Occipital nerve stimulation in primary headache syndromes

An Open-Source 3D-Printed Hindlimb Stabilization Apparatus for Reliable Measurement of Stimulation-Evoked Ankle Flexion in Rat

Currently there are numerous methods to evaluate peripheral nerve stimulation interfaces in rats, with stimulation-evoked ankle torque being one of the most prominent. Commercial rat ankle torque measurement systems and custom one-off solutions have been published in the literature. However, commercial systems are proprietary and costly and do not allow for customization. One-off lab-built systems have required specialized machining expertise, and building plans have previously not been made easily accessible. Here, detailed building plans are provided for a low-cost, open-source, and basic ankle torque measurement system from which additional customization can be made. A hindlimb stabilization apparatus was developed to secure and stabilize a rat's hindlimb, while allowing for simultaneous ankle-isometric torque and lower limb muscle electromyography (EMG). The design was composed mainly of adjustable 3D-printed components to accommodate anatomical differences between rat hindlimbs. Additionally, construction and calibration procedures of the rat hindlimb stabilization apparatus were demonstrated in this study. In vivo torque measurements were reliably acquired and corresponded to increasing stimulation amplitudes. Furthermore, implanted leads used for intramuscular EMG recordings complemented torque measurements and were used as an additional functional measurement in evaluating the performance of a peripheral nerve stimulation interface. In conclusion, an open-source and noninvasive platform, made primarily with 3D-printed components, was constructed for reliable data acquisition of evoked motor activity in rat models. The purpose of this apparatus is to provide researchers a versatile system with adjustable components that can be tailored to meet user-defined experimental requirements when evaluating motor function of the rat hindlimbs.

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.

Implantable Subcutaneous Peripheral Nerve Stimulation Improves Degenerative Ataxia

Degenerative cerebellar ataxias have no pharmacological or rehabilitation evidence-based treatment so far. Patients remain highly symptomatic and disabled despite receiving the best medical treatment available. This study investigates the clinical and neurophysiologic outcomes of the use of subcutaneous cortex stimulation (in keeping with the established protocol of peripheral nerve stimulation applied in chronic intractable pain) in degenerative ataxia. We report a case of a 37-year-old right-handed man who developed moderate degenerative cerebellar ataxia at the age of 18 years. His symptoms progressively worsened and impaired his daily activities. We observed clinical improvement for at least one month following an initial two-week trial of parietal transcranial direct current stimulation. Although preoperative non-invasive transcranial neuromodulation application does not predict invasive cortex stimulation outcome, we pursued a long-lasting effect by implanting parietal and occipital subcutaneous electrodes. At 12 months following permanent implantation, the patient exhibited amelioration of his symptoms and a change in neurophysiologic parameters. Central neuromodulation based on peripheral stimulation is considered part of neurosurgical clinical practice for the treatment of a variety of neurological disorders. The underpinning neurophysiological mechanism that explains the effectiveness of the method has not been fully elucidated. We believe that further studies are warranted to investigate these promising results in such devastating conditions.

Updated management of occipital nerve stimulator lead migration: case report of a technical challenge

Electrode migration is a challenge, even with adequate anchoring techniques, due to the high mechanical stress on components of occipital nerve stimulation (ONS) for headache disorders. When a lead displacement of an ONS implant is diagnosed, there are currently different approaches described for its management. Nevertheless current neuromodulation devices are designed like a continuum of components without any intermediate connector, and if a lead displacement is diagnosed, the solution is the complete removal of the electrode from its placement, and its repositioning through an ex-novo procedure. The described technique can allow ONS leads to be revised while minimizing the need to reopen incisions over the IPG, thus improving patients' intraoperative and postoperative discomfort, shortening surgical time and medical costs, reasonably reducing the incidence of infective postoperative complications.

Explant rates of electrical neuromodulation devices in 1177 patients in a single center over an 11-year period

Introduction

The publication of explant rates has established risk factors and a definitive objective outcome of failure for spinal cord stimulation (SCS) treating neuropathic pain. We present a UK study analyzing explants of electrical neuromodulation devices for different conditions over 11 years in a single center specializing in neuromodulation.

Methods

A retrospective analysis was performed using a departmental database between 2008 and 2019. Explants were analyzed according to condition, mode of stimulation and other demographics using logistic regression and Kaplan-Meier graphs with log-rank (Mantel-Cox) test.

