A 32-year-old male presents to a primary care nurse practiti…

A 32-year-old male presents to a primary care nurse practitioner with complaints of severe facial pain and headache. He reports that the pain often follows shaving or facial washing and occurs repeatedly for period of several seconds to a minute over an hour and then spontaneously resolves. The pain is described as knife-life. This is a new complaint.  These findings are most likely related to altered function of which structure?