Sphenopalatine ganglion block in primary headaches

Abstract

Background

The sphenopalatine ganglion (SPG), in the pterygopalatine fossa, is a known current and historical target for therapeutic intervention in headache disorders because of its role in cranial autonomics and vasodilation. There remains an overall lack of well-established SPG treatment protocols, particularly with the advent of newer commercial devices.

Methods

A 22 multiple-choice question survey was created to evaluate clinical practice patterns with SPG block and sent to members of the American Headache Society (AHS). Questions focused on determining indications, preferred applicators, medications applied, perceived efficacy, tolerability, and reimbursement.

Results

One hundred seventy-two of 1,346 (12.8%) AHS members participated. Ninety-three respondents (56.3%) had performed SPG blocks on 50 or fewer patients. The SphenoCath (42.4%) and the Tx360 (41.8%) were the most common methods of application. Ease of use was the top reason for provider preference in applicator type. SPG blocks were mostly used as an as-needed one-time procedure. When a scheduled protocol was used, twice weekly for 6 weeks was most common. Chronic migraine was the most commonly treated headache disorder and rated the most likely to respond to SPG block. Experienced clinicians found SPG more helpful as a stand-alone treatment and tended to report that acute relief was not predictive of enduring response.

Conclusions

The variety of responses strongly suggests that clinicians would benefit from formalized protocols for SPG blocks. More experienced clinicians may have developed individualized protocols that they feel are more effective. The lack of evidence-based protocols contribute to clinicians not performing SPG blocks more frequently.

The sphenopalatine ganglion (SPG) is a predominantly parasympathetic ganglion in the pterygopalatine fossa providing innervation of the lacrimal gland and nasal mucosa as well as meningeal vessels. It receives parasympathetic input from the greater petrosal nerve and input from trigeminal branches (mainly V2) and sympathetic fibers (from the superior cervical ganglion and carotid plexus).¹

As early as 1908, when Sluder described using cocaine or alcohol application to treat headache, SPG block has been used in migraine, trigeminal autonomic cephalalgias, and other headache disorders, with varying levels of success.^1–4 Historically, SPG blockade was performed with intranasal lidocaine or cocaine, although silver nitrate, phenol, ketorolac, bupivacaine, and onabotulinumtoxinA have been tried.¹

A recent systematic literature review of SPG blockade and ablation for head and facial pain disorders found the strongest evidence for blockade, radiofrequency ablation, and neurostimulation of the SPG for cluster headache.⁵ There was also limited evidence for SPG block in treating migraine, trigeminal neuralgia, and postsurgical sinus pain.⁵

Newer commercial intranasal delivery systems, including the Allevio and SphenoCath catheters and the Tx360 intranasal applicator, have also raised interest in SPG block. To date, only the Tx360 has had randomized trials evaluating its use as a treatment delivery device, with an unclear basis of how these protocols were developed.^2,3,6–9 In addition, differences in efficacy and tolerability between the different applicators and traditional SPG-blocking techniques are unknown.

Given the growing use of clinic-based SPG blocks and lack of consensus regarding their indications, we intended to explore the current clinical experience of headache specialists in their use of clinic-based SPG-blocking interventions. As a first step toward the development of treatment guidelines and protocols, we surveyed the American Headache Society (AHS) membership to report current clinician practices with SPG block.

Methods

A workgroup of headache specialists from the Procedural Headache Medicine special interest section of the AHS (study authors) formulated a 22-question survey to evaluate clinical practice patterns related to SPG blocks. Questions focused on determining indications, preferred applicators, medications applied, perceived efficacy and tolerability, and reimbursement. Survey answers featured both multiple choices and write-in answers when appropriate to allow participants to clarify responses as necessary. The survey was created online through the use of the SurveyMonkey website. The survey was approved by the executive board of the AHS and then emailed to AHS members on 2 occasions between August and October 2016. This was a closed, voluntary survey available only to active AHS members who received the link through email. There were no missing data from the survey; however, responders were not required to answer every question; those who did not answer either of the questions regarding the number of patients they had treated or whether they had obtained reimbursement were removed from the analysis, out of concern that they may represent nonusers.

Statistical analyses

Survey data were summarized using frequencies and percentages for categorical responses. Bivariate analyses were conducted using χ² and Fisher exact tests as appropriate.

Statistical analyses were conducted in Stata 15.1, StataCorp LLC, College Station, TX. A p value < 0.05 was considered statistically significant.

Bivariate analysis was also performed by stratifying providers by experience. Providers were noted as more experienced when they had performed SPG blocks in 51 or more patients (42 respondents) or less experienced when they had treated 0–50 patients (93 respondents).

