Efficacy of Erenumab in the Treatment of Trigeminal Neuralgia: A Retrospective Case Series

Chronic orofacial pain and pharmacological management-a clinical guide

Orofacial pain is a widespread health concern that significantly hinders an individual's capacity to engage in daily activities. This type of pain can be classified into three main categories: nociceptive pain, neuropathic pain, and nociplastic pain. Each category involves different mechanisms and requires specific treatment approaches. For optimal treatment of orofacial pain disorders, a multidisciplinary pain management approach is essential. This approach should integrate both nonpharmacological and pharmacological modalities to address the diverse underlying causes and manifestations of pain. In this review, we focus on the current evidence and advancements in the pharmacological management of chronic orofacial pain. We explored the effectiveness of different medications, their mechanisms of action, and their role within a comprehensive pain management plan.

Pathophysiology and Management of Refractory Trigeminal Neuralgia

PURPOSE OF REVIEW

Discuss the current understanding of the pathophysiology and management of refractory trigeminal neuralgia (TN). This includes a discussion on why TN can recur after microvascular decompression and a discussion on "outside of the box" options when both first- and second-line management strategies have been exhausted.

RECENT FINDINGS

This review discusses second- and third-line oral medication options, botulinum toxin A, repeat microvascular decompression, repeat ablative procedures, internal neurolysis, trigeminal branch blockade, and neuromodulation using TMS or peripheral stimulation. Additional management for chronic neuropathic facial pain such as deep brain stimulation, motor cortex stimulation, and focused ultrasound thalamotomy are also discussed, though evidence in trigeminal neuralgia is limited. Treatment of recurrent TN despite multiple surgeries can be challenging, and multiple minimally invasive and more invasive management options have been reported in small studies and case reports. Further studies are needed to determine an optimal stepwise approach.

An update on pharmacotherapy for trigeminal neuralgia

INTRODUCTION

Trigeminal neuralgia is a rare condition that can be effectively treated by carbamazepine or oxcarbazepine but these older drugs are associated with dose-dependent and potentially treatment-limiting adverse effects. Third-generation anticonvulsants, new calcitonin gene-related peptide blockers for migraine, and older drugs such as ketamine and cannabinoids may be promising adjuvants or monotherapeutic options.

AREAS COVERED

The new drugs, their presumed mechanisms of action, safety and efficacy are discussed herein. There is a paucity of robust clinical evidence in support of these drugs for trigeminal neuralgia. New migraine agents are considered as well although migraines and trigeminal neuralgia are distinct, albeit similar, conditions. No new drugs have been released to market in recent years with the specific indication of trigeminal neuralgia.

EXPERT OPINION

In real-world clinical practice, about half of trigeminal neuralgia patients take more than one agent for prevention and combination therapy may be the optimal approach. Combination therapy might allow for lower doses of carbamazepine or oxcarbazepine, thus reducing the number and severity of potential adverse events but the potential for pharmacokinetic drug-drug interactions must be considered. Drug therapy for trigeminal neuralgia involves acute or abortive treatments, often administered in hospital versus long-term preventive therapy, usually involving oral agents.

Trigeminal neuralgia

Trigeminal neuralgia (TN) is a facial pain disorder characterized by intense and paroxysmal pain that profoundly affects quality of life and presents complex challenges in diagnosis and treatment. TN can be categorized as classical, secondary and idiopathic. Epidemiological studies show variable incidence rates and an increased prevalence in women and in the elderly, with familial cases suggesting genetic factors. The pathophysiology of TN is multifactorial and involves genetic predisposition, anatomical changes, and neurophysiological factors, leading to hyperexcitable neuronal states, central sensitization and widespread neural plasticity changes. Neurovascular compression of the trigeminal root, which undergoes major morphological changes, and focal demyelination of primary trigeminal afferents are key aetiological factors in TN. Structural and functional brain imaging studies in patients with TN demonstrated abnormalities in brain regions responsible for pain modulation and emotional processing of pain. Treatment of TN involves a multifaceted approach that considers patient-specific factors, including the type of TN, with initial pharmacotherapy followed by surgical options if necessary. First-line pharmacological treatments include carbamazepine and oxcarbazepine. Surgical interventions, including microvascular decompression and percutaneous neuroablative procedures, can be considered at an early stage if pharmacotherapy is not sufficient for pain control or has intolerable adverse effects or contraindications.

Cranial Neuralgias

OBJECTIVE

The cranial neuralgias are relatively rare, but recognizing these syndromes and distinguishing among them is critical to reducing unnecessary pain and disability for affected patients. Despite their distinctive features, cranial neuralgias may go undiagnosed or misdiagnosed for several years. A notable proportion of cranial neuralgia presentations are due to secondary causes and require targeted treatment. The purpose of this article is to review the diagnosis and management of cranial neuralgias encountered in clinical practice.

LATEST DEVELOPMENTS

In 2020, the International Classification of Orofacial Pain was released for the first time. Modeled after the International Classification of Headache Disorders, it includes updated terminology for cranial neuralgias. The underlying pathophysiology of the cranial neuralgias is currently believed to be rooted in both peripheral and central nociceptive systems. In addition, a growing number of familial cases are being identified. Recent therapeutic advancements include a better understanding of how to utilize older therapies and procedures more effectively as well as the development of newer approaches.

