Occipital nerve stimulation in pediatric patients with refractory occipital neuralgia

Purpose Occipital neuralgia (ON) is a disabling problem within the pediatric population. Many of these patients fail medical therapies and continue to suffer without further surgical management. Occipital nerve stimulation (ONS) is used to treat ON in the adult population leading to a 72–89% reduction in pain; however, there are limited studies regarding its use in the pediatric population. In this study, we examined the outcomes of ONS in pediatric patients with medically refractory ON. Methods We performed a chart review of pediatric patients at our institution who have undergone ONS for the same indications. Results We identified 3 patients at our institution who underwent ONS trial and/or permanent implantation for ON. One patient had complete pain relief after the trial and declined permanent implantation. The other patient had fewer attacks compared to his pre-trial baseline and controlled them by adjusting his permanent implant stimulation settings. The last patient had near complete relief of her symptoms and no longer required any pain medication. Conclusion Our study highlights the paucity of studies evaluating the utility of ONS in the pediatric ON population. Limited data from both the literature and our institution’s experience reveal that pediatric patients may benefit from trial and/or permanent implantation of ONS for medically refractory ON pain. Supplementary Information The online version contains supplementary material available at 10.1007/s00381-024-06376-x.


Introduction
Chronic occipital neuropathic pain is a pervasive and disabling problem within the pediatric population with a USA population-based estimate of 17% prevalence of all debilitating headaches [1][2][3][4].Occipital pain is considered a "red flag" symptom, prompting clinicians to rule out etiologies requiring emergent interventions [4].The more common and nonemergent etiologies include pain secondary to occipital neuralgia, Chiari malformation, paroxysmal hemicrania, chronic migraines, and trauma.First-line treatment consists of conservative and pharmacological therapies followed by occipital and other nerve blocks, as well as botulinum toxin injections for refractory cases [5][6][7].Unfortunately, many patients who undergo anesthetic nerve blocks or steroid injections will have recurrence of their symptoms despite repeated treatments [8].In these refractory patients, surgical interventions can be employed.Occipital nerve stimulation (ONS) is used in the adult population as a minimally invasive neuromodulatory therapy for chronic cranial neuropathic pain, occipital neuralgia, migraine, post-herpetic neuralgia, and cervicogenic headaches [9][10][11][12].Studies of ONS have demonstrated a 72-89% reduction in pain in subjects compared to their pre-operative baseline; however, there is a paucity of studies regarding the safety and efficacy of ONS in the pediatric population [10,[13][14][15][16].In fact, in this study, we performed systematic literature review and could not identify a single article dedicated to the use of ONS in pediatric ON patients.Therefore, in this retrospective chart review, we examined our outcomes of occipital nerve stimulation in patients with medically refractory occipital neuralgia.

Search strategy and study selection
We conducted a comprehensive literature search through four large, widely accessed databases (PubMed, Cochrane, Web of Science, and SCOPUS) using the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement in August 2023 [17].Search terms included "implantable neurostimulators," "peripheral nerve stimat," occipital nerve stimulat," and electric stimulation therapy," as well as terms that captured a pediatric population, including "adolescent," "pediatric," or children."In addition, our search included the occipital neuralgia diagnosis as "occipital neuralgia."Our complete search algorithm can be accessed in Supplementary Fig. 1.One author (J.M.) screened for titles, abstracts, and full texts of the resulting articles.

Institutional chart review
We reviewed demographic, surgery, and outcome data of occipital nerve stimulator placement used to treat three patients with pediatric occipital headaches between 2022 and 2023 (Table 1).This study was approved by the local institutional review board with a waiver of consent.All statistical analyses were performed in RStudio (RStudio Team, 2023).

Trial implant
Following a full informed consent, patients are brought to the operating room and placed prone, awake.We trace the greater and lesser occipital arteries as surrogate markers of the occipital nerves using ultrasonography.Two trajectories targeting the mastoidal tip and the superior nuchal line traversing the course of the arteries are planned from midline.Following a 4-step skin preparation, sterile draping, and surgical pause, we anesthetize the entry points with 0.5% lidocaine and then introduce curved 14-guage Tuohy needles into the subcutaneous and epifascial space.Fluoroscopy confirms placement.We remove the stylet and None place 8-contact cylindrical electrodes to the depth of the needle tip and remove the needle.The electrodes are connected to the external neurostimulator which is turned on with escalating current to confirm physiologic coverage of the typical pain pattern.Following confirmation of paresthesia coverage, fluoroscopy is used to record the final tip location and the electrode is sutured down to the skin with a 2-0 nylon suture at both the exit site and a second winged silastic anchor site.We further secure the electrodes with Tegaderm™ and secure them with a dressing.The trial lasts 7 days; at the trial end, the electrodes are removed in clinic and steri-strips are placed over the electrode exit site(s).

Permanent implant
The patient is positioned the same as in the trial implantation, this time under general anesthesia.The 4-step skin preparation now includes the back and flank.Landmarks are identified as in the trial.A midline incision allows surgical access to the nuchal fascia, and the Tuohy needles are positioned exactly as in the trial.The electrodes are placed through the needles, which are then withdrawn, using fluoroscopy to ensure stable position of the electrodes.
An anchoring system is placed around the leads, and they are secured to the fascia with 2-0 Ti-cron stitches.The flank incision is opened sharply, a subcutaneous pocket is created, and the electrodes are tunneled between the incisions.The electrodes are connected to the pulse generator (IPG), the impedances are checked, and then the electrode and IPG are placed into the pocked and secured.A final fluoroscopy picture confirms placement compared to the trial, followed by wound irrigation with vancomycin irrigation then placement of vancomycin antibiotic powder.We change our gloves and close with antimicrobial suture in layered fashion.

