What would cause slurred speech after a person substains a concussion ?

Common symptom: Slurred speech is a common symptom after sustaining a concussion, along with headaches, confusion, ringing in the ears, nausea, vomiting, fatigue, etc. I do hope you have been seen for this condition to make sure everything seems to be getting better. Rest is very important, both physically and intellectually (meaning not returning to school or work for several days in most cases).