It is related to infection, trauma, and normal aging. Basilar impression increases the risk of neurologic damage and circulatory embarrassment.Ī calcified cerebral falx appears as a single sheet of calcification extending from the frontal bone.

If the resulting angle (Martin’s basilar angle, see Chapter 4) is greater than 152 degrees, platybasia is present. Platybasia is assessed by constructing approximations of the hard palate and clivus. (See Chapter 4 for more detail on construction of these roentgenometrics.) In contrast to describing the relationship of the odontoid to the skull base, as is done for basilar invagination, the term platybasia (meaning “flat base”) describes the morphology of the skull base without using the odontoid as a reference point. The deformity is identified on the lateral projection by constructing lines from the posterior extreme of the hard palate to either the posterior margin of the foramen magnum (Chamberlain’s line) or lower margin of the base of the occiput (McGregor’s line), and examining the distance between the constructed line and the tip of the odontoid process. Primary basilar impression is also known as Bull-Nixon syndrome. The presentation is either primary (congenital syndromes such as Klippel-Feil syndrome and Arnold-Chiari malformation) or acquired (bone softening pathologies such as osteomalacia, fibrous dysplasia, or Paget’s disease). Although some authors separate the upward displacement of the foramen magnum (basilar invagination) from the resulting deformity of the skull base (basilar impression), most sources use the terms as synonyms. It is discussed more fully in Chapter 33.īasilar invagination describes a cephalic deformity of the margins of the foramen magnum with resulting deformity of the condyles and skull base (basilar impression). TABLE 7-1 Skeletal Variants, Anomalies, and Defects of the SkullĬommon artifacts visualized are hearing aids, hairpins, dental fillings, etc.Īrnold-Chiari malformation describes the presence of a myelomeningocele with varying degrees of caudal displacement of the cerebellar tonsils and hindbrain.

Oblique upper cervical spine x ray