Determination of Current Flow Induced by Transcutaneous Electrical Nerve Stimulation for the Treatment of Migraine: Potential for Optimization

Introduction: Transcutaneous electrical nerve stimulation (TENS) for migraine involves the application of pulsatile stimulation through electrodes placed on the forehead to target the underlying trigeminal nerves. It is a simple, safe modality and has secured clinical approval in several markets including the European Union and the United States. Despite nearing almost 7 years of use (postclinical approval), the exact mechanism of action is not fully known. Guided by the need to stimulate the trigeminal nerves bilaterally, electrode dimensions are simply required to extend enough to cover the underlying nerves. The goal of this study is to examine induced current flow [magnitude and spatial distribution of electric field (EF)] and another driver of stimulation [activating function (AF)] due to TENS therapy for migraine for the first time. We further consider the effect of changing the electrode dimension and shape and propose a design modification to deliver optimal flow.Methods: We developed the first ultra-high-resolution finite element (FE) model of TENS for migraine incorporating the target supratrochlear (ST) and the supraorbital (SO) nerves. We first simulated the clinically approved V-shaped geometry. We then considered three additional designs: extended V-shaped, idealized pill-shaped, and finally an extended V-shaped but with greater contact spacing (extended V-shaped +CS).Results: Our findings revealed that the clinically approved electrode design delivered substantially higher mean current flow to the ST nerve in comparison with the SO nerves (Medial: 53% and Lateral: 194%). Consideration of an extended design (~10 mm longer and ~ 4 mm shorter) and a pill-like design had negligible impact on the induced current flow pattern. The extended V-shaped +CS montage delivered relatively comparable current flow to each of the three target nerves. The EF induced in the ST nerve was 49 and 141% higher in the Medial and Lateral SO nerve, respectively. When considering maximum induced values, the delivery of comparable stimulation was further apparent. Given the existing electrode design's established efficacy, our results imply that preferential targeting of the ST nerve is related to the mechanism of action. Additionally, if comparable targeting of all three nerves continues to hold promise, the extended V-shaped +CS montage presents an optimized configuration to explore in clinical studies.

Mechanisms of Peripheral and Central Pain Sensitization: Focus on Ocular Pain

Persistent ocular pain caused by corneal inflammation and/or nerve injury is accompanied by significant alterations along the pain axis. Both primary sensory neurons in the trigeminal nerves and secondary neurons in the spinal trigeminal nucleus are subjected to profound morphological and functional changes, leading to peripheral and central pain sensitization. Several studies using animal models of inflammatory and neuropathic ocular pain have provided insight about the mechanisms involved in these maladaptive changes. Recently, the advent of new techniques such as optogenetics or genetic neuronal labelling has allowed the investigation of identified circuits involved in nociception, both at the spinal and trigeminal level. In this review, we will describe some of the mechanisms that contribute to the perception of ocular pain at the periphery and at the spinal trigeminal nucleus. Recent advances in the discovery of molecular and cellular mechanisms contributing to peripheral and central pain sensitization of the trigeminal pathways will be also presented.

Investigation of the Transport Pathways Associated with Enhanced Brain Delivery of Peptide Drugs by Intranasal Coadministration with Penetratin

We previously found that coadministering peptides and proteins with the cell-penetrating peptide L-penetratin intranasally significantly increased transport to the brain and enhanced pharmacological effects. The present study aimed to clarify the mechanisms of nose-to-brain drug delivery enhancement by L-penetratin coadministration. First, we compared the concentrations of Exendin-4 in plasma and brain after intranasal and subcutaneous administration and suggested that coadministration with L-penetratin facilitated the direct nose-to-brain transport of Exendin-4. Second, we demonstrated that L-penetratin did not stimulate the transport of Cy7-labeled Exendin-4 and insulin through the trigeminal nerves but shifted their distribution to the olfactory mucosal pathway. Third, we investigated the distribution of insulin into the deeper regions of the brain after delivery via the olfactory pathway and suggested that insulin had entered the olfactory bulb, bottom part of the brain, and perivascular space through the cerebrospinal fluid and had diffused throughout the brain. We further demonstrated that intranasally delivered insulin with L-penetratin specifically accumulated on the hippocampus neuronal cells. Thus, this study suggested that administrating peptide drugs intranasally with L-penetratin allows direct transport to the olfactory bulb, bottom part of the brain, and perivascular space of the cerebral artery. This technique also potentially allows targeting of specific brain areas.

