Treatment of hemicrania continua by non-invasive vagus nerve stimulation in 2 patients previously treated with occipital nerve stimulation

Non-invasive neuromodulation of the cervical vagus nerve in rare primary headaches

Primary headache disorders can be remarkably disabling and the therapeutic options available are usually limited to medication with a high rate of adverse events. Here, we discuss the mechanism of action of non-invasive vagal nerve stimulation, as well as the findings of the main studies involving patients with primary headaches other than migraine or cluster headache, such as hemicrania continua, paroxysmal hemicrania, cough headache, or short-lasting neuralgiform headache attacks (SUNCT/SUNA), in a narrative analysis. A bibliographical search of low-prevalence disorders such as rare primary headaches retrieves a moderate number of studies, usually underpowered. Headache intensity, severity, and duration showed a clinically significant reduction in the majority, especially those involving indomethacin-responsive headaches. The lack of response of some patients with a similar diagnosis could be due to a different stimulation pattern, technique, or total dose. The use of non-invasive vagal nerve stimulation for the treatment of primary headache disorders represents an excellent option for patients with these debilitating and otherwise refractory conditions, or that cannot tolerate several lines of preventive medication, and should always be considered before contemplating invasive, non-reversible stimulation techniques.

Hemicrania Continua: An Update

Background

Hemicrania continua (HC) is not uncommon in clinical practice, and several large case series have been published in the recent past.

Objectives

This review provides an overview of the recent advancement in different aspects of HC.

Methods

We reviewed the articles published on HC in the last 2 decades.

Results

HC constitutes 1.7% of patients with headache in the clinics. It presents with unilateral continuous background pain with periodic exacerbations, usually accompanied by cranial autonomic features and restlessness. The continuous background headache is the most consistent and central feature of HC. Although the duration of exacerbations varies from a few seconds to a few weeks, the frequency ranges from >20 attacks/day to one attack in several months. The background pain is mild to moderate in intensity and does not hamper routine activity. Patients and physicians frequently ignore the basal pain, and a case of HC is misdiagnosed as other headaches, depending on the pattern of exacerbations. The exacerbation mimics several primary headaches and neuralgias. There are about 75 cases of secondary HC, due to 29 different pathologies. Although an absolute response to indomethacin is part of the diagnostic criteria, a subset of patients may respond to several other drugs. Headache reappears immediately on skipping a single dose of effective drug. Several surgical procedures have been tried in patients who are intolerant to indomethacin.

Conclusion

Misdiagnosis of HC is common. Continuous background pain and response to indomethacin are two essential features for the diagnosis of HC.

Therapeutic Approaches for the Management of Trigeminal Autonomic Cephalalgias

Trigeminal autonomic cephalalgia (TAC) encompasses 4 unique primary headache types: cluster headache, paroxysmal hemicrania, hemicrania continua, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing and short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms. They are grouped on the basis of their shared clinical features of unilateral headache of varying durations and ipsilateral cranial autonomic symptoms. The shared clinical features reflect the underlying activation of the trigeminal-autonomic reflex. The treatment for TACs has been limited and not specific to the underlying pathogenesis. There is a proportion of patients who are refractory or intolerant to the current standard medical treatment. From instrumental bench work research and neuroimaging studies, there are new therapeutic targets identified in TACs. Treatment has become more targeted and aimed towards the pathogenesis of the conditions. The therapeutic targets range from the macroscopic and structural level down to the molecular and receptor level. The structural targets for surgical and noninvasive neuromodulation include central neuromodulation targets: posterior hypothalamus and, high cervical nerves, and peripheral neuromodulation targets: occipital nerves, sphenopalatine ganglion, and vagus nerve. In this review, we will also discuss the neuropeptide and molecular targets, in particular, calcitonin gene-related peptide, somatostatin, transient receptor potential vanilloid-1 receptor, nitric oxide, melatonin, orexin, pituitary adenylate cyclase-activating polypeptide, and glutamate.

