One mechanism by which transcranial direct current stimulation (tDCS) has been proposed to improve attention is by transcutaneous stimulation of cranial nerves, thereby activating the locus coeruleus (LC). Specifically, placement of the electrodes over the frontal bone and mastoid is thought to facilitate current flow across the face as a path of least resistance. The face is innervated by the trigeminal nerve, and the trigeminal nerve is interconnected with the LC. In this study, we tested whether stimulating the trigeminal nerve impacts indices of LC activity and performance on a sustained attention task. We replicated previous research that shows deterioration in task performance, increases in the rate of task-unrelated thoughts, and reduced pupil responses due to time on task irrespective of tDCS condition (sham, anodal, and cathodal stimulation). Importantly, tDCS did not influence pupil dynamics (pretrial or stimulus-evoked), self-reported attention state, nor task performance in active versus sham stimulation conditions. The findings reported here are consistent with theories about arousal centered on a hypothesized link between LC activity indexed by pupil size, task performance, and self-reported attention state but fail to support hypotheses that tDCS over the trigeminal nerve influences indices of LC function.

BACKGROUND: The olfactory and trigeminal system are closely interlinked. Existing literature has primarily focused on characterizing trigeminal stimulation through mechanical and chemical stimulation, neglecting thermal stimulation thus far. The present study aimed to characterize the intranasal sensitivity to heat and the expression of trigeminal receptors (transient receptor potential channels, TRP).
METHODS: A total of 20 healthy participants (aged 21-27 years, 11 women) were screened for olfactory function and trigeminal sensitivity using several tests. Under endoscopic control, a thermal stimulator was placed in 7 intranasal locations: anterior septum, lateral vestibulum, interior nose tip, lower turbinate, middle septum, middle turbinate, and olfactory cleft to determine the thermal threshold. Nasal swabs were obtained in 3 different locations (anterior septum, middle turbinate, olfactory cleft) to analyze the expression of trigeminal receptors TRP: TRPV1, TRPV3, TRPA1, TRPM8.
RESULTS: The thermal threshold differed between locations (p = 0.018), with a trend for a higher threshold at the anterior septum (p = 0.092). There were no differences in quantitative receptor expression (p = 0.46) at the different sites. The highest overall receptor RNA expression was detected for TRPV1 over all sites (p<0.001). The expression of TRPV3 was highest at the anterior septum compared to the middle turbinate or the olfactory cleft. The thermal sensitivity correlated with olfactory sensitivity and results from tests were related to trigeminal function like intensity ratings of ammonium, a questionnaire regarding trigeminal function, nasal patency, and CO2 thresholds. However, no correlation was found between receptor expression and psychophysical measures of trigeminal function.
CONCLUSIONS: This study provided the first insights about intranasal thermal sensitivity and suggested the presence of topographical differences in thermal thresholds. There was no correlation between thermal sensitivity and trigeminal mRNA receptor expression. However, thermal sensitivity was found to be associated with psychophysical measures of trigeminal and olfactory function.

Port-wine stains (PWSs), also called port-wine birthmarks or nevus flammeus, are hamartomatous vascular capillary malformations that clinically appear as erythematous areas on the buccal mucosa, vermilion border of the lip, gingiva, or pink to port-wine-colored patches on skin since birth and persist throughout life. On the face, they occur in the area supplied by the trigeminal nerve. PWSs have structural abnormalities of the intradermal capillaries. PWSs on the skin and oral mucosa contain ectatic capillaries in the dermis and submucosa, respectively. PWSs occur anywhere, and the oral mucosa is no exception. PWSs on the facial skin lead to cosmetic disfigurement and create social stigma. Clinically, PWSs start as flat, pink, or red patches and may darken, thicken, and develop nodules over time. The diagnosis of PWSs is primarily clinical. PWSs are complex vascular malformations with significant clinical, psychosocial, and therapeutic challenges. This article enlightens a series of cases of PWSs on the facial skin and capillary hemangioma on the gingiva, buccal mucosa, and lip diagnosed by a diascopy test, etiopathogenesis, differential diagnosis, and management of PWSs.

