Admittedly Wikipedia is not the best source for medical information, but this sounds right in line with what Dirrell did:

In one in about seventy concussions, concussive convulsions occur, but these are not actual post-traumatic seizures and are not predictive of post-traumatic epilepsy, which results from structural brain damage.[32] Concussive convulsions are thought to result from temporary loss of brain function rather than from structural damage and are usually associated with a good outcome.[33]

Cognitive symptoms include confusion, disorientation, and difficulty focusing attention. Loss of consciousness may occur but is not necessarily correlated with the severity of the concussion if it is brief.[15] Post-traumatic amnesia, in which the person cannot remember events leading up to the injury or after it, or both, is a hallmark of concussion.[18] Confusion, another concussion hallmark, may be present immediately or may develop over several minutes.[18] A patient may, for example, repeatedly ask the same questions,[34] be slow to respond to questions or directions, have a vacant stare, or have slurred[18] or incoherent speech.[35] Other MTBI symptoms include changes in sleeping patterns[11] and difficulty with reasoning,[31] concentrating, and performing everyday activities.[18]
Affective results of concussion include crankiness, loss of interest in favorite activities or items,[36] tearfulness,[5] and displays of emotion that are inappropriate to the situation.[35] Common symptoms in concussed children include restlessness, lethargy, and irritability.[37]