Extracranial projections of meningeal afferents and their impact on meningeal nociception and headache

Comparative Gene Signature of Nociceptors Innervating Mouse Molar Teeth, Cranial Meninges, and Cornea

BACKGROUND

The trigeminal ganglion (TG) collects afferent sensory information from various tissues. Recent large-scale RNA sequencing of neurons of the TG and dorsal root ganglion has revealed a variety of functionally distinct neuronal subpopulations, but organ-specific information is lacking.

METHODS

To link transcriptomic and tissue-specific information, we labeled small-diameter neurons of 3 specific subpopulations of the TG by local application of lipophilic carbocyanine dyes to their innervation site in the dental pulp, cornea, and meninges (dura mater). We then collected mRNA-sequencing data from fluorescent neurons. Differentially expressed genes (DEGs) were analyzed and subjected to downstream gene set enrichment analysis (GSEA), and ion channel profiling was performed.

RESULTS

A total of 10,903 genes were mapped to the mouse genome (>500 reads). DEG analysis revealed 18 and 81 genes with differential expression (log 2 fold change > 2, Padj < .05) in primary afferent neurons innervating the dental pulp (dental primary afferent neurons [DPAN]) compared to those innervating the meninges (meningeal primary afferent neurons [MPAN]) and the cornea (corneal primary afferent neurons [CPAN]). We found 250 and 292 genes differentially expressed in MPAN as compared to DPAN and to CPAN, and 21 and 12 in CPAN as compared to DPAN and MPAN. Scn2b had the highest log 2 fold change when comparing DPAN versus MPAN and Mmp12 was the most prominent DEG when comparing DPAN versus CPAN and, CPAN versus MPAN. GSEA revealed genes of the immune and mitochondrial oxidative phosphorylation system for the DPAN versus MPAN comparison, cilium- and ribosome-related genes for the CPAN versus DPAN comparison, and respirasome, immune cell- and ribosome-related gene sets for the CPAN versus MPAN comparison. DEG analysis for ion channels revealed no significant differences between the neurons set except for the sodium voltage-gated channel beta subunit 2, Scn2b . However, in each tissue a few ion channels turned up with robust number of reads. In DPAN, these were Cacna1b , Trpv2 , Cnga4 , Hcn1 , and Hcn3 , in CPAN Trpa1 , Trpv1 , Cacna1a , and Kcnk13 and in MPAN Trpv2 and Scn11a .

CONCLUSIONS

Our study uncovers previously unknown differences in gene expression between sensory neuron subpopulations from the dental pulp, cornea, and dura mater and provides the basis for functional studies, including the investigation of ion channel function and their suitability as targets for tissue-specific analgesia.

Onabotulinumtoxina (craniotomy scar combined with cranial suture line injections) for persistent post craniotomy headache: Case series with long-term follow-up

BACKGROUND

There is no defined preventive treatment protocol for persistent post-craniotomy headache. In several small case series and individual case reports onabotulinumtoxinA injected into the craniotomy scar has shown possible efficacy. What is lacking is long term follow-up and if focusing on the cranial suture lines along with the craniotomy scar can enhance improvement and provide more sustained benefit.

METHODS

Retrospective chart review with case series.

RESULTS

Four patients (three women, one man) with ICHD-3 defined persistent post craniotomy headache were treated using a novel onabotulinumtoxinA injection protocol. All the patients presented with continuous head pain of moderate to severe intensity. All had severe allodynia on the side of their craniotomy. All had significant reduction in quality of life. Our application of onabotulinumtoxinA involved injection into both the surgical scar and the transected/irritated cranial suture lines noted on neuroimaging and physical examination. With treatment all patients demonstrated significant benefit including a reduction in daily pain intensity (75%-100%), developing periods of pain freedom (2-7 days per week) and having a dramatic improvement in quality of life (close to 100% in all). The benefit was sustained for at least five years of follow-up.

CONCLUSION

From our case series it appears that injection not only along the painful craniotomy scar but into the involved cranial suture lines provides positive efficacy and sustained improvement in patients with persistent post craniotomy headache.

Implications of high homocysteine levels in migraine pain: An experimental study of the excitability of peripheral meningeal afferents in rats with hyperhomocysteinemia

OBJECTIVES

Investigation of chronic homocysteine action on the excitability and N-methyl-D-aspartate (NMDA) sensitivity of the peripheral trigeminovascular system of rats.

BACKGROUND

Migraine is a neurological disease that affects 15%-20% of the general population. Epidemiological observations show that an increase of the sulfur-containing amino acid homocysteine in plasma-called hyperhomocysteinemia-is associated with a high risk of migraine, especially migraine with aura. In animal studies, rats with hyperhomocysteinemia demonstrated mechanical allodynia, photophobia, and anxiety, and higher sensitivity to cortical spreading depression. In addition, rats with hyperhomocysteinemia were more sensitive in a model of chronic migraine induced by nitroglycerin which indicated the involvement of peripheral nociceptive mechanisms. The present work aimed to analyze the excitability of meningeal afferents and neurons isolated from the trigeminal ganglion of rats with prenatal hyperhomocysteinemia.

METHODS

Experiments were performed on male rats born from females fed with a methionine-rich diet before and during pregnancy. The activity of meningeal afferents was recorded extracellularly in hemiskull preparations ex vivo and action potentials were characterized using cluster analysis. The excitability of trigeminal ganglion neurons was assessed using whole-cell patch clamp recording techniques and calcium imaging studies. Meningeal mast cells were stained using toluidine blue.

RESULTS

The baseline extracellular recorded electrical activity of the trigeminal nerve was higher in the hyperhomocysteinemia group with larger amplitude action potentials. Lower concentrations of KCl caused an increase in the frequency of action potentials of trigeminal afferents recorded in rat hemiskull ex vivo preparations. In trigeminal ganglion neurons of rats with hyperhomocysteinemia, the current required to elicit at least one action potential (rheobase) was lower, and more action potentials were induced in response to stimulus of 2 × rheobase. In controls, short-term application of homocysteine and its derivatives increased the frequency of action potentials of the trigeminal nerve and induced Ca2+ transients in neurons, which are associated with the activation of NMDA receptors. At the same time, in rats with hyperhomocysteinemia, we did not observe an increased response of the trigeminal nerve to NMDA. Similarly, the parameters of Ca2+ transients induced by NMDA, homocysteine, and its derivatives were not changed in rats with hyperhomocysteinemia. Acute incubation of the meninges in homocysteine and homocysteinic acid did not change the state of the mast cells, whereas in the model of hyperhomocysteinemia, an increased degranulation of mast cells in the meninges was observed.

CONCLUSIONS

Our results demonstrated higher excitability of the trigeminal system of rats with hyperhomocysteinemia. Together with our previous finding about the lower threshold of generation of cortical spreading depression in rats with hyperhomocysteinemia, the present data provide evidence of homocysteine as a factor that increases the sensitivity of the peripheral migraine mechanisms, and the control of homocysteine level may be an important strategy for reducing the risk and/or severity of migraine headache attacks.

The chronicle of headache treatment throughout human history from trepanation to perisutural botulinum toxin injections

To provide a historic snapshot as regards the evolution of headache treatment throughout the human history, i.e. starting from trepanation to perisutural botulinum toxin (BoNT) injections. Ancient surgeons had aimed to reach the cranium with trepanation (a surgical operation) for headache. As BoNT inhibits the release of nociceptive and pro-inflammatory neuropeptides, it has been recently suggested as an effective alternative in the prophylactic treatment of chronic migraine headache. Chronic migraine is a complex neurological disorder for which the underlying pathophysiology is yet not totally explained. According to the generally accepted hypotheses, peripheral neurogenic activation and central trigeminal sensitization are the two main mechanisms through which its pain develops. Since the headache most commonly occurs around the perisutural areas, and as the primary pathogenesis stem from the meningeal nerve fibers; collateral sensorial branches of the meningeal nerves can be optimal paths to transport BoNT inside the cranium. Concerning the therapeutic efficacy, we anticipate that perisutural injections would be technically challenging with blind techniques and actually possible only if performed under an imaging guidance, e.g. very conveniently with high frequency ultrasound.

