Alterations in the spinal cord, trigeminal nerve ganglion, and infraorbital nerve through inducing compression of the dorsal horn region at the upper cervical cord in trigeminal neuralgia

BACKGROUND

Idiopathic trigeminal neuralgia (TN) cases encountered frequently in daily practice indicate significant gaps that still need to be illuminated in the etiopathogenesis. In this study, a novel TN animal model was developed by compressing the dorsal horn (DH) of the upper cervical spinal cord.

METHODS

Eighteen rabbits were equally divided into three groups, namely control (CG), sham (SG), and spinal cord compression (SCC) groups. External pressure was applied to the left side at the C3 level in the SCC group. Dorsal hemilaminectomy was performed in the SG, and the operative side was closed without compression. No procedure was implemented in the control group. Samples from the SC, TG, and ION were taken after seven days. For the histochemical staining, damage and axons with myelin were scored using Hematoxylin and Eosin and Toluidine Blue, respectively. Immunohistochemistry, nuclei, apoptotic index, astrocyte activity, microglial labeling, and CD11b were evaluated.

RESULTS

Mechanical allodynia was observed on the ipsilateral side in the SCC group. In addition, both the TG and ION were partially damaged from SC compression, which resulted in significant histopathological changes and increased the expression of all markers in both the SG and SCC groups compared to that in the CG. There was a notable increase in tissue damage, an increase in the number of apoptotic nuclei, an increase in the apoptotic index, an indication of astrocytic gliosis, and an upsurge in microglial cells. Significant increases were noted in the SG group, whereas more pronounced significant increases were observed in the SCC group. Transmission electron microscopy revealed myelin damage, mitochondrial disruption, and increased anchoring particles. Similar changes were observed to a lesser extent in the contralateral spinal cord.

CONCLUSION

Ipsilateral trigeminal neuropathic pain was developed due to upper cervical SCC. The clinical finding is supported by immunohistochemical and ultrastructural changes. Thus, alterations in the DH due to compression of the upper cervical region should be considered as a potential cause of idiopathic TN.

Herpes zoster of posterior division of mandibular branch of trigeminal nerve

Herpes zoster is a disease caused by the reactivation of dormant varicella zoster virus present in the sensory root ganglion. It presents with a vesicular rash on an erythematous base similar to that seen in classical varicella, however, with only a single dermatomal distribution. The rash is usually seen throughout the affected dermatome as the dorsal root ganglia for each dermatome are clustered together. We present a case of an otherwise healthy male who developed a vesicular rash confined to the distribution of the posterior division of the mandibular nerve. Though the entire mandibular nerve arises from a single ganglion, the skin area supplied by the anterior division of the mandibular nerve was spared. This case provides evidence to show that there is anatomic segregation of cell bodies of nerves traversing anterior and posterior divisions of mandibular division in the trigeminal ganglion and that partial involvement of a sensory root ganglion is possible in immunocompetent patients.

[Left mandibular osteonecrosis following herpes zoster of the third branch of left trigeminal nerve: A case report]

Herpes zoster of trigeminal nerve was a common skin disease caused by varicella-zoster virus infection. Simple involvement of the third branch of trigeminal nerve was rare, and so were oral complications such as pulpitis, periodontitis, spontaneous tooth loss, bone necrosis, etc. This article presented a case of herpes zoster on the third branch of the left trigeminal nerve complicated with left mandibular osteonecrosis. We reported the case of a 64-year-old man with sudden pain in the left half of the tongue 1 month ago, and then herpes on the left facial skin appeared following with acute pain.The local hospital diagnosed it as herpes zoster and treated it with external medication. A few days later, he developed gum pain in the left mandibular posterior tooth area. He was admitted to Peking University School and Hospital of Stomatology one week ago with loose and dislodged left posterior tooth accompanied by left mandibular bone surface exposure. Clinical examination showed bilateral symmetry and no obvious restriction of mouth opening. Visible herpes zoster pigmentation and scarring on the left side of the face appeared. The left mandibular posterior tooth was missing, the exposed bone surface was about 1.5 cm×0.8 cm, and the surrounding gingiva was red and swollen, painful under pressure, with no discharge of pus. The remaining teeth in the mouth were all Ⅲ degree loosened. Imageological examination showed irregular low-density destruction of the left mandible bone, unclear boundary, and severe resorption of alveolar bone. The patient was diagnosed as left mandibular osteonecrosis. Under general anesthesia, left mandibular lesion exploration and curettage + left mandibular partial resection + adjacent flap transfer repair were performed. The patient was re-exmained 6 months after surgery, there was no redness, swelling or other abnormality in the gums and the herpes pigmentation on the left face was significantly reduced. Unfortunately, the patient had complications of postherpetic neuralgia. This case indicate that clinicians should improve their awareness of jaw necrosis, a serious oral complication of trigeminal zoster, and provide early treatment. After the inflammation was initially controlled, surgical treatment could be considered to remove the necrotic bone, curettage the inflammatory granulation tissue, and extraction of the focal teeth to avoid further deterioration of the disease.

Complementary and Integrative Medicine for the Treatment of Trigeminal Neuralgia and Trigeminal Autonomic Cephalalgia

PURPOSE OF REVIEW

Trigeminal neuralgia (TN) and trigeminal autonomic cephalalgias (TACs) are both painful diseases which directly impact the branches of the trigeminal nerve, which supply the face. Patients who have experienced adverse effects, have not responded to mainstream treatments, or have a personal preference for nonmedication options, often turn to complementary and integrative medicine (CIM). The aim of this review is to discuss the efficacy and safety of CIM therapies available for the treatment of TN and TACs.

RECENT FINDINGS

Not only are there limited therapeutic options for TN and TAC patients, but also is there a proportion of patients who are intolerant to standard medical treatments. Recent findings have illustrated that 86% of patients with headache disorders utilize CIM modalities in combination with mainstream medical therapy. CIM modalities can be helpful for these diseases and have primarily been studied in combination with standard medical therapy. There is limited evidence for CIM and behavioral therapies in managing these conditions, and more research is needed to confirm which therapies are safe and effective.

Chronic Constriction Injury of the Distal Infraorbital Nerve (DIoN-CCI) in Mice to Study Trigeminal Neuropathic Pain

Animal models remain necessary tools to study neuropathic pain. This manuscript describes the distal infraorbital nerve chronic constriction injury (DIoN-CCI) model to study trigeminal neuropathic pain in mice. This includes the surgical procedures to perform the chronic constriction injury and the postoperative behavioral tests to evaluate the changes in spontaneous and evoked behavior that are signs of ongoing pain and mechanical allodynia. The methods and behavioral readouts are similar to the infraorbital nerve chronic constriction injury (IoN-CCI) model in rats. However, important changes are necessary for the adaptation of the IoN-CCI model to mice. First, the intra-orbital approach is replaced by a more rostral approach with an incision between the eye and the whisker pad. The IoN is thus ligated distally outside the orbital cavity. Secondly, due to the higher locomotor activity in mice, allowing rats to move freely in small cages is replaced by placing mice in custom-designed and constructed restraining devices. After DIoN ligation, mice exhibit changes in spontaneous behavior and in response to von Frey hair stimulation that are similar to those in IoN-CCI rats, i.e., increased directed face grooming and hyperresponsiveness to von Frey hair stimulation of the IoN territory.