ESSENTIAL POINTS

Cranial neuralgia syndromes are rare but important to recognize due to their debilitating nature and greater likelihood of having potentially treatable underlying causes. While management options have remained somewhat limited, scientific inquiry is continually advancing the understanding of these syndromes and how best to address them.

Neuropathic pain; what we know and what we should do about it

Neuropathic pain can result from injury to, or disease of the nervous system. It is notoriously difficult to treat. Peripheral nerve injury promotes Schwann cell activation and invasion of immunocompetent cells into the site of injury, spinal cord and higher sensory structures such as thalamus and cingulate and sensory cortices. Various cytokines, chemokines, growth factors, monoamines and neuropeptides effect two-way signalling between neurons, glia and immune cells. This promotes sustained hyperexcitability and spontaneous activity in primary afferents that is crucial for onset and persistence of pain as well as misprocessing of sensory information in the spinal cord and supraspinal structures. Much of the current understanding of pain aetiology and identification of drug targets derives from studies of the consequences of peripheral nerve injury in rodent models. Although a vast amount of information has been forthcoming, the translation of this information into the clinical arena has been minimal. Few, if any, major therapeutic approaches have appeared since the mid 1990's. This may reflect failure to recognise differences in pain processing in males vs. females, differences in cellular responses to different types of injury and differences in pain processing in humans vs. animals. Basic science and clinical approaches which seek to bridge this knowledge gap include better assessment of pain in animal models, use of pain models which better emulate human disease, and stratification of human pain phenotypes according to quantitative assessment of signs and symptoms of disease. This can lead to more personalized and effective treatments for individual patients. Significance statement: There is an urgent need to find new treatments for neuropathic pain. Although classical animal models have revealed essential features of pain aetiology such as peripheral and central sensitization and some of the molecular and cellular mechanisms involved, they do not adequately model the multiplicity of disease states or injuries that may bring forth neuropathic pain in the clinic. This review seeks to integrate information from the multiplicity of disciplines that seek to understand neuropathic pain; including immunology, cell biology, electrophysiology and biophysics, anatomy, cell biology, neurology, molecular biology, pharmacology and behavioral science. Beyond this, it underlines ongoing refinements in basic science and clinical practice that will engender improved approaches to pain management.

Ten open questions in migraine prophylaxis with monoclonal antibodies blocking the calcitonin-gene related peptide pathway: a narrative review

The monoclonal antibodies (mAbs) blocking the calcitonin-gene related peptide (CGRP) pathway, collectively called here "anti-CGRP/rec mAbs", have dramatically improved preventive migraine treatment. Although their efficacy and tolerability were proven in a number of randomized controlled trials (RCTs) and, maybe even more convincingly, in real world settings, a number of open questions remain. In this narrative review, we will analyze published data allowing insight in some of the uncertainties related to the use of anti-CGRP/rec mAbs in clinical practice: their differential efficacy in migraine subtypes, outcome predictors, switching between molecules, use in children and adolescents, long-term treatment adherence and persistence, effect persistence after discontinuation, combined treatment with botulinum toxin or gepants, added-value and cost effectiveness, effectiveness in other headache types, and potential contraindications based on known physiological effects of CGRP. While recent studies have already provided hints for some of these questions, many of them will not find reliable and definitive answers before larger studies, registries or dedicated RCTs are available.

Maresin-2 inhibits inflammatory and neuropathic trigeminal pain and reduces neuronal activation in the trigeminal ganglion

Pain is a common symptom associated with disorders involving the orofacial structures. Most acute orofacial painful conditions are easily recognized, but the pharmacological treatment may be limited by the adverse events of current available drugs and/or patients' characteristics. In addition, chronic orofacial pain conditions represent clinical challenges both, in terms of diagnostic and treatment. There is growing evidence that specialized pro-resolution lipid mediators (SPMs) present potent analgesic effects, in addition to their well characterized role in the resolution of inflammation. Maresins (MaR-1 and MaR-2) were the last described members of this family, and MaR-2 analgesic action has not yet been reported. Herein the effect of MaR-2 in different orofacial pain models was investigated. MaR-2 (1 or 10 ng) was always delivered via medullary subarachnoid injection, which corresponds to the intrathecal treatment. A single injection of MaR-2 caused a significant reduction of phases I and II of the orofacial formalin test in rats. Repeated injections of MaR-2 prevented the development of facial heat and mechanical hyperalgesia in a model of post-operative pain in rats. In a model of trigeminal neuropathic pain (CCI-ION), repeated MaR-2 injections reversed facial heat and mechanical hyperalgesia in rats and mice. CCI-ION increased c-Fos positive neurons and CGRP⁺ activated (nuclear pNFkB) neurons in the trigeminal ganglion (TG), which were restored to sham levels by MaR-2 repeated treatment. In conclusion, MaR-2 showed potent and long-lasting analgesic effects in inflammatory and neuropathic pain of orofacial origin and the inhibition of CGRP-positive neurons in the TG may account for MaR-2 action.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