Sonographic guide for botulinum toxin injections for chronic migraine headache: EURO-MUSCULUS/USPRM approach

Application of botulinum toxin A (BoNT-A) into the muscles of the head and neck area has become a widespread and reliable treatment modality for chronic migraine. The mechanism of action for BoNT-A is the inhibition of acetylcholine and local nociceptive peptide release at the terminal nerve endings. Cranial sutures have the highest concentration of nociceptive structures; therefore BoNT-A injection into the suture lines - as opposed to head and neck muscles - has been proposed for the treatment of chronic migraine. Nerve endings in sutures rapidly absorb BoNT-A and transfer it across the afferent nerve fibers in dura mater via orthodromic and antidromic transmission. In this article, ultrasound-guided BoNT-A application around the cranial sutures will be illustrated. It is noteworthy that suture injections would be safer and more efficient when applied with such guidance.

Botox (onabotulinumtoxinA) mechanism of action

Studies in the 1920s found that botulinum neurotoxin type A (BoNT/A) inhibited the activity of motor and parasympathetic nerve endings, confirmed several decades later to be due to decreased acetylcholine release. The 1970s were marked by studies of cellular mechanisms aided by use of neutralizing antibodies as pharmacologic tools: BoNT/A disappeared from accessibility to neutralizing antibodies within minutes, although it took several hours for onset of muscle weakness. The multi-step mechanism was experimentally confirmed and is now recognized to consist broadly of binding to nerve terminals, internalization, and lysis or cleavage of a protein (SNAP-25: synaptosomal associated protein-25 kDa) that is part of the SNARE (Soluble NSF Attachment protein REceptor) complex needed for synaptic vesicle docking and fusion. Clinical use of the BoNT/A product onabotulinumtoxinA was based on its ability to reduce muscle contractions via inhibition of acetylcholine from motor terminals. Sensory mechanisms of onabotulinumtoxinA have now been identified, supporting its successful treatment of chronic migraine and urgency in overactive bladder. Exploration into migraine mechanisms led to anatomical studies documenting pain fibers that send axons through sutures of the skull to outside the head-a potential route by which extracranial injections could affect intracranial processes. Several clinical studies have also identified benefits of onabotulinumtoxinA in major depression, which have been attributed to central responses induced by feedback from facial muscle and skin movement. Overall, the history of BoNT/A is distinguished by basic science studies that stimulated clinical use and, conversely, clinical observations that spurred basic research into novel mechanisms of action.

Epicranial headaches part 2: Nummular headache and epicrania fugax

BACKGROUND

Nummular headache and epicrania fugax are two primary headaches that fall under the heading of epicranial headaches.

METHODS

This article reviews the epidemiological and clinical features of nummular headache and epicrania fugax, proposed pathogenic mechanisms and state-of-the-art management, according to the literature.

RESULTS AND CONCLUSIONS

Nummular headache and epicrania fugax are generally viewed as rare headache disorders, but no population-based epidemiological data are available. Nummular headache is characterized by continuous or intermittent head pain, which remains circumscribed in a round or oval area of the scalp, typically one to six centimeters in diameter. Epicrania fugax manifests with brief paroxysms of pain that move along the surface of the head, following a linear or zigzag trajectory through different nerve territories. Nummular headache and epicrania fugax are mostly primary headaches, but some secondary cases have been reported. The pathogenesis of these headaches is not fully understood. Nummular headache could probably originate in epicranial tissues or adjacent intracranial structures, while the origin of epicrania fugax could be extracranial or intracranial. Diagnostic assessment requires careful examination of the symptomatic areas. Underlying disorders should be excluded by additional investigations, including neuroimaging and appropriate blood tests. No controlled clinical trials have been conducted in nummular headache or epicrania fugax. Analgesics and anti-inflammatory drugs, botulinum toxin and gabapentin are currently the most recommended treatment options for nummular headache. In epicrania fugax, the most used treatments are gabapentin, lamotrigine, and other antiseizure medications.

Pain sensitivity in relation to frequency of migraine and tension-type headache with or without coexistent neck pain: an exploratory secondary analysis of the population study

OBJECTIVES

We aimed to investigate whether coexistent self-reported neck pain influences cephalic and extracephalic pain sensitivity in individuals with migraine and tension-type headache (TTH) in relation to diagnosis and headache frequency.

METHODS

A population of 496 individuals completed a headache interview based on ICHD criteria, providing data collected by self-administered questionnaires, assessments of pericranial total tenderness score (TTS) and pressure pain thresholds (PPT). Stimulus-response (SR) functions for pressure vs. pain were recorded. Presence of neck pain in the past year was assessed by the self-administered questionnaire. We categorized participants by primary headache type. We also categorized participants into 3 groups by headache frequency: chronic (≥15) or episodic (<15 headache days/month) headache and controls. TTS, PPTs and the area under the SR curve were compared between subgroups using Generalized Linear Models with pairwise comparisons controlling for age and sex.

RESULTS

Individuals with chronic followed by episodic headache had higher TTS than controls (overall p≤0.001). The difference between chronic and episodic headache subgroups was significant in the group with neck pain (p≤0.001) but not in the group without neck pain. In individuals with neck pain, mean TTS was higher in coexistent headache (migraine and TTH), 23.2 ± 10.7, and pure TTH, 17.8 ± 10.3, compared to pure migraine, 15.9 ± 10.9 and no headache 11.0 ± 8.3 (overall p<0.001). Temporal and finger PPTs did not statistically differ among the chronic headache, the episodic headache and controls in individuals with and without neck pain. Temporalis and trapezius SR-functions showed that tenderness was increased in individuals with chronic headache to higher degree than in those with episodic headache, and more so in those with neck pain.

CONCLUSIONS

Coexistent neck pain is associated with greater pericranial tenderness in individuals with chronic headache and to a lesser degree in those with episodic headache. Sensitization may be a substrate or consequence of neck pain and primary headache, but a longitudinal study would be needed for further clarification.

OnabotulinumtoxinA: Still the Present for Chronic Migraine

OnabotulinumtoxinA (BT-A) is one of the few drugs approved for the preventive treatment of chronic migraine (CM). Despite this, some aspects of its mechanism of action are still a matter of debate, and the precise magnitude of BT-A effects needs to be completely elucidated. BT-A acts primarily upon trigeminal and cervical nerve endings, by inhibiting the release of inflammatory mediators such as calcitonin gene-related peptide, as well as reducing the insertion of ionotropic and metabotropic receptors into the neuronal membrane. These actions increase the depolarization threshold of trigeminal and cervical nerve fibers, thus reducing their activation. The central actions of BT-A are still a matter of debate: a retrograde axonal transport has been postulated, but not clearly assessed in humans. Clinically, the efficacy of BT-A in CM has been assessed by large, randomized placebo-controlled trials, such as the Phase 3 REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) trials. Those results were also confirmed in a wide range of open-label studies, even for long-term periods. Recently, novel findings have led to a better understanding of its pharmacological actions and clinical usefulness in migraine prevention. This narrative review summarizes, updates and critically revises the available data on BT-A and its possible implementation in chronic migraine. Moreover, the current role of BT-A in CM treatment has been discussed.

Role of ATP in migraine mechanisms: focus on P2X3 receptors

Migraine is a major health burden worldwide with complex pathophysiology and multifarious underlying mechanisms. One poorly understood issue concerns the early steps in the generation of migraine pain. To elucidate the basic process of migraine pain further, it seems useful to consider key molecular players that may operate synergistically to evoke headache. While the neuropeptide CGRP is an important contributor, we propose that extracellular ATP (that generally plays a powerful nociceptive role) is also a major component of migraine headache, acting in concert with CGRP to stimulate trigeminal nociceptive neurons. The aim of the present focused review is to highlight the role of ATP activating its P2X3 membrane receptors selectively expressed by sensory neurons including their nerve fiber terminals in the meninges. Specifically, we present data on the homeostasis of ATP and related purines in the trigeminovascular system and in the CNS; the basic properties of ATP signalling at peripheral and central nerve terminals; the characteristics of P2X3 and related receptors in trigeminal neurons; the critical speed and persistence of P2X3 receptor activity; their cohabitation at the so-called meningeal neuro-immune synapse; the identity of certain endogenous agents cooperating with ATP to induce neuronal sensitization in the trigeminal sensory system; the role of P2X3 receptors in familial type migraine; the current state of P2X3 receptor antagonists and their pharmacological perspectives in migraine. It is proposed that the unique kinetic properties of P2X3 receptors activated by ATP offer an interesting translational value to stimulate future studies for innovative treatments of migraine pain.