Assessing the Efficacy of Allogeneic Nerve Grafts in Trigeminal Nerve Repair: A Systematic Review

PURPOSE

Our primary objective was to assess the efficacy of allogeneic nerve grafts in inferior alveolar nerve or lingual nerve repair. We hypothesized that using allogeneic nerve grafts would be effective, as evidenced by achieving high rates of functional sensory recovery (FSR). Additionally, we looked if sex, time from injury to repair, etiology of nerve damage, and graft length affected outcomes.

METHODS

A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted. PubMed and Scopus databases were searched using specific search strategies to generate eligible studies. Inclusion criteria encompassed studies reporting use of allogeneic grafts, assessing FSR using either Medical Research Council Scale or Neurosensory Testing, and published within the past 15 years.

RESULTS

Across 10 studies conducted between 2011 and 2023, analysis was performed on 149 patients and 151 reconstructed nerves. Allogeneic nerve grafts showed an average FSR rate of 88.0%. Kaplan-Meier analysis of time to FSR postoperatively revealed that of those achieving FSR, 80% achieved it within 6 months and 98% achieved it by 1 year. The mean graft length was 29.92 mm ± 17.94 mm. The most common etiology for nerve damage was third molar extractions (23.3%). Sex distribution among patients revealed that 85 were female (57.0%) and 64 were male (43.0%).

CONCLUSION

Our primary hypothesis was supported as nerve allografts achieved high rates of FSR. FSR was achieved in normative timeframes, which is 6 to 12 months postoperatively. Furthermore, allografts reduced the risk of posttraumatic trigeminal neuropathy. Time from injury to repair, graft length, etiology of nerve damage, and sex did not affect FSR. As the assessed variables in our study did not affect outcomes, there needs to be a more nuanced approach to understanding and addressing various factors influencing sensory recovery.

In situ tissue profile of rat trigeminal nerve in trigeminal neuralgia using spatial transcriptome sequencing

BACKGROUND

Trigeminal neuralgia (TN) is the most common neuropathic disorder in the maxillofacial region. The etiology and pathogenesis of TN have not been clearly determined to date, although there are many hypotheses.

OBJECTIVE

The goal of this study was to investigate the interactions between different types of cells in TN, particularly the impact and intrinsic mechanism of demyelination on the trigeminal ganglion, and to identify new important target genes and regulatory pathways in TN.

METHODS

TN rat models were prepared by trigeminal root compression, and trigeminal nerve tissues were isolated for spatial transcriptome sequencing. The gene expression matrix was reduced dimensionally by PCA and presented by UMAP. Gene function annotation was analyzed by Metascape. The progression of certain clusters and the developmental pseudotime were analyzed using the Monocle package. Modules of the gene coexpression network between different groups were analyzed based on weighted gene coexpression network analysis and assigned AddModuleScore values. The intercellular communication of genes in these networks via ligand-receptor interactions was analyzed using CellPhoneDB analysis.

RESULTS

The results suggested that the trigeminal ganglion could affect Schwann cell demyelination and remyelination responses through many ligand-receptor interactions, while the effect of Schwann cells on the trigeminal ganglion was much weaker. Additionally, ferroptosis may be involved in the demyelination of Schwann cells.

CONCLUSIONS

This study provides spatial transcriptomics sequencing data on TN, reveals new markers, and redefines the relationship between the ganglion and myelin sheath, providing a theoretical basis and supporting data for future mechanistic research and drug development.

Three-dimensional topography of rat trigeminal ganglion neurons using a combination of retrograde labeling and tissue-clearing techniques

The trigeminal nerve is the sensory afferent of the orofacial regions and divided into three major branches. Cell bodies of the trigeminal nerve lie in the trigeminal ganglion and are surrounded by satellite cells. There is a close interaction between ganglion cells via satellite cells, but the function is not fully understood. In the present study, we clarified the ganglion cells' three-dimensional (3D) localization, which is essential to understand the functions of cell-cell interactions in the trigeminal ganglion. Fast blue was injected into 12 sites of the rat orofacial regions, and ganglion cells were retrogradely labeled. The labeled trigeminal ganglia were cleared by modified 3DISCO, imaged with confocal laser-scanning microscopy, and reconstructed in 3D. Histograms of the major axes of the fast blue-positive somata revealed that the peak major axes of the cells innervating the skin/mucosa were smaller than those of cells innervating the deep structures. Ganglion cells innervating the ophthalmic, maxillary, and mandibular divisions were distributed in the anterodorsal, central, and posterolateral portions of the trigeminal ganglion, respectively, with considerable overlap in the border region. The intermingling in the distribution of ganglion cells within each division was also high, in particular, within the mandibular division. Specifically, intermingling was observed in combinations of tongue and masseter/temporal muscles, maxillary/mandibular molars and masseter/temporal muscles, and tongue and mandibular molars. Double retrograde labeling confirmed that some ganglion cells innervating these combinations were closely apposed. Our data provide essential information for understanding the function of ganglion cell-cell interactions via satellite cells.

The long-term outcome of CT-guided radiofrequency ablation of the peripheral branches of the trigeminal nerve in trigeminal neuralgia

Radiofrequency thermocoagulation (RFTC) of the peripheral branches of the trigeminal nerve has been used for trigeminal neuralgia. However, the long-term outcomes of radiofrequency thermocoagulation have not been established. To evaluate the long-term efficacy of RFTC of peripheral branches in patients with refractory trigeminal neuralgia. A retrospective cohort study was conducted in a comprehensive medical center in China. Patients who underwent radiofrequency thermocoagulation of peripheral branches for refractory trigeminal neuralgia from May 2014 to March 2021 were included for analysis. A total of 84 patients with refractory trigeminal neuralgia underwent 105 procedures. BNI I-II which represents treatment success was achieved in 76/84 (90%) patients and 93/105 (89%) procedures. During follow-up, BNI I and II were maintained in 64/76 (84%), 40/73 (55%), 20/67 (30%), 17/65 (26%), 12/61 (20%), and 8/58 (14%) of patients at 1, 2, 3, 4, 5, and 6 years, after the first procedure, respectively. For all the 105 procedures, BNI I and II were maintained in 68/93 (73%), 41/89(46%), 22/82(27%), 15/79 (19%), 8/74 (11%), and 3/72 (4%) at 1, 2, 3, 4, 5, and 6 years, respectively. There is no significant difference between the first and repeat thermocoagulation in terms of immediate (90% vs. 81%, P=0.140) and long-term efficacies (24 months vs.18 months, P=0.266). Radiofrequency thermocoagulation resulted in better long-term outcomes in patients with typical purely paroxysmal pain (24 months vs. 11 months, P=0.033). Radiofrequency ablation of the peripheral branches of the trigeminal nerve might be a safe and effective method in the treatment of refractory trigeminal neuralgia.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

A Predictive Model for the Risk of Postsurgery Pain Recurrence in the V1 Branch of the Trigeminal Nerve

BACKGROUND

The factors influencing pain recurrence following V1 trigeminal nerve surgery are still unknown.

