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Three cases of atlanto-axial interspinous articulation (AIA) were reported. In a case, the articulating C1 posterior arch and C2 spinal process were removed en bloc during surgery. In an other case, articulating parts of C1 and C2 arches were excised by chisel. These had facets with glistening smooth surfaces and were consisted of fibrocartilage histologically. The facets were connected by a membrane containing the synovial layer, loose connective tissue layer with small vessels and the dense fibrous layer. With review of X-ray findings of present cases and cases reported in the literature, the AIA was classified into (1) simple type and (2) hyperplastic type. It was stressed that the hyperplastic type of AIA can produce definite cord compression.

The craniocervical syndrome is an entity whose symptoms: vertigo, cephalea, tinnitus, facial pain, otalgia, dysphagia, pain of the carotid artery are thought to be caused by cervical factors. In the majority of cases the cranio-cervical syndrome is caused by a spondylarthrogenic segmental dysfunction whose pathophysiology is explained. In the pathogenesis lesions of the joints of the skull which may be responsible for pain and dysfunction in the segmental areas are of great importance. The neurology of the joints of the skull, as well as the pathological mechanisms of spondylarthrogenic disturbances, responsible for the different kinds of dysfunction of the equilibrium and for cephalea are discussed. The pathophysiological basis of manual diagnosis is explained; also the radiological findings of the upper cervical vertebral column are principally discussed. A short review of therapeutic recommendations is given.

A case of long standing atlanto-axial subluxation following relatively minor trauma is reported. Progressive development of pain and spastic quadriparesis led to clinical and radiological investigation at Groote Schuur Hospital which revealed a spontaneous fusion of C1 and C2 with marked compromise of the spinal cord. The possibility of a pre-existing unfused odontoid process (os odontoideum) is discussed. A brief review of the literature is presented.

Atlantoaxial instability in rheumatoid arthritis patients presents a particular hazard for endoscopists. The basic pathology, while well known to orthopedists, is not common knowledge among bronchoesophagologists or anesthesiologists. The paper describes the syndrome, potential complications and possible approaches to avoiding serious neurologic sequellae.

Odontoid dysplasia in the absence or presence of atlanto-axial instability was found in all cases. In general, this correlated well with the overall clinical severity of the condition and illustrates the importance of careful follow-up of these patients. Symptoms or signs of cervical cord compression merit further investigation. Proven compromise of the upper cervical cord is an indication for posterior fusion of the upper cervical spine.

Radiography of the lateral neck was performed on all children with Down's syndrome aged 4-15 in the Southern Derbyshire health district (n = 67) and a random selection of adults (n = 94). Atlantoaxial instability, defined as a gap of over 4 mm, was present in seven (10%) children and two (2%) adults. Odontoid hypoplasia, defined as an odontoid peg two standard deviations below the mean in an age matched population, was present in 15 (22%) children and 14 (15%) adults, with accessory odontoid ossicles present in two (2%) and two (3%) respectively. No one was found to have symptoms or clinical signs of spinal cord compression. Atlantoaxial instability was therefore found to be commoner in children than adults. Different programmes of management are suggested, in terms of regular clinical examination for signs and symptoms and by radiographic screening. Particular care should be taken with those who have both atlantoaxial instability and odontoid hypoplasia or accessory ossicles as they are at particular risk of spinal cord damage.

The usefulness of the recently developed Ranawat and Redlund-Johnell craniometric methods was compared with that of the conventional McGregor method for diagnosing vertical settling (VS) of the skull and the atlas on the axis in 209 patients with rheumatoid arthritis (RA). Statistical analysis of the values obtained from roentgenograms revealed close correlations among the three methods. The first two methods were superior to the McGregor method because the measuring points could be identified on plain roentgenograms of the cervical spine in virtually all cases. The McGregor value could not be determined in 38 (18%) patients. Since medullary compression could be detected by magnetic resonance imaging in all patients who showed abnormal Redlund-Johnell values, the Redlund-Johnell method may be useful for diagnosing advanced VS. It also detects not only atlantoaxial lesions but also atlantooccipital lesions. Thus, the Redlund-Johnell method appears to be the best method for diagnosing VS in RA patients.

The pathomechanism of atlantoaxial rotatory fixation (AARF) was studied using roentgenography and computerized tomography in affected children as well as cadaver studies of upper cervical spine anatomy. The increased incidence of AARF in children may be related to certain anatomical differences between children and adults. The dens-facet angle of the axis was steeper in children than in adults. Meniscus-like synovial folds were found in the C0/1 and C1/2 facet joints of the spines of children but not in those of adults.

Ten patients with severe chronic rheumatoid arthritis with atlantoaxial subluxation were examined with conventional radiography and MR imaging of the cervical spine before and at an average of 6 months after posterior occipitocervical fusion. Periodontoid pannus formation was revealed by MR preoperatively in nine patients, all with mobile horizontal atlantoaxial subluxation. Compression of the medulla and/or upper cervical cord, due to subluxation and periodontoid pannus bulging into the spinal canal, was seen in seven patients. After the stabilizing surgery the periodontoid pannus had decreased in size in all patients with preoperative pannus. This reduction in the pannus seems to be the result of the atlantoaxial immobility achieved by the posterior fusion. Postoperatively, three patients had some remaining compression of the medulla and/or cord secondary to immobile subluxation, while the pannus posterior to the odontoid process had disappeared. Artifacts from the surgical stainless steel fixation material were confined to the posterior part of the neck on short TR/short TE MR images and did not interfere with the evaluation of the periodontoid region and the anterior part of the medulla/cervical cord. We found that flexion and extension lateral radiographs, combined with sagittal short TR/short TE MR images in the neutral position, enable preoperative evaluation of patients with rheumatoid arthritis in the cervical spine. Postoperative MR should be performed only if there are residual or new symptoms.

Occipito-atlanto-axial malformation with atlanto-axial subluxation was diagnosed radiographically in a 4-day-old Holstein calf with a short neck, symmetric ataxia, and tetraparesis, indicative of a cervical spinal cord lesion. Necropsy confirmed the clinical diagnosis and revealed ribs on C-7, with partial fusion of C-7 and T-1. Histologic examination revealed focal degeneration of the spinal cord in the second cervical segment at the level of the atlanto-axial joint and extensive secondary neuronal fiber degeneration possibly caused by spinal cord trauma that occurred in utero.