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Differential Diagnosis of Skull and Spine Disorders

Craniovertebral Junction Anomaly!!navigator!!

mnemonic: PF ROACH

  • Paget disease
  • Fibrous dysplasia
  • Rheumatoid arthritis, Rickets
  • Osteogenesis imperfecta, Osteomalacia
  • Achondroplasia
  • Cleidocranial dysostosis, Chiari malformation
  • Hyperparathyroidism

Cx: compression of brainstem

  1. →aqueductal stenosis → hydrocephalus
  2. →cord edema, syrinx

Rx: surgical decompression of posterior cranial fossa / foramen magnum (posterior approach); resection of odontoid (anterior approach)

Basilar Invagination

= congenital primary developmental anomaly with abnormally high position of vertebral column prolapsing into skull base ← bone softening

Associated with: Chiari malformation, syringohydromyelia in 25–35%

Cause: mnemonic: MACKO

  • Mucopolysaccharidosis
  • Achondroplasia
  • Cleidocranial dysostosis
  • Klippel-Feil syndrome
  • Osteogenesis imperfecta
  • limitation in range of motion of CVJ
  • abnormal craniometry:
    1. Condylus tertius = ossicle at distal end of clivus
      • pseudojoint with odontoid process / anterior arch of C1
    2. Condylar hypoplasia
      • lateral masses of atlas may be fused to condyles
      • violation of Chamberlain line
      • widening of atlanto-occipital joint axis angle
      • tip of odontoid >10 mm above bimastoid line
    3. Basiocciput hypoplasia
      • shortening of clivus
      • violation of Chamberlain line
      • clivus-canal angle typically decreased
    4. Atlanto-occipital assimilation
      = complete / partial failure of segmentation between skull + 1st cervical vertebra
      • violation of Chamberlain line
      • clivus-canal angle decreased

      May be associated with: fusion of C2 + C3
      Cx: atlantoaxial subluxation (50%); sudden death
  • C-spine + foramen magnum bulge into cranial cavity
  • elevation of posterior arch of C1

Basilar Impression

= acquired form of basilar invagination with bulging of C-spine and foramen magnum into cranial cavity with normal bone

  • tip of odontoid process protrudes upward through foramen magnum into cranium = projects >5 mm above Chamberlain line (= line between hard palate + opisthion)

Cause: mnemonic: HORRIFic P

  • Hyperparathyroidism
  • Osteomalacia
  • Rickets
  • Rheumatoid arthritis
  • Infection of skull base
  • Fibrous dysplasia
  • Paget disease

Platybasia!!navigator!!

= anthropometric term referring to flattening of skull base

May be associated with: basilar invagination

  • cord symptoms
  • craniovertebral = clivus-canal angle becomes acute (<150°)
  • Welcher basal angle = sphenoid angle >140–145°
  • bowstring deformity of cervicomedullary junction

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