Greater occipital nerve block modulates nociceptive signals within the trigeminocervical complex

Somatosensory Profiling of Patients With Cluster Headache: A Systematic Review and Meta-analysis

The objectives were 1) to synthesize quantitative sensory testing results in cluster headache (CH) patients and to identify somatosensory differences from healthy subjects (HS), and 2) between symptomatic and asymptomatic sides in CH patients. Two independent reviewers conducted a literature search in MEDLINE, EMBASE, Web of Science, and CINAHL databases. Studies with observational designs were included. Methodological quality and risk of bias were assessed with the Newcastle Ottawa Scale. The selected studies underwent qualitative and quantitative analyses. The qualitative analysis showed inconsistent findings among multiple studies. Meta-analysis showed lower pressure pain thresholds (PPTs) on the symptomatic side of CH patients than HS in V2 (standardized mean difference [SMD] -1.01 [95% confidence interval (CI) -1.79, -.23], P = .01, I2 = 73%, n = 114), V3 (SMD -1 [95% CI -1.54, .45], P < .01, I2 = 82%, n = 354), and cervical region (SMD -1.25 [95% CI -2.07, -.44], P < .01, I2 = 84%, n = 194). Furthermore, lower PPTs than those detected in HS were found on the asymptomatic side in V3 (SMD -.77 [95% CI -1.27, -.27], P < .01, I2 = 79%, n = 354) and in the cervical region (SMD -1.13 [95% CI -1.97, -.3], P < .01, I2 = 85%, n = 194). However, no differences were found in V1 or the extratrigeminal points between these groups. No significant changes were found between symptomatic and asymptomatic sides in trigeminal and extratrigeminal regions. Mechanical hyperalgesia in the trigemino-cervical region of patients with CH could suggest the presence of central pain mechanisms. These results are of clinical relevance because their presence could be associated with a poorer prognosis, chronification, and treatment response. PERSPECTIVE: This study provides consistent findings on the somatosensory profile characterizing patients with CH. Clinicians should assess PPTs and other quantitative sensory testing variables in the trigeminal and extratrigeminal (cervical) regions.

Recent advances in diagnosing, managing, and understanding the pathophysiology of cluster headache

Cluster headache, characterised by attacks of severe, recurrent, unilateral headache and ipsilateral cranial autonomic symptoms, remains a primary headache with an elusive pathophysiology. Recent advances have introduced effective treatments and broadened understanding of the clinical features of cluster headache. These features are similar in patients globally, but regional differences in prevalence and burden exist. International collaborations have led to identification of eight genetic loci associated with cluster headache. The pathophysiological mechanisms are still not fully understood but recent studies show that targeting the trigeminal autonomic reflex by neurostimulation, or targeting the neuropeptide calcitonin gene-related peptide (CGRP), might lessen the attack burden. The US Food and Drug Administration has approved galcanezumab, a monoclonal antibody targeting CGRP, as the first specific preventive treatment for episodic cluster headache. However, a preventive effect was not replicated in chronic cluster headache, and the European Medicines Agency did not approve galcanezumab, restricting its availability in Europe. Owing to the low prevalence of cluster headache, continued collaboration through multicentre clinical trials and data sharing will be imperative for further breakthroughs in understanding and management.

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.

Clinical predictors of therapeutic failure of occipital nerve stimulation in refractory chronic cluster headache

BACKGROUND

Occipital nerve stimulation (ONS) is a treatment with evidence in refractory chronic cluster headache (CCH). However, the variable response rate and cost make it necessary to investigate predictors of response.

METHODS

This is a cross-sectional study conducted through the review of medical records of CCH patients from six hospitals in Madrid. Epidemiological and clinical variables were compared between patients with ONS failure and the rest. ONS failure was defined as the need for device withdrawal or switch off because of lack of response or adverse events.

RESULTS

From a series of 88 CCH, 26 (29.6%) underwent ONS surgery, of whom 13/26 (50.0%) failed because lack of response. ONS failure group had an earlier headache onset (mean ± SD) of 27.7 ± 6.9 vs. 36.7 ± 11.8 years, p = 0.026) and a higher smoking rate (100% vs. 42.9%, p = 0.006). Stational fluctuations (58.3% vs. 7.7%, p = 0.007) and nocturnal exacerbations (91.7% vs. 53.9%, p = 0.035) were more frequent in the ONS failure group as well. There was no difference between groups in diagnostic delay, years of evolution prior to surgery, mental illness, comorbidity with other headache disorders or chronic pain conditions or prior response to occipital nerves anesthetic blocks.

CONCLUSIONS

Some clinical features such as an early debut, smoking and seasonal or circadian fluctuations could be related to failure of ONS in refractory CCH.

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.