Standard protocol approvals, registrations, and patient consents

The AHS reviewed and approved this study.

Data availability

Data supporting the conclusions of this manuscript will be made available by the authors, without undue reservation, to any qualified researcher.

Results

Respondents and experience with SPG blocks

Of a membership of 1,346, 172 (12.8%) AHS members participated in the survey; however, 11 did not report using any of the techniques listed, and 3 reported they were not using the treatment themselves. Sixty-two (36.0%) reported having performed the procedure on 25 or fewer patients, 35 (20.3%) on 26–50 patients, 30 (17.4%) on 51–100 patients, 2 (1.2%) on 101–150 patients, 4 (2.3%) on 151–200 patients, and 7 (4.1%) reported having treated more than 200 patients with SPG block. Thirty-two (18.6%) clinicians did not provide a response regarding the number of patients they had treated. As mentioned above, respondents were not required to answer every question, and those who did not answer the questions regarding the number of patients they had treated or whether they had obtained reimbursement were removed from the analysis, out of concern that they may represent nonusers. This led to the removal of 32 participants from our analysis.

Delivery method

The SphenoCath (used by 42.4% of survey responders) and the Tx360 (41.8%) were the most commonly reported methods of application, followed by the Allevio (23.4%) and Q-tip cotton swab (17.7%). In total, 19.6% of respondents also wrote in other methods used, including fluoroscopy-guided SPG blockade or application of anesthetic by syringe. When asked to comment on why they preferred their specific delivery method, and given the option to choose all reasons that applied, top reasons included ease of use (70.9%), followed by availability (46.2%), efficacy (36.7%), cost (34.8%), and tolerability (34.8%).

Treatment protocol

The most common anesthetic used for blockade was 2% lidocaine; however, formulations varied because the liquid version was used by 77 respondents (48.7%) and viscous lidocaine was used by 32 respondents (20.2%); 0.5% bupivacaine was the second most commonly chosen, as per 83 respondents (52.5%), followed by 4% viscous lidocaine used by 36 respondents (22.8%). Of note, some providers reported using more than 1 formulation. Similarly, 2% liquid lidocaine (29.7%) and 0.5% bupivacaine (31.6%) were the highest ranked among the most preferred anesthetics, as opposed to 7.0% and 10.1% for 2% and 4% viscous lidocaine. Regarding the volume of medication given with the Tx360, 50.0% of those responded to this question reported 0.5 mL, 8.1% responded 0.25 mL, and 40.3% responded other, with many write-in responses noting 0.3 and 0.6 mL as amounts given.

Regarding the frequency of treatment, most respondents reported performing blocks as a one-time procedure as needed, whereas the next most frequently chosen protocol was twice per week for 6 weeks then as needed. Most clinicians performed blocks bilaterally for migraine (74.6%, 103 respondents). For cluster headache, 44.0% (59 respondents) always performed blocks bilaterally, but 38.8% (52 respondents) said it depended on the patient.

Of the 138 members who shared their experience with the pediatric population, 23.2% (32 respondents) reported treating pediatric patients (younger than 18 years of age) with SPG blocks, 34.1% (47 respondents) deferred its use in pediatrics, and 42.8% (59 respondents) reported that they did not treat pediatric patients with headache.

Repeat blocks at multiple visits were generally felt to be more helpful than a one-time block, though quite a few respondents were unsure if repeat blocks truly provided additional benefit.

When asked whether they felt the SPG block was useful as a stand-alone treatment for their patients, 32.3% (43 respondents) of clinicians felt it could act as a sole treatment, 36.1% (48 respondents) felt it was not effective as the only treatment, and 31.6% (42 respondents) were not sure.

Clinical efficacy (140 respondents included, subtracting 32 who did not answer the number treated or reimbursement)

The most common diagnosis to be treated by SPG block was chronic migraine (figure 1). Chronic migraine was also the diagnosis that clinicians rated as the one helped most by SPG block. These data are displayed in figure 2 by percentages of clinicians who ranked each diagnosis as most helped (figure 2). The rated effectiveness of the SPG block for specific diagnoses remained the same even after stratifying by clinician level of experience.

Figure 1. The top 5 diagnoses which sphenopalatine ganglion survey respondents ranked as their most common diagnosis treated.

Figure 2. Diagnoses that survey respondents ranked as the most likely to be helped by sphenopalatine ganglion block.

