Diploic epidermoid cyst associated with focal brain pseudohypertrophy.

We present an 82-year-old woman, admitted for generalized status epilepticus, showing an osteolytic lesion of the right parietal bone associated with underlying focal brain pseudohypertrophy. A radiological diagnosis of diploic epidermoid cyst based on MRI characteristics was made. The aspect of focal brain pseudohypertrophy was probably caused by direct involvement of the underlying meningeal structures preventing the brain parenchyma locally from being retracted (i.e., retraction due to age-related brain atrophy). This aspect of focal brain pseudohypertrophy can potentially be seen in all chronic primary cranial bone lesions associated with meningeal involvement.