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

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 and supratrochlear nerves at the frontal trigger site. The authors' aim was to describe the intraoperative anatomy of the supraorbital and supratrochlear nerves at the level of the supraorbital bony rim in patients undergoing frontal migraine surgery and to investigate associated pain.

PATIENTS: scheduled for frontal-site surgery were enrolled prospectively. The senior author (W.G.A.) evaluated intraoperative anatomy and recorded variables using a detailed form and operative report. The resulting data were analyzed.

One hundred eighteen sites among 61 patients were included. The supraorbital nerve traversed a notch in 49 percent, a foramen in 41 percent, a notch plus a foramen in 9.3 percent, and neither a notch nor a foramen in one site. The senior author noted macroscopic nerve compression at 74 percent of sites. Reasons included a tight foramen in 24 percent, a notch with a tight band in 34 percent, and supraorbital and supratrochlear nerves emerging by means of the same notch in 7.6 percent or by means of the same foramen in 4.2 percent. Preoperative pain at a site was significantly associated with nerve compression by a foramen.

The intraoperative anatomy and cause of nerve compression at the frontal trigger site vary greatly among patients. The authors report a supraorbital nerve foramen prevalence of 50.3 percent, which is greater than in previous cadaver studies of the general population. Lastly, the presence of pain at a specific site is associated with macroscopic nerve compression.