The nature of concussion: a speculative hypothesis

Concussion is one of the commonest forms of neurological injury seen throughout the world. Although common in sport, this condition has parallels in the types of injury suffered in motor vehicle crashes, falls, and other forms of brain trauma.1 Despite the fact that the effects of brain injuries have been recognised for at least 3000 years and the clinical state of concussion initially described over 1000 years ago,2 the understanding of the pathophysiology of these injuries remains limited. One issue that remains difficult to reconcile is the absence of consistent neuroimaging abnormalities in the face of dramatic symptoms. This may in part be because concussion is due to a functional rather than structural lesion but also that the anatomical locus may be not cortical as is often assumed. The acute symptoms of concussion are described in detail in many published studies. Prospectively validated signs and symptoms include amnesia, loss of consciousness, headache, dizziness, blurred vision, attentional deficit, and nausea.3–7 The attentional deficit is often loosely described by clinicians as “confusion” or “disorientation”. While these terms are often seen as sine qua non of concussion, it is more scientifically appropriate to use the correct terminology. Other recently documented clinical features …