Concussion is a clinical diagnosis and generally requires no further investigations. However, if concerning clincial features are present such as focal neurological signs or persistent or worsening symptoms, neuroimaging may be warranted.
For additional information on concussion, see the Canadian Paediatric Society Position Statement on Sport-related concussion (2014).
http://www.cps.ca/documents/position/sport-related-concussion-evaluation-management
http://www.cps.ca/fr/documents/position/commotion-cerebrales-liees-au-sport
See also the Canadian Paediatric Society Position Statement on Management of the paediatric patient with acute head trauma (2013)
http://www.cps.ca/documents/position/paediatric-patient-with-acute-head-trauma
http://www.cps.ca/fr/documents/position/patient-age-pediatrique-victime-traumatisme-cranien-aigu