Migraine Surgery at the Frontal Trigger Site: An Analysis of Intraoperative Anatomy

Abstract

Purpose: The development of migraine headaches may involve the entrapment of peripheral craniofacial nerves at specific sites. Cadaveric studies in the general population have confirmed potential compression points of the supraorbital (SON) and supratrochlear (STN) nerve at the frontal trigger site. Our aim was to describe the intraoperative anatomy of the SON and STN at the level of the supraorbital bony rim in patients undergoing frontal migraine surgery and to investigate associated pain. Methods: Patients scheduled for frontal site 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. Results: 118 sites among 61 patients were included. The SON traversed a notch in 49%, foramen in 41%, notch plus foramen in 9.3%, and neither a notch nor foramen in one site. The senior author noted macroscopic nerve compression at 74% of sites. Reasons 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%. Preoperative pain at a site was significantly associated with nerve compression by a foramen. Conclusions: 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 previous cadaver studies of the general population. Lastly, the presence of pain at a specific site is associated with macroscopic nerve compression.