Experimental evidence of a functional relationship within the brainstem trigeminocervical complex in humans

Similarities and differences between chronic primary pain and depression in brain activities: Evidence from resting-state microstates and auditory Oddball task

BACKGROUND

In 2019, the International Association for the Study of Pain introduced the concept of 'chronic primary pain (CPP)', characterized by persistent non-organic pain with emotional and functional abnormalities. Underdiagnosed and linked to depression, CPP has poorly understood neural characteristics. Electroencephalogram (EEG) microstates enable detailed examination of brain network dynamics at the millisecond level. Incorporating task-related EEG features offers a comprehensive neurophysiological signature of brain dysfunction, facilitating exploration of potential neural mechanisms.

METHODS

This study employed resting-state and task-related auditory Oddball EEG paradigm to evaluate 20 healthy controls, 20 patients with depression, and 20 patients with CPP. An 8-minute recording of resting-state EEG was conducted to identify four typical microstates (A-D). Additionally, power spectral density (PSD) features were examined during an auditory Oddball paradigm.

RESULTS

Both CPP and Major Depressive Disorder (MDD) patients exhibited reduced occurrence rate and transition probabilities of other microstates to microstate C during resting-state EEG. Furthermore, more pronounced increase in Gamma PSD was observed in the occipital region of CPP during the Oddball task. In CPP, both resting-state microstate C and task-related Gamma PSD correlated with pain and emotional indicators. Notably, microstate C occurrence positively correlated with occipital Gamma PSD in MDD.

CONCLUSION

Conclusively, both CPP and MDD display dynamic abnormalities within the salient network, closely associated with pain and depressive symptoms in CPP. Unlike MDD, CPPs' dynamic network changes appear unrelated to perceptual integration function, indicating differing microstate functional impacts. Combining resting-state microstates and Oddball tasks may offer a promising avenue for identifying potential biomarkers in objectively assessing chronic primary pain.

Neuromodulation treatments for migraine: a contemporary update

PURPOSE OF REVIEW

Neuromodulation approaches have been a part of a revolution in migraine therapies with multiple devices approved or in development. These devices vary in the nerve(s) being targeted, implantable versus noninvasive form factors as well as their effectiveness for acute pain reduction or migraine prevention. This review will summarize these recent advancements and approaches that are being developed which build upon prior work and improved technology that may help enhance the effectiveness as well as the patient experience.

RECENT FINDINGS

Both noninvasive and implantable devices primarily targeting cranial nerves have shown the ability to help alleviate migraine symptoms. Multiple prospective and retrospective studies have demonstrated clinically meaningful reductions in headache intensity with noninvasive approaches, while prevention of migraine demonstrates more modest effects. Implantable neuromodulation technologies focusing on occipital and supraorbital stimulation have shown promise in migraine/headache prevention in chronic migraine patients, but there is a need for improvements in technology to address key needs for surgical approaches.

SUMMARY

Electrical neuromodulation approaches in the treatment of migraine is undergoing a transformation towards improved outcomes with better technologies that may suit various patient needs on a more individualized basis.

Orofacial Migraine-A Narrative Review

The diagnosis of migraine is based on clear criteria outlined in the International Classification of Headache Disorders version 3 (ICHD-3). Notably, the criteria in ICHD-3 omit the location of the migraine. There are increasing reports of migraine in the facial region. Facial presentations of migraine are not easy to diagnose as they appear in the lower two-thirds of the face, often in the maxillary sinus region, around the ear, the upper/lower jaws, and the teeth. Additionally, a similar but distinct entity, neurovascular orofacial pain, has been established. The symptomatology of facial presentations of these headaches often resembles sinusitis and dental pathology. We will review these presentations, their diagnosis, and possible pathophysiology.

The effectiveness of cervical rehabilitation interventions for pain in adults with myogenic temporomandibular disorders: A systematic review and meta-analysis

OBJECTIVE

Little evidence exists for the most effective conservative treatment approach for adults with myogenic temporomandibular disorders (MTMD). We aim to assess the effectiveness of cervical rehabilitation interventions on pain intensity and sensitivity in adults with MTMD compared to comparison intervention such as placebo, sham treatment, education or no intervention.

