Epidural Hematoma

An epidural hematoma is a collection of blood between the dura mater and the inner table of the skull, usually following closed head trauma. The majority of these are associated with fracture of the squamous temporal bone, which can tear the middle meningeal artery at its exit from the skull base (foramen spinosum) or at its adjacent entry into the dura. However, in infants and young children, epidural hematomas may develop insidiously due to venous bleeding from the diploic space after a skull fracture or from torn dural venous sinuses. While the classic clinical presentation of epidural hematoma is that of a post-traumatic 'lucid interval' during which the patient has normal, or near-normal, mental status, a variable clinical course is the norm. The lucid period is followed by rapid neurological deterioration caused by the expanding arterial blood clot. Shift of the underlying temporal lobe may result in compression of the ipsilateral oculomotor nerve and midbrain (see Table 4).

In virtually all cases, the hematoma location should be confirmed by CT imaging prior to surgery. CT imaging often demonstrates a squamous temporal bone fracture, which may extend into the skull base (see Fig. 1). Care should be taken to inspect the foramina of the petrous temporal and sphenoid bones for possible indirect signs of carotid artery or cranial-nerve injuries. The epidural hematoma itself appears as a hyperdense (white) biconvex (lens-shaped) crescent underlying the skull (see Fig. 2). Generally, hematoma extension is limited by the attachments of dura to the cranial sutures (usually frontal and parietal). Effacement of the basilar CSF cisterns (especially the perimesencephalic cistern lateral to the midbrain) on the side of the hematoma suggests impending or ongoing uncal herniation syndrome (see Table 4). Scalp lacerations, combined with the skull fracture, may admit air to the epidural space and/or intradural space ('pneumocephalus').

The treatment of epidural hematoma is most commonly surgical evacuation (cran-iotomy). Some centers manage small lesions (never larger than 1 cm in thickness) with observation and mild analgesics for associated headache. However, because pediatric patients have relatively small ventricles and extra-axial CSF spaces, even small epidural hematomas may be dangerous in children. Only trivial epidural hematomas may be observed. Craniotomy for epidural hematoma involves fashioning scalp and bone flaps adequate to expose and evacuate the hematoma and directly control arterial sources of bleeding. Sutures are used to tack the outer leaf of the dura to the edges of the craniotomy flap before the bone is replaced, thereby obliterating the epidural space and reducing the risk of rebleeding. Any coagulation abnormalities should be vigorously corrected in the perioperative period. An epidural drain is sometimes left for one day to evacuate residual blood or fluid.

Figure 1. Temporal bone fracture. Axial computed tomography, using a bone algorithm, demonstrates an irregular defect in the squamous temporal bone on the right. Acute fractures in this region are sometimes associated with injury to the middle meningeal artery and formation of epidural hematoma (see Fig. 2).

Figure 2. Epidural hematoma. Axial computed tomography, using a soft tissue algorithm, demonstrates a biconvex hyperdensity in the right temporal-parietal region. This large epidural hematoma causes significant mass effect and midline shift. The extent of the hematoma is limited by the coronal and lambdoid sutures. This 7-year-old patient presented in coma but regained normal neurological function after surgical evacuation of the hematoma (same patient as in Fig. 1).

Figure 3. Posterior fossa epidural hematoma due to birth trauma. Axial computed tomography demonstrates a small intracranial hyperdensity, representing an epidural hematoma. An associated skull fracture and subgaleal hematoma are also seen. This infant presented with normal neurological function and recovered without any surgical intervention.

Posterior fossa epidural hematomas account for only about 5% to 10% of the total, although their incidence is higher in children (see Fig. 3). They are related to bleeding from torn venous sinuses. Neurologically normal children with small hematomas and no cerebellar compression or shift of the 4th ventricle on CT imaging

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