Spontaneous otogenic pneumocephalus is a rare entity. We describe the case of a 55-year-old patient with intraventricular pneumocephalus associated with a bony defect at the level of the right petrous bone caused by otomastoiditis. She presented herself at the emergency department with a 1-month history of progressive balance problems, tinnitus and fullness in the right ear. Head-CT showed pneumocephalus secondary to chronic otomastoiditis with focal erosion of the petrous bone. Nasal fluid analysis tested positive on the presence of beta-transferrin. MRI before and after intrathecal gadolinium administration showed leakage of gadolinium into the right mastoid air cells. The dural defect was closed by an artificial graft. Post-operatively, gait problems, rhinorrhea and tinnitus resolved, but of mild-to-moderate headache persisted at a 3-month outpatient evaluation. This article shows that CT is the imperative for the diagnosis of pneumocephalus and to detect the underlying cause. When there is doubt about the fistula location, MR-cisternography with gadolinium can be a valuable tool to detect or confirm the fistulous site.