Literature Review: Pericranial Nerve Blocks for Chronic Migraines

Purpose of Review

Headaches, especially migraines, are one of the most pervasive neurological disorders affecting up to 15.9% of the population. Current methods of migraine treatment include lifestyle changes, pharmacologic, and minimally invasive techniques such as peripheral nerve stimulation (PNS) and pericranial nerve blocks (PNB).

Recent Findings

PNBs are used to treat and prevent migraines and involves injection of local anesthetics with or without corticosteroids. PNBs include the greater occipital, supraorbital, supratrochlear, lesser occipital, auriculotemporal, sphenopalantine ganglion, and cervical root nerve blocks. Of the PNBs, the most extensively studied is the greater occipital nerve block (GONB) which has been shown to be an efficacious treatment for migraines, trigeminal neuralgia, hemi-crania continua, and post-lumbar puncture, post-concussive, cluster, and cervicogenic headaches but not medication overuse and chronic tension type headaches.

Summary

In this review, we aim to summarize the recent literature on PNBs and their efficacy in the treatment of migraines including a brief discussion of peripheral nerve stimulation.

Headache Attributed to Disorder of the Cranium and Base of the Skull

The article describes the approach to imaging that clinicians should adopt in cases of headaches suspected to be secondary to cranial vault or skull-base disorder. As a rule, computed tomography (CT) is superior to MRI for most of the osseous lesions, and lesions of the middle and external ear. MRI provides a complimentary role to CT and is the modality of choice in a few conditions such as extraosseous neoplasms of the skull base.

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.

Outcomes of transcutaneous nerve stimulation for migraine headaches: a systematic review and meta-analysis

BACKGROUND

Implanted and transcutaneous nerve stimulators have shown promise as novel non-pharmacologic treatment for episodic and chronic migraines. The purpose of this study was to summarize the reported efficacy of transcutaneous single nerve stimulators in management of migraine frequency and severity.

METHODS

A systematic review of five databases identified studies treating migraines with transcutaneous stimulation of a single nerve. Random effects model meta-analyses were conducted to establish the effect of preventive transcutaneous nerve stimulation on headache days per month and 0-10 numeric rating scale pain severity of headaches for both individuals with episodic and chronic migraines.

RESULTS

Fourteen studies, which treated 995 patients, met inclusion criteria, including 7 randomized controlled trials and 7 uncontrolled clinical trials. Transcutaneous nerve stimulators reduced headache frequency in episodic migraines (2.81 fewer headache days per month, 95% CI 2.18-3.43, I² = 21%) and chronic migraines (2.97 fewer headache days per month, 95% CI 1.66-4.28, I² = 0%). Transcutaneous nerve stimulators reduced headache severity in episodic headaches (2.23 fewer pain scale points, 95% CI 1.64-2.81, I² = 88%).

CONCLUSIONS

Preventive use of transcutaneous nerve stimulators provided clinically significant reductions in headache frequency in individuals with chronic or episodic migraines. Individuals with episodic migraines also experienced a reduction in headache pain severity following preventive transcutaneous nerve stimulation.

FollowTheSutures: Piloting a new way to administer onabotulinumtoxinA for chronic migraine

Background

Anatomical and experimental data indicate that onabotulinimtoxin A could be more efficient and cost-effective for treating chronic migraine with injections targeting the cranial sutures, where collaterals from the meninges penetrate the skull.

Methods

A new injection paradigm (FollowTheSutures) was tested for safety, tolerability and feasibility in a Phase II, open-label, non-controlled, single-center pilot study. Ninety units of onabotulinimtoxin A (Botox®), were injected in 18 sites over the area of the cranial sutures. Adverse events and potential beneficial effects were recorded in a headache diary at least 4 weeks before, and for 12 weeks after the injections. A higher dilution than normal of onabotulinimtoxin A was used to get better diffusion.

Results

Nineteen (of 20 included) women with chronic migraine received the injections and were evaluable. There was only one treatment-related adverse event (reduced power of chewing for some weeks). Otherwise, the procedure was overall well tolerated. Patients improved on most efficacy parameters after the injections. There was little or no effect on glabellar or forehead lines.

Conclusions

The protocol was safe and well tolerated. Lower risk of unblinding due to the absence of cosmetic effects should make the injection procedure well suited for a large, randomized, placebo-controlled study. If efficacy is confirmed, it will be markedly less costly than the standard procedure.

Trial registration: EUDRACT (2017-002516-13), ClinicalTrials.gov (NCT03543254).

Manual medicine, manual therapy

Manual medicine is the medical discipline that deals with diagnosis, treatment, and prevention of reversible functional disturbances in the locomotor system and other related organ systems. The current article illustrates neuroanatomical and neurophysiological fundamentals of the mechanisms of manual diagnostics and treatment. Based on the recent literature and consideration of different scientifically based clinical guidelines, the evidence-based effectiveness of manual therapeutic procedures is presented. Acute and chronic low back pain, cervicogenic headache, neck and shoulder pain, radicular arm pain, dysfunctional thoracic pain syndromes, diseases of the rotator cuff, carpal tunnel syndrome, and plantar fasciitis are included. Clinical case studies illustrate the clinical procedures. The term, the origin, and the clinical presence of “osteopathy” are addressed in detail, and the national and international societies of manual medicine (Deutsche Gesellschaft für Manuelle Medizin [DGMM], European Scientific Society of Manual Medicine [ESSOMM], Fédération Internationale de Medicine Manuelle [FIMM]) are portrayed lexically. Finally, contraindications to manual intervention are presented and an outlook on the requirements and possibilities of scientific pain analysis is given in accordance with the preamble of the Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie (GSOOC) guidelines on specific low back pain.

Beyond chronic migraine: a systematic review and expert opinion on the off-label use of botulinum neurotoxin type-A in other primary headache disorders

Introduction: Botulinum neurotoxin type-A (BoNTA) is licensed for the treatment of chronic migraine (CM), but it has been tested off-label as a therapeutic choice in other primary headaches (PHs). We aimed to provide a systematic review and expert opinion on BoNTA use in PHs, beyond CM.Areas covered: After providing an overview on PHs and mechanism of BoNTA action, we report the results of a systematic review, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations, of BoNTA therapeutic trials in PHs beyond CM. Studies and results were reviewed and discussed, and levels of evidence were graded. We also collected data on relevant ongoing trials.Expert opinion: Although there are contradictory findings on PHs other than CM, BoNTA may represent a therapeutic option for patients who do not respond to conventional prophylactic treatments. Based on limited available evidence, BoNTA may be considered in refractory tension-type headache, trigeminal autonomic cephalalgias, primary stabbing headache, nummular headache, hypnic headache, and new daily persistent headache, after the primary nature of cephalalgia has been documented and other drugs have failed. Experienced physicians in BoNTA treatment are required to guide the therapeutic protocol for each patient to optimize good and safe outcomes.