BACKGROUND: Von Hippel-Lindau disease (VHL) is an autosomal dominant tumor predisposition syndrome caused by mutations in the VHL gene. Patients with VHL are predisposed to developing numerous neoplasms, including central nervous system hemangioblastomas that typically arise within the cerebellum, brainstem, or spinal cord. The authors present the unusual case of a 69-year-old patient with a hemangioblastoma of the trigeminal nerve as his initial presentation of VHL.
METHODS: A 69-year-old male presented with progressive right-sided V3 paresthesias, gait disturbance, and diplopia. Magnetic resonance imaging demonstrated an enhancing 0.5-cm nodule within the right trigeminal nerve and an associated peritumoral cyst exerting mass effect on the cerebral peduncle. Neural axis imaging demonstrated pia-based enhancing lesions concerning for multiple spinal hemangioblastomas. The patient underwent an uncomplicated retrosigmoid craniotomy for trigeminal nerve hemangioblastoma resection. The patient had postoperative improvement in his gait, diplopia, and facial paresthesias. Genetic testing revealed that the patient was heterozygous for a pathological mutation in the VHL gene.
CONCLUSIONS: Hemangioblastomas in adults over 50 years of age should prompt a workup for VHL. Recognizing that cranial nerves are a possible site of hemangioblastoma occurrence is important for neurosurgeons and radiologists alike. Resection of cranial nerve hemangioblastomas is technically challenging but can lead to symptom improvement for patients. https://thejns.org/doi/10.3171/CASE24149.

BACKGROUND: We present a case of a 29-year-old male patient without immunodeficiency who suffered from rapid osteonecrosis and tooth exfoliation resulting from herpes zoster (HZ) infection in the left maxillary branch of the trigeminal nerve. Various complications associated with shingles infections have been reported, cases of osteonecrosis and tooth exfoliation due to HZ infection among young people without immunodeficiency are rare. In this case, we focus on the particular manifestation of HZ infection.
METHODS: The patient presented with clusters of erythema and papules, along with non-hemorrhagic blisters on the left face and the loss of the left upper incisor. All lesions were localized to the left side of the face without exceeding the midline. After receiving antibacterial and antiviral treatment, successful control over the infection was achieved; however, he experienced the loss of all upper teeth on the left side except for the first and second upper left molars.
CONCLUSIONS: This case highlights that rapid osteonecrosis and tooth exfoliation may occur among young individuals without immunodeficiency after HZ infection. HZ infection of the face should be taken very seriously to obtain prompt treatment to prevent the rare complications of bone necrosis and tooth loss as much as possible.

UNASSIGNED: In this study, we investigated the blink reflex (BR) after simultaneous and asynchronous stimulation of two trigeminal nerve branches. The objective was to characterize the physiology of trigeminal and facial circuits.
UNASSIGNED: We performed three sets of experiments: recording BR response i. after supraorbital nerve stimulation (SON), after mental nerve stimulation (MN), and after simultaneous SON and MN stimulation (SON+MN) in 18 healthy individuals; ii. after MN (at an intensity eliciting BR response) preceding SON at various interstimulus intervals (ISIs) in seven healthy subjects; iii after MN (at sensory threshold) preceding SON at various ISIs. We compared the magnitudes of early and late responses.
UNASSIGNED: The R1 amplitude after simultaneous SON+MN stimulation was greater than responses after single stimulation of the same branches. After simultaneous stimulations, the R2 and R2c areas under the curve (AUC) were smaller than the arithmetic sums of R2 and R2c AUC obtained after single stimulations. The second experiment provided a recovery excitability curve. In the third step, we obtained facilitation of R1 and inhibition of late responses.
UNASSIGNED: The SON+MN stimulation caused an increased R1 circuit excitability compared to the arithmetic sum of the single stimulations; however, magnitudes of late responses did not potentiate. Thus, we have provided evidence for R1 circuit enhancement by simultaneous stimulation in humans, whereas modulation of late responses exhibited a recovery curve similar to that shown for paired SON stimulation.

Investigating the evolutionary trajectory of synapsid sensory and cephalic systems is pivotal for understanding the emergence and diversification of mammals. Recent studies using CT-scanning to analyze the rostral foramina and maxillary canals morphology in fossilized specimens of probainognathian cynodonts have contributed to clarifying the homology and paleobiological interpretations of these structures. In the present work, μCT-scannings of three specimens of Riograndia guaibensis, an early Norian cynodont from southern Brazil, were analyzed and revealed an incomplete separation between the lacrimal and maxillary canals, with points of contact via non-ossified areas. While the maxillary canal exhibits a consistent morphological pattern with other Prozostrodontia, featuring three main branches along the lateral region of the snout, the rostral alveolar canal in Riograndia displays variability in the number of extra branches terminating in foramina on the lateral surface of the maxilla, showing differences among individuals and within the same skull. Additionally, pneumatization is observed in the anterior region of the skull, resembling similar structures found in reptiles and mammals. Through this pneumatization, certain branches originating from the maxillary canal extend to the canine alveolus. Further investigation is warranted to elucidate the functionality of this structure and its occurrence in other cynodont groups.

