AC-PC line

The “AC-PC line” connects the anterior commissure (AC) and the posterior commissure (PC) on a mid-line sagittal image. The AC is the horizontally positioned white matter tract that crosses in front of the fornix. The PC is the white-matter band at the level of the pineal that crosses at the posterior third ventricle. The AC-PC line is used in functional neurosurgery and is also used as the baseline for axial MRI scans (and for recent CT scanners). In the more entrenched Talairach definition, it passes through the superior edge of the AC and the inferior edge of the PC. Alternative Schaltenbrand definition: a line passing through the midpoint of the AC & PC, allowing both AC & PC to be imaged on a single thin axial MRI slice. These definitions differ by 5.81° ± 1.07°.5 The orbitomeatal line (used in older CT scanners) is ≈ 9° steeper than the Talairach AC-PC line.