Presentation
Progressive painless head swelling, now presented with severe headache
Patient Data
Right occipito-parietal extra-axial inhomogeneous mass without penetration of the dura. It elicits isointense signal with internal areas of high signal at T1 WI and low signal at T2 WI , non homogeneous high signal at T2 WI, In diffusion weighted images there was a restriction of diffusion with low signal in the ADC maps.
Significant compression of the right cerebellar hemisphere, brainstem and 4th ventricle. No perifocal cerebral edema suggesting a slow growing tumor.
Subsequent mild/moderate supratentorial ventricular system dilatation is noted.
Giant expansive osteolytic lesion involves the pareito-occipital bone,marked thinning and breaching of the inner and outer tables with well defined sclerotic margins of the bony defects.
Case Discussion
Diagnosis is presumptive by radiological criteria (diffusion restriction).
Differentials are Langerhans cell histiocytosis, hemangioma, metastasis or plasmacytoma.
Key to diagnosis is well-demarcated lytic lesion expanding both the inner and outer tables of the skull with sharply sclerotic margins. The MRI findings of marked restricted diffusion are typical of epidermoid.
Case courtesy of Dr Ayman Al Basmy, Dr Mohamed Hommos & Dr Mohamed Ibrahim