We report a case of a temporal bone pneumatocele with full-thickness erosion of the cranium associated with aggressive nose blowing. This condition presented 9 years after traumatic fracture of the temporal bone. There are 17 reported cases of mastoid sinus hyperpneumatisation in the literature. Eleven of the 17 are associated with Valsalva manoeuvres or elevated middle ear pressure. However, no other cases of full-thickness erosion at the site of a former fracture have been reported. We propose that the fracture, in combination with elevated mastoid sinus pressure from aggressive nose blowing, led to escape and trapping of pressurised air in the epidural and subcutaneous spaces, which resulted in bone erosion.