Intracranial nociception

Understanding intracranial nociceptive innervation is essential to understand the pathophysiology of headaches. Our knowledge about human intracranial nociception comes from sparse observations during neurosurgical procedures performed in awake patients, from human anatomical studies and from experimental studies in animals. In this article we review the anatomical and functional organization underlying nociceptive innervation. Intracranial nociception is mainly mediated by the trigeminal system, except in the posterior cranial fossa that is innervated by the first cervical roots. For decades, the dura mater, its vessels and major cerebral blood vessels were considered as the only intracranial pain-sensitive structures. Recent animal and human studies have suggested that smaller brain arteries and potentially pia mater might also be pain sensitive. Nociceptive neurons innervating intracranial blood vessels project via the ophthalmic division (V1) to the trigeminal ganglion and store several neurotransmitters including glutamate, substance P and calcitonin gene-related peptide (CGRP). The trigeminal ganglion, root and brainstem nuclei have a specific topographic and functional somatotopy. Progressive transition between the trigeminal spinal nucleus and the dorsal horn of the cervical spinal cord, and convergence of nociceptive inputs from the face, intracranial structures and the occipital area on the so-called "trigemino-cervical complex" may explain some headache features, relations between facial and occipital pain, and efficacy of occipital nerve stimulation in headache. The specific anatomic organization of the trigeminal system, from the primary-order neuron in the trigeminal ganglion, to the second-order neuron is the trigeminal nuclei, may explain a part of the various characteristics of headaches.

Efficacy of an opioid-sparing analgesic protocol in pain control after less invasive cranial neurosurgery

An opioid-sparing protocol for postoperative pain management in less invasive cranial neurosurgery significantly lowered opioid usage while reducing pain scores.

Introduction:

Opioid overuse in postoperative patients is a worrisome trend, and potential alternatives exist which warrant investigation. Nonsteroidal anti-inflammatory drug use in treating postoperative cranial surgery pain has been hampered by concern for inadequate pain control and increased risk of hemorrhagic complications. A safe and effective alternative to opioid-based pain management is critical to improving postoperative care.

Objective:

The objective of this retrospective study was to determine whether an NSAID-based opioid-sparing pain management protocol (OSP) is effective in analgesic control of less invasive cranial surgery patients at 6-, 12-, and 24-hour postoperatively. Secondary aims included investigating differences in hemorrhagic complications.

Methods:

Five hundred sixty-six consecutive patients who underwent cranial surgery before and after implementation of the celecoxib-based OSP were eligible. Propensity score matching was used to match patients in each cohort.

Results:

The opioid-sparing cohort had lower pain scores at 6 hours (3.45 vs 4.19, P = 0.036), 12 hours (3.21 vs 4.00, P = 0.006), and 24 hours (2.90 vs 3.59, P = 0.010). Rates of postoperative hemorrhage were not significantly different (5% intervention vs 8% control, P = 0.527). The opioid-sparing pain management protocol provided comparable or better pain control in the first 24 hours after less invasive cranial surgery. Hemorrhage rates did not change with the use of an NSAID-based OSP.

Conclusion:

An effective alternative to the current standard opioid-based pain management is feasible for less invasive cranial surgery. Determinations of hemorrhage risk and more complex cranial surgery will require larger prospective randomized trials.

Interleukin-6 induces spatially dependent whole-body hypersensitivity in rats: implications for extracephalic hypersensitivity in migraine

Background

Migraine is a complex neurological disorder that is characterized by throbbing head pain, increased sensitivity to light, sound, and touch, as well as nausea and fatigue. It is one of the most common and most disabling disorders globally but mechanisms causing migraine are poorly understood. While head pain is a typical feature of attacks, they also often present with cutaneous hypersensitivity in the rest of the body. In contrast, primary pain conditions in the lower parts of the body are less commonly associated with cephalic hypersensitivity. Previous studies indicate that application of stimuli to the meninges of rodents causes cutaneous facial as well as hindpaw hypersensitivity. In the present study, we asked whether widespread hypersensitivity is a unique feature of dural stimulation or whether body-wide responses occur similarly when the same stimulus is given in other locations.

Methods

Rats were given the same dose of IL-6 either via dural, intraplantar, subcutaneous, intramuscular, intracisternal, or intrathecal injection. Cutaneous facial and hindpaw allodynia was assessed using Von Frey following injection into each location.

Results

Hindpaw allodynia was observed following dural and intraplantar injection of IL-6 in both males and females. Hindpaw allodynia was only observed in females following intracisternal and intrathecal IL-6 injections. In contrast, facial allodynia was only observed in either sex following dural and intracisternal injections, which would activate meningeal afferents and the trigeminal nucleus caudalis (TNC), respectively.

Conclusions

Here we show that while stimulation of upper body regions with IL-6 including the meninges and brainstem can cause widespread hypersensitivity spreading to the paws, similar stimulation of the lower body does not cause the spread of hypersensitivity into the head. These data are consistent with the observations that whole body hypersensitivity is specific to conditions such as migraine where pain is present in the head and they may provide insight into co-morbid pain states associated with migraine.

[Manual medicine, manual treatment : Principles, mode of action, indications and evidence]

Manual medicine is the medical discipline that comprehensively deals with the diagnosis, treatment and prevention of reversible functional disorders of the musculoskeletal system and other related organ systems. The article illustrates the neuroanatomical and neurophysiological basic elements and mechanisms of manual medical diagnostics and treatment. Based on the most recent literature and in consideration of various scientific guidelines, the evidence-based effectiveness of manual medical procedures is presented. In detail: acute and chronic low back pain, cervicogenic headache, neck and shoulder pain, radicular arm pain, dysfunctional thoracic pain syndromes, diseases of the rotator cuff, carpal tunnel syndrome and plantar fasciitis. Clinical case examples illustrate the clinical approach. The terminology, origin and clinical presence of "osteopathy" are described in detail and the national and international associations and societies of manual medicine, the German Society for Manual Medicine (DGMM), the European Scientific Society of Manual Medicine (ESSOMM) and the Fédération Internationale de Medicine Manuelle (FIMM) are lexically presented. Finally, contraindications for manual interventions and an outlook on requirements and possibilities of the scientific analysis of pain are presented, as they are postulated in the preamble of the guidelines on specific low back pain of the German Society for Orthopedics and Orthopedic Surgery (DGOOC).

Transient activation of spinal trigeminal neurons in a rat model of hypoxia-induced headache

ABSTRACT

The mechanisms underlying headaches attributed to hypoxia are poorly known. The activation of spinal trigeminal neurons with meningeal afferent input is believed to be responsible for the generation of headaches. In the caudal spinal trigeminal nucleus of anaesthetized and ventilated rats, the spontaneous firing of neurons with input from the exposed parietal dura mater and the activity evoked by mechanical stimuli to the dura and the adjacent periosteum were recorded, whereas the O2 fraction of the ventilation gas was stepwise reduced by omitting O2 and adding nitrogen. The expiratory CO2 level, the arterial pressure, the pulse rate, and the peripheral O2 saturation (SpO2) were registered. The meningeal blood flow was recorded using laser Doppler flowmetry; video imaging was used to measure the diameter of dural and medullary arteries. Lowering O2 in the ventilation gas from hyperoxic to normoxic and finally hypoxic conditions was followed by an increase in spontaneous activity up to 300% of the initial activity in most neurons, whereas the activity in a minor fraction of neurons ceased. The mechanical threshold was reduced under hypoxia. Arterial pressure, pulse rate, and SpO2 fell during stepwise lowering of the O2 concentration, whereas the arteries of the dura mater and the medulla dilated. Increased neuronal activity in the spinal trigeminal nucleus following lowering of the inhaled O2 goes along with variations in cardiovascular parameters. The experiments may partly model the conditions of high altitudes and other hypoxic states as risk factors for headache generation.

Craniofacial sensations induced by transient changes of barometric pressure in healthy subjects – A crossover pilot study

Background:

Changes in atmospheric pressure are suggested to trigger headaches. This pilot study was made to determine craniofacial sensations accompanying short phases of changing barometric pressure.

Methods:

In a crossover design, 15 adult healthy subjects were exposed in a climate chamber to 8 min phases of barometric pressure lowering by 0, 20 and 40 hPa. The subjects rated their sensations of ear pressure, head compression and the occurrence of headache every minute on a visual analogue scale (VAS, range 0–10). Pulse rate was recorded as a parameter for autonomic functions.

Results:

Nearly all subjects experienced ear pressure and half of them compression of their head at variable degrees. These sensations started in most subjects during the phase of lowering barometric pressure and increased to an average rating of about 3 VAS when returning to ambient atmospheric pressure. Heart rate slightly decreased during this phase. Three subjects reported mild to moderate headache for various durations within these phases.

