Idiopathic brain herniation into the middle ear and the mastoid process is a rare clinico-pathological entity, with only 41 cases described in the literature. It should be suspected in presence of spontaneous otoliquorrhea/rhinoliquorrhea, refractory serous otitis media, or meningitis following acute otitis media in an adult. A new case is presented, with a brief review of the pathogenesis, clinico-pathological, and radiological characteristics of these lesions.