Right CPA Epidermoid Cyst-Case Discussion CaseNo.HN.1.1.1.1.001

Clinical History : 15-year-old female presented with mild sensory changes on the right side of the face and intermittent dizziness.

Radiological Findings:  MRI: Right CPA lesion approximately 20 mm.

T1: Hypointense

T2: Hyperintense

Contrast-enhanced: No enhancement

DWI: Restricted diffusion

Diagnosis: Epidermoid cyst (confirmed by pathological examination)

Teaching Points: 

*Epidermoid cysts contain keratin and slowly desquamating cellular debris; this dense, viscous content produces marked diffusion restriction on DWI.

*This feature is key in differentiating them from arachnoid cysts, which typically do not restrict diffusion.

*When combined with T1 hypointensity and T2 hyperintensity, diffusion restriction strongly suggests an epidermoid cyst even before pathology.

*Lack of contrast enhancement and slow growth further support the benign nature of the lesion and help us differentiate it from other lesions such as meningiomas and schwannomas.

*Surgical planning considers the lesion’s non-extension into the internal acoustic canal and relationship with neurovascular structures to minimize operative risk.