Brief unconsciousness due to disturbance of the electrical activity in the brain following a violent blow to the head or neck. Common symptoms following concussion include confusion, inability to remember events immediately before the injury, dizziness, blurred vision, and vomiting. If symptoms persist, or new ones develop, such as drowsiness, difficulty breathing, repeated vomiting, or visual disturbances, they could signify brain damage or an extradural haemorrhage. Repeated concussion can cause punchdrunk syndrome. (See also head injury.)


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