Conclusions:

Changes in barometric pressure can be associated with sensations of ear pressure and head compression and may trigger headaches. The generation of these sensations is discussed with regard to convergent trigeminal innervation of the ear, the paranasal sinuses and the cranial meninges.

The trigeminal system: The meningovascular complex- A review

Supratentorial sensory perception, including pain, is subserved by the trigeminal nerve, in particular, by the branches of its ophthalmic division, which provide an extensive innervation of the dura mater and of the major brain blood vessels. In addition, contrary to previous assumptions, studies on awake patients during surgery have demonstrated that the mechanical stimulation of the pia mater and small cerebral vessels can also produce pain. The trigeminovascular system, located at the interface between the nervous and vascular systems, is therefore perfectly positioned to detect sensory inputs and influence blood flow regulation. Despite the fact that it remains only partially understood, the trigeminovascular system is most probably involved in several pathologies, including very frequent ones such as migraine, or other severe conditions, such as subarachnoid haemorrhage. The incomplete knowledge about the exact roles of the trigeminal system in headache, blood flow regulation, blood barrier permeability and trigemino-cardiac reflex warrants for an increased investigation of the anatomy and physiology of the trigeminal system. This translational review aims at presenting comprehensive information about the dural and brain afferents of the trigeminovascular system, in order to improve the understanding of trigeminal cranial sensory perception and to spark a new field of exploration for headache and other brain diseases.

Differential effects of the Piezo1 agonist Yoda1 in the trigeminovascular system: An electrophysiological and intravital microscopy study in rats

Migraine is associated with the activation and sensitisation of the trigeminovascular system and is often accompanied by mechanical hyperalgesia and allodynia. The mechanisms of mechanotransduction during a migraine attack are yet unknown. We have proposed that the ion channel Piezo1 may be involved, since it is expressed in endothelial cells as well as in trigeminal ganglion neurons, and thus, may contribute to the activation of both the vascular and neuronal component of the trigeminovascular system. We took advantage of extracellular recordings from the trigeminocervical complex - a key relay centre in the migraine pain pathway, to directly assess the impact of the differently applied Piezo1 agonist Yoda1 on the sensory processing at the spinal level. At a low dose, Yoda1 slightly facilitated the ongoing firing of central trigeminovascular neurons, however, at a high dose, this substance contributed to the suppression of their activity. Using intravital microscopy, we have revealed that Yoda1 at high dose can also induce the dilation of meningeal arteries innervated by trigeminal afferents. Collectively, here we have identified both neuronal and vascular modulation via selective activation of mechanosensitive Piezo1 channels, which provide new evidence in favour of the Piezo1 role in migraine pathogenesis. We propose several mechanisms that may underlie the revealed effects of Yoda1.

Implications of Transient Receptor Potential Cation Channels in Migraine Pathophysiology

Migraine is a common and debilitating headache disorder. Although its pathogenesis remains elusive, abnormal trigeminal and central nervous system activity is likely to play an important role. Transient receptor potential (TRP) channels, which transduce noxious stimuli into pain signals, are expressed in trigeminal ganglion neurons and brain regions closely associated with the pathophysiology of migraine. In the trigeminal ganglion, TRP channels co-localize with calcitonin gene-related peptide, a neuropeptide crucially implicated in migraine pathophysiology. Many preclinical and clinical data support the roles of TRP channels in migraine. In particular, activation of TRP cation channel V1 has been shown to regulate calcitonin gene-related peptide release from trigeminal nerves. Intriguingly, several effective anti-migraine therapies, including botulinum neurotoxin type A, affect the functions of TRP cation channels. Here, we discuss currently available data regarding the roles of major TRP cation channels in the pathophysiology of migraine and the therapeutic applicability thereof.

Responses of spinal trigeminal neurons to noxious stimulation of paranasal cavities - a rat model of rhinosinusitis headache

BACKGROUND

The pathophysiology of headaches associated with rhinosinusitis is poorly known. Since the generation of headaches is thought to be linked to the activation of intracranial afferents, we used an animal model to characterise spinal trigeminal neurons with nociceptive input from the dura mater and paranasal sinuses.

METHODS

In isoflurane anaesthetised rats, extracellular recordings were made from neurons in the spinal trigeminal nucleus with afferent input from the exposed frontal dura mater. Dural and facial receptive fields were mapped and the paranasal cavities below the thinned nasal bone were stimulated by sequential application of synthetic interstitial fluid, 40 mM potassium chloride, 100 µM bradykinin, 1% ethanol (vehicle) and 100 µm capsaicin.

RESULTS

Twenty-five neurons with input from the frontal dura mater and responses to chemical stimulation of the paranasal cavities were identified. Some of these neurons had additional receptive fields in the parietal dura, most of them in the face. The administration of synthetic interstitial fluid, potassium chloride and ethanol was not followed by significant changes in activity, but bradykinin provoked a cluster of action potentials in 20 and capsaicin in 23 neurons.

CONCLUSION

Specific spinal trigeminal neurons with afferent input from the cranial dura mater respond to stimulation of paranasal cavities with noxious agents like bradykinin and capsaicin. This pattern of activation may be due to convergent input of trigeminal afferents that innervate dura mater and nasal cavities and project to spinal trigeminal neurons, which could explain the genesis of headaches due to disorders of paranasal sinuses.

Peripheral Occipital Nerve Decompression Surgery in Migraine Headache

Migraine headache in the occipital region is characterized by a recurrent pain of moderate to severe intensity. However, the diagnosis can be difficult because of the multitude of symptoms overlapping with similar disorders and a pathophysiology that is not well-understood. For this reason, the medical management is often complex and ineffective.

A Comprehensive Review of Surgical Treatment of Migraine Surgery Safety and Efficacy

BACKGROUND

Recent clinical experience with migraine surgery has demonstrated both the safety and the efficacy of operative decompression of the peripheral nerves in the face, head, and neck for the alleviation of migraine symptoms. Because of the perceived novelty of these procedures, and the paranoia surrounding a theoretical loss of clinical territory, neurologists have condemned the field of migraine surgery. The Patient Safety Subcommittee of the American Society of Plastic Surgeons ventured to investigate the published safety track record of migraine surgery in the existing body of literature.

METHODS

A comprehensive review of the relevant published literature was performed. The relevant databases and literature libraries were reviewed from the date of their inception through early 2018. These articles were reviewed and their findings analyzed.

RESULTS

Thirty-nine published articles were found that demonstrated a substantial, extensively replicated body of data that demonstrate a significant reduction in migraine headache symptoms and frequency (even complete elimination of headache pain) following trigger-site surgery.

CONCLUSIONS

Migraine surgery is a valid method of treatment for migraine sufferers when performed by experienced plastic surgeons following a methodical protocol. These operations are associated with a high level of safety. The safety and efficacy of migraine surgery should be recognized by plastic surgeons, insurance companies, and the neurology societies.

Trigeminal activation patterns evoked by chemical stimulation of the dura mater in rats

BACKGROUND

Although migraine is one of the most common primary headaches, its therapy is still limited in many cases. The use of animal models is crucial in the development of novel therapeutic strategies, but unfortunately, none of them show all aspects of the disease, therefore, there is a constant need for further improvement in this field. The application of inflammatory agents on the dura mater is a widely accepted method to mimic neurogenic inflammation in rodents, which plays a key role in the pathomechanism of migraine. Complete Freund's Adjuvant (CFA), and a mixture of inflammatory mediators, called inflammatory soup (IS) are often used for this purpose.

METHODS

To examine the activation pattern that is caused by chemical stimulation of dura mater, we applied CFA or IS over the right parietal lobe. After 2 h and 4 h (CFA groups), or 2.5 h and 4 h (IS groups), animals were perfused, and c-Fos immunoreactive cells were counted in the caudal trigeminal nucleus. To explore every pitfall, we examined whether our surgical procedure (anesthetic drug, stereotaxic apparatus, local lidocaine) can alter the results under the same experimental settings. c-Fos labeled cells were counted in the second-order neuron area based on the somatotopic organization of the trigeminal nerve branches.

