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Neuroradiology Case of the Week

Case 430

August 2009

J. Scott Thomson, MD

Clinical Presentation: Patient is a 53-year-old woman with recent torticollis. She had a very recent right basal ganglia hemorrhage. No known trauma.

Imaging Findings: Rotatory subluxation of C1 on C2,  seen on the CT. Much improved alignment on the CT nine days later after traction.

Diagnosis: Rotatory subluxation of C1 on C2

Discussion: Atlantoaxial rotatory subluxation is more common in the pediatric age group than in adults. It may be associated with trauma, inflammatory conditions such as rheumatoid arthritis, infection such as upper respiratory infection, or head and neck surgery. Torticollis is a characteristic clinical association. A few reports suggest that atlantoaxial rotatory subluxation may be secondary to a primary cervical dystonia/ torticollis. It is theorized that laxity of the stabilizing ligaments of the atlantoaxial joint, namely the transverse and alar ligaments, predispose to this condition. This condition may be associated with fracture especially in cases of trauma.
     Rotation of the head occurs primarily through rotation of C1 on C2. The maximum normal rotation of the atlantoaxial joints is 45-47 degrees. Fixed rotatory subluxation may occur when rotation occurs beyond this physiological limit, and when the rotation of C1 on C2 cannot be reduced with neutral neck position. This can be a difficult diagnosis by plain radiographs, which may be misleading. The modality of choice is CT with 3D reconstructions, by which the diagnosis can be readily made. This may require general anesthesia, especially in children, which would allow neutral and contralateral position of the head during the scan.
     Prompt reduction is important, since reduction becomes more difficult as times passes. Atlantoaxial rotatory subluxation may be associated with neurologic dysfunction, including vertebral artery compromise. Closed reduction with traction, as above, is often successful when the condition is promptly diagnosed and treated. Open surgical reduction with fusion of C1-C2 is indicated when closed reduction fails.

References:

1. Been HD, Kerkhoffs GM, Maas M. Suspected atlantoaxial rotatory fixation-subluxation: the value of multidetector computed tomography scanning under general anesthesia. Spine. 2007 Mar 1;32(5):E163-7. PMID: 17334278 [PubMed]
2. Maile S, Slongo T. Atlantoaxial rotatory subluxation: realignment and discharge within 48 h. Eur J Emerg Med. 2007 Jun;14(3):167-9. PMID: 17473614 [PubMed]
3. Pang D, Li V. Atlantoaxial rotatory fixation: part 3-a prospective study of the clinical manifestation, diagnosis, management, and outcome of children with alantoaxial rotatory fixation. Neurosurgery. 2005 Nov;57(5):954-72; discussion 954-72. PMID: 16284565 [PubMed]
4. Tonomura Y, Kataoka H, Sugie K, Hirabayashi H, Nakase H, Ueno S. Atlantoaxial rotatory subluxation associated with cervical dystonia. Spine. 2007 Sep 1;32(19):E561-4. PMID: 17762799 [PubMed]