Results

Out of a total of 1177 patients, the explant rate was 17.8% at 5 years and 25.2% at 10 years. Loss of efficacy was the most frequent reason for explant 119/181 (65%). Multivariant regression analysis indicated patients with back pain without prior surgery had a reduced risk of explant (p=0.03). Patients with SCS systems that had 10 kHz, options of multiple waveforms, and rechargeable batteries also had a decreased risk of explant (p<0.001). None of these findings were confirmed when comparing Kaplan-Meier graphs, however. Contrary to other studies, we found gender and age were not independent variables for explant.

Conclusion

These data contribute to a growing list of explant data in the scientific literature and give indications of what factors contribute to long-term utilization of electrical neuromodulation devices.

[Peripheral neurostimulation in headache treatment]

According to rough estimates, at least one third of the population in developed countries suffers, to varying degrees, from certain forms of primary headache, the modern pharmacotherapy of which is not always effective and has a number of limitations. The non-pharmacological treatment of headache can be an alternative to the prescription of pharmacological agents and the only possible assistance option for patients developing drug-resistant cephalalgias. This review describes various methods of electrical neuromodulation that are used for the management of primary headaches. The authors provide information on current stages in implementation of implantable and non-invasive equipment into clinical practice, which makes possible electrical stimulations of peripheral nerves and of the sphenopalatine ganglion, as well as allows transcranial magnetic stimulation. Also the appearance and usage of portable electrical devices available on the world market are described, and mechanisms that can underlie anticephalgic action of neuromodulation therapy are discussed. Special attention is paid to the methods that are applied for electrostimulation of the vagus nerve and occipital nerves.

Rationale for electrical parameter determination in external trigeminal nerve stimulation (eTNS) for migraine: A narrative review

Background

Migraine is a primary headache disorder involving dysregulation of central and peripheral pain pathways. Medical treatment is often limited by drug side effects, comorbidities and poor compliance. This makes neuromodulation an ideal option for migraine treatment. Cefaly® is a transcutaneous electrical neurostimulator designed specifically for migraine treatment. It results in external trigeminal nerve stimulation of the supraorbital and supratrochlear nerves. External trigeminal nerve stimulation is effective for acute and preventive migraine treatment and may result in normalization of dysregulated pain pathways.

Objective

Our objective was to provide a narrative review of the neuroanatomical and pathophysiological basis of external trigeminal nerve stimulation for migraine treatment and to provide the rationale behind the choice of the electrical parameters used for external trigeminal nerve stimulation.

Methods

We reviewed external trigeminal nerve stimulation clinical trial publications, basic science neurostimulation literature, publications describing pathophysiological mechanisms in migraine, and documentation used in the application for the Food and Drug Administration approval of external trigeminal nerve stimulation.

Results

The electrical parameters used for external trigeminal nerve stimulation were chosen to maximize safety and efficacy. Critical parameters include generator characteristics, pulse shape, pulse duration, pulse frequency and session duration and frequency. We explain the rationale behind determination of each parameter. There is evidence of dysregulated central and peripheral pathways in migraine and evidence that external trigeminal nerve stimulation may normalize function of these pathways.

Conclusion

External trigeminal nerve stimulation is a safe and effective Food and Drug Administration-approved option for the acute and preventive treatment of migraine. The electrical parameters were optimized specifically for external stimulation of the trigeminal nerve to maximum safety, comfort and efficacy.

Occipital Nerve Stimulation Attenuates Neuronal Firing Response to Mechanical Stimuli in the Ventral Posteromedial Thalamus of a Rodent Model of Chronic Migraine

BACKGROUND

Chronic migraine (CM) is a highly debilitating disease, and many patients remain refractory to medicinal therapy. Given the convergent nature of neuronal networks in the ventral posteromedial nucleus (VPM) and the evidence of sensitization of pain circuitry in this disease, we hypothesize CM rats will have increased VPM neuronal firing, which can be attenuated using occipital nerve stimulation (ONS).

OBJECTIVE

To determine whether VPM firing frequency differs between CM and sham rats, and whether ONS significantly alters firing rates during the application of mechanical stimuli.

METHODS

Fourteen male Sprague-Dawley rats were infused with inflammatory media once daily through an epidural cannula for 2 wk to induce a CM state. Sham animals (n = 6) underwent cannula surgery but received no inflammatory media. ONS electrodes were implanted bilaterally and single-unit recordings were performed in the VPM of anesthetized rats during mechanical stimulation of the face and forepaw in the presence and absence of ONS.

