Abstract
We report about a case of a woman in her 50s with a chondrosarcoma of the petrous apex. She has a strabism due to a right-sided amblyopia since childhood and noticed a slowly progressive squint angle in the last months. Her general practitioner (GP) referred her to an ophthalmologist who diagnosed a left abducens paresis and initiated an MRI demonstrating a mass in the left petrous apex. A transnasal endoscopic transsphenoidal biopsy revealed a grade I chondrosarcoma. The patient underwent an endoscopic transsphenoidal anterior petrosectomy approach with complete removal of the tumour. After surgery the squint angle gradually improved to previous levels, so that the patient was able to resume her work. This report demonstrates that even slight changes of a squint angle without diplopia, in this case because of pre-existing amblyopia, could be a hallmark of an intracranial process.