CEREBRAL CONCUSSION

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Abstract
The author suggests that concussion can be defined as a transitory and reversible nervous reaction with immediate onset following physical stress of sufficient violence and brevity, and characterized by progressive recovery thereafter. In man, amnesia both retrograde and postgrade is its chief external sign, accompanied by a loss of reactivity which is its clearest feature in animals. The loss of activity affects all tissue subjected to such stress but the duration of paralysis varies with the complexity of the nervous mechanism as well as the intensity of injury. Cerebral concussion is a phenom- enon which has not only important practical considerations, but also merits attention as a fundamental mode of reaction of nervous tissue. Some of the factors that determine the presence or absence of concussion in penetrating gunshot injuries to the brain are now explained. The separation of the effects of concussion and of multiple hemorrhages, and the greater understanding of the pulmonary lesions due to explosive violence have seemed to clear up many of the doubtful features of the effects of explosive blast. No convincing evidence is found to support the hypothesis that explosive blast can produce a cerebral lesidn comparable to concussion. The introduction of methods of reproducing standard degrees of the condition and of measuring both the quantity of injury-inflicted and the amt. of effect produced have opened the possibility of measuring its relation to nervous metabolism. Its effect on synaptic transmission and the delayed development of a cycle of histologic changes are at present complete enigmas which invite investigation. Its relationship to shock, to fatigue and to the similar but different changes induced by anoxia are unexplored. The cumulative effect of repeated minor concussion would appear to offer a good starting point in such investigations.