C1-C2 Instability



C1-C2 Instability


Julia Crim, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Trauma



    • Jefferson C1 Fracture


    • Odontoid C2 Fracture


    • Hyperflexion Injury, Cervical


    • Rotary Subluxation, Atlantoaxial


    • Os Odontoideum


    • Pathologic Vertebral Fracture


  • Non-Traumatic



    • Rheumatoid Arthritis, Adult


    • Spondyloarthropathy, Seronegative


Less Common



  • Non-Traumatic



    • CPPD


    • Osteomyelitis, C1-C2


    • Grisel Syndrome


    • Achondroplasia


    • Trisomy 21 (10-20%, 1-2% Symptomatic)


    • Spondyloepiphyseal Dysplasia


    • Mucopolysaccharidoses (MPS)


  • Mimics of Instability



    • Normal Variant


    • Incomplete Fusion, Posterior Element


    • Craniovertebral Junction Variants


    • Calcific Tendinitis, Longus Coli


    • Pseudosubluxation (Childhood)


ESSENTIAL INFORMATION


Helpful Clues for Common Diagnoses



  • Imaging Evaluation of Instability



    • Transverse ligament of dens critical to anteroposterior stability


    • Normal distance from inferior margin C1 arch to dens < 2 mm in adults


    • Increased distance indicates rupture transverse ligament



      • Flexion-extension views useful


      • May be false negative in 1st week after injury


    • Jefferson fracture unstable if combined lateral displacement of C1 lateral masses relative to articular pillars of C2 ≥ 7 mm


  • Incomplete fusion of posterior elements does not cause instability because ligaments intact


  • Grisel syndrome in association with retropharyngeal infection, primarily seen in children


  • Rheumatoid arthritis often also involves atlanto-axial articulations, lower cervical uncovertebral and facet joints



    • Will not be present in C-spine unless peripheral involvement also present


    • RA pannus does not calcify


  • Calcified inflammatory tissue around dens usually due to CPPD


Other Essential Information



  • Craniocervical junction injuries often multilevel


  • Os odontoideum felt to represent nonunited dens fracture






Image Gallery









Axial bone CT shows lateral dislocation of lateral masses of C1 image relative to C2 articular pillars image. Combined lateral displacement of lateral masses > 7 mm confirms instability.

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on C1-C2 Instability

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