Non-invasive vagus nerve stimulation for the management of refractory primary chronic headaches: A real-world experience

Background

Non-invasive vagus nerve stimulation has initial evidence of efficacy in migraine and cluster headache. However, little is known about its role in the management of refractory chronic headaches.

Methods

We evaluated the preventive and abortive effects of non-invasive vagus nerve stimulation in 41 consecutive patients with refractory primary chronic headaches in an open-label prospective clinical audit. Headache diaries were used to collect clinical information. Those who obtained at least 30% reduction in headache days/episodes after three months of treatment were considered responders and were offered treatment continuation.

Results

Twenty-three patients with chronic migraine, 12 with chronic cluster headache, four with hemicrania continua and two with short-lasting unilateral neuralgiform headache attacks with autonomic symptoms (SUNA) were treated. Two of 23 chronic migraine patients, one of 12 chronic cluster headache patients, and two of four hemicrania continua patients were considered responders. None of the patients with SUNA benefited from the therapy. Two chronic migraine patients were able to reduce the pain severity of moderate migraines with non-invasive vagus nerve stimulation.

Conclusion

Non-invasive vagus nerve stimulation may not constitute an effective acute nor preventive treatment in refractory chronic primary headaches. The encouraging effect in hemicrania continua warrants further evaluation in larger studies.

The appropriate use of neurostimulation: stimulation of the intracranial and extracranial space and head for chronic pain. Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The International Neuromodulation Society (INS) has identified a need for evaluation and analysis of the practice of neurostimulation of the brain and extracranial nerves of the head to treat chronic pain.

METHODS

The INS board of directors chose an expert panel, the Neuromodulation Appropriateness Consensus Committee (NACC), to evaluate the peer-reviewed literature, current research, and clinical experience and to give guidance for the appropriate use of these methods. The literature searches involved key word searches in PubMed, EMBASE, and Google Scholar dated 1970-2013, which were graded and evaluated by the authors.

RESULTS

The NACC found that evidence supports extracranial stimulation for facial pain, migraine, and scalp pain but is limited for intracranial neuromodulation. High cervical spinal cord stimulation is an evolving option for facial pain. Intracranial neurostimulation may be an excellent option to treat diseases of the nervous system, such as tremor and Parkinson's disease, and in the future, potentially Alzheimer's disease and traumatic brain injury, but current use of intracranial stimulation for pain should be seen as investigational.

CONCLUSIONS

The NACC concludes that extracranial nerve stimulation should be considered in the algorithmic treatment of migraine and other disorders of the head. We should strive to perfect targets outside the cranium when treating pain, if at all possible.

Noninvasive vagus nerve stimulation as treatment for trigeminal allodynia

Implanted vagus nerve stimulation (VNS) has been used to treat seizures and depression. In this study, we explored the mechanism of action of noninvasive vagus nerve stimulation (nVNS) for the treatment of trigeminal allodynia. Rats were repeatedly infused with inflammatory mediators directly onto the dura, which led to chronic trigeminal allodynia. Administration of nVNS for 2 minutes decreased periorbital sensitivity in rats with periorbital trigeminal allodynia for up to 3.5 hours after stimulation. Using microdialysis, we quantified levels of extracellular neurotransmitters in the trigeminal nucleus caudalis (TNC). Allodynic rats showed a 7.7±0.9-fold increase in extracellular glutamate in the TNC after i.p. administration of the chemical headache trigger glyceryl trinitrate (GTN; 0.1 mg/kg). Allodynic rats that received nVNS had only a 2.3±0.4-fold increase in extracellular glutamate after GTN, similar to the response in control naive rats. When nVNS was delayed until 120 minutes after GTN treatment, the high levels of glutamate in the TNC were reversed after nVNS. The nVNS stimulation parameters used in this study did not produce significant changes in blood pressure or heart rate. These data suggest that nVNS may be used to treat trigeminal allodynia.