RESULTS

CM rats had significantly higher neuronal firing rates (P < .001) and bursting activity (P < .01) in response to mechanical stimuli when compared to shams. ONS significantly reduced neuronal firing in the VPM of CM rats during the application of 0.8 g (P = .04), 4.0 g (P = .04), and 15.0 g (P = .02) Von Frey filaments. ONS reduced bursting activity in CM rats during the 4.0 and 15 g filaments (P < .05). No significant changes in bursting activity or firing frequency were noted in sham animals during ONS.

CONCLUSION

We demonstrate that neuronal spike frequencies and bursting activity in the VPM are increased in an animal model of CM compared to shams. Our results suggest that the mechanism of ONS may involve attenuation of neurons in the VPM of CM rats during the application of mechanical stimuli.

Inhibitory effect of high-frequency greater occipital nerve electrical stimulation on trigeminovascular nociceptive processing in rats

Electrical stimulation of the greater occipital nerve (GON) has recently shown promise as an effective non-pharmacological prophylactic therapy for drug-resistant chronic primary headaches, but the neurobiological mechanisms underlying its anticephalgic action are not elucidated. Considering that the spinal trigeminal nucleus (STN) is a key segmental structure playing a prominent role in pathophysiology of headaches, in the present study we evaluated the effects of GON electrical stimulation on ongoing and evoked firing of the dura-sensitive STN neurons. The experiments were carried out on urethane/chloralose-anesthetized, paralyzed and artificially ventilated male Wistar rats. Extracellular recordings were made from 11 neurons within the caudal part of the STN that received convergent input from the ipsilateral facial cutaneous receptive fields, dura mater and GON. In each experiment, five various combinations of the GON stimulation frequency (50, 75, 100 Hz) and intensity (1, 3, 6 V) were tested successively in 10 min interval. At all parameter sets, preconditioning GON stimulation (250 ms train of pulses applied before each recording) produced suppression of both the ongoing activity of the STN neurons and their responses to electrical stimulation of the dura mater. The inhibitory effect depended mostly on the GON stimulation intensity, being maximally pronounced when a stimulus of 6 V was applied. Thus, the GON stimulation-induced inhibition of trigeminovascular nociceptive processing at the level of STN has been demonstrated for the first time. The data obtained can contribute to a deeper understanding of neurophysiological mechanisms underlying the therapeutic efficacy of GON stimulation in primary headaches.

Treatment of Allodynia by Occipital Nerve Stimulation in Chronic Migraine Rodent

BACKGROUND

Occipital nerve stimulation (ONS) is a therapy that benefits one-third of medically refractory chronic migraine (CM) patients. How ONS affects sensory thresholds and whether modulation of thresholds could predict which patients respond to the therapy remains unclear.

OBJECTIVE

To examine the effects of ONS on mechanical and thermal thresholds in a rodent CM model to better elucidate its mechanism of action.

METHODS

Male Sprague-Dawley rats were implanted bilaterally with electrodes to produce ONS. The CM cohort was infused with inflammatory media epidurally based on a validated model, whereas shams were not. Thresholds were evaluated with von Frey filaments and hot plate and thermode tests.

RESULTS

No baseline differences in sensory thresholds were found between the sham (n = 16) and CM (n = 16) groups. After headache induction, CM animals demonstrated mechanical allodynia in the occiput, periorbital region, forepaws, and hind paws (P < .05). In CM animals, ONS increased mechanical thresholds in all regions (P < .001), whereas in shams, it did not. ONS did not affect thermal thresholds in either group.

CONCLUSION

We show that ONS improves mechanical thresholds in a rodent CM model, but not in shams. Our finding that mechanical but not thermal thresholds are altered with ONS suggests a more significant modulation of A-α/β fibers than of C fibers. Assessing the ability of ONS to reduce mechanical thresholds during a trial period could potentially be used to predict which patients respond.

Percutaneous nerve field stimulation (PENS) of the occipital region as a possible predictor for occipital nerve stimulation (ONS) responsiveness in refractory headache disorders? A feasibility study

Background

Occipital nerve stimulation (ONS) has been reported to diminish pain levels in intractable chronic headache syndromes of different origin. No reliable objective markers exist to predict ONS responsiveness. This study investigated the predictive value of occipital percutaneous nerve field stimulation (PENS) prior to ONS.

