case_images: PMC10316224_01
case_images: Computed tomography on admission, showing a hypodense, cystic lesion with bone thinning in the right convexity.
case_images: SNI-14-224-g001.jpg
case_images: PMC10316224_01_SNI-14-224-g001.jpg
case_images: F1
case_images: Computed tomography (CT) revealed a low-density cystic lesion with bone thinning on the left convexity [Figure 1].
case_images: T1- (a), T2- (b), and fluid-attenuated (c) magnetic resonance images on admission, showing an extra-axial cystic lesion in the left convexity. No cerebral contusions or hemorrhages are visible.
case_images: SNI-14-224-g002.jpg
case_images: PMC10316224_01_SNI-14-224-g002.jpg
case_images: F2
case_images: After assessment by experienced neurologists (no AI assistance), the absence of contusions and hemorrhaging was confirmed and the cyst (isointensive with the CSF) was diagnosed as an incidentally discovered AC on the convexity [Figure 2].
case_images: Computed tomograms, showing changes in arachnoid cysts (ACs), the intracystic hemorrhage, and subdural hematoma (SDH) over time (a: 4 weeks, b: 6 weeks, c: 8 weeks, and d: 10 weeks after injury). The intracystic hemorrhage occurred first and the cystic component spread into the subdural space forming an SDH, where it was gradually absorbed while the AC disappeared simultaneously.
case_images: SNI-14-224-g003.jpg
case_images: PMC10316224_01_SNI-14-224-g003.jpg
case_images: F3
case_images: At that time, the AC appeared as a high-density lesion on CT images, suggesting intracystic hemorrhaging [Figure 3a]. AC size appeared slightly reduced. CT 8 weeks after injury showed further reductions in SDH and cyst size [Figure 3c], while CT 10 weeks after injury showed that both had nearly disappeared [Figure 3d]. At 6 months post-injury, follow-up outpatient visits were completed with no symptoms or complications.