title: Syndromic versus nonsyndromic atlantoaxial dislocation: do clinico-radiological differences have a bearing on management?
abstract: BACKGROUND
  This prospective study attempts to study the clinico-radiological differences between patients with syndromic AAD (SAAD), non-syndromic AAD (NSAAD), and AAD with Klippel-Feil anomaly (AADKFA) that may impact management.
  
  
  METHODS
  In 46 patients with AAD [SAAD (including Morquio, Down, Larson and Marshall syndrome and achondroplasia; n = 6); NSAAD(n = 20); and, AADKFS (n = 20)], myelopathy was graded as mild (n = 17, 37 %), moderate (15, 32.5 %) or severe (14, 30.5 %) based on Japanese Orthopaedic Association Score modified for Indian patients (mJOAS). Basilar invagination (BI), basal angle, odontoid hypoplasia, facet-joint angle, effective canal diameter, Ishihara curvature index, and angle of retroversion of odontoid and vertebral artery (VA) variations were also studied.
  
  
  METHODS
  Clinico-radiological differences were assessed by Fisher's exact test, and mean craniometric values by Kruskal-Wallis test (p value ≤ 0.05 significant)
  
  
  RESULTS
  Incidence of irreducible AAD in SAAD (n = 0), NSA AD (11.55 %) and AADKFS (n = 18.90 %) showed significant difference (p = 0.01). High incidence of kyphoscoliosis (83 %) and odontoid hypoplasia (83 %) in SAAD, and assimilated atlas and BI in NSAAD and AADKFA groups were found. In AADKFA, effective canal diameter was significantly reduced(p = 0.017) with increased Ishihara index and increased angle of odontoid retroversion; 61 % patients had VA variations. Thirty-five patients underwent single-stage transoral decompression with posterior fusion (for irreducible AAD) or direct posterior stabilization (for reducible AAD). Postoperative mJOAS evaluation often revealed persistent residual myelopathy despite clinical improvement.
  
  
  CONCLUSIONS
  Myelopathy is induced by recurrent cord trauma due to reducible AAD in SAAD, and compromised cervicomedullary canal diameter in NSAAD and AADKFA. SAAD in children may be missed due to incomplete odontoid ossification or coexisting angular deformities. In AADKFA, decisions regarding vertebral levels to be included in posterior stabilization should take into consideration intact intervening motion segments and compensatory cervical hyperlordosis. Following VA injury, endovascular primary vessel occlusion/stenting across pseudoaneurysm preempts delayed rehemorrhage.
authors: Department of Neurosurgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, 226014, Uttar Pradesh, India.
authors: Jayesh
authors: J
authors: Sardhara
authors: Sanjay
authors: S
authors: Behari
authors: Awadhesh K
authors: AK
authors: Jaiswal
authors: Arun
authors: A
authors: Srivastava
authors: Rabi Narayan
authors: RN
authors: Sahu
authors: Anant
authors: A
authors: Mehrotra
authors: Shubha
authors: S
authors: Phadke
authors: Uttam
authors: U
authors: Singh
mesh_terms: D000293:Adolescent; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000601:surgery*; D001270:Cervical Atlas / Q000473:pathology; D002648:Child; D019299:Decompression, Surgical / Q000379:methods; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000601:surgery*; D008297:Male; D011446:Prospective Studies; D011859:Radiography; D013123:Spinal Fusion / Q000379:methods; D016896:Treatment Outcome