OBJECTIVE

We aimed to analyze the risk factors affecting pain recurrence following surgery in the V1 branch of the trigeminal nerve, construct a nomogram-based therapeutic efficacy prediction model using logistic regression analysis, and validate the model's predictive performance.

STUDY DESIGN

A retrospective study.

SETTING

This study was performed at the Affiliated Hospital of Jiaxing University, People's Republic of China.

METHODS

Data were retrospectively collected from 131 patients with trigeminal neuralgia and V1 branch algesia who underwent either radiofrequency thermocoagulation through the supraorbital foramen or percutaneous balloon compression at the Pain Department of the Affiliated Hospital of Jiaxing University from March 2017 through January 2021. The patients were randomly divided into a training group (n = 92) and a testing group (n = 39) in a 7:3 ratio. A least absolute shrinkage and selection operator (LASSO) regression was used to screen independent predictive factors. The outcome variable was whether the patient experienced pain recurrence within 2 years postsurgery. Those results were used to construct a nomogram-based predictive model, followed by a multivariate logistic regression analysis. The feasibility of the nomogram-based predictive model was evaluated by the validation group. Finally, the predictive model's discrimination ability, accuracy, and clinical usability were evaluated using a receiver operating characteristic curve, calibration curves, and decision curve analysis, respectively.

RESULTS

The results indicate that among the total 131 patients, 76 patients did not experience pain recurrence within 2 years postsurgery, while 55 patients suffered a pain recurrence. The results of the LASSO regression, combined with a multivariate logistic regression analysis, showed that age, pre-Numeric Rating Scale score, and surgery type were the influencing factors for patients with V1 branch pain who experienced pain recurrence within 2 years postsurgery (P < 0.05). From this data a nomogram-based predictive model was established. The area under the curve of the nomogram-based predictive model for the training group was found to be 0.890 (95% CI, 0.818 - 0.961); in the test group it was 0.857 (95% CI, 0.748 - 0.965) in the test group. The Hosmer-Lemeshow goodness-of-fit test revealed an excellent fit (P > 0.05), while the decision curve analysis showed that the net benefit of using the nomogram-based predictive model to predict the risk of recurrence after 2 years was higher when the patient's threshold probability was 0 to 0.990.

LIMITATIONS

This was a single-center study.

CONCLUSION

A high-precision nomogram-based predictive model was successfully established and validated (with predictive variables including age, pre-Numeric Rating Scale score, and surgery type). We envisage this model will help improve the early identification and screening of high-risk patients for postsurgery pain recurrence of the V1 trigeminal nerve branch.

Trigeminal or peripheral nerve stimulation improves functional outcomes of nerve recovery in a rodent forelimb gap repair model

BACKGROUND

The hypothesis of this study was that trigeminal nerve stimulation (TNS) or peripheral nerve stimulation (PNS) could improve functional outcomes of peripheral nerve injury in a rat forelimb model when compared to control rats not receiving electrical stimulation (ES). While PNS is known to improve outcomes after nerve surgery, the role of TNS has not been explored.

METHODS

Lewis rats were trained to perform a reach and grasp task before receiving a 2 mm gap repair of the ulnar and median nerves and randomized into four treatment groups: (1) sham injury, (2) nerve injury with sham ES, (3) nerve injury with PNS, and (4) nerve injury with TNS. Functional motor (median pull force and percent success in motor task) and sensory metrics (forelimb paw withdrawal thresholds) were collected both pre-injury and throughout rehabilitation. Nerves stained using Gomori's trichrome were assessed quantitatively and qualitatively.

RESULTS

The sham ES group did not recover their pre-injury baseline functional outcomes. In contrast, the TNS and PNS groups fully recovered following injury, with no difference in functional outcomes between the pre-injury baseline and the final week of rehabilitation (P > 0.05, all). Histomorphology results demonstrated no quantitative difference, but qualitative differences in architecture were evident.

CONCLUSIONS

Electrical stimulation of the trigeminal nerve or the injured nerve improved the functional outcomes of nerve regeneration in rodents. Histomorphology results of nerves from the TNS group support the proposed central mechanisms. This is an important step in translating this therapy as an adjunct, non-invasive treatment for high, mixed nerve injuries in humans.

Trigeminal neuralgia caused by a persistent primitive trigeminal artery variant passing through Meckel's cavity: a case report

BACKGROUND

Persistent primitive trigeminal artery variant (PPTAv) is a rare remnant of the primitive intracranial embryonic anastomotic arteries, and its persistence has an unknown etiology. Trigeminal neuralgia attributed to a PPTAv passing through Meckel's cavity is extremely uncommon.

CASE PRESENTATION

A 73-year-old woman presented with right-sided facial pain for 10 years that had failed to respond to medication. Magnetic resonance angiography suggested the presence of a PPTAv compressing the trigeminal nerve, as the abnormal artery originated from the right internal carotid artery. During microvascular decompression (MVD), the offending vessel was inferred to be a PPTAv, as it continued to become the anterior inferior cerebellar artery after passing through Meckel's cavity. Postoperative computed tomography angiography showed the PPTAv continuing posteriorly as the anterior inferior cerebellar artery and supplying the cerebellar hemisphere, which confirmed the intraoperative judgment. The pain resolved after MVD and has not recurred in 12 months of follow-up.

CONCLUSION

MVD is the best surgical choice for trigeminal neuralgia combined with a PPTAv. For patients with neurovascular conflicts, particularly those with suspected vascular variations, preoperative imaging examinations play a critical role in meticulously evaluating the anatomical locations of the nerves and blood vessels. Semilunar puncture (for radiofrequency ablation or percutaneous balloon compression) is contraindicated in patients with a PPTAv.

Sex differences in trigeminal neuralgia: a focus on radiological and clinical characteristics

BACKGROUND

It is well established that trigeminal neuralgia is more prevalent in females than in males. Neurovascular compression with morphological changes of the trigeminal root represents the most recognized etiological factor. However, other factors may play a role in the framework of a multi-hit model. The primary aim of this study was to investigate sex differences in radiological and clinical characteristics of trigeminal neuralgia to better understand the multifactorial origin of this peculiar neuropathic pain condition.

METHODS

In this cross-sectional study patients with a definite diagnosis of primary trigeminal neuralgia were consecutively enrolled. Each patient underwent 3T MRI with sequences dedicated to the study of neurovascular compression. Major morphological changes of the trigeminal root were quantitatively assessed. Clinical characteristics were systematically collected through a dedicated questionnaire. A logistic regression model was implemented to predict radiological and clinical characteristics based on sex.

