Cerebral trauma
Multiple realities
(covers information from several alternate timelines)
Cerebral trauma was an injury to the brain (brain damage) as a result of head injury from an external force such as sudden acceleration or deceleration, falling, weapon projectile, or traffic accident. Cerebral trauma could lead to a number of symptoms such as emotional and behavioral issues, disability, or death.
In an alternate 2266, massive cerebral trauma was one of the injuries that Spock received after the USS Enterprise was attacked by Romulan ships near the Romulan Neutral Zone and hit by a plasma torpedo. Nurse Christine Chapel was not sure whether he would recover, but he would not be the same if he did. (SNW: "A Quality of Mercy")