Pharmacological Management of Orofacial Pain

Orofacial pain is a category of complex disorders, including musculoskeletal, neuropathic and neurovascular disorders, that greatly affect the quality of life of the patient. These disorders are within the fields of dentistry and medicine and management can be challenging, requiring a referral to an orofacial pain specialist, essential for adequate evaluation, diagnosis, and care. Management is specific to the diagnosis and a treatment plan is developed with diverse pharmacological and non-pharmacological modalities. The pharmacological management of orofacial pain encompasses a vast array of medication classes and approaches. This includes anti-inflammatory drugs, muscle relaxants, anticonvulsants, antidepressants, and anesthetics. In addition, as adjunct therapy, different injections can be integrated into the management plan depending on the diagnosis and needs. These include trigger point injections, temporomandibular joint (TMJ) injections, and neurotoxin injections with botulinum toxin and nerve blocks. Multidisciplinary management is key for optimal care. New and safer therapeutic targets exclusively for the management of orofacial pain disorders are needed to offer better care for this patient population.

Potential novel therapeutic strategies for neuropathic pain

Purpose

To explore the potential therapeutic strategies of different types of neuropathic pain (NP) and to summarize the cutting-edge novel approaches for NP treatment based on the clinical trials registered on ClinicalTrials.gov.

Methods

The relevant clinical trials were searched using ClinicalTrials.gov Dec 08, 2022. NP is defined as a painful condition caused by neurological lesions or diseases. All data were obtained and reviewed by the investigators to confirm whether they were related to the current topic.

Results

A total of 914 trials were included in this study. They were divided into painful diabetic neuropathy (PDN), postherpetic neuralgia (PHN), sciatica (SC), peripheral nerve injury-related NP (PNI), trigeminal neuralgia (TN), chemotherapy-induced NP (CINP), general peripheral NP (GPNP) and spinal cord injury NP (SCI-NP). Potential novel therapeutic strategies, such as novel drug targets and physical means, were discussed for each type of NP.

Conclusion

NP treatment is mainly dominated by drug therapy, and physical means have become increasingly popular. It is worth noting that novel drug targets, new implications of conventional medicine, and novel physical means can serve as promising strategies for the treatment of NP. However, more attention needs to be paid to the challenges of translating research findings into clinical practice.

From basic mechanisms to therapeutic perspectives in cluster headache

PURPOSE OF REVIEW

The pathophysiological understanding of cluster headache has evolved significantly over the past years. Although it is now well known that the trigeminovascular system, the parasympathetic system and the hypothalamus play important roles in its pathomechanism, we increasingly understand the functional role several neurotransmitters and hormones play in the communication between these structures.

RECENT FINDINGS

This work will give an overview of the current understanding of the role of calcitonin gene-related peptide, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, melatonin and orexins in cluster headache. On the basis of recent evidence, this study will also review the relevance of the monoclonal calcitonin gene-related peptide antibody galcanezumab as well as the sleep-regulating hormone melatonin in the treatment of cluster headache.

SUMMARY

Herein, we aim to review the basic mechanisms implicated in the pathophysiology of cluster headache and how the increased mechanistic understanding may lead to the discovery of novel therapeutic targets.

Occipital headache evaluation and rates of migraine assessment, diagnosis, and treatment in patients receiving greater occipital nerve blocks in an academic pain clinic

OBJECTIVE

Diagnosis of patients with occipital headache can be challenging, as both primary and secondary causes must be considered. Our study assessed how often migraine is screened for, diagnosed, and treated in patients receiving greater occipital nerve blocks (GONBs) in a pain clinic.

DESIGN

IRB-approved, retrospective observational study.

SETTING

Academic multidisciplinary pain clinic.

SUBJECTS

143 consecutive patients who received GONBs.

RESULTS

About 75% of patients had been evaluated by neurologists and about 25% by non-neurologist pain specialists only. 62.2% of patients had photophobia, phonophobia, and nausea assessed. Patients who had been evaluated by a neurologist were more likely to have photophobia, phonophobia, and nausea assessed (75.9% vs 20.0%, OR 12.6, 95% CI 4.90-32.2), more likely to be diagnosed with migraine (48.1% vs 14.3%, OR 5.6, 95% CI 2.0-15), less likely to be diagnosed with occipital neuralgia (39.8% vs 65.7%, OR 0.3, 95% CI 0.2-0.8), and equally likely to be diagnosed with cervicogenic headache (21.3% vs 25.7%, OR 0.8, 95% CI 0.3-1.9) than those evaluated by non-neurologists. Among patients diagnosed with migraine, 82.5% received acute migraine treatment, 89.5% received preventive migraine treatment, and 52.6% were documented as receiving migraine lifestyle counseling.

CONCLUSIONS

62.2% of patients with occipital headache receiving GONBs were assessed for migraine, and most received appropriate acute, preventive, and lifestyle treatments when diagnosed. Patients seen by neurologists were significantly more likely to be screened for, and diagnosed with, migraine than those evaluated by non-neurologist pain medicine specialists only. All clinicians should remain vigilant for migraine in patients with occipital headache.