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. In absence of these symptoms and based on the history a diagnosis of concussion is given.