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2Brain

pecially in the absence of other traumatic brain injuries (contusion, subdural hema-toma, epidural hematoma) or with minor trauma, is more consistent with subarach-noid hemorrhage due to a ruptured aneu-rysm. It is important to keep in mind that the accident leading to a patient’s head injury may have been precipitated by loss of consciousness due to an aneurysmal hemorrhage. CT or conventional angiog-raphy can be performed to address this possibility.

SAH is associated with increased mor-bidity and mortality in trauma, reflecting its potential to induce vasospasm and itsassociation with more severe mechanismsof head injury. Subarachnoid blood is alsotoxic to the underlying cortex and can inter-fere with normal CSF absorption, which canlead to later complications of chronic hydro-cephalus or superficial siderosis (Fig. 2.10).

◆Traumatic Subarachnoid Hemorrhage

Traumatic subarachnoid hemorrhage (SAH) is a consequence of either direct pial vas-cular injury or extension from a hemor-rhagic cortical contusion, parenchymal hematoma, or extra-axial hematoma. Al-though traumatic SAH is often seen in as-sociation with other brain injuries, it can be subtle, particularly if it is the only find-ing in minor head trauma. Blood that col-lects between the pia and the arachnoid membrane fills cerebral sulci and forms fine serpentine juxtacortical high-density collections. Hemorrhage is also common in the perimesencephalic cisterns. Over a period of days, blood becomes isodense to brain and ultimately resolves.

Traumatic SAH may be limited to cor-tical sulci, the interpeduncular cistern, or the posterior perimesencephalic cisterns. Extensive hemorrhage in the suprasellar and middle cerebral artery cisterns, es-

Fig. 2.10a–d a,b Isolated traumatic subarachnoid hemorrhage. Generalized cerebral swelling with eacement of perimesencephalic cisterns and cortical sulci. Subarachnoid hemorrhage in the interpeduncular and ambi-ent cisterns. Hemorrhage lls numerous frontal and parietal convexity sulci.

c,d Traumatic subarachnoid hemorrhage associated with other cerebral injuries. Generalized cerebral swelling, right frontal cortical contusions, pneumocephalus, clot within the ventricles, and small tentorial subdural hematoma. Traumatic subarachnoid hemorrhage in the interpeduncular cistern and left Sylvian ssure.