There is controversy regarding the influence of the benign enlargement of the subarachnoid space on intracranial injuries in the field of the shaken baby syndrome. In the literature, several terminologies exists to define this entity illustrating the lack of unicity on this theme, and often what is "benign" enlargement is mistaken with an old subdural bleeding or with abnormal enlargement due to brain pathology. This certainly led to mistaken conclusions. To investigate the influence of the benign enlargement of the subarachnoid space on child head injury and especially its influence on the bridging veins, we used a finite element model of a 6-month-old child head on which the size of the subarachnoid space was modified. Regarding the bridging veins strain, which is at the origin of the subdural bleeding when shaking an infant, our results show that the enlargement of the subarachnoid space has a damping effect which reduces the relative brain/skull displacement. Our numerical simulations suggest that the benign enlargement of the subarachnoid space may not be considered as a risk factor for subdural bleeding.