Methods

This trial included 12 patients (CCH, CM, PTH, CH) with chronic refractory headache syndromes eligible for ONS. Repetitive PENS (3 × /10 days) was performed and the headache severity/frequency monitored over four weeks before ONS implantation. Further assessment of PENS/ONS outcomes were stimulation-related complications, perception/tolerance stimulation threshold, the Migraine Disability Scale (MIDAS) and the Beck Depression Inventory (BDI).

Results

All PENS responders benefited from ONS. Of the seven PENS-nonresponders with VAS 6.1(±1.1), six experienced significant pain relief from ONS after three months and one patient failed the PENS/ONS trial (VAS 3.7 (±1.6)); (95% CI 3.6 to 5.7, p < 0.001). The VAS baseline was 8.4 (±0.5) and decreased significantly (50% reduction in severity/frequency) in five patients after PENS, while seven failed to improve (VAS 4.9 (±1.1); (95% CI 2.5 to 4.5, p < 0.001). BDI baseline (from 22.6 (±4.2) to 10.6 (±5.9) (95% CI 7.4 to 16.6, p < 0.001)) and MIDAS baseline (from 143.9 (±14.5) to 72.8 (±28.7) (95% CI 1.17 to 2.3, p < 0.001)) significantly declined after ONS. No PENS/ONS-related complications occurred.

Conclusions

Presurgical applied occipital PENS failed to identify ONS responders sufficiently according to our study protocol, thus requiring further specific investigations to determine its predictive usefulness.

Treatment of hemicrania continua with radiofrequency ablation and long-term follow-up

OBJECTIVE

The objective of this research is to describe novel procedural treatments for hemicrania continua that allow patients to remain off indomethacin.

METHODS

Case reports are presented.

RESULTS

We describe four distinct patients with indomethacin-responsive hemicrania continua who were unable to discontinue the use of indomethacin without headache recurrence. No other medications were effective for their syndrome. Secondary causes of headache were ruled out in each case. Each patient underwent diagnostic blockade of either the atlanto-axial joint, C2 dorsal root ganglion or sphenopalantine ganglion depending on their clinical examination and presence of cranial autonomic symptoms. A positive response led to a radiofrequency ablation of the C2 ventral ramus, C2 dorsal root ganglion or sphenopalantine ganglion, which provided headache relief in all case patients as complete as indomethacin. Long-term follow-up of these patients has shown that all have remained essentially headache free without the need for indomethacin. One patient has needed repeat radiofrequency procedures with consistent response.

CONCLUSION

Hemicrania continua is defined by its sensitivity to indomethacin but very few patients are able to discontinue the medication without headache recurrence. As the risks of chronic indomethacin use are substantial, alternative treatments are necessary to protect patient health. We are now able to suggest several radiofrequency ablation procedures as effective as indomethacin with long-term follow-up.

Occipital nerve stimulation

Occipital nerve stimulation (ONS) is a form of neuromodulation therapy aimed at treating intractable headache and craniofacial pain. The therapy utilizes neurostimulating electrodes placed subcutaneously in the occipital region and connected to a permanently implanted programmable pulse generator identical to those used for dorsal column/spinal cord stimulation. The presumed mechanisms of action involve modulation of the trigeminocervical complex, as well as closure of the physiologic pain gate. ONS is a reversible, nondestructive therapy, which can be tailored to a patient's individual needs. Typically, candidates for successful ONS include those patients with migraines, Chiari malformation, or occipital neuralgia. However, recent MRSA infections, unrealistic expectations, and psychiatric comorbidities are generally contraindications. As with any invasive procedure, complications may occur including lead migration, infection, wound erosion, device failure, muscle spasms, and pain. The success of this therapy is dependent on careful patient selection, a preimplantation trial, meticulous implantation technique, programming strategies, and complication avoidance.

Imaging sensory effects of occipital nerve stimulation: a new computer-based method in neuromodulation

BACKGROUND

Within the last years, occipital nerve stimulation (ONS) has proven to be an important method in the treatment of severe therapy-resistant neurological pain disorders. The correspondence between lead placement as well as possible stimulation parameters and the resulting stimulation effects remains unclear.

OBJECTIVE

The method aims to directly relate the neuromodulatory mechanisms with the clinical treatment results, to achieve insight in the mode of action of neuromodulation, to identify the most effective stimulation sets and to optimize individual treatment effects.

