Pain Physician. 2017 Jan-Feb;20(1):E151-E159.

Occipital Nerve Stimulation for Refractory Chronic Migraine: Results of a Long-Term Prospective Study.

Rodrigo D, Acin P, Bermejo P.

Hospital Clinico Universitario Lozano Blesa, Zaragoza Spain.

Pubmed

 

Supplement:

Published in January 2017, the article OCCIPITAL NERVE STIMULATION FOR REFRACTORY CHRONIC MIGRAINE: RESULTS OF A LONG-TERM PROSPECTIVE STUDY had been finalized and submitted to Pain Physician in April 2016. One year later, all data were reviewed and updated for their presentation in the annual Congress of the Spanish Pain Society in June 2017, in an oral communication entitled “Occipital Stimulation in the Treatment of Cephalic and Craniofacial Pain“. Therefore, the present text constitutes a supplementary report for the article published in Pain Physician, in which all 36 patients implanted with occipital nerve stimulation (ONS) systems have been reviewed with an average follow-up one year longer than in the cited article.

Since the patient group, surgical technique and methodologies are exactly the same, we don’t consider it of interest to add anything to the introduction, objectives, design and methods described in the article, and will focus on the updated results, providing some additional data and analyses.

 

UPDATE OF THE RESULTS

In this report, the evolution of the pain symptoms remains unchanged or improved with regard to the previously published data:

  • Continuous pain scores have slightly improved from 4.9±2.0 to 4.63±2.34[i] according to the VAS.
  • In addition to the 5 patients cited in the study, other 2 refer to be free from migraine attacks.
  • Average pain VAS decrease during the attacks has greatly improved from 3.8±2.5 to 5.5±2.8, although the number of migraine days remains unchanged (17.9±9.1[ii]).
  • One additional patient has stopped painkilling medication (15 vs 14).
  • There was a new lead externalization event which required lead explantation. However, the patient declared being pain-free even without stimulation therapy, so the whole system was explanted and not replaced.
  • A new infection event in the implantable pulse generator (IPG) pocket was detected 74 months post-implantation, was successfully managed with antibiotics and did not require any surgical revision.
  • 4 additional systems have been totally removed in addition to the 7 described in the published article. Of the 11 systems explanted up to date, on two occasions it was due to total remission of migraine symptoms (3 more than in the original article), and 2 due to inefficacy (same as in the article). Additionally, one system was removed due to a severe lipoma in the IPG pocket. This system has not yet been replaced, as the patient is free from continuous pain and migraine attacks have decreased in frequency (4 to 2/month) and intensity (VAS 9 to 3), so we are evaluating the potential symptom recurrence versus the appropriateness of implanting a new stimulation system.
  • In addition to the 2 cited in the article, there have been other 4 IPGs replaced due to end of operating lifetime (EOL), all of them PrimeAdvanced (Medtronic, MN, USA). Two of these devices were replaced by IPGs of the same model, while the other 2 were substituted by EonC and Proclaim Elite (St. Jude Medical, MN, USA).
  • One patient suffered total loss of therapy efficacy, with the subsequent recurrence of migraine symptoms. In this case, the system remains deactivated, awaiting for further assessment.
  • One patient died for reasons beyond the stimulation therapy, which had been very positive in this case (disappearance of continuous pain and associated symptoms, 88% relief in attacks).

 

In summary, after the latest revision with an average follow-up close to 10 years, the patients situation is as follows:

  • Of the 41 patients initially selected, 4 did not pass the diagnostic block test and were withdrawn.
  • 1 patient did not pass the ONS trial phase.
  • Of the 36 patients who received the permanent implantation, the current situation is:
    • In 8 patients the stimulation system was removed because all migraine symptoms had disappeared even with stimulation off.
    • In 1 patient the system was removed due to complications in the IPG pocket and, given the great improvement of the symptoms, we are evaluating the convenience of replacing the ONS system.
    • In 3 patients the therapy has turned out ineffective, with 2 systems totally explanted and 1 turned off awaiting for further assessment.
    • One patient died for reasons other than the therapy, after obtaining great benefit and satisfaction from it.
    • There are currently 23 patients in ONS treatment, which has been assessed as “very good” (n=11), “good” (n=10) or “fair” (n=2). 13 patients are very satisfied, 9 satisfied and 1 fairly satisfied with the therapy. The global improvement of these patients still receiving ONS is 68.3±22.6% (see “Global Analgesic Assessment” in the following section).

