![]() In 2011, the tumor became obvious and invaded the SOS, prevertebral space, clivus, and upper C2. A subtle recurrent tumor was noted in the anterior supraodontal space (SOS) in 2008 ( white arrow ). Serial follow-up sagittal T1-weighted MR images (A – C) from 2008 to 2013. For details, please see the following section.Ī patient with nasopharyngeal carcinoma has secondary basilar invagination due to local bone destruction. This type of developmental basilar invagination is considered to be related to atlantoaxial dislocation stemming from aplasia and hypoplasia of the atlas. ![]() The other group of patients had imaging findings such as horizontal orientation of the clivus and anatomic alignment of the odontoid process and clivus despite the presence of basilar invagination, violation of the Chamberlain line but not the McRae and Wackenheim lines, and normal or fused horizontal C1-2 facet joints. 14.2 ) of odontoid process protrusion into the foramen magnum in the cephalad direction, C1-2 dislocation or dens-clivus dislocation causing direct compression of the pontomedullary junction with violation of the Chamberlain, McRae, and Wackenheim lines, and listhesis of the oblique C1 and C2 facets. One group of patients had classical imaging findings ( Fig. Our and previous observations indicate there may be two different types of developmental basilar invaginations based on imaging findings. Some patients present with vertebral artery insufficiency. The patients might have symptoms and signs of increased intracranial pressure because of blockage of cerebrospinal fluid (CSF) circulation or vertical or lateral nystagmus because of compression of the cerebellum and vestibular apparatus. The most common local finding is short neck and torticollis. The symptoms and signs of developmental basilar invagination usually occur in the second or third decade. In about 25%–35% of cases, basilar invagination is associated with Arnold-Chiari malformation, syringomyelia, and hydrocephalus. ![]() Basilar invagination is divided by etiology into two types: primary or developmental invagination, which is more common, and secondary or acquired invagination.ĭevelopmental invagination is associated with atlantooccipital assimilation, hypoplasia of the basiooccipital or atlas, incomplete fusion of the posterior arch of the atlas, odontoid anomalies, Klippel-Feil syndrome, and vertebral artery anomalies. Most patients with basilar invagination actually have a normal basal angle and thus do not have associated platybasia. Platybasia alone does not usually cause symptoms unless it is associated with basilar invagination or other anomalies.īasilar Invagination (Basioccipital Hypoplasia, Basilar Impression)īasilar invagination implies that the floor of the skull is pressed in by the dens and the tip of the odontoid is more cephalad and protrudes into the foramen magnum, resulting in compression of the brainstem or its neurovascular structures. Platybasia is an anthropometric term referring to the flattening of the skull base resulting in an increase in the Welcher basal angle (>143–145 degrees). ![]() Patients are prone to develop multiple congenital anomalies of the CVJ owing to the complexity of embryonic development. The first spinal sclerotome forms the C1 posterior arch and body of the C2 dens, whereas the second spinal sclerotome forms the body, facets, and posterior arch of the C2. Yet, the first four sclerotomes (first occipital, second occipital, third occipital, and fourth proatlas) follow a different course, ending in the formation of the basiocciput, exoccipital centers (i.e., the lateral margins of the foramen magnum, occipital condyles, and hypoglossal canal), jugular tubercles, posterior portions of the foramen magnum, most of the C1, and apex of the C2 dens. Generally, the upper half of one sclerotome unites with the lower half of its neighbor to form the vertebral body. The medial sclerotomes form the vertebral bodies. Each somite differentiates into three parts (the outer dermatome, inner myotome, and medial sclerotome). In brief, a total of 42 somites are formed in the fourth week of gestation. Embryonic development of the CVJ has been discussed in detail in many previous reports.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |