Neurostimulation in chronic cluster headache

Mechanism of Peripheral Nerve Stimulation in Chronic Pain

INTRODUCTION

With the advancement of technology, peripheral nerve stimulation (PNS) has been increasingly used to treat various chronic pain conditions. Its origin is based on the gate control theory postulated by Wall and Melzack in 1965. However, the exact mechanism behind PNS' analgesic effect is largely unknown. In this article, we performed a comprehensive literature review to overview the PNS mechanism of action.

DESIGN

A comprehensive literature review on the mechanism of PNS in chronic pain.

METHODS

Comprehensive review of the available literature on the mechanism of PNS in chronic pain. Data were derived from database searches of PubMed, Scopus, and the Cochrane Library and manual searches of bibliographies and known primary or review articles.

RESULTS

Animal, human, and imaging studies have demonstrated the peripheral and central analgesic mechanisms of PNS by modulating the inflammatory pathways, the autonomic nervous system, the endogenous pain inhibition pathways, and involvement of the cortical and subcortical areas.

CONCLUSIONS

Peripheral nerve stimulation exhibits its neuromodulatory effect both peripherally and centrally. Further understanding of the mechanism of PNS can help guide stimulation approaches and parameters to optimize the use of PNS.

Neurostimulation in cluster headache: A review of current progress

Purpose of review

Neurostimulation has emerged as a viable treatment for intractable chronic cluster headache. Several therapeutic strategies are being investigated including stimulation of the hypothalamus, occipital nerves and sphenopalatine ganglion. The aim of this review is to provide an overview of the rationale, methods and progress for each of these.

Latest findings

Results from a randomized, controlled trial investigating sphenopalatine ganglion stimulation have just been published. Reportedly the surgery is relatively simple and it is apparently the only therapy that provides relief acutely.

Summary

The rationale behind these therapies is based on growing evidence from clinical, hormonal and neuroimaging studies. The overall results are encouraging, but unfortunately not all patients have benefited. All the mentioned therapies require weeks to months of stimulation for a prophylactic effect to occur, suggesting brain plasticity as a possible mechanism, and only stimulation of the sphenopalatine ganglion has demonstrated an acute, abortive effect. Predictors of effect for all modes of neurostimulation still need to be identified and in the future, the least invasive and most effective strategy must be preferred as first-line therapy for intractable chronic cluster headache.

Long-term outcome in occipital nerve stimulation patients with medically intractable primary headache disorders

INTRODUCTION

€‚ Occipital nerve stimulation (ONS) may provide relief for refractory headache disorders. However, scant data exist regarding long-€term ONS outcomes.

METHODS

€‚ The methods used were retrospective review of the medical records of all (nonindustry study) patients who were trialed and implanted with occipital nerve stimulator systems at our institution, followed by a phone interview. Up to three attempts were made to contact each patient, and those who were contacted were given the opportunity to participate in a brief phone interview regarding their ONS experience. Data for analysis were gleaned from both the phone interview and the patient's medical records.

RESULTS

€‚ Twenty-nine patients underwent a trial of ONS during the 8.5-€year study period. Three patients did not go on to permanent implant, 12 could not be contacted, and 14 participated in the phone interview. Based upon the phone interview (if the patient was contacted) or chart review, ONS was deemed successful in five of the 12 migraine, four of the five cluster headache, and five of the eight miscellaneous headache patients, and therapy was documented as long as 102 months. In one of the 26 patients, success of ONS could not be determined. Among patients deemed to have successful outcomes, headache frequency decreased by 18%, severity by 27%, and migraine disability score by 50%. Fifty-€eight percent of patients required at least one lead revision.

DISCUSSION

€‚ These results, although limited by their retrospective nature, suggest that ONS can be effective long term despite technical challenges. The number of patients within each headache subtype was insufficient to draw conclusions regarding the differential effect of ONS.

CONCLUSIONS

€‚ Randomized controlled long-€term studies in specific, intractable, primary headache disorders are indicated.

Supraorbital transcutaneous neurostimulation has sedative effects in healthy subjects

Background

Transcutaneous neurostimulation (TNS) at extracephalic sites is a well known treatment of pain. Thanks to recent technical progress, the Cefaly^® device now also allows supraorbital TNS. During observational clinical studies, several patients reported decreased vigilance or even sleepiness during a session of supraorbital TNS. We decided therefore to explore in more detail the potential sedative effect of supraorbital TNS, using standardized psychophysical tests in healthy volunteers.

Methods

We performed a double-blind cross-over sham-controlled study on 30 healthy subjects. They underwent a series of 4 vigilance tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale, d2 test). Each subject was tested under 4 different experimental conditions: without the neurostimulation device, with sham supraorbital TNS, with low frequency supraorbital TNS and with high frequency supraorbital TNS.

Results

As judged by the results of three tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale) there was a statistically significant (p < 0.001) decrease in vigilance and attention during high frequency TNS, while there were no changes during the other experimental conditions. Similarly, performance on the d2 test was impaired during high frequency TNS, but this change was not statistically significant.

