1. An apparatus for assessment of traumatic brain injury in a patient, comprising: a patient sensor comprising at least one neurological electrode; and a handheld base unit operatively coupled to the patient sensor, the base unit comprising: a digital signal processor configured to perform automatic identification and removal of artifacts from brain electrical signals acquired by the at least one neurological electrode, extract one or more features from the acquired brain electrical signals, and execute at least one classification function to classify the patient into one of four a plurality of categories indicative of the presence and severity of traumatic brain injury; wherein the at least one classification function is designed using a training database comprising a population of controls and patients who reportedly sustained closed head injuries and the training database is organized using Standard Assessment of Concussion (SAC) scores.