METHODS

For this systematic review and meta-analysis, we searched PubMed, EMBASE, Medline, PEDro databases, forward and backward citations and grey literature studies through PROSPERO, clinical trials and data registries without language or date restrictions between inception and 1 December 2021. We selected randomised controlled trials (RCTs) based on adult populations with MTMD who had a cervical rehabilitation intervention which was defined as any conservative intervention targeting the anatomical structures of the cervical spine. The primary outcome measures for pain were self-reported pain intensity and pain sensitivity through the pressure pain threshold (PPT) of the masseter and temporalis muscles. Secondary outcome measures of maximal mouth opening (on MMO) were included. Included studies were assessed for bias with the Cochrane risk of bias tool for randomised trials. Evidence from RCTs was synthesised to determine treatment effect size as differences between standardised mean difference (SMD) for changes in pain intensity, PPT and MMO comparing adults with MTMD who were treated with cervical rehabilitation interventions compared to a control group. This study is registered on Prospero, number CRD 42021289299.

RESULTS

Our general search yielded 2647 studies where seven RCTs met eligibility criteria with low to some concerns in their risk of bias. Pain intensity (five studies, n = 223, SMD -0.98, 95% CI -1.67 to -0.28, I2 = 79%), PPT of the masseter muscle (six studies, n = 395, SMD 0.64, 95% CI 0.43 to 0.86, I2 = 90%) and the temporalis muscles (five studies, n = 295, SMD 0.76, 95% CI 0.07 to 1.45, I2 = 84%) showed large treatment effect estimates favouring cervical rehabilitation interventions compared to no treatment, sham cervical treatment, patient education or non-cervical neuromuscular techniques. Compared to control interventions, one type of cervical rehabilitation intervention, cervical manual therapy alone or in combination with a neck exercise program was associated with statistically significant, large treatment effect estimates on pain intensity (four studies, n = 203, SMD -1.52, 95% CI -2.50 to -0.55).

CONCLUSIONS

This review found that in the short-term, cervical rehabilitation interventions especially upper cervical MT alone or in combination with a neck exercise program are effective in improving multiple pain outcomes in adults with MTMD. However, further research is needed to measure the long-term effects of this type of intervention.

Cerebellar somatotopy of the trigemino-cervical complex during nociception

INTRODUCTION

The somatotopic organization of the human cerebellum processes somato-motoric input. Its role during pain perception for nociceptive input remains ambiguous. A standardized experimental trigeminal nociceptive input in functional imaging might clarify the role of the cerebellum in trigeminal nociception. Also of interest is the greater occipital nerve, which innervates the back of the head, and can influence the trigeminal perception due to functional coupling within the brainstem, forming the so-called trigemino-cervical complex.

METHODS

In our preregistered study (clinicaltrials.gov: NTC03999060), we stimulated the greater occipital as well as the three main branches of the trigeminal nerve during functional magnetic resonance imaging in two independent cohorts of young healthy volunteers without psychiatric, neurological or pain-related disorders to disentangle overlapping somatotopic cerebellar organization of the nerves innervating the human head.

RESULTS

We found a dominant effect of the first trigeminal branch in the cerebellum, underpinning its particular role for headache diseases, and somatotopic representations in bilateral cerebellar lobules I-IV, V, VIIb, VIIIa and Crus I as well as in the brainstem.

SIGNIFICANCE

The study expands the current knowledge on facial and head pain processing by the cerebellum and provides an initial somatotopic map of the trigemino-cervical complex in the human cerebellum with a predominant representation of the first trigeminal branch.

Functional representation of trigeminal nociceptive input in the human periaqueductal gray

The periaqueductal gray (PAG) is located in the mesencephalon in the upper brainstem and, as part of the descending pain modulation, is considered a crucial structure for pain control. Its modulatory effect on painful sensation is often seen as a systemic function affecting the whole body similarly. However, recent animal data suggest some kind of somatotopy in the PAG. This would make the PAG capable of dermatome-specific analgesic function. We electrically stimulated the three peripheral dermatomes of the trigemino-cervical complex and the greater occipital nerve in 61 humans during optimized brainstem functional magnetic resonance imaging. We provide evidence for a fine-grained and highly specific somatotopic representation of nociceptive input in the PAG in humans and a functional connectivity between the individual representations of the peripheral nerves in the PAG and the brainstem nuclei of these nerves. Our data suggest that the downstream antinociceptive properties of the PAG may be rather specific down to the level of individual dermatomes.

