Suppuration in the Mastoid and Petrous Portions of the Temporal Bone: Roentgen Findings

THE temporal bone is composed of four parts: the mastoid process, the petrous pyramid, the squamous, and tympanic portions. The mastoid process and the petrous pyramid are the portions of particular interest because of the prevalence of suppurations within these parts of the temporal bone. A roentgen study of the temporal bone should include an examination of the mastoid processes and the petrous pyramids. The Law position, or a modification of it, is usually employed for the mastoid processes, and a film of the base of the skull or some other position, for the petrous pyramids. The examination may include other and additional positions, depending upon the type and location of the lesion which is under investigation. Individual preferences enter here. Other positions commonly employed are: Obliques for the mastoid tip, modifications of the Law position, Stenvers, Schüller, Mayer, Granger, MacMillan, and others. When complications to otitic infections are under investigation, it is desirable and often necessary to utilize several of the above-named positions, in order to arrive at a diagnosis. At birth, the temporal bone is not pneumatized. The mastoid antrum is the only cell present. Pneumatization of the mastoid portion of the temporal bone is a normal process. According to Wittmaack, this follows the invagination of the epithelial lining of the middle ear into the diploic bone of the mastoid process, and the replacement of the latter by the subsequent development of pneumatic cells. Associated with this, there is a proliferation of the embryonal myxomatous connective tissue. The process of pneumatization in the petrous pyramid is identical with that in the mastoid. It starts either from the inner antral wall, the epitympanic space, or from the peritubal region, and goes forward to the petrous tip. Anything which interferes with the normal process of pneumatization will result in an undeveloped mastoid, or cause a faulty type of pneumatization, with the result that throughout life there will be either a diploic or an incompletely pneumatized mastoid process. This also holds true for the petrosa. Pneumatization varies considerably, and does not respect boundaries or suture lines. When pneumatization is extensive it may extend into the zygoma, squamosa, occipital bone adjacent to the mastoid, and also into the basilar process of the occipital bone. Pneumatization in the temporal bones is usually symmetrical. Asymmetrical pneumatization does occur, but infrequently. The mastoid process is usually pneumatized between the ages of three and five. Before the age of three, little or no pneumatization may be present. Roentgenograms of the temporal bone reveal the following anatomical landmarks: