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American Society for Peripheral Nerve

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The Role of Diagnostic Nerve Blocks in Headache Surgery
Lisa Gfrerer, M.D., Ph.D.1, Maria E. Casari, NA2, Christian Chartier, NA2, Ricardo Ortiz, MD1 and William G., Jr. Austen, MD1, (1)Massachusetts General Hospital, Harvard Medical School, Boston, MA, (2)Massachusetts General Hospital, Boston, MA


Evidence-based patient selection in headache surgery is extremely important to achieve satisfactory outcomes. In headache surgery, nerve blocks have become an important diagnostic tool to confirm trigger sites and identify suitable candidates for surgery. Wide availability, low cost, easy administration, and immediate patient feedback make nerve blocks an attractive in- office screening tool. Resolution of headache symptoms after nerve block has been seen as a good prognostic sign based on expert opinion. However, the relationship between nerve block response and surgical outcome has not been studied.


Patients were asked to stop their regular pain medication and present to the office in pain. If patients had no pain at the time of the visit, they were asked to return when they experienced their next headache/ migraine. All patients with suspected nerve compression underwent a diagnostic nerve block. Pre- and post- injection pain scores (on a 0- 10 scale) were recorded prospectively at each injected site to quantify improvement/ worsening of pain. A positive response to the nerve block was defined as ≥ 50% decrease in pain score. Further, the length of nerve block response was documented by follow-up phone call, and during subsequent clinical visits. Surgical outcomes were documented prospectively by calculating the Migraine Headache Index scores preoperatively, at 3 months, 12 months and every year thereafter [migraine headache frequency (0-30) x pain (on a scale of 0-10) x duration (1/24)]. Nerve block response was correlated with surgical outcome.


The study population included 105 patients who underwent a preoperative nerve block. Of these, 90% (n= 94) achieved ≥ 50% immediate pain relief following nerve block (positive response). Mean follow-up time was 12.8 months for patients with successful nerve block and 14.5 months for patients with unsuccessful nerve block (p= 0.35). The mean MHI score improvement was significantly greater in patients who responded positively to nerve block (73± 38%) than in those who did not (41± 44%; p= 0.02). With respect to duration of response to nerve block, patients who reported relief for ≥ 24 hours achieved significantly greater mean reduction in MHI scores (p= 0.02, 77± 35% vs. 50± 41%).


Headache surgery patients who respond positively to preoperative nerve blocks achieve better surgical outcomes as compared to patients who have a limited response. Given these findings, nerve blocks should be considered as a preoperative screening tool for headache surgery.
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