Occipital Nerve Stimulation for Recurrent Trigeminal Neuralgia Without Occipital Pain

OBJECTIVES

Trigeminal neuralgia (TN) is a severe, debilitating pain condition causing physical and emotional distress. Although the management of TN is well codified with medical and then surgical treatments, 15% to 30% of patients will experience intractable pain. Neuromodulation techniques have been scarcely used for refractory TN, with only small case series and short-term follow-up.

MATERIALS AND METHODS

We conducted a retrospective study of patients treated with occipital nerve stimulation (ONS) for medically and surgically resistant TN without painful trigeminal neuropathy. The effectiveness of the ONS was evaluated using the Barrow Neurological Institute (BNI) pain score and the pain relief (0%-100%) at best and at last follow-up.

RESULTS

Seven patients who have refractory TN were included. The mean age at ONS was 49 years. The mean pain duration was 8.6 years. The mean number of medical and surgical treatments before ONS was six and five, respectively. A percutaneous trial was performed in five of seven patients; all responded (pain relief > 40%), and four of five patients experienced pain recurrence after explantation. Eventually, six patients had a permanent ONS implantation. The average BNI pain score before implantation was V. The mean follow-up after implantation was 59 months. All patients reported an improvement after implantation. The average BNI score and mean pain relief at best were IIIa and 86.7%, respectively. At last follow-up, the average BNI score and mean pain relief were IIIa and 58.0%, respectively, with three patients experiencing pain recurrence. Adverse events were reported for four patients who required surgical revision for lead breakage (1), erosion (1), migration (1), or hardware-related discomfort (1). One patient finally underwent explantation because of infection.

CONCLUSIONS

Although ONS is not validated in this indication, these results suggest that it can induce an improvement in TN recurring after several surgical treatments, and the benefit of the stimulation can be sustained in the long term.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT01842763.

Utilizing directional preference in the management of cervicogenic headache: a case series

BACKGROUND/PURPOSE

Headaches are among the most common complaints requiring medical care, and annual expenditures for this condition are estimated to be 14 billion US dollars. The International Headache Society (IHS) describes cervicogenic headache (CGH) as a secondary type of headache emanating from the cervical spine which may be referred to one or more regions of the head and/or face. Mechanical Diagnosis and Therapy (MDT) is an approach shown to be effective in the management of spinal musculoskeletal disorders; however, there is limited evidence as to its efficacy in the management of CGH. The purpose of this case series was to examine the MDT approach in the assessment, classification, and management of a sample of patients experiencing cervicogenic headache.

CASE DESCRIPTION

This study was a prospective case series. Following IRB approval, 15 patients meeting the study inclusion criteria were recruited from a hospital-based outpatient physical therapy clinic. All subjects received a physical therapy examination by a Diploma trained MDT clinician which included but was not limited to patient self-report forms and the testing of repeated end range movements. The Numerical Pain Rating Scale (NPRS), Neck Disability Index (NDI), Headache Disability Index (HDI), Yellow Flag Risk Form (YFRF), Cervical Flexion Rotation Test (CFRT), and the Craniocervical Flexion Test (CCFT) were administered at the initial visit, 5th visit, and 10th visit or discharge, whichever occurred first. The NPRS, NDI, and HDI were re-administered at a 3 month follow up. Following the initial examination, patients were classified into the MDT categories of derangement, dysfunction, postural, or 'other' and then received intervention based on directional preference.

OUTCOMES

Fifteen subjects (mean age, 45.9 years; F = 11, M = 4; symptom duration, 44.3 months; average visits, 8.8) received an examination and intervention and completed follow-up outcome measures. Based on MDT classification criteria, all 15 subjects in this case series were classified as derangements. A non-parametric Friedman test of Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation differences among repeated measures was conducted on all outcome measures revealing statistically significant improvements in NPRS (p < .01), NDI(p < .01), and HDI (p < .01) scores at visit 10 and 3 month follow up. The mean change scores exceeded the minimal clinical important difference (MCID) for NPRS (4.2), NDI (7.6), and HDI (28.5). CCFT scores improved significantly from the initial examination to visit 5 (p < .01) and YFRF scores improved significantly between visits 5 and 10 (p < .01).

