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Anatomy of Skull and Spine

  1. METOPIC / FRONTAL SUTURE

    = from nasion to anterior angle of bregma
    [bregma, Greek = top of head]
    Closure: by 3 months – 6 years of age; in up to 10% open until adulthood
    Sutura frontalis persistens = metopism
    = no closure of incomplete / complete metopic suture
    DDx: anterior vertical fracture
  2. SAGITTAL SUTURE
    [sagitta, Latin = arrow]
    = fibrous connective tissue joint between two parietal bones
    Average width: 5.0 ± 0.2 mm (at birth), 2.4 ± 0.1 mm (1 month of age); narrowing further over time
    Closure: 21–30 years of age; fusing anteriorly beginning at intersection with lambdoid suture
  3. CORONAL SUTURE
    = separates frontal from parietal bones
    Average width: 2.5 ± 0.1 mm (at birth), 1.3 ± 0.1 mm (1 month of age)
    Closure: 24 years of age
  4. SQUAMOSAL SUTURE
    1. temporosquamosal suture
      = connects temporal bone squama with lower border of parietal bone; arches posteriorly from pterion (= contact point between frontal, parietal, temporal, sphenoid)
      [pteron, Greek = wing]
      • often visualized at two points at CT with lambdoid suture acting as a useful posterior reference point

      = continuous posteriorly with parietomastoid suture uniting mastoid process of temporal bone with region of mastoid angle of parietal bone
    2. sphenosquamosal suture
      = courses inferiorly from pterion separating sphenoid bone from squama of temporal bone
      N.B.: often mistaken for skull base fracture
  5. LAMBDOID SUTURE
    [upper case Greek letter lambda = L]
    = connects parietal with occipital bone
    Closure: 26 years of age
    N.B.: the most common site of wormian bones
  6. OCCIPITOMASTOID SUTURE

    = inferior continuation of lambdoid suture at the point where lambdoid suture intersects with temporosquamosal suture
  7. PARIETOMASTOID SUTURE
    = links temporosquamosal and lambdoid sutures
    • often not seen on axial CT images
  8. OCCIPITOMASTOID SUTURE
    = between occipital bone + mastoid process of temporal bone as a continuation of the lambdoid suture toward skull base
    N.B.: not infrequently mistaken for a skull base fracture
  9. SPHENOFRONTAL SUTURE
    = transverse suture between anterior margin of lesser sphenoid wing + posterior margin of horizontal orbital plate
    • lesser sphenoid wing (posterior to suture) is a useful landmark for suture localization
  10. ACCESSORY PARIETAL SUTURE (rare)
    = the most common of all usually bilateral and symmetric accessory sutures
    Location: parietal and occipital bone → multiple ossification centers
  11. MENDOSAL / ACCESSORY OCCIPITAL SUTURE
    Frequency: 3% in an Indian subcontinent population
    Closure: in utero / first few days of life; may persist up to 6 years of age
    Os incae = large single centrally located intrasutural bone at junction of lambdoid and sagittal sutures; often forms in a persistent mendosal suture
  12. SKULL BASE SUTURES
    Ossification: 50% (84%) of anterior base by 6 (24) months
    1. innominate / intraoccipital
      Closure: 4 years of age
    2. lambdoid
    3. occipitomastoid
    4. parietomastoid
    5. temporosphenoidal
      Symmetry and knowledge of the anatomic appearances of basal sutures are important for avoiding misdiagnosis.
      A persistent hypoattenuating area of any length extending from foramen magnum beyond 4 years of age indicates a fracture.