Basic anatomy

Motor cortex: 4 to 5.4 cm behind the coronal suture (개인차 있음)

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. These are just approximations since individual variability causes the motor strip to lie anywhere from 4 to 5.4 cm behind the coronal suture.13 The central sulcus cannot even be reliably identified visually at surgery.

 

1. method 1: the superior aspect of the motor cortex is almost straight up from the EAM near the midline

2. method 2: the central sulcus is approximated by connecting:

• a) the point 2 cm posterior to the midposition of the arc extending from nasion to inion (illustrated in ▶ Fig. 1.6), to
• b) the point 5 cm straight up from the EAM

3. method 3: using T-H lines, the central sulcus is approximated by connecting:

• a) the point where the “posterior ear line” intersects the circumference of the skull (▶ Fig. 1.6; usually about 1 cm behind the vertex, and 3–4 cm behind the coronal suture), to
• b) the point where the “condylar line” intersects the line representing the Sylvian fissure

4. method 4: a line drawn 45°to Reid’s base line starting at the pterion points in the direction of the motor strip