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Information

Differential Diagnosis of Skull and Spine Disorders

Atlas Anomalies!!navigator!!

  1. POSTERIOR ARCH ANOMALIES
    1. Posterior atlas arch rachischisis (4%)
      location: midline (97%); lateral through sulcus of vertebral artery (3%)
      • absence of arch-canal line (LAT view)
      • superimposed on odontoid process / axis body simulating a fracture (open-mouth odontoid view)
    2. Total aplasia of posterior atlas arch
    3. Keller-type aplasia with persistence of posterior tubercle
    4. Aplasia with uni- / bilateral remnant + midline rachischisis
    5. Partial / total hemiaplasia of posterior arch
  2. ANTERIOR ARCH ANOMALIES
    1. Isolated anterior arch rachischisis (0.1%)
    2. Split atlas = anterior + posterior arch rachischisis
      • plump rounded anterior arch overlapping the odontoid process making identification of predental space impossible (LAT view)
      • duplicated anterior margins (LAT view)

Axis Anomalies!!navigator!!

  1. Persistent ossiculum terminale = Bergman ossicle
    • unfused odontoid process >12 years of age
      DDx: type 1 odontoid fracture
  2. Odontoid aplasia (extremely rare)
  3. Os odontoideum
    = independent os cephalad to axis body in location of odontoid process
    • absence of odontoid process
    • anterior arch of atlas hypertrophic + situated too far posterior in relation to axis body
      Cx: atlantoaxial instability
      DDx: type 2 odontoid fracture (uncorticated margin)

Odontoid Erosion

mnemonic: P LARD

  • Psoriasis
  • Lupus erythematosus
  • Ankylosing spondylitis
  • Rheumatoid arthritis
  • Down syndrome

Atlantoaxial Subluxation!!navigator!!

= displacement of atlas with respect to axis

  1. Posterior atlantoaxial subluxation (rare)
  2. Anterior atlantoaxial subluxation (common)
    = distance between dens + anterior arch of C1 (measurement along midplane of atlas on lateral view):
    1. predental space: >2.5 mm >4.5 mm (in children)
    2. retrodental space: <18 mm

Causes of subluxation:

  1. Congenital
    1. Occipitalization of atlas 0.75% of population; fusion of basion + anterior arch of atlas
    2. Congenital insufficiency of transverse ligament
    3. Os odontoideum / aplasia of dens
    4. Down syndrome (20%)
    5. Morquio syndrome
    6. Bone dysplasia
  2. ARTHRITIS
    due to laxity of transverse ligament or erosion of dens
    1. Rheumatoid arthritis
    2. Psoriatic arthritis
    3. Reiter syndrome
    4. Ankylosing spondylitis
    5. SLE
      rare: in gout + CPPD
  3. INFLAMMATORY PROCESS
    pharyngeal infection in childhood, retropharyngeal abscess, coryza, otitis media, mastoiditis, cervical adenitis, parotitis, alveolar abscess
    • dislocation 8–10 days after onset of symptoms
  4. TRAUMA (very rare without odontoid fracture)
  5. MARFAN DISEASE
    mnemonic: JAP LARD
    • Juvenile rheumatoid arthritis
    • Ankylosing spondylitis
    • Psoriatic arthritis
    • Lupus erythematosus
    • Accident (trauma)
    • Retropharyngeal abscess, Rheumatoid arthritis
    • Down syndrome

Pseudosubluxation of Cervical Spine

= ligamentous laxity in infants allows for movement of the vertebral bodies on each other, esp. C2 on C3

Outline