DISCUSSION/CONCLUSION

The diagnosis of CGH is difficult to determine based on pathoanatomical assessment. This case series suggests that the patient's response to repeated end range movements may indicate a directional preference for manual procedures and exercises which may be used in management of musculoskeletal conditions such as CGH.

Management of cluster headache: Treatments and their mechanisms

BACKGROUND

The management of cluster headache is similar to that of other primary headache disorders and can be broadly divided into acute and preventive treatments. Acute treatments for cluster headache are primarily delivered via rapid, non-oral routes (such as inhalation, nasal, or subcutaneous) while preventives include a variety of unrelated treatments such as corticosteroids, verapamil, and galcanezumab. Neuromodulation is becoming an increasingly popular option, both non-invasively such as vagus nerve stimulation when medical treatment is contraindicated or side effects are intolerable, and invasively such as occipital nerve stimulation when medical treatment is ineffective. Clinically, this collection of treatment types provides a range of options for the informed clinician. Scientifically, this collection provides important insights into disease mechanisms.

METHODS

Two authors performed independent narrative reviews of the literature on guideline recommendations, clinical trials, real-world data, and mechanistic studies.

RESULTS

Cluster headache is treated with acute treatments, bridge treatments, and preventive treatments. Common first-line treatments include subcutaneous sumatriptan and high-flow oxygen as acute treatments, corticosteroids (oral or suboccipital injections) as bridge treatments, and verapamil as a preventive treatment. Some newer acute (non-invasive vagus nerve stimulation) and preventive (galcanezumab) treatments have excellent clinical trial data for episodic cluster headache, while other newer treatments (occipital nerve stimulation) have been specifically tested in treatment-refractory chronic cluster headache. Most treatments are suspected to act on the trigeminovascular system, the autonomic system, or the hypothalamus.

CONCLUSIONS

The first-line treatments have not changed in recent years, but new treatments have provided additional options for patients.

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.

Additional effects of pain neuroscience education combined with physiotherapy on the headache frequency of adult patients with migraine: A randomized controlled trial

Aim To assess the efficacy of pain neuroscience education combined with physiotherapy for the management of migraine.Background Physiotherapy can significantly reduce the frequency of migraine, but the evidence is based only on a few studies. Pain neuroscience education might pose a promising treatment, as it addresses migraine as a chronic pain disease.Methods In this non-blinded randomized controlled trial, migraine patients received physiotherapy + pain neuroscience education or physiotherapy alone, preceded by a three-month waiting period. Primary outcomes were frequency of headache (with and without migraine features), frequency of migraine and associated disability.Results Eighty-two participants were randomized and analyzed. Both groups showed a decrease of headache frequency (p = 0.02, d = 0.46) at post-treatment (physiotherapy: 0.77 days, 95%CI: -0.75 to 2.29 and physiotherapy + pain neuroscience education: 1.25 days, 95%CI: -0.05 to 2.55) and at follow-up (physiotherapy: 1.93, 95%CI: 0.07 to 3.78 and physiotherapy + pain neuroscience education: 3.48 days, 95%CI: 1.89 to 5.06), with no difference between groups (p = 0.26, d = 0.26). Migraine frequency was reduced significantly in the physiotherapy + pain neuroscience education group, and not in the physiotherapy group, at post-treatment (1.28 days, 95%CI: 0.34 to 2.22, p = 0.004) and follow-up (3.05 days, 95%CI: 1.98 to 5.06, p < 0.0001), with a difference between groups at follow-up (2.06 days, p = 0.003). Migraine-related disability decreased significantly in both groups (physiotherapy: 19.8, physiotherapy + pain neuroscience education: 24.0 points, p < 0.001, d = 1.15) at follow-up, with no difference between groups (p = 0.583). Secondary outcomes demonstrated a significant effect of time with no interaction between time and group. No harm or adverse events were observed during the study.Conclusion In comparison to physiotherapy alone, pain neuroscience education combined with physiotherapy can further reduce the frequency of migraine, but had no additional effect on general headache frequency or migraine-related disability.Trial Registration The study was pre-registered at the German Clinical Trials Register (DRKS00020804).

