Answer for BIR CoW 21 Jun 2026
Intracranial Epidermoid cyst
Findings
Evidence of well defined lobulated T1 hypointense , T2 hyperintense, FLAIR heterogeneously hypointense lesion noted in left cerebellopontine angle cistern extending to quadrigeminal cistern with significant compression of cerebellar vermis, left cerebellar hemisphere, left middle cerebellar peduncle, hemipons and hemimedulla causing mass effect in the form of effacement of fourth ventricle. The lesion extends inferiorly into cervical spinal canal posterior to the spinal cord. The lesion shows diffusion restriction and no gradient blooming. The lesion measures 4.4(anteroposterior) x 5.5(cranio caudal) x 4.9(transverse) cm. Impression: Well defined lobulated T1 hypointense , T2 hyperintense, FLAIR heterogenously hypointense lesion in left cerebellopontine angle cistern extending to quadrigeminal cistern with significant compression of cerebellar vermis, left cerebellar hemisphere, left middle cerebellar peduncle, hemipons and hemimedulla extending inferiorly into cervical spinal canal. - Possibility Epidermoid cyst.
Discussion
Intracranial epidermoid cysts are uncommon congenital lesions that account for about 1% of all intracranial tumors. They result from the inclusion of ectodermal elements during neural tube closure, and typically present in middle age due to mass effect on adjacent structures. Their content, derived from desquamated epithelial cells, mimics CSF on CT and MRI, except on DWI, which shows restricted diffusion. In CT,The combination of cellular debris along with a high cholesterol content lower the density of epidermoids to approximately 0 HU, and can thus be identical in density to CSF, and look the same as an arachnoid cyst.Calcification is seen in a minority of case In MRI, In T1, usually isointense to CSF,higher signal compared to CSF around the periphery of the lesion is frequently seen,rarely they can be of high signal and are known as white epidermoids Rare intralesional hemorrhage can also result in intrinsic high signal T1 C+ (Gd):Thin enhancement around the periphery may sometimes be seen in the rare cases of malignant degeneration, enhancement becomes more pronounced T2:usually isointense to CSF (65%) slightly hyperintense (35%) to grey matter Rarely hypointense to grey matter, usually in the setting of the so-called white epidermoid (the term refers to the T1 appearance) 2 FLAIR:often heterogeneous/dirty signal; higher than CSF DWI/ADC: very bright on DWI similar ADC values compared to adjacent brain parenchyma
Refences:
1. Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003) ISBN:032300508X.
2. Chen CY, Wong JS, Hsieh SC et-al. Intracranial epidermoid cyst with hemorrhage: MR imaging findings. AJNR Am J Neuroradiol. 2006;27 (2): 427-9. AJNR Am J Neuroradiol (full text) - Pubmed citation
3. Swartz JD, Harnsberger HR. Imaging of the temporal bone. George Thieme Verlag. (1998) ISBN:0865777004.
4. deSouza CE, deSouza R, da Costa S et-al. Cerebellopontine angle epidermoid cysts: a report on 30 cases. J. Neurol. Neurosurg. Psychiatr. 1989;52 (8): 986-90. doi:10.1136/jnnp.52.8.986
5. Albright AL, Adelson PD, Pollack IF. Principles and practice of pediatric neurosurgery. Thieme Medical Pub. (2007) ISBN:1588903958.
6. DeMonte F, Gilbert MR, Mahajan A. Tumors of the Brain and Spine. Springer Verlag. (2007) ISBN:0387292012.
7. Miller NR, Walsh FB, Hoyt WF. Walsh and Hoyt's Clinical Neuro-Ophthalmology. Philadelphia : Lippincott Williams & Wilkins, c2005. (2005) ISBN:0781748127.
Findings
Evidence of well defined lobulated T1 hypointense , T2 hyperintense, FLAIR heterogeneously hypointense lesion noted in left cerebellopontine angle cistern extending to quadrigeminal cistern with significant compression of cerebellar vermis, left cerebellar hemisphere, left middle cerebellar peduncle, hemipons and hemimedulla causing mass effect in the form of effacement of fourth ventricle. The lesion extends inferiorly into cervical spinal canal posterior to the spinal cord. The lesion shows diffusion restriction and no gradient blooming. The lesion measures 4.4(anteroposterior) x 5.5(cranio caudal) x 4.9(transverse) cm. Impression: Well defined lobulated T1 hypointense , T2 hyperintense, FLAIR heterogenously hypointense lesion in left cerebellopontine angle cistern extending to quadrigeminal cistern with significant compression of cerebellar vermis, left cerebellar hemisphere, left middle cerebellar peduncle, hemipons and hemimedulla extending inferiorly into cervical spinal canal. - Possibility Epidermoid cyst.
Discussion
Intracranial epidermoid cysts are uncommon congenital lesions that account for about 1% of all intracranial tumors. They result from the inclusion of ectodermal elements during neural tube closure, and typically present in middle age due to mass effect on adjacent structures. Their content, derived from desquamated epithelial cells, mimics CSF on CT and MRI, except on DWI, which shows restricted diffusion. In CT,The combination of cellular debris along with a high cholesterol content lower the density of epidermoids to approximately 0 HU, and can thus be identical in density to CSF, and look the same as an arachnoid cyst.Calcification is seen in a minority of case In MRI, In T1, usually isointense to CSF,higher signal compared to CSF around the periphery of the lesion is frequently seen,rarely they can be of high signal and are known as white epidermoids Rare intralesional hemorrhage can also result in intrinsic high signal T1 C+ (Gd):Thin enhancement around the periphery may sometimes be seen in the rare cases of malignant degeneration, enhancement becomes more pronounced T2:usually isointense to CSF (65%) slightly hyperintense (35%) to grey matter Rarely hypointense to grey matter, usually in the setting of the so-called white epidermoid (the term refers to the T1 appearance) 2 FLAIR:often heterogeneous/dirty signal; higher than CSF DWI/ADC: very bright on DWI similar ADC values compared to adjacent brain parenchyma
Refences:
1. Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003) ISBN:032300508X.
2. Chen CY, Wong JS, Hsieh SC et-al. Intracranial epidermoid cyst with hemorrhage: MR imaging findings. AJNR Am J Neuroradiol. 2006;27 (2): 427-9. AJNR Am J Neuroradiol (full text) - Pubmed citation
3. Swartz JD, Harnsberger HR. Imaging of the temporal bone. George Thieme Verlag. (1998) ISBN:0865777004.
4. deSouza CE, deSouza R, da Costa S et-al. Cerebellopontine angle epidermoid cysts: a report on 30 cases. J. Neurol. Neurosurg. Psychiatr. 1989;52 (8): 986-90. doi:10.1136/jnnp.52.8.986
5. Albright AL, Adelson PD, Pollack IF. Principles and practice of pediatric neurosurgery. Thieme Medical Pub. (2007) ISBN:1588903958.
6. DeMonte F, Gilbert MR, Mahajan A. Tumors of the Brain and Spine. Springer Verlag. (2007) ISBN:0387292012.
7. Miller NR, Walsh FB, Hoyt WF. Walsh and Hoyt's Clinical Neuro-Ophthalmology. Philadelphia : Lippincott Williams & Wilkins, c2005. (2005) ISBN:0781748127.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!