RESULTS

We could not find any difference between the CFA and physiological saline group neither 2 h, nor 4 h after dural stimulation. IS caused significant difference after both time points between IS treated and control group, and between treated (right) and control (left) side. Stereotaxic frame usage had a substantial effect on the obtained results.

CONCLUSIONS

Counting c-Fos immunoreactive cells based on somatotopic organization of the trigeminal nerve helped to examine the effect of chemical stimulation of dura in a more specific way. As a result, the use of IS over the parietal lobe caused activation in the area of the ophthalmic nerve. To see this effect, the use of lidocaine anesthesia is indispensable. In conclusion, application of IS on the dura mater induces short-term, more robust c-Fos activation than CFA, therefore it might offer a better approach to model acute migraine headache in rodents.

Mechanism of Action of OnabotulinumtoxinA in Chronic Migraine: A Narrative Review

Objective

To review the literature on the mechanism of action of onabotulinumtoxinA in chronic migraine.

Background

OnabotulinumtoxinA is a chronic migraine preventive treatment that significantly reduces headache frequency. The traditional mechanism described for onabotulinumtoxinA – reducing muscle contractions – is insufficient to explain its efficacy in migraine, which is primarily a sensory neurological disease.

Methods

A narrative literature review on the mechanism of action of onabotulinumtoxinA in chronic migraine.

Results

Following injection into tissues, onabotulinumtoxinA inhibits soluble N‐ethylmaleimide‐sensitive fusion attachment protein receptor (SNARE)‐mediated vesicle trafficking by cleaving one of its essential proteins, soluble N‐ethylmaleimide‐sensitive fusion attachment protein (SNAP‐25), which occurs in both motor and sensory nerves. OnabotulinumtoxinA inhibits regulated exocytosis of motor and sensory neurochemicals and proteins, as well as membrane insertion of peripheral receptors that convey pain from the periphery to the brain, because both processes are SNARE dependent. OnabotulinumtoxinA can decrease exocytosis of pro‐inflammatory and excitatory neurotransmitters and neuropeptides such as substance P, calcitonin gene‐related peptide, and glutamate from primary afferent fibers that transmit nociceptive pain and participate in the development of peripheral and central sensitization. OnabotulinumtoxinA also decreases the insertion of pain‐sensitive ion channels such as transient receptor potential cation channel subfamily V member 1 (TRPV1) into the membranes of nociceptive neurons; this is likely enhanced in the sensitized neuron. For chronic migraine prevention, onabotulinumtoxinA is injected into 31‐39 sites in 7 muscles of the head and neck. Sensory nerve endings of neurons whose cell bodies are located in trigeminal and cervical ganglia are distributed throughout the injected muscles, and are overactive in people with migraine. Through inhibition of these sensory nerve endings, onabotulinumtoxinA reduces the number of pain signals that reach the brain and consequently prevents activation and sensitization of central neurons postulated to be involved in migraine chronification.

Conclusion

OnabotulinumtoxinA likely acts via sensory mechanisms to treat chronic migraine.

[Osteopathy under scrutiny]

Osteopathic medicine is a medical specialty that enjoys a high level of recognition and increasing popularity among patients. High-quality education and training are essential to ensure good and safe patient treatment. At a superficial glance, osteopathy could be misunderstood as a myth; accurately considered, osteopathic medicine is grounded in medical and scientific knowledge and solid theoretical and practical training. Scientific advances increasingly confirm the empirical experience of osteopathy. Although more studies on its efficacy could be conducted, there is sufficient evidence for a reasonable application of osteopathy. Current scientific studies show how a manually executed osteopathic intervention can induce tissue and even cellular reactions. Because the body actively responds to environmental stimuli, osteopathic treatment is considered an active therapy. Osteopathic treatment is individually applied and patients are seen as an integrated entity. Because of its typical systemic view and scientific interpretation, osteopathic medicine is excellently suited for interdisciplinary cooperation. Further work on external evidence of osteopathy is being conducted, but there is enough knowledge from the other pillars of evidence-based medicine (EBM) to support the application of osteopathic treatment. Implementing careful, manual osteopathic examination and treatment has the potential to cut healthcare costs. To ensure quality, osteopathic societies should be intimately involved and integrated in the regulation of the education, training, and practice of osteopathic medicine.

Signaling Interaction between Facial and Meningeal Inputs of the Trigeminal System Mediates Peripheral Neurostimulation Analgesia in a Rat Model of Migraine

Peripheral neurostimulation within the trigeminal nerve territory has been used for pain alleviation during migraine attacks, but the mechanistic basis of this non-invasive intervention is still poorly understood. In this study, we investigated the therapeutic role of peripheral stimulation of the trigeminal nerve, which provides homosegmental innervation to intracranial structures, by assessing analgesic effects in a nitroglycerin (NTG)-induced rat model of migraine. As a result of neurogenic inflammatory responses in the trigeminal nervous system, plasma protein extravasation was induced in facial skin by applying noxious stimulation to the dura mater. Noxious chemical stimulation of the dura mater led to protein extravasation in facial cutaneous tissues and caused mechanical sensitivity. Trigeminal ganglion (TG) neurons were double-labeled via retrograde tracing to detect bifurcated axons. Extracellular recordings of wide dynamic range (WDR) neurons in the spinal trigeminal nucleus caudalis (Sp5C) demonstrated the convergence and interaction of inputs from facial tissues and the dura mater. Peripheral neurostimulation of homotopic facial tissues represented segmental pain inhibition on cephalic cutaneous allodynia in the migraine model. The results indicated that facial territories and intracranial structures were directly connected with each other through bifurcated double-labeled neurons in the TG and through second-order WDR neurons. Homotopic stimulation at the C-fiber intensity threshold resulted in much stronger inhibition of analgesia than the same intensity of heterotopic stimulation. These results provide novel evidence for the neurological bases through which peripheral neurostimulation may be effective in treating migraine in clinical practice.

Chronic migraine and Botulinum Toxin Type A: Where do paths cross?

Migraine is a highly prevalent and disabling disorder accounted among the primary headaches. It is the expression of a complex, and not yet fully understood, pathophysiology involving the sensitization of peripheral and central nociceptive pathways. In this review we succinctly illustrate the molecular, anatomical, and functional abnormalities underlying the migraine attack that are relevant for understanding in more depth the neurobiology behind the therapeutic effect of Botulinum Toxin Type A (BoNT-A). BoNT-A has proved effective in several neurological conditions and, more recently, also in chronic migraine. Its antimigraine mechanism of action was initially thought to be limited to the periphery and interpreted as an inhibitory activity on the processes associated to the local release of neuropeptides, with subsequent induction of peripheral sensitization. Increasing experimental evidence has become available to suggest that additional mechanisms are possibly involved, including the direct/indirect inhibition of sensitization processes in central nociceptive pathways.

TRP Channels in the Focus of Trigeminal Nociceptor Sensitization Contributing to Primary Headaches

Pain in trigeminal areas is driven by nociceptive trigeminal afferents. Transduction molecules, among them the nonspecific cation channels transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1), which are activated by endogenous and exogenous ligands, are expressed by a significant population of trigeminal nociceptors innervating meningeal tissues. Many of these nociceptors also contain vasoactive neuropeptides such as calcitonin gene-related peptide (CGRP) and substance P. Release of neuropeptides and other functional properties are frequently examined using the cell bodies of trigeminal neurons as models of their sensory endings. Pathophysiological conditions cause phosphorylation, increased expression and trafficking of transient receptor potential (TRP) channels, neuropeptides and other mediators, which accelerate activation of nociceptive pathways. Since nociceptor activation may be a significant pathophysiological mechanism involved in both peripheral and central sensitization of the trigeminal nociceptive pathway, its contribution to the pathophysiology of primary headaches is more than likely. Metabolic disorders and medication-induced painful states are frequently associated with TRP receptor activation and may increase the risk for primary headaches.