Orofacial Migraine or Neurovascular Orofacial Pain from Pathogenesis to Treatment

The purpose of the present study is to examine possible differences between orofacial migraine (OFM) and neurovascular orofacial pain (NVOP). Facial presentations of primary headache are comparable to primary headache disorders; but occurring in the V2 or V3 dermatomes of the trigeminal nerve. These were classified and recently published in the International Classification of Orofacial Pain, 1st edition (ICOP). A category in this classification is "orofacial pains resembling presentations of primary headaches," which encompasses OFM and NVOP. The differences between NVOP and OFM are subtle, and their response to therapy may be similar. While classified under two separate entities, they contain many features in common, suggesting a possible overlap between the two. Consequently, their separation into two entities warrants further investigations. We describe OFM and NVOP, and their pathophysiology is discussed. The similarities and segregating clinical signs and symptoms are analyzed, and the possibility of unifying the two entities is debated.

Electroacupuncture alleviates orofacial allodynia and anxiety-like behaviors by regulating synaptic plasticity of the CA1 hippocampal region in a mouse model of trigeminal neuralgia

Objective

Trigeminal neuralgia (TN), one of the most severe and debilitating chronic pain conditions, is often accompanied by mood disorders, such as anxiety and depression. Electroacupuncture (EA) is a characteristic therapy of Traditional Chinese Medicine with analgesic and anxiolytic effects. This study aimed to investigate whether EA ameliorates abnormal TN orofacial pain and anxiety-like behavior by altering synaptic plasticity in the hippocampus CA1.

Materials and methods

A mouse infraorbital nerve transection model (pT-ION) of neuropathic pain was established, and EA or sham EA was used to treat ipsilateral acupuncture points (GV20-Baihui and ST7-Xiaguan). Golgi-Cox staining and transmission electron microscopy (TEM) were administrated to observe the changes of synaptic plasticity in the hippocampus CA1.

Results

Stable and persistent orofacial allodynia and anxiety-like behaviors induced by pT-ION were related to changes in hippocampal synaptic plasticity. Golgi stainings showed a decrease in the density of dendritic spines, especially mushroom-type dendritic spines, in hippocampal CA1 neurons of pT-ION mice. TEM results showed that the density of synapses, membrane thickness of the postsynaptic density, and length of the synaptic active zone were decreased, whereas the width of the synaptic cleft was increased in pT-ION mice. EA attenuated pT-ION-induced orofacial allodynia and anxiety-like behaviors and effectively reversed the abnormal changes in dendritic spines and synapse of the hippocampal CA1 region.

Conclusion

EA modulates synaptic plasticity of hippocampal CA1 neurons, thereby reducing abnormal orofacial pain and anxiety-like behavior. This provides evidence for a TN treatment strategy.

A Review of Current Perspectives on Facial Presentations of Primary Headaches

Orofacial pain (OFP) has recently been classified and subdivided into a number of groups, similar to headache disorders in the International Classification of Headache Disorders (ICHD). A novel group of OFP has been established whose major feature is that they resemble primary headache disorders occurring in the V2 or V3 dermatomes. These follow the clinical criteria and associated symptoms of the eponymous headache syndromes. Following the recent International Classification of Orofacial Pain (ICOP), three types are differentiated: Headache which spread into the face (type 1), facial pain which replaced headache but maintained the same characteristics and associated symptoms of the former headache (type 2), and de-novo orofacial pain that resembles primary headache types without any involvement of the ophthalmic trigeminal branch (type 3). The epidemiology is unclear: type 1 and 2 are not exactly common, they certainly exist in a notable proportion of headache patients, whereas type 3 may be rather rare. Since effective treatment options are available, it is important for clinicians to recognize such syndromes early to avoid misdiagnosis and unnecessary treatment, which most of these patients still experience. This review gives an up-to-date summary of diagnosis, pathophysiology and treatment of attack-like non-dental facial pain disorders.