Figure 1. MRI of the brain with MRA and MRV showing (A) CSF signal intensity area in the right CP angle (~2.1 × 1.2 × 0.9 cm) causing a widening of the lateral cerebellar medullary cistern abutting the seventh (red arrow) and eighth (blue arrow) cranial nerves, its inferior aspect, and AICA branches diagnostic of arachnoid cyst (green arrow in A and yellow arrow in B).
MRI: magnetic resonance imaging; MRA: magnetic resonance angiography; MRV: magnetic resonance venography; AICA: anterior inferior cerebellar artery; CSF: cerebrospinal fluid; CP: cerebellopontine