Interestingly, only 20.0% (27 respondents) reported that patients experiencing immediate headache relief correlated with preventative response, 34.8% (47 respondents) did not note this association, and 45.2% (61 respondents) were unsure. In total, 48.2% (66 respondents) felt that repeating blocks at multiple visits was more helpful than a one-time block, 37.2% (51 respondents) were unsure, and 14.6% (20 respondents) felt that repetition did not help.

Clinical experience (158 respondents)

A few important findings were noted when stratifying responders by the number of blocks performed. For instance, experienced users were more likely to find SPG blocks helpful as stand-alone treatment, 52.5% (21 respondents) vs 23.1% (21 less experienced respondents) (p value = 0.001). Experienced providers were also more likely to believe that acute relief after the SPG block was not predictive of a more enduring preventative response (25.0% vs 18.5%, p = 0.004). More than half of the experienced providers believed repeat SPG blocks were better than one-time SPG treatments, but the difference was not significant between the 2 groups (61.0% vs 43.0%, p = 0.063). In total, 57.1% (24 respondents) of the more experienced users selected efficacy as the reason to use their current technique, whereas only 31.2% (29 respondents) of the less experienced users did the same (p value: 0.004). The experience level did not seem to be associated with preference in applicator type and technique used.

Tolerability (158 respondents)

There were no serious adverse events reported by any responders. The most common side effects observed were bad taste (68.4%), numbness of the oropharynx (34.8%), and lightheadedness (19.0%).

Reimbursement (136 respondents)

Most (64.7%, 88 respondents) of the clinicians reported obtaining reimbursement for the procedure most of the time, whereas 19.1% said they were not reimbursed most of the time and 16.2% were unsure.

Discussion

We report a survey study of a group of headache clinicians with varying experience levels using SPG blocks to treat headache disorders. Our survey demonstrates a great heterogeneity of experience and results and suggests that clinicians would benefit from a study to formalize a protocol for SPG blocks. For many of our survey questions, there was not an overwhelming majority response, including questions regarding the preferred applicator type, medication used, use as a stand-alone therapy, most common diagnosis treated, diagnosis most helped, or number of SPG block visits required for response. Questions were formulated to be more generalized to keep the survey length within reason and maximize AHS member participation while also allowing participants to write in responses. Although more nuanced practice pattern questions exist, this survey was a first step toward obtaining a general view of current SPG block usage in clinical practice.

[C]linicians using SPG blocks found them to be most beneficial in the management of chronic migraine compared to other diagnoses, regardless of clinician level of experience.

Despite the variety in responses, there were some noteworthy findings. For instance, clinicians using SPG blocks found them to be most beneficial in the management of chronic migraine compared with other diagnoses, regardless of clinician level of experience. The Sphenocath and Tx360 were used almost equally among our respondents, and their choices appeared to be mostly influenced by the ease of use of these devices.

Repeat blocks at multiple visits were generally felt to be more helpful than a one-time block, although quite a few respondents were unsure whether repeat blocks truly provided additional benefit. Lidocaine 2%, in viscous and liquid formulations, was the most commonly used anesthetic for SPG blockade, but not by an overwhelming margin, and the choice of anesthetic was not influenced by clinician level of experience. No serious adverse events were reported, and clinicians were generally able to obtain reimbursement.

Although there were a few very experienced survey responders who had treated more than 200 patients, most of our responders (77.3%) had treated 50 or fewer patients. Combined with the low response rate, this may indicate that clinical experience is relatively limited within the AHS membership. It seems possible that the lack of evidenced-based protocols may be one reason that providers may not use SPG blockade more frequently. Within the responders of our survey, we suspect that the experienced clinicians may have developed protocols over time that they feel yield better clinical outcomes. We would hope that this anecdotal experience could be translated into more evidence-based high quality data and protocols in the future. Another possibility is that many headache specialists refer to interventionalists for SPG blocks to be performed percutaneously instead. Although there are no comparative studies examining these different SPG-blocking techniques, there is recent anatomical and imaging evidence which suggests that the pterygopalatine foramen may be a longer distance than previously appreciated and may not even be patent.¹⁰

Likely, because of their familiarity with the procedure, the more experienced responders in our survey tended to be precise in their application and techniques of SPG blocks and were less likely to choose “unsure” as a response. Based on our analysis, the more experienced responders were more comfortable using SPG blocks as a stand-alone treatment and felt that acute relief did not necessarily predict the long-term outcome. Experienced headache specialists also tended to believe that repetition of blocks was helpful; however, there was no statistical difference between the groups (p = 0.06). This increased uncertainty among less experienced providers regarding SPG effectiveness and whether to perform the procedure more than once, along with recent studies featuring equivocal results, could be a contributing factor to the lower rates of repeated use.^2,4 Technique choice did not appear to be influenced by the experience level nor did the decision to perform SPG block unilaterally or bilaterally.