Malignancies in Immunoglobulin G4-Related Ophthalmic Disease

Purpose: Clinical phenotypes in Immunoglobulin G4-related disease (IgG4-RD) according to the affected organs affected have different risks of malignancies. We attempt to determine the association of malignances with IgG4-related ophthalmic disease (IgG4-ROD). Design: Retrospective cohort study. Methods: Review of medical records, orbital images and histopathology reports in a territory-wide cohort of patients fulfilling the “probable” or “definite” comprehensive diagnostic criteria of IgG4-RD from 2005-2019. Findings: Among 122 patients who had biopsies taken from adnexal lesions including lacrimal glands (n=108), orbital mass (n=30), infiltrated orbital fat (n=10), conjunctiva (n=2) or extraocular muscles (n=3), 16 (13%) developed malignancies over 73±48months’ follow-up. There were 9 cases of ocular adnexal lymphoma (OAL) and 7 extra-orbital malignancies. Compared with the general population, the incidence of OAL was significantly higher (standardized incidence ratios, SIRs=10.0, 95%CI=4.5-17.6) while that of extraorbital malignancy was similar. The SIR was highest within the first year (SIR=46.7, 95%CI=18.5-87.6) when 7 OAL were concomitantly diagnosed. Patients who developed OAL or extra-orbital malignancies were older than other patients when diagnosed of IgG4-ROD (64.9±7.1, 68.3±8.5 versus 55.2±15.0 years, p<0.05). Asymmetric lacrimal gland enlargement (78% versus 13%), lack of frontal (0% versus 12%) or infraorbital nerve enlargement (0% versus 36%)were associated with OAL (all p<0.05). Pre-treatment serum IgG4 level or pattern of extraorbital involvement was similar among patients with or without malignancies. Conclusion: In this biopsy-proven IgG4-ROD cohort, 7% developed OAL which was 10 times higher than the general population. Patients with asymmetric lacrimal gland enlargement or without trigeminal nerves involvement radiologically were associated with OAL.

Intranasal Drug Delivery: Novel Delivery Route for Management of Parkinson’s and Depression Neurological Disorders

Neurological disorders are increasing worldwide due to the rapidly aging population, which increases healthcare costs. Drug delivery to the brain is challenging because of the brain's anatomy, and orally administered drugsare mostly unable to cross BBB. Intranasal (Nose to Brain) administration of drugs is one novel approach to address this challenge. Intranasal delivery has appeared to evade the blood-brain barrier (BBB) and deliver the drug into the CNS at a higher rate and degree than another traditional route. Transport of drugs from the nasal cavity to the brain along with olfactory and trigeminal nerves. The purpose of this review is drug delivery by the intranasal route for treating neurological disorders like Parkinson’s and depression because drug delivery by other routes is unable to cross BBB. Still, delivery through the intranasal route by using the nanotechnology approach is possible to deliver the drug directly to CNS.

Loss of Elp1 disrupts trigeminal ganglion neurodevelopment in a model of Familial Dysautonomia

Familial Dysautonomia (FD) is a sensory and autonomic neuropathy caused by a mutation in Elongator complex protein 1 (ELP1). FD patients have small trigeminal nerves and impaired perception of facial pain and temperature. These signals are relayed by nociceptive neurons in the trigeminal ganglion, a structure comprised of both neural crest- and placode-derived cells. Mice lacking Elp1 in neural crest derivatives (Elp1 CKO) are born with smaller trigeminal ganglia, suggesting Elp1 is important for trigeminal ganglion development, yet the function of Elp1 in this context is unknown. We demonstrate Elp1 expression in both neural crest- and placode-derived trigeminal neurons, which our data suggest give rise to primarily TrkA- and TrkB/C-expressing neurons, respectively. While Elp1 is not required for initial trigeminal ganglion formation, Elp1 CKO trigeminal neurons exhibit abnormal axon outgrowth and decreased target innervation. Developing nociceptors that express the receptor TrkA are especially vulnerable to Elp1 loss. TrkA expression is decreased in Elp1 CKO trigeminal nerve endings, coinciding with increased cell death. Subsequently, fewer TrkA neurons are present in the Elp1 CKO trigeminal ganglion, indicating Elp1 supports the target innervation and survival of trigeminal nociceptors. These findings explain the loss of facial pain and temperature sensation in FD.

