after compression injury, there were no statistical differences in the ratios of A1/A2 astrocytes between the sham and TN groups. There was no significant difference in Iba-1-positive cells between the two groups. The ratios of infiltrating lymphocytes (CD45+CD11b−) (p = 0.0075) and infiltrating macrophages (CD45highCD11b+) (p = 0.0388) were significantly higher than those of the sham group. In conclusion, different subtypes A1/A2 astrocytes in the TREZ were activated after compression injury, infiltrating macrophages and lymphocytes increased, these neuroimmune cells in the TREZ may participate in the pathogenesis of TN rat model.

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. KEY WORDS: Animal model, compression injury, hub gene, rat, RNA-seq, transcriptome, trigeminal neuralgia, trigeminal root entry zone

Potential Molecular Targets for Treating Neuropathic Orofacial Pain Based on Current Findings in Animal Models

This review highlights potential molecular targets for treating neuropathic orofacial pain based on current findings in animal models. Preclinical research is currently elucidating the pathophysiology of the disease and identifying the molecular targets for better therapies using animal models that mimic this category of orofacial pain, especially post-traumatic trigeminal neuropathic pain (PTNP) and primary trigeminal neuralgia (PTN). Animal models of PTNP and PTN simulate their etiologies, that is, trauma to the trigeminal nerve branch and compression of the trigeminal root entry zone, respectively. Investigations in these animal models have suggested that biological processes, including inflammation, enhanced neuropeptide-mediated pain signal transmission, axonal ectopic discharges, and enhancement of interactions between neurons and glial cells in the trigeminal pathway, are underlying orofacial pain phenotypes. The molecules associated with biological processes, whose expressions are substantially altered following trigeminal nerve damage or compression of the trigeminal nerve root, are potentially involved in the generation and/or exacerbation of neuropathic orofacial pain and can be potential molecular targets for the discovery of better therapies. Application of therapeutic candidates, which act on the molecular targets and modulate biological processes, attenuates pain-associated behaviors in animal models. Such therapeutic candidates including calcitonin gene-related peptide receptor antagonists that have a reasonable mechanism for ameliorating neuropathic orofacial pain and meet the requirements for safe administration to humans seem worth to be evaluated in clinical trials. Such prospective translation of the efficacy of therapeutic candidates from animal models to human patients would help develop better therapies for neuropathic orofacial pain.

A Cadaver Study Confirming the Location of Dye after Trigeminal Ganglion Rhizotomy

Background: Radiofrequency thermal rhizotomy demonstrates an excellent treatment outcome with a high success rate among patients of intractable trigeminal neuralgia. The triangular plexus which is an immediate retrogasserian portion of the trigeminal root is suggested as the best place of lesioning during radiofrequency thermal rhizotomy. However, the anatomy of the triangular plexus has been relatively unrecognized, while the anatomical study related to therapeutic procedure is scarce. Objective: The purpose of this study is to confirm with gross and microscopic finding of the trigeminal system whether, if an electrode tip is placed on the petroclival junction in lateral cranial view, it actually arrives at the triangular plexus or not. In relation to therapeutic procedure, we examined the triangular plexus with morphological and histological methods. Study Design: Human cadaveric study. Setting: An anatomical laboratory in South Korea. Methods: Percutaneous procedure of radiofrequency thermal rhizotomy under C-arm guidance was performed in 8 cadavers. Final target of the electrode tip was the petroclival junction under true lateral cranial view. The location of the electrode tip was determined under observation of the presence of an injected dye. Triangular plexus size was measured grossly and microscopically. Gross and microscopic evaluation of the triangular plexus was performed. Results: Among 15 trigeminal systems, 8 showed dye appearance in the triangular plexus, while 6 showed it in the trigeminal ganglion. Overall, 53% of radiofrequency thermal rhizotomy could reach the triangular plexus when an electrode tip was placed on the petroclival junction. The grossly measured average triangular plexus vertical and transverse diameters were 0.8 cm and 1.3 cm, respectively. Limitation: Only radiologic landmark was used to confirm the location of the electrode tip. However, further study confirming the location of the electrode tip under the guidance of electrical stimulation is needed. Conclusion: When an electrode tip was placed on the petroclival junction, 53% of radiofrequency thermal rhizotomy could reach the triangular plexus. Key words: Petroclival junction, trigeminal neuralgia, triangular plexus, radiofrequency thermal rhizotomy

