Answer for BIR CoW 15 Feb 2026
Epidermoid cyst
Findings
Evidence of relatively well defined T1 heterointense, T2 heterogenous hyperintense lesion with areas of FLAIR suppression showing diffusion restriction with gradient blooming noted involving sellar region, left frontal, left anterior temporal region, left ganglio capsular region and left corona radiata region. The lesion causes mass effect over left hemi midbrain, effacement of left lateral ventricle causing dilation of occipital and temporal horn and midline shift to the right T1 hyperintense foci noted in ambient cistern, quadrigeminal cistern and body of left lateral ventricle. On contrast administration, the lesion shows peripheral enhancement on the cisternal aspect - Possibilty of 1) Ruptured Dermoid cyst. 2) Epidermoid cyst.
Discussion
Excision was done and final HPE came as Epidermoid cyst Intracranial epidermoid cysts are typically non-calcified lesions, but calcification can occur and has diagnostic significance. Fat containing epidermoid is known as white epidermoid. In some cases, the intrinsic high T1 signal is due to a high protein content, which renders them also relatively hyperattenuating on CT . In such cases, T2 signal can vary from hyper to hypointense. Calcification is uncommon but not rare reported in approximately 10–25% of cases. Calcifications may be: Peripheral (rim-like) – most common, Focal/nodular, Occasionally coarse or irregular. They are usually located in the cyst wall or within the capsule. Intracranial epidermoid cysts are uncommon congenital lesions which account for about 1% of all intracranial tumours. They result from 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, with the exception of DWI which demonstrates restricted diffusion. Intracranial Epidermoid Cysts are congenital inclusion cysts from ectodermal remnants.They are slow-growing, benign lesions Common locations: Cerebellopontine angle Suprasellar region Parasellar region Fourth ventricle MRI findings: T1: usually CSF intensity rarely they can be of hyperintense due to fat are known as white epidermoids rare intralesional haemorrhage 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 hyperintense(65%) Rarely hypointense to grey matter, usually in the setting of the so-called white epidermoid (the term refers to the T1 appearance) FLAIR shows incomplete supression DWI/ADC: Very bright on DWI Similar ADC values compared to adjacent brain parenchymaUseful for differentiation from arachnoid cysts due to increased signal (due to a combination of abnormal restricted diffusion and T2 shine through), which is not seen with arachnoid cysts. Differential diagnosis: 1)CSF cysts : Arachnoid cyst or mega cisterna magna 2)Dermoid cyst: Often fat density due to sebum Typically located along the midline 3)Inflammatory cyst such as Neurocysticercosis May have associated oedema Usually no restricted diffusion 4)Cystic tumours Eg: Acoustic schwannoma or craniopharyngioma A solid enhancing component is usually identifiable 5)Neurenteric cyst
References:
Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003) ISBN:032300508X. Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. 2006;239 (3): 650-64. Radiology (full text)- doi:10.1148/radiol.2393050823 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
Findings
Evidence of relatively well defined T1 heterointense, T2 heterogenous hyperintense lesion with areas of FLAIR suppression showing diffusion restriction with gradient blooming noted involving sellar region, left frontal, left anterior temporal region, left ganglio capsular region and left corona radiata region. The lesion causes mass effect over left hemi midbrain, effacement of left lateral ventricle causing dilation of occipital and temporal horn and midline shift to the right T1 hyperintense foci noted in ambient cistern, quadrigeminal cistern and body of left lateral ventricle. On contrast administration, the lesion shows peripheral enhancement on the cisternal aspect - Possibilty of 1) Ruptured Dermoid cyst. 2) Epidermoid cyst.
Discussion
Excision was done and final HPE came as Epidermoid cyst Intracranial epidermoid cysts are typically non-calcified lesions, but calcification can occur and has diagnostic significance. Fat containing epidermoid is known as white epidermoid. In some cases, the intrinsic high T1 signal is due to a high protein content, which renders them also relatively hyperattenuating on CT . In such cases, T2 signal can vary from hyper to hypointense. Calcification is uncommon but not rare reported in approximately 10–25% of cases. Calcifications may be: Peripheral (rim-like) – most common, Focal/nodular, Occasionally coarse or irregular. They are usually located in the cyst wall or within the capsule. Intracranial epidermoid cysts are uncommon congenital lesions which account for about 1% of all intracranial tumours. They result from 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, with the exception of DWI which demonstrates restricted diffusion. Intracranial Epidermoid Cysts are congenital inclusion cysts from ectodermal remnants.They are slow-growing, benign lesions Common locations: Cerebellopontine angle Suprasellar region Parasellar region Fourth ventricle MRI findings: T1: usually CSF intensity rarely they can be of hyperintense due to fat are known as white epidermoids rare intralesional haemorrhage 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 hyperintense(65%) Rarely hypointense to grey matter, usually in the setting of the so-called white epidermoid (the term refers to the T1 appearance) FLAIR shows incomplete supression DWI/ADC: Very bright on DWI Similar ADC values compared to adjacent brain parenchymaUseful for differentiation from arachnoid cysts due to increased signal (due to a combination of abnormal restricted diffusion and T2 shine through), which is not seen with arachnoid cysts. Differential diagnosis: 1)CSF cysts : Arachnoid cyst or mega cisterna magna 2)Dermoid cyst: Often fat density due to sebum Typically located along the midline 3)Inflammatory cyst such as Neurocysticercosis May have associated oedema Usually no restricted diffusion 4)Cystic tumours Eg: Acoustic schwannoma or craniopharyngioma A solid enhancing component is usually identifiable 5)Neurenteric cyst
References:
Grossman RI, Yousem DM. Neuroradiology, the requisites. Mosby Inc. (2003) ISBN:032300508X. Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. 2006;239 (3): 650-64. Radiology (full text)- doi:10.1148/radiol.2393050823 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
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!