Preparation and in vitro evaluation of thermosensitive and mucoadhesive hydrogels for intranasal delivery of phenobarbital sodium

Background: Recently, intranasal administration has been suggested as a potential direct route to transport pharmaceuticals into the brain through the olfactory and trigeminal nerves, bypassing the blood–brain barrier. Materials & methods: The nasal hydrogels were prepared by a cold method using pluronic F-12 and chitosan. Results: All the selected formulations were gelled at 30°C. The gelation time varied from 5 to 10 min. The mucoadhesive strength was adequate to provide prolonged mucosal adhesion. The formulations exhibited good drug content after stability period of 3 months. The permeability studies revealed a high permeation of the drug through the surgically removed nasal tissue. Conclusion: The results suggest that the obtained hydrogels might be suitable candidates for the nasal delivery of phenobarbital sodium.

Idiopathic hypertrophic cranial polyneuropathy: a rare cause of orbital pain

Hypertrophic cranial polyneuropathy (HCP) is sporadically encountered in clinical practice. Aetiologies of HCP have been classified as autoimmune, infectious and demyelinating. However, an accurate diagnosis remains elusive in some cases despite rigorous investigations. These cases represent idiopathic HCP. Given the high clinical variance in presenting symptoms, HCP often leaves medical practitioners in a diagnostic quandary. Here, we seek to expand current knowledge by reporting the first documented case of idiopathic HCP presenting atypically with unilateral orbital pain and exclusively involving the bilateral trigeminal nerves.

Chlamydia muridarum Can Invade the Central Nervous System via the Olfactory and Trigeminal Nerves and Infect Peripheral Nerve Glial Cells

Chlamydia pneumoniae can infect the brain and has been linked to late-onset dementia. Chlamydia muridarum, which infects mice, is often used to model human chlamydial infections. While it has been suggested to be also important for modelling brain infection, nervous system infection by C. muridarum has not been reported in the literature. C. pneumoniae has been shown to infect the olfactory bulb in mice after intranasal inoculation, and has therefore been suggested to invade the brain via the olfactory nerve; however, nerve infection has not been shown to date. Another path by which certain bacteria can reach the brain is via the trigeminal nerve, but it remains unknown whether Chlamydia species can infect this nerve. Other bacteria that can invade the brain via the olfactory and/or trigeminal nerve can do so rapidly, however, whether Chlamydia spp. can reach the brain earlier than one-week post inoculation remains unknown. In the current study, we showed that C. muridarum can within 48 h invade the brain via the olfactory nerve, in addition to infecting the trigeminal nerve. We also cultured the glial cells of the olfactory and trigeminal nerves and showed that C. muridarum readily infected the cells, constituting a possible cellular mechanism explaining how the bacteria can invade the nerves without being eliminated by glial immune functions. Further, we demonstrated that olfactory and trigeminal glia differed in their responses to C. muridarum, with olfactory glia showing less infection and stronger immune response than trigeminal glia.

Acute inflammatory polyradiculoneuropathy of atypical presentation.

Introduction: Guillain-Barré syndrome is an acute / subacute inflammatory polyradiculoneuropathy that classically results in flaccid areflex palsy. However, there are other possibilities of clinical presentation that must be remembered so that an adequate diagnosis and treatment is carried out. Case report: Female patient, 23 years old, without comorbidities, with complaint of paresthesia in extremities and right peripheral facial paralysis, having diagnosis until then of Bell’s Palsy. She denied previous or current infectious complaints. The neurological examination revealed facial diparesis, proximal weakness of the lower limbs that made walking difficult, tactile and painful hypoesthesia in the feet, with reflexes 1+/4+ in the lower limbs and 3+/4+ in the upper limbs. An investigation was started with CSF collection that showed albuminocytological dissociation (proteins 440 mg/dl and leukocytes 01 mm3). Neuroimaging exams showed contrast impregnation in facial and trigeminal nerves. A diagnosis of acute inflammatory polyradiculoneuropathy was made and treatment with human immunoglobulin was initiated for 5 days. Electroneuromyography showed peripheral, sensory-motor polyradiculoneuropathy and questioned the physiopathological possibility of juxtaparanodopathy. The patient presented a significant and early improvement after treatment. Conclusions: It is essential to consider that Guillain-Barré syndrome has symptom variability, especially according to its pathophysiology and clinical and electrophysiological variant, thus avoiding that conditions such as this one are underdiagnosed.