Congenital implantation cholesteatomas of the occipitoparietotemporal junction.

Two cases of cranial cholesteatomas centered at the occipitoparietotemporal junction are presented, and 12 similar cases reported as diploic cholesteatomas involving the temporal bone are reviewed. Among the reported diploic cholesteatomas, 3 involved the occipitoparietotemporal junction and had the same clinical characteristics as the ones presented here. These 5 lesions did not produce expansion of the cranial tables, they had a predominantly intracranial growth, and their matrix was bonded to the dura, so that their complete excision was prevented. It is proposed that cranial cholesteatomas involving the occipitoparietotemporal junction arise, not from within the tables of the skull, but from squamous cells trapped during closure of the mastoid fontanelle and formation of the suture. Hence, they should be recognized as having an origin different from that of diploic lesions, and termed congenital implantation cholesteatomas.