MRI brain shows an extra-axial lesion at the cerebellopontine angle with T1 hypointense, T2 hyperintense signal, restricted diffusion on DWI, and no enhancement post-gadolinium. The diagnosis is:
- A Acoustic neuroma (vestibular schwannoma)
- B Epidermoid cyst ✓
- C Meningioma
- D Arachnoid cyst
Correct answer: B. Epidermoid cyst
Explanation
Epidermoid cysts (congenital squamous inclusion cysts) are characterised by restricted diffusion on DWI (appearing bright on DWI and dark on ADC map), which is the key distinguishing feature from arachnoid cysts (which follow CSF signal on all sequences, including DWI). Epidermoids do not enhance. Acoustic neuroma is solid and enhances. Meningioma shows intense homogeneous enhancement with a dural tail.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.