Microsurgical Anatomy of the Endoscopy-Assisted Retrosigmoid Intradural Suprameatal Approach to the Meckel's Cave

BACKGROUND Understanding the microsurgical anatomical features of the endoscopy-assisted retrosigmoid intradural suprameatal approach (RISA) is critical for surgeons treating petroclival tumors or lesions in the cerebellopontine region that extend into Meckel's cave. OBJECTIVE To evaluate increased exposure for Meckel's cave in the RISA and assess the surgical landmarks for this approach. METHODS A standard retrosigmoid craniotomy to the cerebellopontine region was performed in 4 cadaveric specimens (8 hemispheres) with microscope-assisted endoscopy. The length and depth of the drilling region from the suprameatal tubercle to the petrous apex were analyzed. After opening Meckel's cave and mobilizing the trigeminal root completely, the landmarks for this approach were investigated. RESULTS The endoscopy-assisted RISA facilitates mobilization of the trigeminal root and enhances surgical exposure in the region of Meckel's cave and the petrous apex with increases of 10.1 ± 1.3 mm in depth, 21.4 ± 3.2 mm in length, and 6.4 ± 0.6 mm in height. The posterior and superior semicircular canals, internal auditory canal, superior petrous sinus, and internal carotid artery (petrous segment) served as important landmarks for this approach. One case illustration is presented to describe the application of this approach. CONCLUSION The RISA is suitable mainly for lesions in the posterior fossa that extend into Meckel's cave. The endoscopy-assisted reach optimizes accessibility to the petrous apex region, obviates the need for extensive drilling, and decreases the risk of internal carotid artery injury. Better realization and recognition of microsurgical landmarks and parameters of this approach are crucial for successful outcomes.

ANALYSIS OF THE RESULTS OF SURGICAL TREATMENT OF PRIMARY TRIGEMINAL NEURALGIA USING LASER DESTRUCTION OF THE SENSITIVE ROOT IN ELDERLY AND SENILE PATIENTS

Цель исследования - анализ результатов хирургического лечения первичной невралгии тройничного нерва при использовании лазерной деструкции чувствительного корешка у пациентов пожилого и старческого возраста. Проспективно изучены результаты лечения 25 пациентов старше 65 лет с устойчивой к консервативному лечению тригеминальной болью, которым была проведена лазерная деструкция чувствительного корешка тройничного нерва (970 нм, частота 9 Гц и мощность 3 Вт в суммарной дозе 100 Дж) в период 2018-2019 гг. Средний катамнез наблюдения составил 12 мес. В результате установлено значительное снижение интенсивности болевых ощущений по шкале лицевой боли с 87 (83,5; 91,5) до 15,5 (12,5; 18,5) мм ( р =0,002) в отдаленном периоде. В среднем через 12 мес после операции выявлено значимое увеличение показателей физического и психологического компонентов здоровья по опроснику SF-36 ( p =0,02 и p =0,01 соответственно). В катамнезе по шкале Macnab отмечены преимущественно отличные ( n =23; 92 %) и хорошие ( n =2; 8 %) результаты лечения. Зарегистрировано одно (4 %) периоперационное осложнение и два (8 %) неблагоприятных последствия анестезиологического пособия. Таким образом, применение лазерной денервации чувствительного корешка при первичной невралгии тройничного нерва у пациентов пожилого и старческого возраста позволяет значительно снизить уровень дооперационного болевого синдрома и улучшить качество жизни при низком риске формирования неблагоприятных последствий. The aim of the study was to analyze the results of surgical treatment of primary trigeminal neuralgia using laser destruction of the sensitive root in elderly and senile patients. The results of treatment of 25 patients older than 65 years with conservative treatment-resistant trigeminal pain who underwent laser destruction of the sensitive trigeminal root (970 nm, 9 Hz and 3 W power in a total dose of 100 J) in the period from 2018-2019 were prospectively studied. The average follow-up was 12 months. As a result, a significant decrease in the intensity of pain on the scale of facial pain was found from 87 (83,5; 91,5) mm to 15,5 (12,5; 18,5) mm ( p =0,002) in the long-term period. On average, 12 months after the operation, a significant improvement in the indicators of the physical and psychological components of health was revealed on the SF-36 questionnaire ( p =0,02 and p =0,01, respectively). In the follow-up on the Macnab scale, predominantly excellent ( n =23; 92 %) and good ( n =2; 8 %) treatment results were noted. Registered 1 (4 %) perioperative complication and 2 (8 %) adverse effects of anesthesiology benefits. Thus, the use of laser denervation of the sensitive root in primary trigeminal neuralgia in elderly and senile patients can significantly reduce the level of preoperative pain and improve the quality of life, with low risks of adverse effects.