OBJECTIVE: The trigeminocardiac reflex (TCR) has traditionally been characterized by a sudden decrease in heart rate, asystole, or hypotension during the manipulation of the trigeminal nerve (MTN) or its branches. While this classical TCR is well-documented, there is limited literature on alternative forms of TCR, such as the development of intraoperative hypertension (HTN) or tachycardia, and the underlying pathogenesis. Furthermore, a gap exists in understanding the correlation between intraoperative blood pressure readings and postoperative outcomes, particularly regarding pain relief in patients with trigeminal neuralgia (TN). Our study aims to examine intraoperative blood pressure trends during microvascular decompression (MVD) for TN and assess their impact on postoperative outcomes.
METHODS: We selected 90 patients who underwent MVD for TN treatment. Blood pressure and heart rate were recorded both preoperatively and during the procedure, specifically during the MTN period, using an arterial line. The Barrow Neurological Institute (BNI) Pain Scale was calculated for all patients both pre- and post-operatively to evaluate pain relief after surgery.
RESULTS: The mean age of the patients was 61.0 ± 12.35 years, with 64.4% being females. Classical TCR (hypotension) was observed in only 2.2% of patients, whereas 80% of patients developed hypertension (≥ 140/90) during MTN. The mean preoperative systolic blood pressure was 128 ± 22.25, and the mean intraoperative systolic blood pressure during MTN was 153.1 ± 20.2. An analysis of covariance, utilizing either preoperative BNI or duration of symptoms as covariate variables, revealed a statistically significant association between intraoperative HTN and postoperative BNI. A linear regression model demonstrated that intraoperative HTN following MTN significantly predicted a lower postoperative BNI score (p = 0.006).
CONCLUSIONS: Intraoperative HTN during MTN, an observed yet underexplored phenomenon, demonstrated a correlation with improved postoperative outcomes. Furthermore, it is recommended to conduct additional investigations into potential neurovascular conflicts in patients not manifesting intraoperative HTN following MTN. A comprehensive understanding of TCR, encompassing its various forms, is vital for optimizing surgical management. This study underscores the imperative for further research to unravel the mechanisms linking intraoperative HTN to surgical outcomes in TN patients.

OBJECTIVE: Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are two major demyelinating diseases affecting the central nervous system (CNS). The objective of this study is to evaluate the prevalence of pontine trigeminal nerve lesions in patients diagnosed with MS and NMOSD using MRI.
METHODS: This retrospective study included patients diagnosed with MS or NMOSD between July 2018 and July 2023. MS patients were clinically diagnosed using the 2017 McDonald criteria, while NMOSD patients were those who met the 2015 International Panel for NMO Diagnosis (IPND) criteria and were positive for Aquaporin-4 Antibody (AQP4-Ab).
RESULTS: The study included a total of 90 patients, with 45 diagnosed with MS and another 45 with NMOSD. Pontine trigeminal nerve lesions were observed in both MS and NMOSD, but were more prevalent in MS patients (20 % vs. 2 %, p = 0.008). Root entry zone (REZ) lesions were found in 4 of 45 MS patients, accounting for 9 % (95 % CI: 3 %-17 %), and were absent in the NMOSD group; however, there was no significant difference between the two groups (p = 0.12). Of the MS patients with pontine trigeminal nerve lesions, 6 out of 9 (63 %; 95 % CI, 36 %-98 %) exhibited bilateral lesions, which was significantly more prevalent compared to the NMOSD group (13 % vs. 0 %, p = 0.03).
CONCLUSIONS: The presence of pontine trigeminal nerve lesions, particularly when bilateral, are significantly more prevalent in MS patients than in those with NMOSD, suggesting their utility as a distinctive marker and potential diagnostic indicator specifically for MS.

The varicella-zoster virus reactivates to cause the \"herpes zoster\" (HZ). \'\'Varicella-zoster virus\'\' (VZV) termed as \'\'HHV-3\'\' or \'\'human herpesvirus-3\'\' infection causes herpes zoster. Varicella, the primary form of the virus, is chickenpox, and the secondary form of the virus is herpes zoster also called shingles. During prior chicken pox episodes, this virus enters the body through cutaneous nerve endings and becomes dormant in the dorsal root ganglia. It sometimes affects the orofacial region and appears as unilaterally distributed burning pain, multiple, painful vesicular lesions, and ulcerations. Immunocompromised people are more likely to have disseminated zoster, which is defined as the involvement of three or more dermatomes. These are most likely to occur in elderly, immunocompromised patients, patients undergoing cancer chemotherapy, patients on immunosuppressants, and patients suffering from AIDS. This is a study of a male geriatric patient, aged 74 years, who reported unilateral pain, swelling, as well as multiple ulcerations on the left side of his face, extraorally as well as intraorally. The case was diagnosed as a herpes zoster infection involving V1 and V2 dermatome of the trigeminal nerve.