THE PROBLEM OF MILD BRAIN INJURY

It is estimated that 2,000,000 traumatic brain injuries (TBIs) occur i n the U.S.A. each year; 90% are classified as ''mild brain injuries'' (MBIs). The epidemiology, pathophysiology, and diagnosis of MBI and th e ''postconcussion syndrome'' (PCS) are reviewed, with particular atte ntion to outcome data and factors that predict outcome. Symptoms of PC S may be quite severe, but severe symptoms are almost invariably trans ient. Persistent deficits may arise from MBI, but persistent problems are usually mild and are rarely disabling. Catastrophic outcomes relat ed to MBI do occur, in the following situations. (a) What appears to b e an MBI is really a severe injury. (b) PCS evolves into a posttraumat ic depression that is unrecognized and untreated. (c) A premorbid psyc hiatric condition is mobilized around the MBI as a focal (but not a ca usative) event. (d) A patient shows signs of a ''functional'' conditio n, i.e., conversion disorder (hysteria), somatoform pain disorder, com pensation neurosis, or malingering.