RESULTS

A total of 114 patients with classical (87) or idiopathic trigeminal neuralgia (27) were enrolled. Female sex was predictive for idiopathic trigeminal neuralgia. Male sex was predictive, among the comorbidities and clinical characteristics, for hypertension, the involvement of the left side and the second trigeminal division, alone or with the ophthalmic division.

DISCUSSION

The preponderance of TN in the female sex and the association between idiopathic TN and the female sex suggest the role of additional etiological factors in the framework of a multi-hit model. The identification of clinical variables predicted by sex suggests the possibility that distinct phenotypes, with peculiar pathophysiological and therapeutic aspects, may occur in females and males.

Unilateral non-healing ulcers in zosteriform pattern

Trigeminal trophic syndrome (TTS) is a rare disease that occurs after injury to the trigeminal nerve. Though this condition has been reported in the early 20th century, it is still a rare entity, with only around 200 cases reported so far. It characteristically presents with persistent facial ulceration with loss of sensation and paraesthesia along the distribution of the trigeminal nerve. We here report a case of TTS developing as a complication of herpes zoster, which possibly occurred due to the nerve damage caused by varicella-zoster virus.

The pathophysiology of trigeminal neuralgia: a molecular review

OBJECTIVE

The goal of this study was to provide a comprehensive overview of the current understanding of molecular and genetic mechanisms underlying the pathophysiology of trigeminal neuralgia (TN).

METHODS

The authors searched PubMed systematically for primary research literature investigating specific molecular mechanisms from samples derived from patients with TN. The genes/molecules of interest from the selected literature were then cross-referenced with corresponding studies in animal models of TN.

RESULTS

From approximately 345 articles, a total of 12 articles were selected and included in the review, focusing on ionotropic channel expressivity and mutations, reactive oxygen species expressivity, inflammatory marker expressivity, and microRNA expressivity. Of the 12 included articles, only 4 had studies completed in other animal models regarding the corresponding TN mechanism found in humans.

CONCLUSIONS

The current literature does not suggest a conclusive disease mechanism for TN in humans. In addition to neurovascular conflict/compression of the trigeminal nerve, recent studies have indicated that TN may be linked to inflammatory and reactive oxygen species signaling as well. Recent genetic studies in patients with TN have yet to be investigated further in animal models.

Trigeminal Nerve Involvement in Bulbar-Onset Anti-IgLON5 Disease

OBJECTIVES

Anti-IgLON5 disease (IgLON5-D) may present with a bulbar-onset motor neuron disease-like phenotype, mimicking bulbar-onset amyotrophic lateral sclerosis. Recognition of their distinctive clinical and paraclinical features may help for differential diagnosis. We report 2 cases of atypical trigeminal neuropathy in bulbar-onset IgLON5-D.

METHODS

Trigeminal nerve involvement was assessed using comprehensive clinical, laboratory, electrophysiologic, and MRI workup.

RESULTS

Both patients were referred for progressive dysphagia, sialorrhea, and hoarseness. They were treated with bilevel positive airway pressure for nocturnal hypoventilation. Patient 1 complained of continuous facial burning pain with allodynia, exacerbated by mastication and prolonged speech. Patient 2 reported no facial pain. Anti-IgLON5 autoantibodies (IgLON5-Abs) were positive in serum for both patients and CSF for patient 1. Cerebral MRI revealed bilateral T2 fluid-attenuated inversion recovery (FLAIR) hyperintensity and enlargement of trigeminal nerves without gadolinium enhancement in both patients. Needle myography showed fasciculations in masseter muscles. Blink-reflex study confirmed bilateral trigeminal neuropathy only in patient 2. Cortical laser-evoked potentials showed a bilateral small-fiber dysfunction in the trigeminal nerve ophthalmic branch in patient 1.

DISCUSSION

In case of progressive atypical bulbar symptoms, the presence of a trigeminal neuropathy or trigeminal nerve abnormalities on MRI should encourage the testing of IgLON5-Abs in serum and CSF.

Local Ulceration following Peripheral Neurolysis with Absolute Alcohol in Patients with Drug-Refractory Trigeminal Neuralgia: A Series of Four Cases

A significant number of patients with trigeminal neuralgia (TGN) are refractory to first-line drugs and require interruption of the pain pathway by various percutaneous procedures. One such percutaneous technique involves an injection of absolute alcohol (AA) into the peripheral branches of the trigeminal nerve. This procedure is useful in elderly and medically compromised drug-refractory cases of TGN who are not interested in undergoing open neurosurgery. Peripheral neurolysis with AA is easy, quick, and safe. It may be carried out in the outpatient department; however, its use is not free from complications. Here, we report four such patients who were complicated with local necrosis and ulceration following administration of AA. The most probable attributable etiologies are sympathetic nerve involvement, intravascular injection of alcohol, vascular spasm of the terminal arteries, distal micro-emboli effect, and faulty technique, including repeated injections.

Clinical and cognitive effects of external trigeminal nerve stimulation (eTNS) in neurological and psychiatric disorders: a systematic review and meta-analysis

This pre-registered (CRD42022322038) systematic review and meta-analysis investigated clinical and cognitive outcomes of external trigeminal nerve stimulation (eTNS) in neurological and psychiatric disorders. PubMed, OVID, Web of Science, Chinese National Knowledge Infrastructure, Wanfang, and VIP database for Chinese technical periodicals were searched (until 16/03/2022) to identify trials investigating cognitive and clinical outcomes of eTNS in neurological or psychiatric disorders. The Cochrane Risk of Bias 2.0 tool assessed randomized controlled trials (RCTs), while the Risk of Bias of Non-Randomized Studies (ROBINS-I) assessed single-arm trials. Fifty-five peer-reviewed articles based on 48 (27 RCTs; 21 single-arm) trials were included, of which 12 trials were meta-analyzed (N participants = 1048; of which ~3% ADHD, ~3% Epilepsy, ~94% Migraine; age range: 10-49 years). The meta-analyses showed that migraine pain intensity (K trials = 4, N = 485; SMD = 1.03, 95% CI[0.84-1.23]) and quality of life (K = 2, N = 304; SMD = 1.88, 95% CI[1.22-2.53]) significantly improved with eTNS combined with anti-migraine medication. Dimensional measures of depression improved with eTNS across 3 different disorders (K = 3, N = 111; SMD = 0.45, 95% CI[0.01-0.88]). eTNS was well-tolerated, with a good adverse event profile across disorders. eTNS is potentially clinically relevant in other disorders, but well-blinded, adequately powered RCTs must replicate findings and support optimal dosage guidance.

Patients with olfactory loss exhibit pronounced adaptation to chemosensory stimuli: an electrophysiological study

BACKGROUND

Pronounced chemosensory adaptation affects many patients with olfactory loss. The study aimed to investigate adaptation to olfactory and trigeminal nasal stimuli in patients with olfactory loss in comparison to controls using electrophysiological measures.

