Case Of the Week (COW) 27 September 2015
Intradiploic Epidermoid Cyst
Findings
Expansile punched out cystic lesion noted involving the right occipital bone with epidural component. DWI screening revealed restricted diffusion. No evidence of intraparenchymal extension. The inner table, outer table and diploic space is not visualised. No fat component / calcification noted
Discussion
The above features are Consistent with Intradiploic Epidermoid Cyst. Intracranial epidermoid cysts are congenital lesions with benign histological features and very slow growth, via progressive accumulation of normally dividing cells (epidermal cells) A possible complication of intradiploic epidermoid tumors is the spontaneous cyst rupture with secondary discharge of the cystic content (keratin, cellular debris and cholesterol) into the subarachnoid space, producing aseptic meningitis which frequently leads to chronic granulomatous arachnoiditis On CT, simultaneous e rosion of inner and outer table of the skull is reported to occur in up to 72% of cases with intradiploic epidermoids The possible differential diagnosis include: calcified cephalhematomas, occult meningocele and eosinophilic granuloma, osteolytic intradiploic metastasis. It is readily differentiated from the above by the characteristic restricted diffusion.
Contributed By:
Prof. S Babu Peter
Barnard Institute of Radiology
Intradiploic Epidermoid Cyst
Findings
Expansile punched out cystic lesion noted involving the right occipital bone with epidural component. DWI screening revealed restricted diffusion. No evidence of intraparenchymal extension. The inner table, outer table and diploic space is not visualised. No fat component / calcification noted
Discussion
The above features are Consistent with Intradiploic Epidermoid Cyst. Intracranial epidermoid cysts are congenital lesions with benign histological features and very slow growth, via progressive accumulation of normally dividing cells (epidermal cells) A possible complication of intradiploic epidermoid tumors is the spontaneous cyst rupture with secondary discharge of the cystic content (keratin, cellular debris and cholesterol) into the subarachnoid space, producing aseptic meningitis which frequently leads to chronic granulomatous arachnoiditis On CT, simultaneous e rosion of inner and outer table of the skull is reported to occur in up to 72% of cases with intradiploic epidermoids The possible differential diagnosis include: calcified cephalhematomas, occult meningocele and eosinophilic granuloma, osteolytic intradiploic metastasis. It is readily differentiated from the above by the characteristic restricted diffusion.
Contributed By:
Prof. S Babu Peter
Barnard Institute of Radiology