The present system is directed in several embodiments to a method of administration of a therapeutic composition for protection of the brain of a subject at risk of injury leading to traumatic brain injury (TBI) and/or treatment of injury to the brain resulting from TBI. The method includes administering one or more therapeutic compositions comprising an effective amount of insulin directly to the subject patient's CNS, with no to minimal systemic exposure. Preferably, this method comprises administration of an effective amount of insulin to the upper third of a patient's nasal cavity, thereby bypassing the patient's blood-brain barrier and delivering the therapeutic composition directly to the patient's central nervous system.