Conclusion

Supraorbital high frequency TNS applied with the Cefaly^® device decreases vigilance in healthy volunteers. Additional studies are needed to determine the duration of this effect, the underlying mechanisms and the possible relation with the stimulation parameters. Meanwhile, this effect opens interesting perspectives for the treatment of hyperarousal states and, possibly, insomnia.

Central modulation in cluster headache patients treated with occipital nerve stimulation: an FDG-PET study

BACKGROUND

Occipital nerve stimulation (ONS) has raised new hope for drug-resistant chronic cluster headache (drCCH), a devastating condition. However its mode of action remains elusive. Since the long delay to meaningful effect suggests that ONS induces slow neuromodulation, we have searched for changes in central pain-control areas using metabolic neuroimaging.

METHODS

Ten drCCH patients underwent an 18FDG-PET scan after ONS, at delays varying between 0 and 30 months. All were scanned with ongoing ONS (ON) and with the stimulator switched OFF.

RESULTS

After 6-30 months of ONS, 3 patients were pain free and 4 had a ≥ 90% reduction of attack frequency (responders). In all patients compared to controls, several areas of the pain matrix showed hypermetabolism: ipsilateral hypothalamus, midbrain and ipsilateral lower pons. All normalized after ONS, except for the hypothalamus. Switching the stimulator ON or OFF had little influence on brain glucose metabolism. The perigenual anterior cingulate cortex (PACC) was hyperactive in ONS responders compared to non-responders.

CONCLUSIONS

Metabolic normalization in the pain neuromatrix and lack of short-term changes induced by the stimulation might support the hypothesis that ONS acts in drCCH through slow neuromodulatory processes. Selective activation in responders of PACC, a pivotal structure in the endogenous opioid system, suggests that ONS could restore balance within dysfunctioning pain control centres. That ONS is nothing but a symptomatic treatment might be illustrated by the persistent hypothalamic hypermetabolism, which could explain why autonomic attacks may persist despite pain relief and why cluster attacks recur shortly after stimulator arrest. PET studies on larger samples are warranted to confirm these first results.

Neurostimulation approaches to primary headache disorders

PURPOSE OF REVIEW

Conventional management options in medically intractable chronic-headache syndromes, such as chronic migraine, chronic cluster headache and hemicrania continua, are often limited. This review summarizes the current concepts, approaches and outcome data of invasive device-based neurostimulation approaches using occipital-nerve stimulation and deep-brain stimulation.

RECENT FINDINGS

Recently, there has been considerable progress in neurostimulation approaches to medically intractable chronic-headache syndromes. Previous studies have analysed the safety and efficacy of suboccipital neurostimulation in drug-resistant chronic-headache syndromes such as in chronic migraine, chronic cluster headache and hemicrania continua. The studies suggest suboccipital neurostimulation can have an effect even decades after onset of headaches, thus representing a possible therapeutic option inpatients that do not respond to any medication. Similarly, to date over 50 patients with cluster headaches underwent hypothalamic deep-brain stimulation. From these, an average of 50-70% did show a significant positive response.

SUMMARY

These findings will help to further elucidate the clinical potential of neurostimulation in chronic headache.

Occipital nerve stimulation (ONS). Surgical technique and prevention of late electrode migration

Occipital nerve stimulation (ONS) is an emerging procedure for the treatment of cranio-facial pain syndromes and headaches refractory to conservative treatments. The aim of this report is to describe in detail the surgical intervention and to introduce some useful tricks that help to avoid late displacement and migration of the suboccipital leads. The careful description of the surgical steps may contribute to a standardization of the procedure and make the interpretation of results easier even if obtained in series of patients operated on by different authors.

Acute treatment of intractable migraine with sphenopalatine ganglion electrical stimulation

BACKGROUND

We report preliminary results of a novel acute treatment for intractable migraine. The sphenopalatine ganglion (SPG) has sensorimotor and autonomic components and is involved in migraine pathophysiology.

METHODS

In 11 patients with medically refractory migraine, the sphenopalatine fossa was accessed with a 20-gauge needle using the standard infrazygomatic transcoronoid approach under fluoroscopy. Patients underwent temporary unilateral electric stimulation of the SPG with a Medtronic 3057 test stimulation lead after induction of full-blown migraine. Both sham and active stimulations with different settings were carried out for < or =60 minutes, and then the lead was removed.

RESULTS

In 11 evaluations, 2 patients were pain-free within 3 minutes of stimulation. Three had pain reduction; 5 had no response; 1 was not stimulated. Five patients had no pain relief. Stimulation settings: mean amplitude of 1.2V, mean pulse rate of 67 Hz, mean pulse width of 462 micros. Lack of headache relief appeared linked to suboptimal lead placement, poor physiologic sensory response to localization stimulation, and diagnosis of medication overuse headache.

CONCLUSION

This study suggests a possible role for SPG stimulation in the treatment of refractory migraine headaches.