[[Subspecialization]] of physicians and regional [[center]]s concentrate the [[volume]] of certain rare [[case]]s into fewer [[hospital]]s. Consequently, the primary [[institution]] of a [[Neurosurgical Resident Training Program]] may not have sufficient [[case volume]] to meet the current Residency Review Committee case minimum requirements in some areas. To ensure the [[competency]] of graduating [[resident]]s through [[comprehensive]] neurosurgical [[education]], programs may need residents to [[travel]] to outside institutions for exposure to cases that are either less common or more regionally focused.