High-dose phenylephrine increases meningeal blood flow through TRPV1 receptor activation and release of calcitonin gene-related peptide

BACKGROUND

The α₁ -adrenoceptor agonist, phenylephrine, is used at high concentrations as a mydriatic agent and for the treatment of nasal congestion. Among its adverse side-effects transient burning sensations are reported indicating activation of the trigeminal nociceptive system.

METHODS

Neuropeptide release, calcium imaging and meningeal blood flow recordings were applied in rodent models of meningeal nociception to clarify possible receptor mechanisms underlying these pain phenomena.

RESULTS

Phenylephrine above 10 mM dose-dependently released calcitonin gene-related peptide (CGRP) from the dura mater and isolated trigeminal ganglia, whereas hyperosmotic mannitol at 90 mM was ineffective. The phenylephrine-evoked release was blocked by the transient receptor potential vanilloid 1 (TRPV1) antagonist BCTC and did not occur in trigeminal ganglia of TRPV1-deficient mice. Phenylephrine at 30 mM caused calcium transients in cultured trigeminal ganglion neurons responding to the TRPV1 agonist capsaicin and in HEK293T cells expressing human TRPV1. Local application of phenylephrine at micromolar concentrations to the exposed rat dura mater reduced meningeal blood flow, whereas concentrations above 10 mM caused increased meningeal blood flow. The flow increase was abolished by pre-application of the CGRP receptor antagonist CGRP_8-37 or the TRPV1 antagonist BCTC.

CONCLUSIONS

Phenylephrine at high millimolar concentrations activates TRPV1 receptor channels of perivascular afferents and, upon calcium inflow, releases CGRP, which increases meningeal blood flow. Activation of TRPV1 receptors may underlie trigeminal nociception leading to cranial pain such as local burning sensations or headaches caused by administration of high doses of phenylephrine.

SIGNIFICANCE

Phenylephrine is used at high concentrations as a mydriaticum and for treating nasal congestion. As adverse side-effects burning sensations and headaches have been described. Phenylephrine at high concentrations causes calcium transients in trigeminal afferents, CGRP release and increased meningeal blood flow upon activation of TRPV1 receptor channels, which is likely underlying the reported pain phenomena.

Botulinum toxin injections to cranial sutures for chronic migraine Rewinding the technique using ultrasound imaging

The treatment of chronic migraine headache is quite challenging and new alternatives are still being explored for its management. Onabotulinum toxin A (BoNT-A) applied into extracranial muscles has been shown to inhibit the release of acetylcholine and local nociceptive peptides at the sensory nerve endings. As the highest concentration of extracranial pain fibers are located at/nearby the sutures, extracranial applications of BoTN-A are suggested to be performed to sutures rather than into the head and neck muscles in the treatment of chronic migraine. Moreover, in an animal study, BoTN-A is found to be more effective for decreasing the chemosensitivity of meningeal nociceptors when the total dose is injected along the sutures in comparison to being divided into sutures and cranial muscles. Of note, since BoNT-A injections performed with the blind/nontargeted technique have lower effectivity and several complications (muscle weakness, ptosis, facial paresis, etc.), the use of ultrasound guidance for targeting the cranial sutures is definitely expected to provide technical ease, better pain relief and toxin tolerance in chronic migraine.

Botulinum Toxin Type A in Dental Medicine

Botulinum toxins (BoNTs) are a product of the bacteria Clostridium botulinum. By entering nerve endings, they cleave and inactivate SNARE proteins, which are essential for neurotransmitter release. Prevention of acetylcholine release at the neuromuscular junction causes long-lasting and potentially fatal flaccid paralysis-a major feature of botulism. However, an intramuscular injection of minute amounts of BoNTs, primarily type A (BoNT-A), has useful long-lasting muscle relaxation effects on spastic motor disorders. This characteristic of BoNT-A is widely used in neurology and cosmetics. Over the last few decades, it has been demonstrated that the functions of BoNT-A are not limited to muscle-relaxing or autonomic cholinergic effects but that it can act as an analgesic agent as well. More recently, it was revealed that this antinociceptive effect starts after entering the sensory nerve endings, where these agents are axonally transported to the central nervous system, suggesting that at least part of their analgesic effect might be of central origin. Because of its antinociceptive effect, BoNT-A is currently approved for treatment of chronic migraine; nonetheless, case reports and preclinical and clinical experiments indicating its benefit in numerous potential painful conditions have increased. In the field of dentistry, the US Food and Drug Administration approved BoNT-A for the treatment of sialorrhea only. Legal status of the use of BoNT-A in other countries is less known. However, there are controlled clinical trials suggesting its efficacy in other conditions, such as bruxism, temporomandibular disorders, and trigeminal neuropathic pain. Thereby, using criteria of the American Academy of Neurology, we critically reviewed the uses of BoNTs in oral medicine and found it effective for trigeminal neuralgia (category A) and probably effective in temporomandibular disorders and bruxism.

Headache in Petrous Apicitis: A Case Report of Chronic Migraine-like Headache Due to Peripheral Pathology

OBJECTIVE

To report a case of petrous apicitis that manifested as chronic migraine without aura and to discuss the pathophysiological mechanisms behind this presentation.

BACKGROUND

Petrous apicitis is a rare complication of acute otitis media with varied clinical presentations that stem from the close proximity of the petrous apex to numerous neurovascular structures. Headache is among the common symptoms of petrous apicitis.

METHODS

A case of new onset headache in the setting of petrous apicitis with symptomatic response to antibiotic therapy was reported. We provided a brief review of peripheral pathophysiological mechanisms of migraine and correlated to mechanism of headache in petrous apicitis.

RESULTS

A 65-year-old man with chronic otitis externa/media presented with ongoing headache fulfilling International Classification of Headache Disorders 3rd edition (ICHD-3) criteria for chronic migraine without aura that persisted despite undergoing right mastoidectomy and tympanoplasty with multiple courses of oral antibiotic therapy for his chronic otitis. MRI brain revealed petrous apicitis, otomastoiditis, and clival osteomyelitis. His imaging findings improved and his migraine-like headache completely resolved after treatment with a prolonged course of antibiotics.

CONCLUSIONS

Petrous apicitis can present as a headache with features of migraine, and in this case in particular, as chronic migraine without aura. The pathophysiological mechanisms that may underlie the generation of migraine-like headache in petrous apicitis may include the activation of nociceptive fibers within the periosteum of the petrous apex and clivus whose cell bodies originate in the trigeminal ganglion and upper cervical dorsal root ganglia. By treating the peripheral pathology, resolution of the headache may be achieved.

Exploring the effects of extracranial injections of botulinum toxin type A on prolonged intracranial meningeal nociceptors responses to cortical spreading depression in female rats

Background

Botulinum neurotoxin type A, an FDA-approved prophylactic drug for chronic migraine, is thought to achieve its therapeutic effect through blocking activation of unmyelinated meningeal nociceptors and their downstream communications with myelinated nociceptors and potentially the vasculature and immune cells. Prior investigations to determine botulinum neurotoxin type A effects on meningeal nociceptors were carried out in male rats and tested with stimuli that act outside the blood brain barrier. Here, we sought to explore the effects of extracranial injections of botulinum neurotoxin type A on activation of meningeal nociceptors by cortical spreading depression, an event which occurs inside the blood brain barrier, in female rats.

Material and methods

Using single-unit recording, we studied myelinated C- and unmyelinated Aδ-meningeal nociceptors' responses to cortical spreading depression 7–14 days after injection of botulinum neurotoxin type A or saline along calvarial sutures.

Results

In female rats, responses to cortical spreading depression were typically more prolonged and, in some cases, began at relatively longer latencies post-cortical spreading depression, than had been observed in previous studies in male rats. Extracranial administration of botulinum neurotoxin type A reduced significantly the prolonged firing of the meningeal nociceptors, in the combined sample of Aδ- and C-fiber, but not their response probability.

Discussion

The findings suggest that the mechanism of action by which botulinum neurotoxin type A prevents migraine differ from the one by which calcitonin gene-related peptide monoclonal antibodies prevent migraine and that even when the origin of migraine is central (i.e. in the cortex), a peripherally acting drug can intercept/prevent the headache.

