Evidence for the Peripheral Trigger Theory in Frontal Migraines: An Analysis of Intraoperative Anatomy
Ricardo Ortiz, BSc, Lisa Gfrerer, MD PhD, Marek Hansdorfer, MD, Kassandra Nealon, BSc, William G. Austen, Jr., MD.
Massachusetts General Hospital, Boston, MA, USA.
Previous studies have suggested that the development of migraine headaches may involve the entrapment of craniofacial peripheral nerves at specific trigger sites. Cadaver studies in the general population have confirmed potential compression points of the supraorbital (SON) and supratrochlear (STN) nerve at the frontal trigger site, including bony supraorbital foramina and tight fascial bands. However, there are limited reports on anatomic compression points in patients undergoing surgery for headaches. Our aim was to describe the intraoperative anatomy of patients undergoing migraine surgery at the frontal trigger site and to investigate which anatomy is associated with pain.
Patients scheduled to undergo frontal site migraine surgery were prospectively enrolled. The senior author evaluated intraoperative anatomy and recorded variables using a detailed form and operative report. The resulting data was analyzed.
A total of 118 sites in 65 patients were included. The SON course was through solely a notch in 49% of sites, a foramen in 41%, a notch plus foramen in 9.3%, and through neither a notch nor foramen in one site (Figure 1). The senior author noted macroscopic nerve compression at 74% of sites. Reasons for compression included a tight foramen in 24%, notch with a tight band in 34%, STN and SON emerging via the same notch in 7.6% or via the same foramen in 4.2% (Table 1). Preoperative pain at a site was significantly associated with nerve compression, specifically by a tight foramen.
The intraoperative anatomy and etiology of nerve compression at the frontal trigger site varies greatly among patients. We report a SON foramen prevalence of 50.3%, which is greater than any previous cadaver studies of the general population. Lastly, the presence of pain at a specific site is associated with macroscopic nerve compression by a tight foramen.
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