Trigeminal neurovascular contact in SUNCT and SUNA: a cross-sectional magnetic resonance study

Emerging data points towards a possible aetiological and therapeutic relevance of trigeminal neurovascular contact in short lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and perhaps in short lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA). We aimed to assess the prevalence and significance of trigeminal neurovascular contact in a large cohort of consecutive SUNCT and SUNA patients and evaluate the radiological differences between them. The standard imaging protocol included high spatial and nerve-cistern contrast resolution imaging acquisitions of the cisternal segments of the trigeminal nerves and vessels. MRI studies were evaluated blindly by two expert evaluators and graded according to the presence, location and degree of neurovascular contact. The degree of contact was graded as with or without morphological changes. Neurovascular contact with morphological changes was defined as contact with distortion and/or atrophy. A total of 159 patients (SUNCT = 80; SUNA = 79) were included. A total of 165 symptomatic and 153 asymptomatic trigeminal nerves were analysed. The proportion of neurovascular contact on the symptomatic trigeminal nerves was higher (80.0%) compared to the asymptomatic trigeminal nerves (56.9%). The odds on having neurovascular contact over the symptomatic nerves was significantly higher than on the asymptomatic nerves [odds ratio (OR): 3.03, 95% confidence interval (CI) 1.84–4.99; P < 0.0001]. Neurovascular contact with morphological changes were considerably more prevalent on the symptomatic side (61.4%), compared to the asymptomatic side (31.0%) (OR 4.16, 95% CI 2.46–7.05; P < 0.0001). On symptomatic nerves, neurovascular contact with morphological changes was caused by an artery in 95.0% (n = 77/81). Moreover, the site of contact and the point of contact around the trigeminal root were respectively proximal in 82.7% (67/81) and superior in 59.3% (48/81). No significant radiological differences emerged between SUNCT and SUNA. The multivariate analysis of radiological predictors associated with the symptomatic side, indicated that the presence of neurovascular contact with morphological changes was strongly associated with the side of the pain (OR: 2.80, 95% CI 1.44–5.44; P = 0.002) even when adjusted for diagnoses. Our findings suggest that neurovascular contact with morphological changes is involved in the aetiology of SUNCT and SUNA. Along with a similar clinical phenotype, SUNCT and SUNA also display a similar structural neuroimaging profile, providing further support for the concept that the separation between them should be abandoned. Furthermore, these findings suggest that vascular compression of the trigeminal sensory root, may be a common aetiological factor between SUNCT, SUNA and trigeminal neuralgia thereby further expanding the overlap between these disorders.