METHODS

We describe a new computer-based imaging method for mapping the spatial, cognitive and affective sensory effects of ONS. The procedure allows a quantitative and qualitative analysis of the relationship between lead positioning, the stimulation settings as well as the sensory and clinical stimulation effects.

CONCLUSION

A regular mapping of stimulation and sensory parameters allows a coordinated monitoring. The stimulation results can be reviewed and compared with regards to clinical effectiveness.

Occipital nerve stimulation for chronic migraine

Occipital nerve stimulation may be effective in treating chronic migraine. Six studies, including three double-blind studies, were performed, with five showing evidence of benefit. However, of the three randomized, controlled trials, none has met a primary endpoint successfully. A separate study suggested a benefit for combined supraorbital and greater occipital nerve stimulation.

Introduction to neuropathic pain syndromes

Chronic pain impairs the quality of life for millions of individuals and therefore presents a serious ongoing challenge to clinicians and researchers. Debilitating chronic pain syndromes cost the US economy more than $600 billion per year. This article provides an overview of the epidemiology, clinical presentation, and treatment outcomes for craniofacial, spinal, and peripheral neurologic pain syndromes. Although the authors recognize that the diagnosis and treatment of the chronic forms of neuropathic pain syndromes represent a clinical challenge, there is an urgent need for standardized classification systems, improved epidemiologic data, and reliable treatment outcomes data.

Drug-resistant chronic migraine: the Italian GON project

Chronic daily headache is a major problem due to severe disability and high socio-economic costs. In the last years, some trials have shown potential benefit from new therapeutic approach by occipital neurostimulation techniques, already applied with some success for the treatment of chronic cluster headache. Due to the extremely heterogeneous population suffering from refractory chronic daily headaches, we propose a national multicenter experimental study involving Italian ANIRCEF Headache Centres with the aim to evaluate the efficacy of occipital neurostimulation in a selected group representative for the drug-resistant chronic migraine. Patients with chronic migraine according to Manzoni's modified IHS criteria-2011, with or without medication overuse headache, will be selected. Duration of illness should be at least 2 years and pharmacological refractoriness defined strictly for experimental-surgical purposes as those patients who have properly tried without success almost all available classes of prophylactic medications. Those presenting with medication overuse should have tried at least two previous detoxification treatments. A full psychopathological assessment will be performed by a psychiatrist, to exclude mainly psychotic disorder, ongoing severe status of an affective disorder, severe post traumatic stress disorder. Headache characteristics and abortive treatments used will be reported daily on a predisposed diary during 3-month baseline and continuously through the post implant follow up, while disability and QoL scale (MIDAS, SF-12) will be completed baseline, 6 and 12 months after implant.

Refractory migraine - a review

Refractory migraine has long been a challenge to all headache specialists. This subgroup of migraine patients experience disability and impaired quality of life, despite optimal treatment. This article reviews the proposed definitions and epidemiology of refractory migraine, as well as the pathophysiology that may contribute to the genesis of this disorder. Aspects of treatment, including pharmacological, complementary/adjunct, and invasive approaches, are reviewed. Comorbid factors, medication overuse, potential pitfalls to treatment, and areas for future investigation are highlighted.

Resilience in migraine brains: decrease of coherence after photic stimulation

Background: During migraine attacks, patients generally have photophobia and phonophobia and seek for environments with less sensorial stimulation. Present work aimed to quantify cortical partial directed coherence (PDC) of electroencephalographic (EEG) recordings from migraine patients and controls in occipital, parietal, and frontal areas with or without photic stimulation. Our hypothesis is that migraine patients with visual aura might have neuronal networks with higher coherence than controls even in interictal periods due to a predisposition in sensory cortical processing. Methods: Eleven adult women with migraine with visual aura (at least 48 h without previous attacks) and seven healthy adult woman were submitted to EEG recording in basal state and during photic stimulation. Results: When compared to healthy volunteers, migraine patients show different coherence profiles. Migraine patients had greater coherence than controls during the basal period (without photic stimulation), showing predisposition for sensory processing in many frequency ranges. After photic stimulation, patients showed a decrease in cortical coherence while controls had an increase. Conclusions: When compared to healty subjects, migraineurs show increased cortical coherence before photic stimulation, but a decrease when stimulation starts. This may be the expression of a resilience mechanism that allows migraineurs the interictal period. The PDC analysis permits to address a patient coherence profile, or “coherence map,” that can be utilized for management of the headache disorder or following up treatments.