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2Brain

Subdural hygromas have the same CT density as CSF and can be indistinguish-able from chronic subdural hematomas. When isolated and identified in the setting of acute trauma, subdural hygromas are considered a benign consequence of head injury, since most are small and clinically insignificant, and do not require surgi-cal intervention. Subdural hygromas are commonly seenin conjunction with other brain injuries, such as contusion, traumatic subarachnoid hemorrhage, and extra-axial hematomas (Fig. 2.9).

◆Subdural Hygroma

Subdural hygromas are due to CSF that leaksinto the subdural space via either a tear oran irritation of the arachnoid. Subdural hy-gromas are usually bilateral, located overthe anterior frontal or temporal lobes, anddevelop 2 to 3 days after acute head trauma.

Depending on CSF absorption and post-traumatic brain swelling, subdural hygromascan fluctuate in size over time. Atrophy or encephalomalacia aords a potential space for the development of hygromas, whereasparenchymal expansion and fluid reabsorp-tion will speed resolution of the hygroma.

Fig. 2.9a–d a,b Subdural hygroma. (a) CT at time of injury. Mild underlying ventricular and sulcal prominence. (b) CT 48 hours later. Interval appearance of symmetric, low-attenuation bifrontal subdural uid collections. c,d Subdural hygroma associated with cortical contusion, epidural hematoma, and traumatic subarach-noid hemorrhage. Low-attenuation bifrontal subdural collections. High-attenuation subarachnoid hemor-rhage lls the left frontal sulci. Left inferior frontal hemorrhagic contusion. Small right temporo-occipital epidural hematoma containing air.