METHODOLOGY

Thirty-four patients with olfactory loss (mean age ± SD = 59 ± 16 years) and 17 healthy volunteers (mean age ± SD = 50 ± 14 years) were recruited. Sniffin’ sticks test was used for evaluation of olfactory function and EEG-derived chemosensory event-related potentials were recorded. Intranasal stimuli were presented using high-precision, computer-controlled stimulators based on the principles of air-dilution olfactometry. Data were analyzed in two different approaches according to the relatively short or long inter-stimulus interval. A decreased peak amplitude or a prolonged latency was considered as an expression of adaptation.

RESULTS

The majority of participants (88%) responded reliably to chemosensory stimulation. Patients with olfactory loss exhibited pronounced olfactory and trigeminal adaptation within the long-term design, without such effects in healthy controls. Odor sensitivity correlated with both olfactory and trigeminal amplitude changes: the worse the olfactory sensitivity, the more pronounced chemosensory adaptation.

CONCLUSIONS

The results help to explain the patients’ complaints in terms of the fast adaptation towards chemosensory stimuli, for example during eating and drinking. The differences in adaptation in patients with olfactory loss and healthy controls could serve as a clinical criterion to gauge olfactory dysfunction.

Unique Measurements of Intranasal Trigeminal Function: A Pilot Study

OBJECTIVE

To investigate novel methods of measuring intranasal trigeminal function and correlate to validated measures of trigeminal function.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary medical center.

METHODS

Forty-one subjects without nasal congestion were assessed. The trigeminal temperature function of the cool/warmth detection threshold and cold/heat pain threshold was measured with the Thermal Sensory Analyzer (TSA) device, as previously validated at buccal mucosa and infraorbital skin. Identical temperature sensory function was assessed at the anterior septum and inferior turbinate. Lateralization of trigeminal odorants eucalyptol, isothiocyanate, and acetic acid was conducted. Visual analog scales (VAS) of trigeminal function were collected.

RESULTS

Extraoral cheek site and oral site thermal measures were moderately correlated, suggesting consistent assessment of trigeminal function. Nearly all intranasal thermal measures correlated between the septum and turbinate (significant correlations [ρ] ranged from .3 to .8). Oral and extraoral cheek sites had modest correlations to intranasal cold and heat pain (ρ = .4-.5). The oral site had modest correlations of cold and heat detection to intranasal sites, with turbinate appearing to have the most correlations. Isothiocyanate lateralization was the most closely correlated to intranasal thermal scores for cold and heat pain. Turbinate thermal measures had weak correlations with trigeminal VAS scores (ρ = .3-.4).

CONCLUSION

Intranasal trigeminal measures of thermal function correlate to validated extraoral and intraoral thermal measures. The turbinate appears to have stronger correlations to the septum than found in the mouth and face. TSA testing might provide a rapid, novel method of intranasal trigeminal function assessment.

Endovascular treatment of trigeminal neuralgia with cranial autonomic symptoms due to a right-sided petrous ridge dAVF

Dural arteriovenous fistula represents a rare cause of secondary Trigeminal Neuralgia. To date, there have been 18 reported cases of successful treatment of trigeminal neuralgia with endovascular embolization. Here we describe a unique case of a 51-year-old man with right-sided petrous ridge dural arteriovenous fistula causing ipsilateral V1 pain and cranial autonomic dysfunction. Cerebral angiography confirmed a Cognard type 3 right-sided tentorial dAVF supplied by an enlarged meningo-hypophpyseal vessel from the extradural ICA and by the middle meningeal artery. The fistula drains towards the midline via deep cerebral veins, the internal cerebral vein and the straight sinus with likely variceal compression of the right trigeminal nerve root entry zone. Transarterial Onyx embolization resulted in complete obliteration of the dural arteriovenous fistula with immediate resolution of facial pain and autonomic symptoms. After 24 months, the patient remains symptom-free and has no radiographic or clinical evidence of fistula recurrence. To date, there have been no other cases reported of trigeminal neuralgia with cranial autonomic symptoms or SUNCT syndrome due to a dural arteriovenous fistula. The presence of cranial autonomic symptoms with trigeminal neuralgia or a diagnosis of SUNCT should not deter endovascular treatments of dural arteriovenous fistulas or treatment of other compressive vascular lesions.

Central myelin-peripheral myelin junction in trigeminal, facial, and vestibulocochlear nerve: A histo-morphometric study

BACKGROUND

The study aimed to locate the central myelin and peripheral myelin junction (CNS PNS Junction, CPJ) in trigeminal, facial and vestibulocochlear nerves.

METHODS

The cisternal segments of the nerves were cut from the brainstem to the proximal margin of trigeminal ganglia (trigeminal nerve) and internal acoustic meatus (facial and vestibulocochlear nerve) from cadavers. Horizontal sections of H&E stained slides were analysed and histo morphometry was performed. The CPJ was confirmed by immunohistochemistry using monoclonal myelin basic protein antibody.

RESULTS

The mean length of the trigeminal, facial and vestibulocochlear nerves were 13.6 ± 3.1 mm, 12.4 ± 1.9 mm and 11.5 ± 2.0 mm respectively; mean length of the centrally myelinated segment at the point of maximum convexity was 4.1 ± 1.5 mm, 3.7 ± 1.6 mm, 3.6 ± 1.4 mm respectively. Six different patterns were observed fortheCPJ.Utilizing the derived values, the CPJwas located at a distance of 18 - 48% and 17 - 61% of the total length of the nerve in all the cases in trigeminal and facial nerve respectively. In vestibulocochlear nerve, it was located at a distance of about 13 - 54% of the total length of the nerve.

CONCLUSIONS

The location of the CPJ in the vestibulocochlear nerve was midway between the brainstem and internal acoustic meatus which is a novel observation.For all the nerves, the CPJ was located either at or before the half way along the length of the nerve in huge majority (97%); never crossing the 60% of the nerve length.

A Patient with Herpes Zoster of the Maxillary Division of Trigeminal Nerve Presents for Oral Evaluation and Toothache

Herpes zoster (HZ) is an acute and painful neurocutaneous infection caused by the reactivation of a latent varicella-zoster virus in the dorsal root or cranial nerve ganglia. It is characterized by 3 stages: prodromal, acute, and chronic. During the prodromal stage, reactivation in the maxillary branch of the trigeminal nerve closely mimics odontalgia, and HZ should be in the differential diagnosis. Patients with HZ develop painful lesions following the affected dermatome. Laboratory testing confirms the diagnosis; treatment is with antiviral agents. Early detection and treatment shorten the course of the infection and lessen the severity of the associated postherpetic neuralgia.

