Epidermoid Cyst (Cerebellopontine Angle)

View Key Images

Diagnosis Definition

Epidermoid cysts arise from ectopic inclusion of ectodermal cells during embryonic development
They represent 5% of all cerebellopontine angle (CPA) tumors
Presentation (most commonly between the 2nd and 5th decades of life) is often a result of mass effect on adjacent cranial nerves
A long history of tinnitus and hearing loss is the most common presentation
The primary differential diagnosis is arachnoid cyst, which is usually managed conservatively, whereas epidermoid cyst is often surgically removed to alleviate symptoms and prevent growth

Imaging Findings

Epidermoid cysts usually follow the intensity of cerebrospinal fluid (CSF) on T1 and T2 sequences, although the T1 signal varies with the amount of protein content (e.g., “white” epidermoids are bright on T1 due to high protein content)
Epidermoid cysts are markedly hyperintense on diffusion weighted imaging (DWI), which distinguishes them from arachnoid cysts
T2 FLAIR sequences show a dirty, heterogeneous appearance with intermediate signal, another feature that may help distinguish epidermoid cysts from arachnoid cysts
Epidermoid cysts generally do not enhance with contrast
They typically have undulating margins, insinuating around and encasing cranial nerves and vessels, and model their shape to conform to the CPA without extending into the internal acoustic meatus

Pearls

When evaluating epidermoid cysts, it is important to evaluate their relationship to adjacent cranial nerves and major vessels

References

Bonneville F, Sarrazin JL, Dupuch KM, Iffenecker C, Cordoliani YS, Doyon D, Bonneville JF. Unusual Lesions of the Cerebellopontine Angle: A Segmental Approach. RadioGraphics 2001; 21:419-438

Case-based learning.
Perfected.

Try MRI Online Premium for free.

Mastery Series video courses

High-yield cases

Expert case reviews

CME & SA-CME credits

Learn from world renowned radiologists anytime,
actice on real, high-yield cases with MRI Online Premium.

Learn from world renowned
radiologistsanytime, anywhere and practice on real, high-yield cases with MRI Online Premium.