PNEUMATIZATION OF TEMPORAL BONE

A review of the literature and study of over 400 temporal bones has provided information for a classification of pneumatization of the temporal bone. It is convenient to divide the bone into four distinct regions based on anatomical landmarks and patterns of air cell development. These regions are: A) the mastoid, B) the perilabyrinthine, C) the petrous apex, and D) the accessory. The mastoid bone is partly squamous and partly petrosal in origin, the line of separation being the petromastoid fissure on the surface and Korner's septum on the inside. This septum usually is undeveloped in well pneumatized bones. At birth the mastoid antrum is already developed and the mastoid mass consists of diploic bone. Pneumatization of the mastoid begins as extensions from the antrum and occasionally from the hypotympanum. The mastoid regions may be subdivided into the antrum, and the periantral, tegmental, sinodural, perisinus, central, perifacial and tip cell areas. The petrous bone (excluding the mastoid portion) may be divided into perilabyrinthine and petrous apex regions separated by a vertical plane passing through the axis of the modiolus of the cochlea. The perilabyrinthine region is further subdivided into supralabyrinthine and infralabyrinthine areas lying superior and inferior to the level of the labyrinth respectively. The petrous apex region, which is anterior to the axis of the modiolus, is subdivided into peritubal and apical areas lying antero lateral and posteromedial to the carotid canal respectively. All of these areas are pneumatized by air cell tracts extending from the tympanic cavity or the mastoid in well established patterns. Air cells also may extend beyond the limits of the mastoid and petrous regions to involve other portions of the temporal bone or the adjacent cranial bones, thus forming the accessory cell areas. These are the zygomatic, the squamous, the occipital and the styloid areas. © 1969, SAGE Publications. All rights reserved.