[Meningoencephalic herniation into the middle ear]

Herniation of meningeal and/or encephalic tissue into the middle ear is a pathology which, even if rarely found by the otologist, can be life-threatening for the patient because of eventual infective intracranial complications. Four different etiological types are possible, infective, post-surgical, traumatic and spontaneous. From a pathogenic point of view, all types are characterized by a bony and dural defect localized in the tegmen through which meningeal and encephalic tissue can herniate. Symptomatology is often non-specific so that some cases are diagnosed during surgery. When there is strong suspicion of herniation neuroradiological assessment procedures must be carried out in order to make a correct pre-operative diagnosis, High Resolution Computed Tomography (HRCT) of the temporal bone in particular, can show the exact limits and location of the bone defect, while Magnetic Resonance Imaging (MRI) allows the nature of the tissue in the middle ear to be determined. Surgery is the only appropriate therapy. Different approaches have been described amongst which the transmastoid with or without temporal minicraniotomy and the middle cranial fossa (MCF) are the most frequently reported literature. From June 1982 to March 1994, 27 consecutive cases underwent surgery at the Gruppo Otologico, Piacenza. As a result of the occurrence of postoperative meningitis in one case, a new surgical technique through the MCF was standardized. The main step of this procedure consist in leaving the herniated tissue in situ so as to make a barrier between the middle ear and subdural space. The technique is indicated either in the case of large, multiple or very anteriorly located bony defects or when there is an infection in the middle ear.