Erenumab in the Treatment of Comorbid Trigeminal Neuralgia in Patients With Migraine

Background Surgical treatment for trigeminal neuralgia (TN) sometimes becomes difficult. Erenumab, an anti-calcitonin gene-related peptide (CGRP)-receptor monoclonal antibody, is used for migraine and potentially has efficacy for TN. Method We retrospectively investigated six migraine patients with comorbidity treated with 70 mg of erenumab. Monthly headache days and a numerical rating scale (NRS) of TN were evaluated before, one, and three months after erenumab administration. Results Before being treated with 70 mg of erenumab, the six migraine patients with comorbid TN had taken at least one sort of preventative medication, but it had been ineffective. During the three-month erenumab use, previous medications were continued. The median age was 71 years (range 59-87). The six patients (five females and one male) had episodic migraine. Three had TN due to vessels, one had TN due to a tumor, one had TN without neurovascular compression, and one had an undetermined etiology. Five (83%) of the six patients reported improved NRS of TN. The median NRS of TN before, one, and three months after treatment were 8 (7-10), 3.5 (0-10), and 2 (0-5, n=4). Monthly headache days were 4 (4-10), 2.5 (0-4), and 1 (1-2, n=4). There were no side effects of erenumab. Conclusion Surgical treatment sometimes cannot be performed for those with TN. Our findings were preliminary and a bigger sample size is required for this study to draw firmer conclusions. However, it is possible, although rare, that there are migraine patients for whom the NRS of comorbid TN improves with the use of erenumab, an anti-CGRP receptor monoclonal antibody.

Safety and efficacy of erenumab in patients with trigeminal neuralgia in Denmark: a double-blind, randomised, placebo-controlled, proof-of-concept study

BACKGROUND

Trigeminal neuralgia is a severe facial pain disorder that is difficult to treat. Erenumab, a monoclonal antibody against the calcitonin gene-related peptide (CGRP) receptor, has proven efficacy in migraine. Erenumab modulates sensory processing in peripheral trigeminal pain pathways in mice and was reported to be effective for patients with trigeminal neuralgia in open-label studies. We aimed to evaluate the efficacy of erenumab in patients with trigeminal neuralgia.

METHODS

We did a randomised, double-blind, placebo-controlled trial in adults (aged 18-85 years) with idiopathic or classic trigeminal neuralgia as defined by the 3rd edition of the International Classification of Headache Disorders. The trial was based at the Danish Headache Center, Copenhagen University Hospital. Eligible participants had no clinically significant cerebrovascular or cardiovascular disease, had self-reported pain intensity of at least 4 on the 11-point Numeric Rating Scale (0=no pain, 10=worst pain imaginable), and had at least three daily pain paroxysms. After a 1-week pre-screening period, patients entered a 4-week baseline period. Participants who met pain inclusion criteria at the end of the baseline period were randomly assigned (1:1) to receive subcutaneous injections of either erenumab 140 mg or placebo and entered the 4-week follow-up period. Randomisation was done in blocks of 10 using a computer-generated schedule by a third-party company. Participants and assessors were masked to treatment allocation, and erenumab and placebo were packed in identical prefilled syringes. The primary outcome was the number of responders, defined as patients who had a reduction of at least 30% in mean average daily pain intensity during the follow-up period compared with during the baseline period, analysed in the intention-to-treat population. This trial is registered with the European Union Drug Regulating Authorities Clinical Trials Database, EudraCT number 2019-000848-95.

FINDINGS

We assessed 860 patients for suitability and excluded 741 between Oct 28, 2019, and Sept 13, 2021. 119 participants entered a 1-week pre-screening period and 26 were excluded, 93 participants entered a 4-week baseline period with 13 excluded before randomisation, and 80 participants were randomly assigned to erenumab 140 mg (n=40) or placebo (n=40). There was no difference between groups in the number of responders at 4 weeks in the intention-to-treat population (14 [35%] of 40 with erenumab vs 18 [45%] of 40 with placebo; estimated effect size -10% [95% CI -31 to 11]; p=0·36). 20 (50%) of 40 participants reported adverse events in each group. The most common adverse events were constipation (28%) and headache (10%) in the erenumab group, and headache (13%), constipation (10%), and abdominal pain (10%) in the placebo group.

INTERPRETATION

Erenumab did not reduce pain intensity compared with placebo in patients with trigeminal neuralgia and CGRP probably does not have an important role in paroxysmal pain. Well tolerated, effective treatments in trigeminal neuralgia are still needed.

FUNDING

Novartis.

Fremanezumab Improved Migraine and Headache Attributed to Glioblastoma

Fremanezumab, one of the anti-calcitonin gene-related peptide monoclonal antibodies, is widely used for migraine prophylaxis. However, its efficacy for headache attributed to glioblastoma has not been reported. We herein report a 66-year-old man who had right temporoparietal glioblastoma which recurred despite surgical and chemo-radiological treatment. He had migraine and headache attributed to glioblastoma, but fremanezumab improved both of them. Our case suggested that fremanezumab's possible efficacy for not only migraine but also headache attributed to intracranial neoplasia.