This study has several limitations. First, the way the survey was written allowed those who were infrequent users of SPG blocks to continue answering questions despite limited use. After the survey was closed, and as noted in the Methods section, 32 participants were removed from our analyses because of concerns that they represented nonusers. Second, because this was a voluntary survey of clinical practice, we were limited by both the recall bias of the respondents and selection bias as the clinicians who filled out the survey may not represent the larger population using the SPG blocks. That is, clinicians with either high satisfaction or high dissatisfaction with the procedure may have been more motivated to participate in our survey. However, our stratification by frequency of use may help to alleviate this limitation some because we were able to analyze the opinions of the more experienced (and possibly more satisfied) users separately. Survey items were also created by the authors and were not previously validated in previous research, so it could be possible that responders did not fully understand an item or the item did not accurately assess what it was intended to. Conflicts of interest of responders were not ascertained, which could include free samples of blocking devices provided to practitioners. Finally, we wish we could have taken the opportunity to ask our providers with limited experience (fewer than 25 patients) why they were not using SPG blocks more frequently. We can only speculate whether their infrequent use was driven by the lack of familiarity with the procedure, an impression of low clinical response, issues of cost/reimbursement, or other reasons. It must also be considered that more experienced clinicians have the higher number of patients seen because they believe that the procedure is effective and thus use it more frequently, regardless of whether this is true or not.

The ability of most survey responders to be able to obtain reimbursement for the procedure is encouraging because cost could otherwise become a technical hurdle to preclude use in otherwise suitable patients. The lack of major side effects is also important both for patients and for increasing the likelihood of a physician to pursue SPG blocks as a treatment option. As discussed previously, some alternative SPG block approaches can be invasive and require fluoroscopy, possibly increasing the chance for adverse events and overall cost for patients. These more invasive approaches are also more difficult to perform in most headache outpatient practices and can require outside referral.

It is important to determine where SPG block fits into the toolbox of the headache practitioner. This survey suggests that according to headache specialists already performing SPG blocks, there is no clear consensus in the therapeutic strategy using SPG blocks as acute vs preventive therapy. It is notable that the Tx360 applicator has had 4 studies evaluating its efficacy in chronic migraine and its efficacy in the emergency department setting for treatment of anterior or global headaches.^2,3,6,8,9 These studies may offer some possible protocols for treatment, dosing, and scheduling of blocks. The Allevio and SphenoCath catheters have, thus far, not had any randomized trials evaluating their use as treatment delivery devices. Because trials have only been performed on one of the 3 commercially available devices, it is also unclear what the basis for the initial protocol development for the Tx360 was and whether it truly represents the best possible protocol. Comparative, prospective, and systematic assessments of delivery devices, medications used, frequency of use, and efficacy may better refine the indications of SPG blockade as a therapy for headache disorders.

Headache specialists who completed this survey use SPG blockade most often in the treatment of chronic migraine. Our study indicates that although there is a tendency as to which devices are preferred by the study respondents, they were unclear on how often to administer SPG blocks and on the appropriate protocol for use as an acute or preventive treatment modality. Although some studies suggest its use as a long-term preventative option, this is can be a very time-consuming protocol.^2,4 Based on our analysis, clinicians with more experience using SPG blocks feel comfortable using them as a stand-alone therapy and that acute relief did not predict the overall efficacy of the procedure for pain relief.

Appendix. Authors

Study funding

No targeted funding reported.

Disclosure

J.G. Burkett reports no disclosures. M.S. Robbins reports no disclosures relevant to the manuscript. C.E. Robertson has received honoraria from Amgen, Eli Lilly, Alder (advisory boards), and UpToDate (author). M. Mete reports no disclosures. N.P. Saikali reports honoraria from Allergan (advisory boards, speaker), Amgen (advisory boards, speaker), Depomed (speaker), Egalet (speaker), gammaCore (speaker), Pernix (speaker), Promius (advisory board, speaker), Supernus (advisory boards, speaker), and Teva (advisory boards, speaker). R.B. Halker Singh reports honoraria from Amgen, Biohaven, and Allergan (advisory boards). J. Ailani reports honoraria from Alder (advisory board), Allergan (advisory board, speaker), Amgen (speaker), Avanir (speaker), Eli Lilly (advisory board, speaker), gammaCore (advisory board, speaker), Promius (advisory board, speaker), Teva (advisory board), Miller Medical Communications, and AlphaSights Consulting. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp.