FIG. 1.

(Case 6) Typical imaging findings of dysautoregulation/second-impact syndrome (DSIS). (A and B) Admission non-contrast axial CT images, and (C) artist's rendition demonstrate a small heterogeneous left frontal subdural hematoma (SDH; white arrows), that causes complete effacement of the basal cisterns and brainstem distortion. Note the subtle linear increased density in the region of the circle of Willis (black arrow), consistent with “pseudo-subarachnoid hemorrhage,” resulting from the marked elevation in intracranial pressure. Although there is preservation of the gray-white matter differentiation, there is asymmetric enlargement of the left hemisphere, consistent with hyperemic cerebral swelling (dysautoregulation). Note how side A is smaller than side B, even though the left hemisphere is mildly compressed by the overlying SDH. The extent of mass effect and midline shift is disproportional to the volume of the SDH (compare with Figs. 3 and 4). This 3-day-postoperative FLAIR MR image (D), and artist's rendition (E), demonstrate bilateral multifocal ischemic lesions involving several vascular territories, including the left posterior cerebral artery, thalamus, insular cortex, basal ganglia, and orbitofrontal cortex. Diffusion-weighted MR images were positive for acute ischemic injury, and the gradient-echo sequence excluded hemorrhage in these areas (not shown).