Concussion

Concussion is a traumatic brain injury that disturbs brain function, caused by a blow to the head or by a knock elsewhere on the body that moves the head rapidly.

It is a functional injury, so standard CT and MRI are usually normal. Loss of consciousness occurs in less than 10% and is not needed for the diagnosis. Most symptoms resolve within 2 to 4 weeks; children and adolescents may take longer.

UK grassroots practice follows the UK Concussion Guidelines for Non-Elite (Grassroots) Sport and NICE head injury guidance: if in doubt, sit them out.

Concussion causes a neurometabolic cascade rather than structural damage. The impact triggers glutamate release and ion shifts, with potassium leaving cells and calcium and sodium entering. Ion pumps then work harder, glucose use rises and later falls, mitochondrial function is impaired and cerebral blood flow no longer matches demand.

During this window the brain is vulnerable. A second impact before recovery can, rarely, cause second impact syndrome: catastrophic cerebral oedema, reported mainly in children and adolescents and sometimes fatal. This is why there is no same-day return.

Microscopic axonal stretch is not seen on routine CT or MRI. Symptoms usually appear immediately or within minutes, but may be delayed over the first 24 to 48 hours.