Neuroanatomy Atlas in Clinical Context

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EPIDURAL AND SUBDURAL HEMORRHAGE 65

and do occur in cases where trauma is not involved. In these examples, trauma on the right side of the head ( C , soft tissue damage at arrows) resulted in a large acute subdural hematoma on the patient’s right side, and trauma on the left side of the head ( D , soft tissue damage at arrows ) resulted in a subdural lesion on the patient’s right. This latter lesion is a type of contrecoup injury in which the lesion is on the side opposite the initial impact. Note that the larger subdural lesion ( C ) has caused considerable midline shift . Subdural hematomas are not restrained by suture lines. Therefore, damage to the dural border cell layer may dissect this friable cell layer over considerable distances and the resultant lesion is thin and long . As seen in B and C in this figure, and in Figure 4-4A and D on the facing page, epidural and subdural lesions may be sufficiently large to result in effacement of the midline as indicated by a shift in the position of the falx cerebri. This appearance, plus the frequent loss of sulci and sometimes cisterns on the side of the lesion, foretells the very real pos sibility of brain herniation. This may present as a subfalcine herniation , which may impinge on both hemispheres, or morph into a transtentorial herniation ; all result in characteristic deficits (see Chapter 9 for further information of herniation syndromes).

4-5 Examples of epidural ( extradural ) hemorrhage/hematoma ( A , B ) and subdural hematoma/hemorrhage ( C , D ) resultant to trauma to the head; all are CTs without contrast, and all are in the axial plane. Epidural hematoma may occur in cases of skull fracture ( A , on the right side) in which the middle meningeal artery (or its larger branches) is lacerated. The resulting hematoma is formed between the inner table of the skull and the outer aspect of the dura ( epidural, B , on the right). In this significant trauma, there is a large epidural hematoma, a small lesion, probably also an epidural (small arrows), and small amounts of air within the cranial cavity ( B, black dots ). The mechanism of epidural hematoma formation is most likely two fold. First, the dura is stripped from the inner table of the skull dur ing the traumatic event creating an artifactual space. Second, the sharp edges of bone lacerate arteries, which bleed into this space, and, it is believed, may further dissect the dura from the skull. Epidural hemat omas, however, do not cross suture lines. Once the dissection reaches a suture line it stops and the lesion becomes lenticular shaped. Trauma to the head, without skull fracture, may also result in sub dural hemorrhage/hematoma; in such cases, it is called acute subdural hematoma ( C , D ). Subdural hematomas may also be subacute or chronic

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