Donaldson’s Line

• Donaldson’s Line is an intraoperative anatomic landmark used to help locate the endolymphatic sac.¹
  • Donaldson’s line is an imaginary line drawn parallel to the horizontal semicircular canal that bisects the posterior semicircular canal.
  • The endolymphatic sac will lie inferior to Donaldson’s line.

Temporal Bone Dissection (Donaldson’s Line)