This is Episode 15A: Perineural Invasion Tracking and Skull Base Extension.The pathology report lands on your desk: “Extensive perineural invasion involving a named nerve measuring zero-point-three millimeters in diameter. Inferior alveolar nerve identified at the deep margin.”Now what?Do you treat the tumor bed and call it a day? Do you track the nerve all the way to the skull base? How far is far enough? And what happens when your C T V starts encroaching on the brainstem and temporal lobe?