 

ADDITIONAL DATA NOT INCLUDED IN THE PUBLISHED ARTICLE

During the whole follow-up period, some additional data were recorded but not included in the article published in Pain Physician, and we think that some of them may be interesting for the reader of this supplementary report. These data relate to assessments with subjective components on the part of the patients (satisfaction) and the evaluator (global analgesic assessment), and can be seen in figures 1a and 1b.

  • Global Analgesic Assessment (GAA), based on pain relief, decrease in the frequency migraine attacks and evolution of associated symptoms, rated as “Very Good”, “Good”, “Fair” or “Poor”.
  • Patient Satisfaction, according to the survey made in every follow-up, and rated as “Very Sastisfied”, “Satisfied”, “Fairly Satisfied” or “Not Satisfied”.

 

Figure 1a: Global Analgesic Assessment

 

 

Figure 1b: Patient Satisfaction

 

 

SELECTIVE SCREENING

Analysis of the “cured” patients:

We have tried to find common features of the patients in which the system was finally removed after symptoms had subsided even with the therapy off (“cured” patients), and compare them to the rest of patients, with the aim of trying to find out common and distinctive profiles that may help to seek for some kind of predictive value. We have not been able to detect any significant differences as far as the age, gender, weight, presence of allergies, trigeminal pain, hypertension, previous evolution time, symptomatic side and irradiation/distribution of pain are concerned. Neither does there seem to be a relation with the occurrence of adverse events. In these patients, basal VAS score was slightly higher in continuous pain (5.9±1.7 vs. 5.5±1,8) and lower in migraine attacks (7.4±1.8 vs. 9.1±0.64).

  • 100% of cured patients suffered allodynia, which differs markedly from the average (30%).
  • None of them suffered nausea, while this symptom was present in 68% of overall patients.
  • 100% of these patients referred that their physical (social and family) activities were 100% normal, vs. 64%. However, as in the rest of patients, most active workers (5/6) were off work due to their pain condition.

 

Analisis of patients in which the ONS has proven to be ineffective

As in the previous section, we have tried to look for common traits in patients in which the ONS therapy has proven to be ineffective. In this case we have also been unable to find distinctive and clearly identifiable signs, although the following data may be mentioned with due caution, given the very limited number of individuals:

  • 2 out of 3 (67%) had allergies versus 24% general
  • All 3 patients (100%) had itching/burning pain versus 24% general

 

DISCUSSION

In the light of the new data extracted from the revision of the article published in Pain Physician, updated with 1-year additional follow-up, the patients evolution remains positive, con moderate improvements in their pain symptoms without observing any upsurge in adverse events. When it’s time for IPG replacement, be it due to battery exhaustion or any other reason, the number of patients who voluntarily decline the replacement because they consider to be healed from their syndrome has grown and currently reaches 22% of the permanent implants.

We have not been able to find clear signs which would enable us to recognize patients with more possibilities of resulting permanently cured of their disease, even after stopping stimulation, but it seems that those individuals who consider themselves less physically disabled by the syndrome (regardless of the intensity of the symptoms) may be more prone

to achieve a permanent cure from the therapy. This does not apply inversely to those patients in which the therapy is useless, but they may possibly be identified for some characteristics of their pain (itching/burning) and associated symptoms (allergies).

In summary, we continue to believe that the permanent and implantable electric stimulation of the occipital nerves can be an effective long-term therapy for the management of chronic refractory migraine.

 

[i] All data are expressed as mean ± standard deviation

[ii] There is a typographical error in the printed article (17.9±0.1 is really 17.9±9.1)