Systematic review
A total of 3 articles (1 from PubMed, 1 from SCOPUS, 1 from Web of Science, and 0 from Cochrane Reviews) were captured by our literature search (Fig. 1), of which none of the 3 articles were specifically dedicated to outcomes of ONS in pediatric ON patients.

Patient outcomes
Our chart review yielded a total of 3 patients (2 female) with an average age of 15.6 years old (range of 15-17 years old).One of these patients had a diagnosis of post-traumatic ON secondary to a football accident.The remaining two patients had a diagnosis of idiopathic ON.All 3 patients rated their pain on the VAS between 9 and 10/10 that had a severe impact on their daily quality of life.In fact, two of the three patients were unable to attend school because of the pain.The frequency of their pain episodes ranged from having attacks 4 days/week to 3-4 attacks/day.All patients had attempted conservative therapies including medications and nerve blocks.All 3 patients had initial symptom relief with anesthetic nerve blocks but, unfortunately, became refractory over time.Each patient underwent a bilateral, percutaneous ONS trial and had remarkable success with a significant reduction in post-trial VAS scores (mean post-VAS 0.67, p = 0.002, paired Student's T-test).One patient remained pain-free following her trial and did not undergo permanent implantation.This phenomenon is not understood, and she remains pain-free at 15 months post-operatively.The other two patients, however, did elect to undergo permanent implantation.One of the patient's attacks persisted following permanent implantation but they were less intense in severity, occurred less frequently, and were able to be aborted with stimulation.The other patient had a 95% reduction in her pain following permanent implantation and no longer required the use of any pain medications to control her symptoms at 9-month follow-up.There were no complications with any of the trial or permanent implantation procedures (Fig. 2).

Discussion
Our study reviews the indications for and outcomes of ONS in pediatric patients with medically refractory ON.A literature review could not identify a single article pertaining to outcomes of ONS in pediatric ON patients.However, our retrospective chart review identified 3 patients who had a significant reduction in both their pain and pain medication usage following ONS trial and/or permanent implantation.The neurosurgical management for medically refractory ON in adults includes both ablative and neuromodulatory techniques; recent reviews for different approaches to treating ON and similar conditions in adults highlight both invasive and non-invasive treatment modalities [5,18].Open surgical neurectomy and C2 ganglionectomy have long been performed with some benefit; the natural evolution of open-to-minimal-access techniques has brought radiofrequency ablation of the occipital nerve into clinical question with some promise in early trials [19][20][21].
Neuromodulation via ONS provides a minimally invasive, adjustable, and reversible therapeutic option for those with refractory ON pain.Raoul et al. further demonstrated the utility of ONS on a cohort of 60 adult patients with refractory ON, which showed a 72.2% reduction in mean VAS score after one year of ONS device implantation [10].Regardless of the etiology, ON pain is a disabling condition often leading to depression, loss of independence, and truancy in the pediatric population which potentially impacts long-term developmental success [4].The treatment algorithm for pediatric patients with medically refractory ON pain mimics that for adults with ON and includes integration of preventative and abortive pharmacological strategies, occipital nerve blocks, and botulinum toxin injections among other interventions.Unfortunately, adult patients who continue to suffer are evaluated for neurosurgical management including ONS while pediatric patients are generally not [5,7].One obstacle is the general lack of the special skills required from subspecialized clinicians to elicit a pain characterization and history from a pediatric patient supportive enough to indicate that a child is a reasonable candidate for a trial of neuromodulation [2].Additional challenges in pediatric patients include hardwarerelated issues such as implications for implanting devices designed for adults in children.These include the potential for growth-related hardware issues due to the accumulation of biomechanical strain and stress.There are additional ethical issues including the lack of FDA indications for the pediatric use of neuromodulation devices, informed consent/assent, and the impact of missing MRI safety labeling.
As in adults, open surgical strategies are implemented in some cases.Villeneuve et al. recently described significant improvement in the VAS (average 8.3 to 1) and statistically significant decrease in polypharmacy in a retrospective single-institutional series of six adolescent patients who underwent greater occipital nerve decompression or neurectomy for post-traumatic ON [22].While effective, surgery caused sensory paresthesias in 100% of the patients (follow-up period was, on average, 10 months post-operatively).This ablative surgical approach therefore might be considered premature in the setting of an equally effective nondestructive strategy like ONS.
Although literature on ONS on the pediatric population is scant, and the pediatric data not discernible from the data from Borius and Valade and Vadivelu et al., it provides preliminary safety and efficacy data and substantiates our own single-institution findings [23,24].It is essential that further trials are undertaken to elucidate the long-term safety and efficacy of ONS as well as to examine for any adverse outcomes or device-related complications which may be unique to the pediatric population [10,15,23].

Limitations
Durable conclusions about safety and efficacy of ONS in children are limited by our small sample size.The quality of data both in the literature and in our single institution study is, at best, Level III and lacks quality of life data granularity which would be improved by using standardized pain surveys.

Conclusion
Medically refractory occipital neuralgia within the pediatric population is a source of severe disability and can be difficult to treat.ONS is an effective, non-permanent, and minimal-access intervention that has been shown to be effective for this condition.This study highlights the scarcity of available data on the indications and long-term effects of ONS within the pediatric population.Additional collaboration is necessary to improve outcomes, identify appropriate indications, and refine the surgical technique in children.

Table 1
Summary of pediatric occipital nerve simulation cases and outcomes