Atlantoaxial subluxation is a known sequela of acute inflammatory processes in the upper neck and has been described frequently in children. A case of severe atlantoaxial subluxation treated conservatively in an adult with group A streptococcus pharyngitis and a retropharyngeal abscess is reported.
A 24-year-old male presented at the emergency room with a one-month history of pharyngitis and recent increasing dysphagia. The patient described shooting pains in the neck and both arms with movement of the head. Physical exam revealed a febrile patient with marked erythema throughout the nasal pharynx and a bulging flocculent posterior pharyngeal wall. The neurologic exam was normal. A soft tissue lateral radiograph of the neck revealed a marked increase in the retropharyngeal space and considerable widening of the articular space between the anterior aspect of the dens and the posterior aspect of the anterior arch of CI measuring 7 mm Fig. 1). Computed tomography of the neck confirmed the presence of retropharyngeal abscess (Fig. 2). No bony involvement was demonstrated. The patient was taken to surgery where 10 cc of purulent material was drained from the retropharyngeal space. Subsequent cultures revealed group A streptococci. Gallium and bone scans followed which demonstrated no evidence of bony abnormality. However, flexion and extension views demonstrated instability with marked widening of the atlantoaxial joint on the flexion view to 14 mm. The patient was placed on appropriate IV antibiotics and was fixed externally with a halo to stabilize the atlantoaxial joint. At 8 weeks, only minimal widening of the articular space remained. At this time the asymptomatic patient was removed from the halo with flexion and extension views demonstrating predens measurements of 7 mm and 5 mm, respectively. The patient subsequently was lost to follow up, disregarding the physician's request to utilize a neck collar.
Fig. 1: Lateral soft tissue view of neck demonstrates widened pre-dens space measuring 7 mm (small arrows) also note widened pre- vertebral space measuring 4.5 cm (large arrows).
Fig. 2: Neck CT with contrast enhancement demonstrates thick enhancing (small arrows) rim (large arrow) and low density necrotic center.
Fig. 3: Postoperative flexion view demonstrates widening of the atlantoaxial joint to 14 mm from resting extension distance of 7 mm (arrows).
Non-traumatic atlantoaxial subluxation is a known sequela of numerous etiologies. These include retropharyngeal abscess, acute tonsilitis, acute mastoiditis, eosinophilic granuloma, and arthritides such as rheumatoid, Reiter's disease, ankylosing spondylosis and Bechet's syndrome. Additionally, atlantoaxial subluxation has been described with os odontoidum, aplasia of the dens, occipitalization of the atlas and in older children with trisomy 21 and Morquio's syndrome.1,2 In the pediatric age group, atlantoaxial subluxation secondary to a retropharyngeal abscess is well described. In the adult population, this has only been sporadically reported.2'3
The atlas and axis articulate through four joints, two median, and the bilateral atlantoaxial joints. The median atlantoaxial (pivot) joints are comprised of the articulation between the posterior surface of the anterior arch of Cl and anterior surface of the dens, and the posterior surface of the dens with the transverse ligament which is the principle ligament. Each of these articulations represent a separate synovial joint. The articulation between the lateral masses of the atlas and axis constitute the lateral atlantoaxial joints.4 Subluxation results from fractures of the arch of Cl, odontoid, or joint ligaments, primarily the transverse ligament. The mechanism of subluxation in inflammatory conditions is attributed to softening of the ligament allowing greater mobility at the joint. The etiology of this process is speculative. It has been considered to result from hyperemia secondary to the adjacent inflammation.5 Other considerations might include the direct effect of the substances liberated by the microorganisms within the abscess directly acting on the ligamentous structures.
Extracellular toxic activities of group A streptococcus include the streptolysins, streptokinase, hyaluronidase, erythrogenic, or scarlatinal toxins, leucocidins, and enterotoxins. Hyaluronidase depolymerizes the ground substance of surrounding tissues increasing the ability of the streptococci to spread while erythrogenic toxin is known to cause marked local erythrema.6 In this case, the subluxation was shown not to be due to direct separation by mass effect from abscess or bony injury on the CT, gallium and bone scans.
The realization of appropriate antibiotic therapy and surgical drainage coupled with conservative external fixation may avoid surgery.3 Confirmation of stability is afforded by follow up radiographically utilizing monitored flexion and extension views. If instability remains, then surgical fusion may be required particularly if any neurological deficits are present.
1. Gehweiler JA, Osborne RL, Becker RF: 77ie Radiology of Vertebral Trauma. Philadelphia: WB Saunders Company.
2. Pinkham JR: Inflammatory subluxation of the atlantoaxial joint. South Med J 1986; 69:1507-1509.
3. Greenberg AD: Atlantoaxial dislocations. Brain 1968; 91:655.
4 . Harris JH: The Radiology of Acute Cervical Spine Trauma . Baltimore, Williams and Wilkins, 1978, ? 10.
5. Marar BC, Baiachandran N: Non-traumatic atlantoaxial dislocation in children. Clin Orthop 1973; 92:220-226.
6. Burrows W: Textbook of Microbiology, 20th ed. Philadelphia, WB Saunders Company, 1973, ? 422.