Photoactivation of olfactory sensory neurons does not affect action potential conduction in individual trigeminal sensory axons innervating the rodent nasal cavity

Olfactory and trigeminal chemosensory systems reside in parallel within the mammalian nose. Psychophysical studies in people indicate that these two systems interact at a perceptual level. Trigeminal sensations of pungency mask odour perception, while olfactory stimuli can influence trigeminal signal processing tasks such as odour localization. While imaging studies indicate overlap in limbic and cortical somatosensory areas activated by nasal trigeminal and olfactory stimuli, there is also potential cross-talk at the level of the olfactory epithelium, the olfactory bulb and trigeminal brainstem. Here we explored the influence of olfactory and trigeminal signaling in the nasal cavity. A forced choice water consumption paradigm was used to ascertain whether trigeminal and olfactory stimuli could influence behaviour in mice. Mice avoided water sources surrounded by both volatile TRPV1 (cyclohexanone) and TRPA1 (allyl isothiocyanate) irritants and the aversion to cyclohexanone was mitigated when combined with a pure odorant (rose fragrance, phenylethyl alcohol, PEA). To determine whether olfactory-trigeminal interactions within the nose could potentially account for this behavioural effect we recorded from single trigeminal sensory axons innervating the nasal respiratory and olfactory epithelium using an isolated in vitro preparation. To circumvent non-specific effects of chemical stimuli, optical stimulation was used to excite olfactory sensory neurons in mice expressing channel-rhodopsin (ChR2) under the olfactory marker protein (OMP) promoter. Photoactivation of olfactory sensory neurons produced no modulation of axonal action potential conduction in individual trigeminal axons. Similarly, no evidence was found for collateral branching of trigeminal axon that might serve as a conduit for cross-talk between the olfactory and respiratory epithelium and olfactory dura mater. Using direct assessment of action potential activity in trigeminal axons we observed neither paracrine nor axon reflex mediated cross-talk between olfactory and trigeminal sensory systems in the rodent nasal cavity. Our current results suggest that olfactory sensory neurons exert minimal influence on trigeminal signals within the nasal cavity.

Botulinum Toxin a Valuable Prophylactic Agent for Migraines and a Possible Future Option for the Prevention of Hormonal Variations-Triggered Migraines

BACKGROUND

In 1989, Botulinum toxin (BoNT) was accepted by the FDA for the management of some ophthalmic disorders. Although it was initially considered a lethal toxin, in recent times, Botulinum toxin A (BoNT-A), which is the more used serotype, has expanded to cover different clinical conditions, primarily characterized by neuropathic pain, including migraines and headaches. Evidence suggests that migraines are influenced by hormonal factors, particularly by estrogen levels, but very few studies have investigated the prevalence and management strategies for migraines according to the hormonal status. The effects of several therapeutic regimens on migraines have been investigated, but the medications used varied widely in proven efficacies and mechanisms of action. BoNT-A is increasingly used in the management of migraine and several placebo-controlled trials of episodic and chronic migraine are currently underway. This paper is a review of the recently published data concerning the administration of BoNT-A in the prevention of chronic migraines. Considering the lack of population-based studies about the effectiveness of BoNT-A in the alleviation of premenstrual and perimenopausal migraines, this study proposes a new perspective of the therapeutic approach of migraine syndrome associated with menopausal transition and the premenstrual period.

METHODS

We selected the reviewed papers from CrossRef, PubMed, Medline, and GoogleScholar, and a total of 21 studies met our inclusion criteria.

RESULTS

To date, no specific preventive measures have been recommended for menopausal women with migraines. BoNT-A often reduces the frequency and intensity of migraine attacks per month; the treatment is well tolerated and does not exhibit a significantly higher rate of treatment-related side effects. No population-based studies were conducted in order to highlight the role of BoNT-A in menopause-related migraines, neither in menstrual migraines.

CONCLUSION

There is a need for further research in order to quantify the real burden of menstrual and perimenopausal migraines and to clarify if BoNT-A could be used in the treatment of refractory postmenopausal and premenstrual migraines.

Emerging evidence of occipital nerve compression in unremitting head and neck pain

Unremitting head and neck pain (UHNP) is a commonly encountered phenomenon in Headache Medicine and may be seen in the setting of many well-defined headache types. The prevalence of UHNP is not clear, and establishing the presence of UHNP may require careful questioning at repeated patient visits. The cause of UHNP in some patients may be compression of the lesser and greater occipital nerves by the posterior cervical muscles and their fascial attachments at the occipital ridge with subsequent local perineural inflammation. The resulting pain is typically in the sub-occipital and occipital location, and, via anatomic connections between extracranial and intracranial nerves, may radiate frontally to trigeminal-innervated areas of the head. Migraine-like features of photophobia and nausea may occur with frontal radiation. Occipital allodynia is common, as is spasm of the cervical muscles. Patients with UHNP may comprise a subgroup of Chronic Migraine, as well as of Chronic Tension-Type Headache, New Daily Persistent Headache and Cervicogenic Headache. Centrally acting membrane-stabilizing agents, which are often ineffective for CM, are similarly generally ineffective for UHNP. Extracranially-directed treatments such as occipital nerve blocks, cervical trigger point injections, botulinum toxin and monoclonal antibodies directed at calcitonin gene related peptide, which act primarily in the periphery, may provide more substantial relief for UHNP; additionally, decompression of the occipital nerves from muscular and fascial compression is effective for some patients, and may result in enduring pain relief. Further study is needed to determine the prevalence of UHNP, and to understand the role of occipital nerve compression in UHNP and of occipital nerve decompression surgery in chronic head and neck pain.

Cranial Osteopathy: Obscurantism and Enlightenment

The application of cranial osteopathic manipulative medicine (OMM) is always controversial in the literature. Primary respiration related to the movement of spheno-basilar synchondrosis in the adult goes against the knowledge of complete ossification that occurs at this articulation after the pubertal phase. The idea that the operator's hands can communicate with the meninges is difficult to accept. The anatomy shows us that the fascial system involves the meninges and that from the microcellular point of view there are no layers that divide one tissue from another. The backing of new sciences, such as quantum physics, suggest that cranial palpation allows the osteopath to come into contact with the meninges. Recent scientific evidence shows that meningeal afferents can affect extracranial areas and that the pericranial musculature itself is able to influence these afferents. The article highlights some reflections in support of cranial osteopathy, based on scientific information that could help the osteopath to improve clinical work.

Is there a difference in response to manual cranial bone tissue assessment techniques between participants with cervical and/or temporomandibular complaints versus a control group?

AIM

Manual cranial bone tissue techniques (CBTT) are used by physiotherapists as a tool for assessment and treatment of complaints in the craniocervical, face, and head regions. The goal of this study was to determine whether CBTT were able to discriminate between subjects with cervical and/or temporomandibular disorders (TMD) and a healthy group. In addition, the inter-rater reliability when applying CBTT was also investigated.

METHODS

A cross-sectional study was conducted and included 60 participants. Six standardized passive techniques were applied and judged for resistance, compliance, and sensory answer. In order to evaluate the inter-rater reliability of these techniques a cohort of participants was measured twice (by two evaluators) prospectively. A logistic regression model and Receiver Operating Curve (ROC) analyses were used to determining the discriminative validity of these techniques.

RESULTS

Logistic regression identified a significant difference for five techniques for resistance and/or compliance and/or the sensory answer between the groups. Based on the Area Under the Curve (AUC) analysis, the discriminative ability of the temporal rotation to distinguish between the groups was fair to good (for resistance AUC = 0.7775 and for compliance AUC = 0.8065). The highest agreement between the two assessors was for the resistance with occipital compression (73%) technique.

CONCLUSION

This study highlights that some of the CBTT could be potentially useful in distinguishing subjects with cervical and/or TMD from healthy subjects. Inter-rater reliability was moderate. CBTT could be potentially integrated in the examination of participants with complaints in the craniofacial region.