The cerebellopontine angle cistern volumetric differences in trigeminal neuralgia patients with and without vertebrobasilar compression: a case-matched study

Previous studies have indicated that the small cerebellopontine angle (CPA) cistern plays a role in the pathogenesis of trigeminal neuralgia (TN), but they are likely not involved in TN associated with vertebrobasilar artery (VBA) compression because of its rarity. Forty-four patients with VBA-associated TN and 44 age-, sex-, and hypertension-matched TN patients without VBA compression (non-VBA-associated) were included. All patients underwent high-resolution MRI. The CPA cistern volumes were measured bilaterally. The presence of vertebrobasilar dolichoectasia (VBD) and laterality of the vertebrobasilar junction (VBJ) were observed. The CPA cistern volume on the affected side was smaller than the unaffected side (714.4 ± 372.8 vs 890.2 ± 462.2 mm3, p < 0.001) in non-VBA-associated TN patients, while VBA-associated TN patients show a larger CPA cistern on the affected side than the unffected side (1107.0 ± 500.5 vs 845.3 ± 314.8 mm3, p < 0.001). The prevalence of VBD was higher in patients with VBA-associated TN than in matched non-VBA-associated TN patients (90.9% vs 4.5%, p < 0.001). A positive correlation between the laterality of VBJ and the affected side was found in the VBA-associated TN group (p < 0.0001). Large CPA cistern may be a neuroradiological feature of VBA-associated TN, and most of the VBA-associated TN is accompanied by VBD. The presence of VBD and the lateral shift of VBJ may expand the CPA cistern by squeezing the surrounding tissue on the affected side and also increase the chance of VBA compression on the trigeminal nerve, resulting in the genesis of VBA-associated TN.

Sympathetic control of the coronary circulation during trigeminal nerve stimulation in humans

PURPOSE

We sought to investigate the sympathetic mechanism controlling coronary circulation during trigeminal nerve stimulation in healthy women.

METHODS

The protocol consisted of 3 min of trigeminal nerve stimulation (TGS) with cold stimuli to the face, in two conditions: (1) control and β-blockade (oral propranolol), and (2) control and α-blockade (oral prazosin).

RESULTS

Thirty-one healthy young subjects (women: n = 13; men: n = 18) participated in the study. By design, TGS decreased heart rate (HR), and increased blood pressure (BP) and cardiac output (CO). Before the β-blockade coronary blood velocity (CBV-Δ1.4 ± 1.3 cm s-1) increased along with the decrease of coronary vascular conductance index (CVCi-Δ-0.04 ± 0.04 cm s-1 mmHg-1) during TGS and the β-blockade abolished the CBV increase and a further decrease of CVCi was observed with TGS (Δ-0.06 ± 0.07 cm s-1 mmHg-1). During the α-blockade condition before the blockade, the CBV increased (Δ0.93 ± 1.48 cm s-1) along with the decrease of CVCi (Δ-0.05 ± 1.12 cm s-1 mmHg-1) during TGS, after the α-blockade CBV (Δ0.98 ± cm s-1) and CVCi (Δ-0.03 ± 0.06 cm s-1 mmHg-1) response to TGS did not change.

CONCLUSION

Coronary circulation increases during sympathetic stimulation even with a decrease in heart rate.

Trigeminal Lipomatosis: A Rare Cause of Intractable Neuralgia

Lipomatosis of nerve, earlier known as fibrolipomatous hamartoma is a rare condition which predominantly affects peripheral nerves, cranial nerve involvement being extremely uncommon. Preoperative consideration of this entity is of paramount importance as its inadvertent complete surgical resection may inevitably result in significant neurological deficit. We report a case of trigeminal lipomatosis in a young patient with trigeminal neuralgia.

Trigeminocardiac Reflex: A Review and Key Implications to Dermatologic Surgery

BACKGROUND

The trigeminocardiac reflex is a common but underreported occurrence that can vary from benign to life threatening. This reflex can be elicited by placing direct pressure on the globe of the eye or from traction of the extraocular muscles, stimulating the trigeminal nerve.

OBJECTIVE

To provide a review of potential stimuli for the trigeminocardiac reflex within dermatologic surgery and to discuss management options for the treatment of the trigeminocardiac reflex.

METHODS

PubMed and Cochrane were used to identify articles and case reports that established scenarios in which the trigeminocardiac reflex was provoked and subsequently how the reflex was managed.

RESULTS

Within the field of dermatologic surgery, the trigeminocardiac reflex can be stimulated during biopsies, cryoablations, injections, laser treatments, Mohs micrographic surgery, and oculoplastic interventions, most often occurring in an office setting. The most common presentations include significant bradycardia, hypotension, gastric hypermobility, and lightheadedness. The most definitive treatment is cessation of the inciting stimulus, monitoring, and symptomatic management. Glycopyrrolate and atropine are common treatments for severe, intractable cases of the trigeminocardiac reflex.

CONCLUSION

The trigeminocardiac reflex, while underreported and underrepresented in dermatologic literature and dermatologic surgery settings, should be considered in the setting of bradycardia and hypotension during dermatologic procedures.

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.

Trigeminal nerve stimulation for prolonged disorders of consciousness: A randomized double-blind sham-controlled study

BACKGROUND

Trigeminal nerve stimulation (TNS) has been proposed as a promising intervention for coma awakening. However, the effect of TNS on patients with prolonged disorders of consciousness (pDoC) is still unclear.

OBJECTIVE

This study aimed to investigate the therapeutic effects of TNS in pDoC caused by stroke, trauma, and anoxia.

METHODS

A total of 60 patients (male =25, female =35) aged over 18 who were in a vegetative state or minimally conscious state were randomly assigned to the TNS (N = 30) or sham TNS (N = 30) groups. 4 weeks of intervention and a followed up for 8 weeks were performed. The Glasgow Coma Scale (GCS) and Coma Recovery Scale-Revised (CRS-R) scores as primary outcomes were assessed at baseline and at 2, 4, 8, and 12 weeks.

RESULTS

The score changes in the TNS group over time for CRS-R (2-week: mean difference = 0.9, 95% CI = [0.3, 1.5], P = 0.006; 4-week: 1.6, 95% CI = [0.8, 2.5], P < 0.001; 8-week: mean difference = 2.4, 95% CI = [1.3, 3.5], P < 0.001; 12-week: mean difference = 2.3, 95% CI = [1.1, 3.4], P < 0.001) and GCS (4-week: mean difference = 0.7, 95% CI = [0.3, 1.2], P = 0.002; 8-week: mean difference = 1.1, 95% CI = [0.6, 1.7], P < 0.001; 12-week: 1.1, 95% CI = [0.5, 1.7], P = 0.003) were higher than those in the sham group. 18-Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) revealed that the metabolism of the right parahippocampal cortex, right precuneus, and bilateral middle cingulate cortex was significantly increased in TNS group.

CONCLUSION

The results of this study indicate that TNS could increase local brain metabolism and may promote functional recovery in patients with prolonged disorders of consciousness.

REGISTRATION INFORMATION

Name of the registry: Chinese Clinical Trial Registry.

REGISTRATION NUMBER

ChiCTR1900025573. The date that the study was submitted to a registry: 2019-09-01. The date when the first patient was enrolled was 2021-01-20.

