Neurosurgery notes/Anatomy/Skull/Craniometrics

Craniometrics

View Details
Status
Done
logo
Parent item
Skull
  • Craniometrics is the measurement of skulls, using standardized anatomical landmarks like nasion, bregma, glabella, porion, zygion, and gonion to acquire reproducible data about skull shape and size.
  • Clinically used
    • Surgical planning
    • Diagnose and track
      • Craniofacial syndromes
      • Congenital anomalies
      • Growth disorders.
 
notion image

Taylor-Haughton (T-H) lines

  • Can be constructed on an angiogram, CT/MRI scout film, or skull X-ray.
  • They can be constructed on the patient in the O.R. based on visible external landmarks.
    • Frankfurt plane, AKA baseline/orbitomeatal line: line from inferior margin of orbit through the upper margin of the external auditory meatus (EAM)
    • The distance from the nasion to the inion is measured across the top of the calvaria and is divided into quarters (can be done simply with a piece of tape which is then folded in half twice)
    • Posterior ear line: perpendicular to the baseline through the mastoid process
    • Condylar line: perpendicular to the baseline through the mandibular condyle
    • Frontozygomatic point
      • Location on the lateral orbital bone (~2.5 cm from the zygoma attachment), which if connected with the 75% point (three-fourths of the distance from the nasion to the inion) approximates the location of the sylvian fissure
      • 7mm superior and posterior to it is the Key hole
notion image
 
  • Can then be used to approximate the Sylvian fissure and the motor cortex
      • Motor cortex
      • Numerous methods utilize external landmarks to locate the motor strip (pre-central gyrus) or the central sulcus (Rolandic fissure) which separates motor strip anteriorly from primary sensory cortex posteriorly.
      • Method 1:
        • The superior aspect of the motor cortex is almost straight up from the EAM near the midline
      • Method 2: the central sulcus is approximated by connecting:
        • The point 2cm posterior to the mid-position of the arc extending from nasion to inion), to
        • The point 5cm straight up from the EAM
      • Method 3: using T-H lines, the central sulcus is approximated by connecting:
        • The point where the "posterior ear line" intersects the circumference of the skull usually about 1cm behind the vertex, and 3-4cm behind the coronal suture), to
        • The point where the "condylar line" intersects the line representing the Sylvian fissure
      notion image
       
      Sylvian Fissure
      • Approximated by a line connecting the lateral canthus to the point 3/4 of the way posterior along the arc running over convexity from nasion to inion (TH lines).
      • On the skull (once it is exposed in surgery): the anterior portion of the Sylvian fissure follows the squamosal suture and then deviates superiorly to terminate at Chater's point, which is located 6cm above the EAM on a line perpendicular to the orbitomeatal line; it is also ≈ 1.5cm above the squamosal
      notion image