Acoustic schwannoma

Arise from schwann cells
Most common CPA lesion
2nd most common extra axial lesion
85% of schwannomas found in this region
A/W arachnoid cyst in 0.5%
Bilateral is diagnostic of NF-2 (Chr 22q)

Clinical presentation:
SNHL, tinnitus, trigeminal or facial neuritis

MR:
Well defined
Oval or round
Low on T1, high on T2, intensely enhance (100%)
Cystic component present
Small lesions are seen as low signal lesions (filling defect ) in IAM on T2
Large lesions show stalk in the IAM (ice cream on cone)
Dural tail sign rare (cf. meningioma)

CT:
Mixed solid and cystic lesion with intense enhancement
No calcium (cf. meningioma)