[Peripheral stimulation of the trigeminal nerve by nasopharyngeal swabbing as a possible trigger of migraine attacks]

INTRODUCTION

The role of the central and peripheral nervous system in the generation of migraine is not well understood. Our aim was to determine whether peripheral trigeminal nerve stimuli, such as nasopharyngeal swabs, could trigger migraine attacks.

SUBJECTS AND METHODS

A survey was sent to 658 doctors, nurses and medical students, asking about the presence of headache suggestive of migraine after carrying out a SARS-CoV-2 swab test, their previous history of migraine, and demographic and headache-related characteristics. Those who tested positive or had associated clinical signs and symptoms of COVID were excluded.

RESULTS

A total of 377 people were recruited, 309 of whom were included in the sample. Forty-seven (15.2%) reported headache suggestive of migraine after the swab test and 42 (89.4%) of them had a previous history of migraine. The risk of developing migraine was higher in the subgroup of patients with a history of headache suggestive of migraine - odds ratio: 22.6 (95% confidence interval: 8.597-59.397); p < 0.001. No differences were found between the main characteristics of attacks suggestive of migraine before and after the swab test, except for a lower percentage of associated aura afterwards (42.8% vs. 26.1%; p = 0.016). Individuals with previous attacks suggestive of migraine with a frequency of more than two episodes per month had a higher risk of developing a headache suggestive of migraine after the test - odds ratio = 2.353 (95% confidence interval: 1.077-5.145); p = 0.03.

CONCLUSIONS

Nasopharyngeal swabbing may trigger migraine attacks, with a greater likelihood in individuals with a higher frequency of previous migraines. This would confirm the idea that peripheral stimuli on the trigeminal nerve can trigger migraine attacks in individuals with migraine, according to their degree of trigeminovascular sensitisation.

Cranial nerve involvement in patients with immune-mediated neuropathy: an observational blink reflex study

OBJECTIVE

This study aimed to assess cranial nerve involvement in a large adult cohort of patients with immune-mediated neuropathy undergoing immunoglobulin treatment by measuring blink reflex R1 latency prolongation in correlation with clinical findings and nerve conduction studies.

METHODS

104 patients underwent blink reflex examination and ulnar nerve conduction studies and were assessed by the Inflammatory Neuropathy Cause and Treatment disability score, the revised Amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) and focused clinical examination.

RESULTS

Prolonged R1 latencies were identified in 23 of 104 patients (22.1 %). These patients had more severe functional impairments according to the ALSFRS-R, yet only five clinically presented with bulbar dysfunction, facial- or trigeminal nerve impairment. Overall R1 latency was inversely correlated to ulnar motor conduction velocity. In preliminary follow-up assessments under continuous immunoglobulin treatment, prolonged R1 latencies partially improved.

CONCLUSIONS

Cranial nerve involvement is a common feature in immune-mediated neuropathies and is associated with a more severe disease stage. Here, R1 prolongation was detected less frequently compared to previously reported untreated cohorts.

SIGNIFICANCE

Blink reflex studies can detect subclinical cranial nerve involvement in immune-mediated neuropathies. Further studies are needed to evaluate the clinical utility of measuring R1 latency.

[Involvement of the trigeminal nerve system in the sense of smell]

A systematic review of literature on the issue of involvement in the sense of smell, as well as the interaction between the trigeminal and olfactory nerves, was carried out. The article discusses the features of the chemical perception systems, as well as the treatment of olfactory disorders using transcranial electrical stimulation of the trigeminal nerve.

Aseptic Meningitis after Amenamevir Treatment for Herpes Zoster in the First Branch of the Trigeminal Nerve

Amenamevir has been approved for the treatment of herpes zoster (HZ); however, its therapeutic efficacy against central nervous system (CNS) infection may be insufficient due to its low spinal fluid permeability. We herein report a case of aseptic meningitis in a 91-year-old Japanese man treated with amenamevir for HZ in the trigeminal nerve region. Several cases of CNS infection have been reported in patients receiving amenamevir treatment for HZ. Patients with CNS complications often have skin rashes near the trigeminal region. Thus, we should be alert for signs of CNS infection when administering amenamevir to patients with such rashes.

Radiofrequency thermoablation of the peripheral branches of trigeminal nerve versus the Gasserian ganglion for treating idiopathic trigeminal neuralgia: A systematic review and meta-analysis

BACKGROUND

Trigeminal neuralgia is characterized by pain at the distribution of one or more of the trigeminal nerve branches and is usually treated with anti-epileptic medication. When first line treatment fails, patients receive other treatment modalities including radiofrequency thermoablation (RFT) of the Gasserian ganglion and peripheral branches of the trigeminal nerve. The aim of this study is to compare RFT of the Gasserian ganglion and peripheral branches of trigeminal nerve in terms of efficacy and rate of complications.

METHODS

This was a systematic review and meta-analysis that searched Medline, Cochrane Central Register of Controlled Trials, and Embase using Medical Subject Headings and the references of the enrolled studies with no restriction on date. We included only RCTs that compared the RFT of the Gasserian ganglion and peripheral branches of trigeminal nerve with one of the following outcomes: pain scales, immediate effective rate, recurrence rate, and complications.

RESULTS

Five articles were eligible for our review and showed that there was no difference between RFT of the peripheral nerves and the Gasserian ganglion in terms of pain scores. There was a non-significant trend for RFT of the peripheral nerve to have higher immediate effect rates and higher recurrence rates. RFT of the Gasserian ganglion group was associated with masticatory weakness, while the other group was associated with facial swelling and numbness of V2.

CONCLUSION

RFT of the peripheral branches is a safe and effective method to treat idiopathic trigeminal neuralgia but leads to a higher recurrence rate when compared with RFT of the Gasserian ganglion.

Anatomy and Physiology of Headache

Headache disorders can produce recurrent, incapacitating pain. Migraine and cluster headache are notable for their ability to produce significant disability. The anatomy and physiology of headache disorders is fundamental to evolving treatment approaches and research priorities. Key concepts in headache mechanisms include activation and sensitization of trigeminovascular, brainstem, thalamic, and hypothalamic neurons; modulation of cortical brain regions; and activation of descending pain circuits. This review will examine the relevant anatomy of the trigeminal, brainstem, subcortical, and cortical brain regions and concepts related to the pathophysiology of migraine and cluster headache disorders.

Effects of Kilohertz Electrical Stimulation of the Trigeminal Nerve on Motor Learning

Neurological disorders such as stroke remain leading causes of disability worldwide. A current thrust in the neurorehabilitation of such disorders involves exogenous neuromodulation of cranial nerves in order to enhance neuro-plasticity and maximize recovery of function. Here we present preliminary results on the effects of kilohertz range electrical stimulation of the trigeminal nerve (TNS) on motor learning, using an upper extremity visuomotor adaptation paradigm. Twenty-five (25) healthy adult subjects were randomly assigned to 2 groups: 3kHz stimulation ( n=13) and sham ( n=12). Participants performed a visuomotor rotation task that involved center-out reaching movements to eight vertically arranged targets. Four blocks of trials were performed: two baseline blocks with veridical visual feedback, one adaptation block involving a 30° CCW rotation of hand visual feedback, and one washout block with no rotation. TNS was applied for 20 minutes before the 2nd baseline block using two electrodes targeting the ophthalmic branches of the trigeminal nerve. Early in the rotation block, learning rates were similar between the 3kHz and sham groups but gradually diverged, with the 3kHz group demonstrating slightly faster rates than sham later in the rotation block. The results provide new information on the potential use of TNS in neurorehabilitation.

