Presentation
Acute confusion following a fall.
Patient Data
There is a 5x3cm low attenuation lesion in the left frontotemporal region. It is located within the CSF space (extra-axial), and has mass effect, including displacement of the cortex, effacement of the left lateral ventricle and midline shift. Thinning and remodeling of the adjacent bone is also noted.
CSF density arachnoid cyst ( * ) with adjacent cortical thinning and remodeling (blue arrow).
Case Discussion
This case demonstrates the characteristic appearances of an arachnoid cyst. These are relatively common lesions and in most cases are asymptomatic and found incidentally.