A
concussion can last for weeks after the head injury. The
symptoms too vary from person to person. Headache, confusion, memory loss, dizziness, nausea vomiting, slurred speech and fatigue are common. Delayed symptoms include depression, irritability, sleep disturbances, seizures, loss of smell etc. A doctor generally looks for focal neurological or generalized neurological symptoms that would show there is a pressure on brain somewhere.