Trigeminal Nerve Stimulation Improves Cerebral Macrocirculation and Microcirculation After Subarachnoid Hemorrhage: An Exploratory Study

BACKGROUND

Delayed cerebral ischemia (DCI) is the most consequential secondary insult after aneurysmal subarachnoid hemorrhage (SAH). It is a multifactorial process caused by a combination of large artery vasospasm and microcirculatory dysregulation. Despite numerous efforts, no effective therapeutic strategies are available to prevent DCI. The trigeminal nerve richly innervates cerebral blood vessels and releases a host of vasoactive agents upon stimulation. As such, electrical trigeminal nerve stimulation (TNS) has the capability of enhancing cerebral circulation.

OBJECTIVE

To determine whether TNS can restore impaired cerebral macrocirculation and microcirculation in an experimental rat model of SAH.

METHODS

The animals were randomly assigned to sham-operated, SAH-control, and SAH-TNS groups. SAH was induced by endovascular perforation on Day 0, followed by KCl-induced cortical spreading depolarization on day 1, and sample collection on day 2. TNS was delivered on day 1. Multiple end points were assessed including cerebral vasospasm, microvascular spasm, microthrombosis, calcitonin gene-related peptide and intercellular adhesion molecule-1 concentrations, degree of cerebral ischemia and apoptosis, and neurobehavioral outcomes.

RESULTS

SAH resulted in significant vasoconstriction in both major cerebral vessels and cortical pial arterioles. Compared with the SAH-control group, TNS increased lumen diameters of the internal carotid artery, middle cerebral artery, and anterior cerebral artery, and decreased pial arteriolar wall thickness. Additionally, TNS increased cerebrospinal fluid calcitonin gene-related peptide levels, and decreased cortical intercellular adhesion molecule-1 expression, parenchymal microthrombi formation, ischemia-induced hypoxic injury, cellular apoptosis, and neurobehavioral deficits.

CONCLUSION

Our results suggest that TNS can enhance cerebral circulation at multiple levels, lessen the impact of cerebral ischemia, and ameliorate the consequences of DCI after SAH.

Neodymium-Doped Yttrium Aluminum Garnet Laser Photobiomodulation May Improve Neurosensory Function after Surgical Injury to Cranial Nerve V: A Report of Three Consecutive Cases

OBJECTIVE

The purpose of this report was to document clinical responses to Nd:YAG laser energy in patients with surgical injury to terminal branches of the trigeminal nerve.

BACKGROUND

Limited evidence from in vitro, animal, and human studies suggests infrared laser energy may positively influence recovery after peripheral or cranial nerve injury, although clinical effects of neodymiumdoped yttrium aluminum garnet (Nd:YAG) lasers remain unstudied in this context.

METHODS

We applied Nd:YAG laser energy in the treatment of three consecutive patients presenting with altered neurosensory function following various oral and maxillofacial procedures. The time interval between surgical injury and laser photobiomodulation ranged from one week to two years.

RESULTS

All patients exhibited reduction in the area of diminished sensation and partial recovery of normal neurosensory function. The two patients with long-standing neurosensory deficiency experienced near complete recovery of intraoral sensation, with residual zones of diminished sensation from the perioral skin.

CONCLUSIONS

Although all patients in this case series demonstrated clinical improvements compared with baseline, controlled studies are needed to determine whether Nd:YAG laser energy accelerates or enhances recovery of neurosensory function after surgical nerve injury. Studies establishing the relative efficacies of Nd:YAG and diode lasers appear warranted.

Malignant lymphomatous invasion of Meckel's cave: pathoanatomical considerations of the petrous apex

Secondary central nervous system lymphoma is rare, occurring in up to 10% of non-Hodgkin's lymphoma patients and in 5% of diffuse large B-cell lymphoma patients. The prognosis is poor, even rarer is metastasis of large B-cell lymphomas into Meckel's cave and the trigeminal nerve roots. We describe a relapsing case of a large B-cell lymphoma that migrated into Meckel's cave, the mandibular branch of the trigeminal nerve and the adjacent cavernous sinus. We review petrous apex anatomy, review the literature of metastatic spread into Meckel's cave and analyse existing pathoanatomical studies that explain the conduits and barriers of tumour spread. Understanding this pathoanatomical relationship is critical for neurologists and neurosurgeons alike to effectively correlate patient signs and symptoms to intracranial pathology and identify origins and sites of metastatic dispersion in similar rare clinical scenarios.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Radiofrequency thermocoagulation of trigeminal nerve assisted by nerve bundle extraction and image fusion based on hamilton-jacobi equation

BACKGROUND AND OBJECTIVE

Radiofrequency thermocoagulation is an effective method for treating classic trigeminal neuralgia. However, the accurate positioning of thermocoagulation is difficult. The purpose of this study was to design an optimal strategy for performing adjuvant surgery.

METHODS

A total of 60 patients with trigeminal neuralgia were divided into two groups. One group received conventional computed tomography (CT) guided treatment (CT group). In the other group, neural fiber bundles were firstly extracted based on the Hamilton-Jacobi equation. Then, the MRI, CT, and fiber bundle images were fused to visualize the relationship among semilunar ganglion, trigeminal nerve, and puncture needle (fusion group).

RESULTS

Trigeminal fiber bundles were extracted quickly by the contour tracking method, and different types of image fusion were realized for radiofrequency surgery navigation. In the fusion group, 13.3% of patients could not reach semilunar ganglion, and 76.9% of the remaining cases reached the ideal damage area. In the CT group, the preoperative design shows that 26.7% of patients may have puncture difficulty, and 54.5% of remaining cases reached the ideal damage area.

CONCLUSION

The technique of neural bundle extraction and image fusion based on the Hamilton-Jacobi equation can be used to plan the personalized puncture path targeting the semilunar ganglion.

Development of Herpes Zoster Ophthalmicus in an Immunocompetent Pediatric Patient Following Facial Trauma

Herpes zoster ophthalmicus (HZO) is a neuro-oculo-dermic infection caused by reactivation of latent varicella zoster virus in the dorsal root ganglia of the ophthalmic division of the trigeminal nerve. Although a rare diagnosis in an otherwise healthy, vaccinated pediatric patient, this entity may occur with increasing frequency among those with preceding trauma, particularly in the month prior to presentation. Herein, we highlight a case of HZO in a vaccinated, immunocompetent adolescent in the setting of recent facial trauma.